SPE London hybrid session features: Geothermal Energy & Well Construction by Prof Andy & John Clegg

Hello it's tim hi tim hi hi hold on you didn't see me here we go i'm so sorry don't worry about it i mean what happened was you did you see that that's sarah booked the ticket and she booked a ticket even though it said this ticket is still is now not available because eventbrite you can't once you've launched an event you can't then delete ticket types uh-huh right Hold on i'm just going to kill that okay google off oh you've got one of them um so i wanted to come in so uh are you

are you managing this because yeah you haven't got adam no no i i'll manage it all but i'll wait till five okay so these people are waiting to be admitted yes uh that we don't have a green room we can Put us i i'm making it right now oh you are oh adam hello sp london apologies i i hate going to work because i have to re-cable everything when i come back okay how are you tim have you recovered i am completely recovered absolutely absolutely fine um took four uh 14 days of uh or i

think it's 17 14 days of positive tests and then changed after after day seven you can actually um you're not infectious anymore i don't agree Well that's that that's according to my friend who runs the intensive care unit at least i had symptoms like i had i had i had symptoms of illness uh chest cough also okay well what do you think about boris then ripping it all up then what do you think about what do you think about it all being ripped up now then i think it's most unwise i think the least you

should insist on on keeping social distancing and masks on Because um they work uh but you know um you know the rest of it can go i don't i don't see the reason of the isolation i mean most people when they've got flu or a serious cold they isolate um and that that can i think more so now i think of the days you're going to go to work with the streaming cold and really hacking cough absolutely agree yeah absolutely that's what we used to do is to feel we Have to go we have a

speaker in apologies that what is the name of the speaker i'm just trying so i will connect the zoom to the because i have only the sponsor slides of mine were cropped up so i will just give you andy woods um [Music] no i was just going to say i'll give you his spell he's got two emails you know The emails because of what he is yes so your eternal dream got it section you guys are going to discuss on thursday about the way forward for the next three events yeah yeah yeah definitely so andy

and john okay i don't see them in go okay and let me get reminds of some sort Then i will move us into a green room yeah okay fine yeah yeah i to be honest i yeah we can we can chat on thursday but i think kate you're right it we should deliver value to the members if maybe the the in-person bets might be separate from the technical lectures Yeah that might why didn't you think about doing a sort of networking summer party no not exactly so that's either works with percy in some kind of

spring so he was thinking about march all right so that's a bit early you think so yeah i do as well you know look at look yeah we you'd expect to get 20 people Signing up for an event you know and i don't i can't imagine what's gonna happen in march um okay you need i've got the ideal place you go to the october gallery which is going outside space which makes people feel it is nice i'm doing an event i'll invite you both i'm doing an event on april the 20th 28th but it's weird

all the journalists all back they're absolutely they're all our events uh They're hybrid but they're full in person it's funny isn't it it depends on the industry i think it does it really does but i think a spring party as in spring summer party yeah and i just think it's just it's too messy to keep changing and i think absolutely yeah yeah and to be honest you you especially with this event you can see the massive disparity if we have 150 people and only three want to go in Person that's that's a clear message yeah

okay everyone's got a damn link in the end uh you've actually got 238 people signed up for this okay i know i know you have a massive dropout you know so it has to be with a pinch of salt oh i see i mean a lot of those people are because they're not they're not london members they're international members how many under members were There in fact did you do you have a chance to seek when you did that last email thing the london one yeah how many members are there i don't know it doesn't

i don't have it doesn't tick okay the box it doesn't have i can do that in the future are you a member or non-member or well no it's not that it's just that because it was advertised globally then uh and it's such an important topic globally that i would Expect the majority of the people to uh to be attending are from other countries oh we'll see one yeah that's why i i didn't realize you hadn't really appreciated that because that's why i was saying that you know you need to make sure it's um it's not

centric yeah yeah and so anyway fast okay but if it's going to be recorded Then maybe we can make it available for people hey recording saturday [Music] um [Music] foreign [Music] ready hello [Music] Um oh foreign yeah my apologies good afternoon everybody thank you very much for attending and uh we are expecting quite a few more people to attend but um maybe maybe they will join as we go on through so there will be a bit of a distraction um but be that as it meant i think we'll start now we're around just around on

Time and uh andy woods uh as you know is our first speaker and i'll just read a little bit from his uh his bio and his talk just to refresh your memories as to uh the nature of the discussion um so andrew's uh talk is geothermal energy some fluid flow challenges and in this talk uh andy will discuss some of the potential for geothermal energy production focusing on the fluid mechanics and the heat transfer Assessing the different approaches to extracting energy in both open and closed systems given the renewed interest which has developed in developing

deep systems for power generation he will also address some of the challenges for ground source heat pump systems especially in high highly populated areas where dense arrays of bore holes may be required andy studied maths at st john's college Cambridge followed by phd in dmtp cambridge on geophysical fluid dynamics two years as a research fellow at st john's college and as a green scholar at the igpd pp san diego before taking up a lectureship for five years at the institute of theoretical geophysics in cambridge after three years as professor of applied mathematics at the university

of bristol he was elected the bp professor and head of the bp institute university Of cambridge he was elected a fellow of the royal society in 2017. andy the floor is yours well thank you very much i'll i'll just put my slides up um [Music] let's continue sorry um thank you is that are these slides all up um all visible great we'll think well thank you very Much for the um very generous invitation and to come and talk to you this evening i i thought i would go through a series of the different types of

flow modelling problems associated with geothermal energy production and talk about some of the research we've been doing um in in cambridge on some of these challenges and In particular the the challenges of the complexity of many of the permeable rocks in which the heat is stored and then talk about how this is um informing some of the recent developments in geothermal power production um so um please do interrupt as we go through if there are questions um so to start off with i just thought i'd put put down a couple of slides just Noting the

um the i guess the origin behind the the present renewed interest in geothermal is really that we're as we're trying to decarbonize the energy system and presently um geothermal energy is only a very small fraction um 0.1 or smaller of the global energy Supply um and yet it's got there's a huge potential um to mine the heat in the earth and generate um get a lot of power production but also have um lower temperature low grade um thermal energy for um heating systems um so um this plot just shows the um prevalence at the moment

of hydrocarbons and the Need to actually try and generate a number of different sources of renewables and other sources of energy production to replace the present enormous fraction of the energy system which is generated from hydrocarbons and just to put some lens on that if we look at the um the next slide what we can see here is the um sort of a Possible projection forward into the ways in which the energy may be sourced in the future and what we can see is the um there's a whole series of different um sources of potential

sources but the other and other renewables i think are the boxes in which geothermal presently sets and yet this has got you know considerable potential i'm going forward to be um you know play an important role particularly in particular in certain areas of the world where they have a lot Of hot um ground near the surface so what we're interested in tonight is trying to understand some of the challenges and um issues associated with growing these um other boxes in this in this picture and and just for context a lot of the new energy production

will be produced by wind and solar power and as we can see here on this slide here this is just Showing up to 2020 the enormous growth in renewables and you can see both in terms of geographic location but also type of renewables and wind is you know is sort of winning the lead at the moment there's a lot of solar renewable power generation um but there's um given that the nature of the challenge the enormity of the challenge um Thinking about geothermal where it may have a big role is very important because and of

course these numbers are extremely big so when we look at these graphs and see the the global challenge um of course power power generation locally um can still be an extremely large scale operation so i think geothermal still has an important role to play So um what and just for contrast we can see that nuclear power hasn't been growing and um sort of um so hydroelectric power has been growing in um far east but elsewhere that's sort of saturated so um but geothermal power really has a big role to play so this this chart just

shows some of the global uses of Global power production um geothermal energy around the globe and we can see the us is by far away the dominant country generating geothermal power today um with a lot of power in the the west but there's there's also other areas where there's a lot of um hot subsurface ground the philippines indonesia um and of course new zealand and iceland so um and and one of the interesting Issues which i think iceland has really been pioneering is the fact that um if you have a lot of um power generation

you can actually bring in industry to that power generation and use the power um for aluminium and other other industries so i so there's a very interesting idea about bringing industry to the source the power um which is perhaps different from um when the nature of the power sources change um from Hydrocarbons which are obviously very transportable but as we see from this chart the growth of geothermal hasn't been as rapid as it could be and um but there are projects happening and um you know so i'd say i think this this chart just shows

how it's it's down to order 0.1 percent of global power in the in the uk focusing on the uk we Have you know the ground has different temperatures around the uk but cornwall is particularly attractive for geothermal power and there was the hot dry rock project that was developed 20 to 30 years ago and there's a new project being developed um at the eden project now in some of this very hot granite and just to show this there's a well that's Just being drilled just north of the eden project site and it's five kilometers deep

so this is very deep um geothermal into the fractured granite at that depth and the plan here is to try and extract heat by drilling two wells but there's just the first well has been drilled and the idea is to put a coaxial pipe down that well and um in your pump and then bring the Water back up the same the same well and use that as a test in the first instance until the second borehole has been drilled and then it'll be possible to drive a net flow through the system but just looking down

at this chart of cornwall we can see how the heat production is very variable but there's an extremely high or high heat production in in parts of central cornwall where there does seem to be a Lot of potential and um in this site the idea is this will become a power plant to actually generate um power the the um temperature goes down to about 180 degrees i think um and so very hot hot um fluids can be extracted from this system and a lot of the challenge lies in trying to understand the flow paths through

the fractures particularly these very high pressures and whether as Cold water is injected and migrates through the structure whether that actually leads to flow focusing and changes in the fracture permeability because of the heat heat transfer um so i think there's a number of interesting challenges that will emerge from this project um but uh but i really wanted to talk about some general fluid mechanical Principles about geothermal energy and geothermal heat production just to see some of the challenges associated with trying to model and predict heat recovery from geothermal systems and so this this cartoon

just shows a sort of generic geothermal plant where there'll be a series of pipes bringing up hot water and then collecting it in a station passing it through A turbine to generate power um and um i think what i wanted to talk about was the the nature of the challenges so what one of the challenges in geothermal systems is that um as you draw out hot water from the system um the system typically if it's an open system it needs to be recharged and so additional water needs to be pumped back in and This can

lead to a lot of very interesting challenges about how effectively that recharge of the system will work where the injected water goes and a lot of the technology from oil and gas in terms of drilling wells can be adopted but the production of scale and other precipitates can obviously be very difficult in geothermal plants So you know typical power generation the steam turbines produce about 11 gigawatts globally and then low grade heating um today produces about 21 8 gigawatts of power um so and of course this is all being drawn off the geothermal temperature gradient

in the earth which may be 25 to 30 degrees c per kilometer so obviously the deeper You go the hotter the system but the more challenging in terms of very high pressure and and of course higher temperature um and the costs for onshore um depends on on the challenge of the nature of the rock but if it's um impermeable rock it can be more expensive than drilling um in in other other industries but the typical numbers for power Generation about 10 cents a kilowatt hour um and there's a lot of interest in generating new geotherm

power so this this slide just shows the historical data from one power plant showing from 1990 up to 2010 um how it can provide you know a very substantial source of power generation and there is a gradual decline over time and of course some of that can be Addressed by um continual recharge but actually predicting and modeling the evolution of these systems is what can can be challenging um so i just so i thought i'd spend the rest of this talk really really looking at some of the fundamental physics of injection into geothermal systems and

and then perhaps move on to look at some of the emerging technologies associated with um Analogous technologies such as aquifer heat storage and um ground source heat pumps so the the the typical traditional idea in geothermal power is that you have a hot rock permeable layer of rock perhaps with some seal there above it and cold water will hot hot water is obviously extracted but in order to regenerate the power cold water will be injected into the system and The idea would be to have a net flow through the system mining the heat as the

water travels through the system um and the typical temperatures might be 150 to 350 degrees so obviously when the when the fluids come up they'll be at high pressure and typically they'll flash at some point and it'll be um steam production but there may be a lot of minerals that are produced with this which can lead to reactions both in the System but also at the surface and which can lead to some very substantial challenges associated with maintaining um these these systems running i mean this is just a picture of one of the power plants

um i think this is from the geezers in italy in northern california so so the first issue about re-injecting and really i wanted to focus on this issue of injecting water into the system And trying to model where that water goes and understand the flow parts and actually the fraction of the reservoir the hot reservoir that you you'd be able to access and mine heat from and a lot of it's about the challenge of water short-circuiting through the system or propagating along only a fraction of the rock so that not all of the thermal energy

in the system Can be um carried to the production wells and actually affected and produced and um of course i i should just note that thermal diffusion um in these systems is very unlikely to have a an important impact on the sort of commercial time scales of years given the the rate of heat conduction so it's really about effecting the heat through the system by driving flow through the system verification there because you talked About advection and we can talk about convection as well do you want to clarify the difference between the various terminologies oh

yeah okay so so i'll come back to this so so advection is which is mainly what i'll be talking about is actually where you're injecting water and it's migrating through the porous system and that carries um heat heat flux with it so it affects that so it's been carried by the flow Convection um is the state of having um fluid motion induced by temperature gradients so if we have a hot in as we move down the geotherm and the temperature increases water lower down in a formation will be warmer and it may be less dense

than water above that and that may lead to that water rising and the the water above it sinking and so you get a a um a circulation pattern which ten which tends to make the Temperature uh more uniform in that layer um and of course that convection does carry heat vertically um with as that fluid moves up and down and but typically you'd be mining the heat from that system by um drawing the water out and the water would carry the um the heat thermal energy with it but if you have impermeable rocks surrounding the

formation um then the rate of heat conduction through those permeable rocks um is very Slow so the the the natural recharge time um once you've mined the heat from the um permeable system um will be you know many tens of years or longer the thermal diffusivity being about 10 to the minus seven or several multiples of ten to the minus seven so we're only talking about diffusing heat distances of meters in a period of years so you're not actually going to be able to mine a lot of the Heat and the in perm people rock

around but i will come back to this when we look at closed systems later on um so so i guess the challenge with with these systems is actually what fraction of the permeable rocker you're able to access and what does the flow path look like and we've been doing a lot of work looking at this system and and the the issue about convection does Become very important because the temperature differences can lead to density changes in the water but in addition to that typically the water that you'll source at the surface um may come from

a variety of sources but it may not have the same composition as the water in the in the reservoir so this this um for water maybe saline with some natural um concentration of different um Salts but the the surface water that you access you might recycle some of the water but you might also be accessing water from rivers or other surface sources and that may tend to be a different density and and so when the fluid goes into the reservoir it's going to have different different density from the fluid in the system and that's going

to lead to a sort of buoyancy effects um impacting the flow as well as the pressure drive On the flow and that's going to be a large theme about my um the rest of my talk so so the first point is that if we're injecting into a permeable system and this is the brickport sandstone um then on the south coast in dorset um and if we were if this was um a formation in a geothermal system with a seal above it and we were going to imagine mining the heat in this system that the formation

um And many of these geological formations consist of many layers that are laid down so this is about 90 meters in height um kilometers in the lateral scale but each of these layers may only be a few meters in thickness and then there's less permeable um precipitate layers between these finer grain materials so this is a very layered and baffled rock and this may be typical of many of these systems and if you're injecting into this rock and then Monitoring where that fluid travels as it travels towards an extraction well um to mine the heat

um it may not travel along the um just a sort of simple horizontal pathway but there may be some effects of the the fact that the water you inject if it's relatively fresh it may be less dense than the saline water in in the system and it'll depend on the temperature Contrast compared to the um the density contrast from the different mineral composition but that can if the fluid you inject is less dense and we have a series of baffles in this maybe which are fractured or provide an imperfect seal it could be that the

plume of water you inject as it spreads through the system actually migrates along baffles and then tries to rise up through the system um Continuously accessing breaks in the seal and producing a plume of injected water that this has a very different topology from a simple fluid rising through the system um and and so we've done some experiments having a look at some of these effects um so this is an experiment in a healy shore cell where we have a series of baffles um this is just looking at a system upside down where we're injecting

fluids and it's Sinking under gravity as as these systems will eventually become once they travel far enough from the injection well and what you can see here is that this develops a plume that spreads out in the horizontal direction even though the main force is the the vertical buoyancy force and um this this particular flow path um that since The flow partitions over each of these baffles and becomes equally partitioned um across each baffle um the distribution of fluid moving through each of these channels here um essentially follows a binomial distribution and if you look

at that over a large a large number of these baffles it basically follows a gaussian so it essentially acts like a dispersion process so we have a horizontal dispersion acting from This heterogeneous structure of the the layered medium and so this may be an effect that leads to um a particular spread of the injected water if it's got a different composition from the water in the system and so you may be bypassing large parts of the system and so actually looking at the fraction of the thermal energy that you can recover um would be an

interesting issue and if the layer is inclined so if It's a tilted layer with the same sort of structure then what you find is that the the flow will partition asymmetrically along each of these baffles and when it finds leaks up to the and goes through the next layer these buoyant type flows will tend to drive a plume that moves at a particular angle um through the medium not not vertical but actually at some some other angle as it moves through the system so characterizing the the The sedimentary structure of the reservoir is going to

be very important in terms of trying to predict how these flows migrate and another effect that happens which can be very important in geothermal systems is that um if you if we have heterogeneities such as for example here this is a series of cross-bedded um formations where there may be bedding planes and they may This is a very small scale and this is a larger scale but the bedding planes of the the cross-bedded formation may vary depending on the geologic history of the sedimentation so we may get a very complex um rock structure and of

course if you're putting this into a reservoir simulator or other calculation tool to model the flow you'd kind of assign this a permeability um an effective horizontal and effective Vertical permeability but in practice um the flow may be somewhat different so as a very simple example of this if we imagine we have a layer um where we have cross bedding as shown here so we have a permeability k1 in across the layers and k2 along the layers and we just drive a flow through this system so this would just be a pressure Driven flow through

the system then um in order for the flow to move through this layer um and we just imagine it's got a seal there above and below in order to move through the the pressure gradient is not actually directed in the x direction but it's in some other direction because of this anisotropic permeability and um so what what you can see is that the the flow if k2 is a bigger permeability than k1 the flow naturally Tends to want to run down in this direction and so there needs to be a vertical pressure gradient to oppose

that flow and that leads to a net distortion of the pressure contours so they're actually in this direction here what we've seen on the slide so if you imagine now that you have a series of cross-bedded layers that are connected together and so in this this is just a Very simple simulation showing um an interface between a layer that's homogeneous and a layer that's cross-bedded in another layer that's homogeneous if we have a flow going through this and we just look at how a tracer moves through this um as we go through this interface between

this layer of rock here and this layer of rock there the pressure contours need to change from Being perpendicular to the flow to being at some angle to the flow as we see in this cross-bedded layer and then they return back to being vertical and the consequence of that is that there's an adjustment in the pressure contours um at the top bottom of the layer which leads to an acceleration of the um fluid at the top compared to the bottom and we get a shearing of the the tracer so this this red line is tracking

out um the the Um if you feel like it's the a tracer of the flow pattern and then when we get through the next boundary if we have a rock with a series of these boundaries in um then we get the opposite effect and the and so we end up getting a net net distortion of the dye like this so ultimately there's a net shear that develops in the layer and that shearing effect is very important within if we're looking at how does that transport temperature because If the if this flow is carrying the thermal

energy in the rock downstream it's going to carry the thermal energy more rapidly in the center of the formation than the edges so if it's cold water we're injecting we're going to get a cold layer running down the middle and that will as this interface spreads out we're going to get a lot of cross-layer diffusion and that's going to cause us spreading or smearing of the Temperature interface between the hot and the cold water and an analogous effect occurs if we have baffles if we have inclusions either of low permeability this is a just a

picture showing some flow going through a layer with low permeability inclusions this is one showing a big picture with high permeability inclusions and in both cases we end up getting a distortion of the flow field um which again has the net effect of a Shear across the flow so that um temperature gradients we're going to start generating vertical temperature gradients as a result of this horizontal flow and we can do a simple calculation to look at how that changes the effective thermal diffusivity or thermal conductivity in the direction of the flow So if we imagine

that we have um a system um of baffles in the layer um where we get very slow flow into those baffles then the flow will come along and it'll bypass these zones of low permeability but there'll be heat diffusion into those so this is cold water we're injecting displacing hot water these are going to cool down and um the um the fluid here is going to advance And start contacting hotter hottest zones downstream so if we want to try and model how quickly heat diffuses through this system what we can do is we can look

at the effect the flow speed of the flow as it moves outside the baffles outside these zones and that flow speed um is um so the actual mean speed um is related to the flow through these high-puntability layers And so if we're then looking at heat conduction through this system what we're going to have is we're going to have we can look at the mean temperature in our layer because ultimately if we have a production well that's going to sample the mean temperature so if we look at the mean temperature averaged across the layer um

so we're just averaging in the cross flow direction that would be an estimate of The mean temperature and that mean temperature is carried downstream um and so this this gives you the effective equation that we should put in our simulator to model the heat flow through this sort of layer where we're not accessing the heat in these layers so the temperature will evolve in time it'll be advected downstream and that advection um will be associated with the this darcy flow through the the layers between the baffles And if we're looking at this the mean transport

there's some diffusion but there's also a term because of the shearing because we have no flow here and we have a high speed flow here and that shearing leads to a temperature gradient um a perturbation temperature gradient and that the combination of the fluctuation in the flow speed across the layer and the fluctuation in the temperature gradient across the layer Can lead to a net transport and that net shock we can calculate that net transport which ends up being a diffusive transport or a dispersive type effect which can be very important for the heat transfer

so so here's our temperature equation again and what we're interested in is actually trying to predict this dispersive term well if we think about this flow going through the layer then in the there's Going to be a cross layer temperature gradient which is going to diffuse heat so there's going to be some perturbation temperature where we're diffusing heat and that's going to be balanced by the spreading out of the temperature in the direction of the flow because of the the variations in velocity from the mean so we have a region of fluid moving more quickly

that's going to carry cold water quickly forward and that cold water will Become in contact with hotter fluid and it'll then diffuse in the cross-flow direction and so we're going to expect to see a balance between the shearing of these temp these velocity fluctuations in the flow direction and the diffusion in the cross-flow direction and if we write that equation down we can then solve for the size of these cross flow temperature fluctuations in terms of the flux of the shear and the velocity And so with this simple example we're getting no flow and flow

and so we can calculate that and when we calculate that we find an effective dispersion term so just popping back this term here associated with the shear plus the the um fluctuations in the temperature gradient leads to an effective diffusion and that effective diffusion term is shown here and so we have to add that onto the thermal diffusivity and this Term here may be 10 or 100 times larger depending on the particular heterogeneity of the system than the the basic thermal diffusivity so what this is going to do is it's going to smear out the

thermal front between our cold water and the hot water as it spreads through the system and of course that's going to mean that the when that water starts becoming near the Production well we're going to have a gradually decreasing temperature of produced fluid rather than a sharp front which is obviously not not ideal in terms of power generation and similar effects are going to happen if we're looking at aquifer thermal storage so we're looking at heat storage and aquifers um for inter-seasonal heat storage the the recovery temperature and i'll come on to this a little

bit later but this Dispersion effect can have a very big impact in degrading the the temperature of the recovered fluid compared to having a more sharp thermal contact between the injected fluid and the fluid that we're recovering so that's sort of one one effect but the next effects i wanted to talk about were all related to the thermal inertia of the the porous layer and the effect of this thermal inertia on how fluids move Through the layer when we we may have density contrasts so what this series of pictures at the top on the right

hand side show are laboratory experiments so this is a porous layer and in this porous layer we have um hot we sort of initially have um cold water and then at the top we are injecting hot water And um so the red is hot water and the clear is cold water but we've dyed the hot water red and then in the center there's this black strip and this is a liquid crystal strip which records uh it changes color at a particular temperature and the temperature it changes color at is the temperature that's between the hot

and the cold temperature so i think the hot water was at about 35 degrees and the cold water was the lab temperature of about 20 and This temperature strip here is about 27 and what we see as time goes on in this experiment is the red fluid drains through the tank displacing the clear fluid is that the dye the red dye moves faster through the pack than the thermal front okay so this is showing the effect of thermal inertia in the porous medium and this is really really a fundamental point and what's happening here is

that the the hot water that's coming in As if we imagine here this hot water is coming into the system this is temperature and distance and um the water that's come in um near the near the inflow point it's hot and then and we have cold water here but the the concentration of the fluid or if you like the dye concentration that front is moves with the interstitial speed because remember the Darcy speed is that the volume transport velocity and the fluid itself moves between the interstices between the grains and so that moves with the

speed upon phi so that moves a lot more quickly than the temperature front because as as this hot water comes in what it's doing is the the um it's heating up all the great all the beads in the bead pack at this region here and all that heat um And then and then what's happening is the the heat that was in the fluid between here and here has has now um disappeared into the beads here and so the fluid is cold but it's still the injected fluid so the injective fluid is not to this point

here but only this part of the injected fluid is still hot because the beads are only hot in this region here and So this region here between the strip on the liquid crystal strip and the red this is actually now cold red fluid and the hot red fluid is only behind that zone there tracking the thermal front and so what you see here is the you know as we look at time the thermal front travels more slowly than the fluid front like andrew said an issue of the is there's two issues that come to mind

what is the porosity of the uh of of the matrix and the other is the relative Thermal capacity of the liquid the water and the rock and are they are they the main the principal components of determining uh this the amount of thermal lag you get yeah so the porosity is very important for this in terms of the and and then of course the specific heat of the water is bigger than the it's about 4 000 or 400 and something and the specific heat of the rock is typically closer to a thousand but the density

of the rock is Higher so it'll be two two and a half thousand compared to the water being about a thousand so that partially compensates so the thermal front typically travels in a real porous rock will travel at about 20 25 of the speed of the the fluid but in the bead pack where we have a 40 porosity that they're more closely related and so it'll be it'll be 25 maybe up to 30 percent in a real rock so the thermal front really lags behind the Fluid front um so the you know the 20 percent

the water in 20 of the space is heating up the grain the 80 of the the volume is ground means that it's heating up and so you need to put a lot of water through that zone to heat up the rock or cool down the rock depending on whether you're putting in hot or cold water and and so that's going to lead to a lot of difference between the where the Injected fluids got to and where the thermal front is so typically it'll be a factor of one to three yeah but it depends on the

specific heat and the density because it's really the heat the heat capacity of the rock and the capacity of the fluid and obviously the porosity so um yeah is that okay absolutely yes thank you absolutely so so we have this lag and so so but the key thing here is that if the fluid we've injected if this red fluid has a Different composition from the fluid in the reservoir what this what this means is that the zone between the red front and this frontier that the the color the temperature front that zone is now fluid

with the reservoir temperature but the composition of the injected fluid and so now we've got three different regions of fluid we've got injected fluid with the injection temperature injected fluid with the reservoir temperature and then Reservoir fluid with the reservoir temperature and these three different fluids may have different densities and that can lead to some very complex flow patterns if we're injecting this into a formation and remember as i mentioned before you know to actually match the composition of the reservoir fluid with the injected fluid it is possible but it may not be something that

you do by default and so what we can imagine is if we plot We have a question for you greg which is hold on for my questions so a fracture basement with a low porosity may have less lag but has the issue of lateral flow efficiency means the volume of contacted rock is less um so i'm not quite sure so the can you see so that if you look in the chat you'll see the question i've tried to read it out i think there's a typo what's the issue the project with a low processing may

have less lag but as the Issue of lateral flow efficiency yeah so the volume of contacted rock will be less if it's going through a fractured rock but um in in that case you may actually be losing heat by thermal diffusion or thermal conduction into the rock around the fracture and you'll get a growing zone of um heat loss in that in that in the in the rock around the fractures which may lead to an effect as i was talking before about The enhanced dispersion and it may spread out that temperature front um so in

these bead packs we're not seeing any of those effects but um the the fractured basement um could lead to quite a lot of thermal dispersion because of the thermal inertia between the rock between the fracture fractures so i think that's going to be very important But the thermal inertia effect will actually be it depends on whether the rock between the fractures is in thermal equilibrium with the fluid and the fractures or it actually lags behind um so i think that's you're probably going to get a slightly more complex thermal picture than the things i'm showing

here but the principles still carry through thank you so that's that's a very interesting Point and i think there's probably more research to do in that to understand that um but but in this in this simpler picture with the porous permeable layer because the grains are so small the thermal equilibration time between the fluid and the grains locally is extremely short and so locally they'll be in equilibrium and that that leads to this Global mismatch where the thermal front lags the fluid front and so the effect is if we look at plotting a graph of

composition versus temperature and we plot lines of constant density so these black lines are showing lines of constant density so you could increase the composition and increase the temperature and they'd compensate for each other and so there's a series of Lines of constant density well if we now imagine that the reservoir has this red that's the reservoir conditions and we imagine now injecting um a series of different fluids we can inject so if we injected fluid a1 at the same temperature but with a higher composition that's going to be denser and b1 is going to

be less dense but if we inject something with a different temperature what's so for example a3 if we injected fluid that's got a higher Composition and a higher temperature well fluid a3 when we inject it is so hot that it's actually less dense than the fluid in the reservoir but as that fluid moves through the reservoir and its temperature adjusts it's going to reach the same temperature of the reservoir as the reservoir but it'll have its original composition and so in that case we're going to get a fluid it's going to go from from this

point to this point and so the density relative To the the reservoir is going to change and that's going to lead to a very different play pattern and similarly we would be injecting cold fluid for example b3 and it could be very cold but fresh and so it could start off being cold enough to be dense and then become less dense with time so so what you can see is this thermal inertia can lead to some very interesting dynamics and we've done a series of experiments and I'll i'll talk through these experiments just to show

the different types of flow pattern that can develop um so so the picture a on on the left hand side this just shows what happens if we inject relatively low concentration fresh relatively fresh water with no temperature difference into salt water and this is in a bead pack and what happens is we get a plume rising to the top of the layer well and this could Be you could imagine this could be a a permeable layer with an incline so there's a component of gravity along the layer and we're going to get a plume migrating

like this because of the buoyancy difference once the source pressure has dissipated so you can imagine this sort of flow but if the fluid we inject is hot into cold water and if you want to turn this upside down we could we could imagine cold into hot water Which would be just sinking rather than rising but here we've got hot water well what happens now is as this fluid comes in its temperature is going to adjust and so at some point beyond the source it's going to cool down and have the same temperature as the

surroundings once that happens it's going to act more like a pressure source and spread in all directions But the continuing flow is going to drive hot fluid further up and so what happens is we get a hot plume structure in the center and you can see this in the third picture where we change the color of the dye and so the fluid comes in it stays hot and then eventually it gets cold and then it spreads out like a source and we get a moving plume of injected fluid with a very different pattern from the

the fresh water we injected And in fact this this light stripe you can see here is actually the result of thermal diffusion um so we're actually heating up the reservoir fluid near the source and that's actually rising up just outside the fluid we've injected causing that little structure there and you can see from that how the fluid spreads out and is left behind as the plume keeps on going well what i'm showing on the right hand Side are two examples where there's a compositional difference as well as a temperature difference and i'm so in this

this case c um we're seeing hot and salty fluid being injected into a cold and fresh system the hot it's sufficiently hot that it's actually less dense than the cold and salty system but as it rises up and cools down it then comes at the same temperature but it's still salty and so It sinks back down and spreads out and so we get an injection plume structure like this but in the case where the fluid is injected at the top hot and salty so the same problem if we start from the top and move down

the fluid spreads out along the top because it's actually less dense but as it cools down it becomes heavy because it's it's now cold and salty and it sinks to the bottom and spreads on the bottom and so in both cases whether we inject The bottom or the top we end up having a flow running along the bottom but we're actually um developing a very different plume type structure and depending on the geometry of the system this could be very important in terms of understanding where we're mining the heat from in the geothermal system andy

we've got uh three questions coming which are not in specific to that slide but let's Let's take them now so that i have a chance so steve miller asks have you also considered the effect of induced fractures due to the injection of cold water so presumably injecting above the frat gradient um yeah i'm not i'm not going to talk about i wasn't going to talk about that this evening but yes yes i mean if you start inducing fractures well in fact like In a little bit i was going to talk about some of the reactions

that you may induce because of these flows um and if you start inducing fractures you're going to start and then short circuiting because you'll you'll tend to have the subsequent flow um running along through those fractures um and that'll where you have the enhanced permeability and you've got a feedback on the flow um but i wasn't i wasn't going to talk about that specifically tonight but okay andy I think your light's gone off suddenly you've got darker did you know that um yeah that's okay sorry i'm in a lab in the okay all right i'll

ask you two more questions then i say mohammed khalid says do you think fracturing the rock or the formation with fractures is favorable for power generation from geothermal wells because it allows heat transfer by convection rather than conduction Thus more power generation is expected do you agree with that statement so i think if you're able to access a bigger surface area of the rock you're going to be you won't be limit as limited by thermal conduction to extract the heat from the system so having um you know a a a more a broader flow front

moving through the system will allow you to access more of the thermal energy um So but but i think the the converse of that may be that if you as you flow through the fractures if if that leads to um cooling of the rock uh it may maybe some contraction you may then open up the fractures and it may lead to short-circuiting um preferential flow um along those those fractures so i think it's um i think it needs some quite detailed study just to just to um Check which one of those effects dominates okay i

think greg waters made a statement there so i'll go on to dr chris green are the pictures of pleu of plumes performed in slots if so what is the width and the width effect oh that's a very good question yes so these are these are two dimensional cells in the sense that they're i think they're three or four centimeters thick and we're seeing through the cells so we Can visualize this but these are the exactly the same effects as in a um 3d cell there's no effect from the conduction from the side walls into the

center of the tank because these are very very fast experiments um and so the conduction time of heat through the walls into the center of the tank is much longer than the time for these experiments to occur so that's a very so that's part of the experimental design the reason they're in Two-dimensional channels is for visualization so we can actually see how the flow evolves but um [Music] these are really going to be three could be three-dimensional effects in a real porous medium and these will be actually symmetric flows but the the flow structures are

going to be very similar okay i will actually read out uh greg walker's comment it's a comment rather than a question just because it's Interesting some of our targets i don't know who greg walker works for are fracture basements so we may also get into something equivalent to a reaction infiltration system due to thermal fracturing which could cause major issues for contacted area yeah so that's that so so you can have reaction reactions occurring because of these Temperature changes and in fact i was just going to show you some of those um so that can

impact the injectivity so i think there's there's issues about how the fractures themselves change as you change the temperature field through the fractures so you can generate the fractures during the injection but then the temperature changes that may change their permeability but then you may also Induce precipitation there may be mixing between the fluids but it may be so you may have reactions induced by mixing but you can also have reactions induced by changing the temperature perhaps i should show that as the next slide with that okay one more question because it's a clarification of

what stephen said before i would like to clarify my question i was questioning the effect of Temperature change to fracturing of the rock rather than a pressure fracturing of the rock well that was my fault because i said pressure um yeah so yes short certainly if you if you start changing the temperature you can induce thermal stress can cause fracturing um yeah so i mean i wasn't i'm not going to present that today but okay yes that's certainly an important effect Right let's move on then okay okay so um just just as a sort of

point that if you if you have a seal rock along an incline and you inject cold water along the seal rock again there may be a thermal front that lags behind the fluid front so the fluid you inject may end up actually once it's warmed up to the reservoir temperature you may get a thermal front where you get a very thin plume running along the Boundary from an injector to a producing well um but the cold front is actually cooling down a much bigger zone of the reservoir than what then as the when the fluid

actually coming out so um you know there's some an important series of calculations to look at in terms of the effects of buoyancy on these flows but but to talk about scale and and um you know the scale build up in geothermal Systems is very important and particularly if we're looking at um the sort of reactions where we have temperature changes so you know that there are simple reactions where i guess with acid cleaning of wells and so on but also where if we have unsaturated fluid being injected so we're injecting fresh water and it

heats up in the system it may be unsaturated and it may Then dissolve some of the minerals in the system um or it may precipitate depending on the solubility but you can imagine having a depleted zone near the injection well um in a similar way to an acid squeeze and then the fluid ahead of that is is at the reservoir temperature and so we get a reaction from migrating out from the um fluid front and again there's going To be a separation between the original reservoir fluid that will be here the injected fluid that's that's

ahead of the reaction front and then the depleted zone um of so this will be injected fluid that's at the injection temperature and composition um so you may again get three zones of flow and with temperature so we have reactions induced by temperature it's possible that when you if you're injecting cold water into a hot Formation what can happen is the the cold water may um migrate to a particular point and then heat up and the fluid composition will change across that thermal front um and you then may have you know the rock being depleted

in composition and so with with a mass balance you can work out the position of these reaction fronts so Um we've carried out a lot of experiments looking at how reaction fronts migrate through through a porous layer so if we take a a bead pack and we put some so in our experiments we put just some um a small amount of salt powder in the bead pack a few percent and then we inject we saturate it with saturated water and then we inject fresh water and we watch how the reaction front moves through and again

we find there's a Reaction front and there's a fluid front um just as we saw with the temperature and if we measure across the reaction front we can see a very rapid change in concentration over a centimeter or two as this propagates in the lab and and this is now showing you the sort of analogous effects that happens um in in a reacting system to the experiments we just saw a minute ago so this is these are this is an experiment where we inject Um in this case fresh water into a salt saturated pack but

where the pack is has a small amount of soluble minerals it's a salt powder in which is soluble so when the fresh water comes in it migrates up and it actually dissolves away that salt and then becomes of the same composition and therefore density as the surroundings and when we continue injecting um that continues rising up as a buoyant flow And what we see is we change the color of the injected liquid and we can see a channel develops a very localized channel a dissolution channel through the system but the fluid we've injected is actually

lagging behind and is left behind once its densities have evolved to the density of the surroundings um this is a similar experiment but in this case the fluid actually um the density change the fluid becomes Denser so we get a again we get a reaction channel um and migrating through this and here's this is the reaction front propagating through but then the other two experiments i showed before where we had buoyant fluid injected which so now we have a sugar salt system so we actually have a pack full of saturated salt water and some salt

powder but we inject sugar sugar water Water containing sugar so which is has solubility with the salt powder and when it dissolves the salt powder the density increases above the density of the salt salty water so again it rises as a buoyant flow um this the sugary water dissolves the salt becomes heavy and then sinks around the outside you can see this flow pattern so we're getting a dissolution channel through here but the fluid driving that dissolution is actually Spreading out at this part of the reservoir so depending on where you're trying to extract from

you can actually get you know quite specific dissolution channels that meant and then this is a similar example but in this case the fluid is dense and remains dense so we have enough sugar in the system that it's dense and spreads out and here's here's the sort of reaction from moving Outwards so i guess the point here is that um these temperature changes of or and compositional changes of the injected fluid can drive reactions and they can either be precipitation or dissolution reactions depending on the solubility and that can have a big impact in actually

changing the permeability structure of the porous layer um And of course if there is a buoyancy contrast you know if it's running laterally along a layer this is just showing how a reaction front can move through through a system so there's a i think you can you can perhaps see here there's a change in the color of blue from the blue here to here and that's the reaction front where we have fresh water injected into a pack with salt water and some salt powder and the fresh water dissolves the Salt this is where the reaction

front is and this blue zone here is is now salty water that's basically becomes salty by dissolving the the salt that was here and so we got a front moving through and it's possible to model how this front migrates through the system we've added red just so we can see how the reaction front moves and this is actually mapping out where that reaction front is Um and so it's possible to model that and i won't give you the sums but we can model how these reaction problems migrate through the system they cause a big impact

um i i see so another area of interest is what happens in superheated systems and in superheated systems so if we're injecting water into a reservoir but it's now above the boiling Temperature what's going to happen is the water we inject is going to cool down the zone near the injection well but eventually it's going to reach a front where the temperature reaches the boiling point and it's going to boil but once it boils and produces steam that steam requires a pressure to actually drive the steam ahead of the liquid front and so that's so

the pressure is going to be So we're going to have this pressure front here and if we inject more and more quickly that pressure at the interface here is going to be higher and higher and that's going to raise the boiling temperature and surprisingly that then has the effect of reducing the amount of boiling we have and so if you inject into a system where it's boiling and you inject it too quickly you're actually going to shut off or suppress the boiling and You'll flood the system with hot water um and so there's a sort

of optimal rate of boiling so that you don't flood the system too quickly with hot water and you can continue producing steam um from the system so in superheated systems understanding the um the dynamics of the boiling front is very important and we've actually done a series of experiments to model this so um again this is the diffusion equation for radial injection so we have a cell Where we inject and this is a system where we're injecting without boiling and we can just model the thermal front and i won't go through the psalms but we

can model the temperature evolution in time and but if we're driving boiling what happens is if we have a temperature pressure plot and this is the clause's cleftron curve if we inject cold water at high pressure what happens is as it moves through the Formation because of the thermal inertia it heats up to a certain temperature and then once it has that temperature the pressure drops towards the boiling front and then the temperature difference between that point there and the temperature of the far-field reservoir provides the thermal energy for boiling and that then boils the

the um water and then this pressure jump here drives the vapor from the interface to the far field And so if you inject very quickly what happens is this point moves up and it moves up further and further so you have less thermal energy available to drive the boiling and if you inject very slowly this point moves down to here and all the superheat of the reservoir becomes available for for boiling and and so you can model both of those limits so again if we solve the equations for the temperature the boiling law with like

the heat of the Interface and an equation for the pressure of the vapor ahead of the interface i want you to do these sums we actually get we can compare the solutions with our experiments so here's temperature and distance and what we see is we get um a zone where the water heats up then we get an isothermal zone then we get the boiling and then we have the hot hot steam moving ahead of that and if we solve this problem what we find is As a function of the injection rate the fraction that vaporizes

drops off and um that that sort of depends on the porosity and other properties too but basically if you inject very quickly you actually end up suppressing the injection but what's very interesting in the system is that if the gravity is very important in driving the water the water tends to spread out along the base of the reservoir And so it only accesses the thermal energy in the base of the reservoir and so that means that the you're only actually um cooling down the rock in a very narrow zone along the base of the reservoir

the steam produced across this moving front adds to the seam up here but we're not able to actually access the thermal energy here to boil off the water so buoyancy can really suppress the access to the hot rock and and the Water coming in from the injection well here spreads out and only and reaches the production well but actually in a very narrow current and cools the water or cools the reservoir at the base of the system um and so that can actually so gravity can have a big impact in suppressing the efficiency of boiling

i have to ask the question that andy if you're talking about uh superheating what about if you go into the uh into the be on the Critical point what happens then to the uh system um well well you're always gonna have to inject so you mean if you injected the water already already above the critical point well we i mean we're thinking more about carbon dioxide which is easy to do but the effects but the logic should be the same yeah um the higher thermal capacity the higher heat capacity well you won't get A phase

change then but you'd have to put the energy in before you inject it i mean i i mean for geothermal you what you're trying to do is extract the thermal energy from the system so you'd inject cold water and try to use the latent heat from the rock you know you're trying to actually take heat out the rock so we so in this experiment you know this is the thermal energy we're Accessing to drive the boiling um if we injected um supercritical water before that we'd have already had to put a lot of energy into

the water to do that um you're thinking about carbon sequestration are you well not actually where carbon dioxide has been it's been looked at as as the the carrier the carrier fluid so yes sequestration but i'm just saying that that it has Been looked at seriously as all yes there's the secret struggle sequestration element but actually it's the it's the properties of the supercritical co2 that are particularly interesting very high thermal capacity that's very interesting i i'd have to think about that but i think if you're injecting and you're not actually not using the thermal

energy in the cyst In the rock to actually um source your latent heat of because what happens is what if you're sourcing that latent heat that's a very high um energy thresh jump and so you can then access that if you extract the um the the vapor phase i'm from the system and that's the idea in these superheated systems so you get a lot higher um heat recovery um so if you injected supercritical co2 i think you'd I think you prob yeah i can see that you because of the phase relation of the co2 in

these in these systems you might have to inject it at that condition but i think that would impact the um it would impact the heat recovery compared to the case where you boil it i need to have a look at that um that's a very interesting point though let's let's pass it i'll just check since i've interrupted you let's just Say the number of messages i wanted to see um uh what issues might you imagine in super hot rock or hot dry rock philip you might have to clarify what you mean by what is used

is there anything in there you can extract and is that enough information what issues might you imagine in super hot rock or hot dry rock um so in hot dry rock uh i i think the Challenge there is actually is there any permeability and you know is it just a fracture that you have which is going to lead to short-circuiting in the system um or you know can you create enough permeable flow paths that you can access you have surface area to access the thermal energy um without short circuiting between an injection and production well

um [Music] okay i'll let i mean i think the question was i wasn't enough there for me to get on to either so i'll try this one cold water injection for completion tests performance at end of drilling operations usually shows the thermal stimulation of existing fractures injectivity index often improves injection time some of the permeability improvement is then lost upon heating of reservoir rock or a comment but just Something that somebody's offered yeah no i mean i think there is a lot of experience from obviously injecting in water into oil systems in terms of stimulating

the near injector with fractures because it's so and that will evolve over time as the thermal front moves okay i think that's everything to raise okay so should i try to crack on Yes please okay okay so um so i you know there has been some interest in recent developments in actually looking at closed geothermal systems so rather than having these open systems where you um pump water through the permeable rock so that you access a lot of the the thermal energy and then extract that you know you have To pump very hard doing that

and there's a some different schemes where the idea is to put in very long wells and actually drive um heat recovery by pumping fluid through a well so um this this these are some cartoons from a company cleaver that are developing a technique of injecting water and extracting it and um these pipes are very long and so the water heats up as it goes through this um so this is a sort of closed loop system This is a very different type of operation from an open system where a lot of the challenges about how we

model the flow through the permeable rock um and this this is this becomes a different problem um and then and then there's the challenge about inter-seasonal heat storage um which um it has relevance for intermittency of renewables but also for um Storing heat rejection in summer and actually then recovering it in winter one of the big challenges with inter-seasonal heat storage and aquifers is actually being able to predict and understand the the temperature at which you can recover that thermal energy and so so the the comments i made earlier on about the effect of thermal

dis about dispersion of the temperature front particularly in layered or Heterogeneous systems where the dispersion becomes much larger is going to be very important in terms of understanding what that thermal recovery curve looks like because it's not just about recovering the thermal energy it's about recovering it at temperature as well and so some of the effects we've looked at here are and if we inject into it either through a line well or a point source Well as the fluid is injected if you're injecting um and in this case i'm showing a relatively dense fluid so

it may be different composition from the composition of the water in the aquifer and so it may spread out under gravity as well as pressure as it moves into the aquifer and that can lead to um a more dispersed front um between the the hot injected fluid and the fluid origin in the aquifer and so um You know the first first simple calculation for thermal energy storage is to look at what happens if we have a series of cycles and see if we have a flow that varies in time so each of these is a

year a summer winter summer winter cycle and because of this thermal diffusivity or dispersivity so the kappa is that general quantity which could be much enhanced from the molecular value because of the heterogeneity in the rock Um you can actually see how the temperature front migrates out gradually and that that reduces the fraction of the thermal energy you inject that you're then recovering because as this grows you're losing more and more of that thermal energy but perhaps more dramatic than that is that if you have a difference in the density of the fluid because the

composition is different then this is just showing um a series of Cycles this is the end of an injection cycle and then an extraction cycle in a lab experiment the second injection the third injection cycle and what we see is that the fluid we're injecting is is dense relative to the fluid in the system and um on each injection cycle the fluid moves a little Bit further into the formation and on each extraction cycle we we remove some of the um fluid and the original reservoir fluid rather than the injected fluid because that keeps on

running out under gravity because it's dense and so you end up um having a less efficient thermal recovery because we're actually recovering original cold fluid from the aquifer rather than the hot fluid we've injected and you can see with time you know so the first few Cycles we're getting 60 50 40 of the recovered fluid is actually aquifer fluid rather than um the the injected fluid so the effects of buoyancy can be very important in impacting the efficiency of of equal thermal energy storage um but eventually you're going to heat up the near well site

and if you heat up the near well site then you know you do have a thermal battery but that may take Many many years of injecting to achieve that um given given the time i thought i should perhaps just finish at this point um and i'll be happy to take more questions so so i think um what i've tried to cover is um there's lots of opportunities for geothermal power um particularly deep geothermal and for power generation where we have very high temperatures Um there's lots of interesting questions about how to how to model and

optimize the way you run super heated systems so that we can optimize the boiling but there's also a lot of um concern a little detail that needs to be considered in terms of access to the rock in heterogeneous rocks and making sure that we don't disperse out thermal fronts and actually miss quite bypass quite a lot of the reservoir because of The heterogeneities because the thermal conduction in the cross-flow direction may be quite slow um on on the time scale of these systems and then i suppose the other aspects of this are about understanding the

the importance of the fractures and um sort of having fracture matrix flow which i haven't gone into and the structure of the geology um and then there's a whole series of New challenges emerging with much shallower systems where we're going to store energy in the shallow crust and with with heat pumps we might have arrays of bore holes where we're going to extract thermal energy but we may also store it in the summer and again there's lots of interesting questions there about using the the shallow subsurface um as a thermal energy store but in terms

of geothermal energy production there's you Know enormous potential and there's an enormous track record a very effective operation um modulo the caveats about scale and precipitation and also i'm trying to optimize injection strategies to maximize the thermal recovery so i'll finish at that point and be very happy to take any more questions thank you very much elliott absolutely brilliant tour de force i really really appreciate your efforts And yes uh because of the questions you couldn't go through the material um of course people are asking whether this has been uh has been recorded and for

everyone's uh yes we are recording this uh so you can replay and listen to what andy has to say a second time um and so what i would like to do is uh open this to general questions i notice that people are still using the chat box that's fine but also because i expect people get bored of my voice by all Means if you know how to raise your hand uh on zoom do so and then we will automatically uh open the microphone to you so that uh you can oppose your own questions and until

somebody does that i will carry on asking questions i see dr chris green uh has has put him put one in the chat box which i'll ask now since i don't suppose you can ask it yourself uh dr green what do you see as the as the issues with some of the shallow hydrocarbon Whale systems what do you see as what do you see as the issue not quite sure what that question is so if it's about using hydrocarbon reservoirs as turning them into geothermal reservoirs i think that's dr green why didn't you why didn't

you uh unmute your microphone and ask the question oh yeah sorry hi everybody um yeah it was you know there's a lot of systems Are being proposed now for reuse of uh old hydrocarbon wells of what i consider a fairly low temperatures i'm just wondering what do you conceive as they being the issues with those whole systems that you've taken a look at so so i well i think there's a number of issues but i think um depends how low the temperature is but um If you're producing fluids from those systems you know why is

it you know what's the non-water fraction of the produced fluid um and are there issues with just managing that that aspect i guess there's issues of scale if you're injecting and the injection waters sort of incompatible with the reservoir water so understanding that in terms of Because you don't want to scale up the um production well so there um but i think you know in principle there's lots of potential because you know these systems are not known about how those systems operate and there's a lot of thermal energy in those systems that can be accessed

i think it depends how hot the system is And what you then do with that thermal energy and because the the temperature of the produced fluid impacts what you can do with it so it's not just about the thermal energy you're recovering it's also the temperature at which you're recovering that so um you know for low grade heating it doesn't need to be terribly hot and that has a huge number Of potential applications in agriculture and um and and for heating systems distributed heating systems but if it's for um power generation you know it needs

it'll need to be a higher temperature and production so um i think it's it's matching up the potential heat flow the temperature of that heat flow in Terms of its utility and then what applications there are in the vicinity that where it could actually be um useful um because it's you know this isn't doesn't have to always be just for power generation um it can be for you know lower grade heating applications yeah thank you thank you chris um there's a question which uh nicholas asked which i think many people were Considering asking but i'll

articulate in a slightly more neutral way than nicholas does which is um you did you showed the everloop uh um you know conduction system there are two or three others which are being banded around and uh getting quite a lot of money in finance four um can you can you give if nothing else a qualitative impression about the relative amount of heat extraction you should expect from a closed loop conduction system compared With the the systems you've been modeling more referring so i think so i think brought i mean broad brush the you know the

open the open systems where we're getting uh flow through the poorest layer put porous rock or a fractured system we're actually accessing um the fluid is coming in contact with a very large surface area or a very large volume of the rock and you know the thermal conduction Is slow so you're um you know the bigger that area you're then able to access a lot of thermal energy um because the the poor scale conduction is almost instant on the grain scale if it's a permeable layer and if it's a pervasively fractured layer um you know

you'll also be able to access a lot of the thermal energy in the blocks between the layers of impermanent rock between the fractures so I guess the you know the advective transport of heat is very effective um and i guess um what you know what you're doing there though is you're actually having to pump the water through and do pressure work because the you know you're going through a low permeability system and so that needs mechanical work to drive the fluids through um Unless you're just gonna let so i guess in a super heated system

you could let the system run down but as the pressure drops um you know that you you ultimately have to recharge the system so um and i guess some of these loop systems obviously you've got um you know pipe which has less less resistance to flow so that that's that that conflicts what's That contrasts but obviously the surface area through which you're conducting is just the surface area of the pipe um so you know so i think they're very different systems um and um you know i think it'll be it'll be very interesting seeing what

sort of data emerges from these closed loop systems yeah i think i think mathematically in one case you're Looking at uh conduction as the the sole uh means or albeit you can you get uh convection when it comes to recirculating the fluids another we've got advection convection and conduction there's a way of harvesting the heat energy from the formation over a much wider uh surface area yeah i mean i mean i think the you know i suppose you don't get the issues of scale And and prioritization that i've been talking about in the natural system

um if you're sort of not not going through the natural system but so i think i think they're very different um yeah okay okay good um another question which i also susan fenner's made on again it must be many people's lips can you can you after this uh meeting uh send me an email with the uh with your the references the academic references that you've you've uh written um so we can All study the the relevant papers on this sure that's fine okay uh let me just see who else has uh picked up something do

please don't work don't wait for me to uh invite you if you've got if you've got questions just open your microphone and uh and ask them you know there aren't enough people here to make that chaotic you can you can simply ask a question rather than writing a chat for me to read Yes peter go ahead you've got you yeah you should peter you need to unmute and now you can ask a question you need to unmute peter since you put your hand up i don't think peter is able to unmute does anybody else want

to ask a question you don't you don't need to put your hand up there are not enough people here to worry about people talking over each other does Anybody have yeah anyone want us to ask a question yes can i ask go ahead [Music] this is sadar from turkey i just would like to check with you do you know any software simulation software that accurately simulates the heat flow inside the reservoir that we can use it to To model and simulate the hot rock reservoirs or the the geothermal reservoirs um so i don't really i

mean like i guess as you've seen from the talk i mean i'm doing um slightly simpler problems trying to understand some of the the controls on the heat recovery and um i mean there are there are i'm sure There are some codes that exist but i don't i don't really use them so i'm not really in a position to um direct you to a particular code okay uh susan fellowes is uh trying to uh suggest cmg to you cmg stars stars is of course used for um uh uh water flow uh heat floods etcetera and

heat stimulation um okay so uh another point yes for you and other Answers you've got there in the have a look at the chat for your answers uh because there's several people coming up with ideas um i also put in dance as well which hasn't been mentioned there um does anybody else want to ask um a question uh i i haven't made uh adam it sounds like one of the uh people couldn't couldn't uh unmute themselves so maybe you need to help allow everybody to unmute that was peter could not unmute so adam if you

Can help everybody on you peter could try again and others can try yeah timothy i have a question john from the united states my question andy is what uh experiments are you planning to do next what are you looking at in your next stages um so what well so there's a so we're i mean we've got very interested in um sort of inter-seasonal heat storage um In in systems and trying to understand in more detail some of the effects of the um dispersion and also the heat loss to the um surrounding impermeable the seal up

and below an aquifer to see um to try and get a handle on the temperature of the recovered water and the controls on that in terms of the efficiency of the system So and then what we can do to try and upgrade that efficiency so um so it's really trying to understand the different effects of dispersion and how they impact or how we can circumvent them in some sense to make aquaphor thermal storage more efficient so that's one one area we're doing a lot of work on and then i i guess just in the the

straight geothermal we're we're still Very interested in understanding um the effect of some of these you know the complex rock structures in terms of access to the thermal energy and again what we can do to try and access more of that thermal energy so i think there's lots of interesting techniques that have been used in enhanced oil recovery for accessing um different parts of the reservoir that Are harder to to reach and i think one of the questions is you know how effectively can we um adopt or adapt some of those effects to to make

you know the geothermal recovery um to increase the efficiency of that recovery but but within a very different cost structure i guess okay anyone else want to ask a question peter you should be at our mute now We've uh we've corrected that anyone else want to i it was always available i've sent peter an unmute request but i will click the button now if it appears that i'm requesting to unmute it should work if not it's not on our site sadly okay anyone else whilst peter is working out whether he can unmute or not does

anybody else want to ask a question any other comment or even just a comment uh a reaction to what you've heard um what it means in terms of uh the Chances of uh geothermal becoming a major source of energy by 2050 anything you want to comment or ask we're in the last few minutes of this so we can we can open this up to more tangential geopolitical issues if you wish and john dewart here again i think one of the big unknowns for closed loop and even the the open systems through the fractures is the

rate of heat coming back through The rocks so the conductive heat so the rock is actually going to get cooled down and at what point do the systems come to equilibrium and therefore at what temperature are they at equilibrium i think that's a bit of an unknown reed greg walker here from repsol we're having an internal discussion the difference between co2 neutral and renewable If we produce the help rock once you have that co2 neutral but we'd rather be in the business for renewable where it's the case of what is that steady state we can

maintain such that it's producing in 50 years time i think i think john that the the the mathematics of uh oh hold on i'm just going to let somebody in the of the conduct of the conduction solution um uh they're quite if you go if you look At the the research papers they're quite well worked out and there are serious concerns about uh about whether it is sustainable in the in the medium term um but you know it looks like we're not we're not going to be looking at the mathematical derivations of that today but

they i can assure you they're in the literature if you want to make reference to them any other remarks or comments i happy to uh To keep randy for a few more minutes does anybody else want or make we'll make a broader remark does anybody want to make a remark uh which looks at a vision for what we should be doing with geothermal maybe that would guide andy in the way he considers his his next research proposals hi timothy it's uh christopher green again um you know one of the questions i've Raised with a lot

of people for geothermal is a frat guy you know one of the big things we look for is he heating up the fluids afterwards and conventional fracks and sometimes that takes months you know the notoriously good insulators rocks and trying to get anything from just conduction and temperature transfer has been an issue you know when we try to rock the well and get Convection set up and you know try and work on any you know in some of these geothermal could be radiation but you know i struggle with just this conduction current model yeah i

mean i mean so i suppose what i've been talking about mainly is advection where you're you're flowing through and you've got sufficiently well it's either it's all the permeable and porous or it's the fractures are Sufficiently pervasive that you can access the thermal energy in the in the formation and i think that's um you know that advective system um is is i guess what i was mainly focusing on today okay well that's field proven unlike you know typically if we have heat some kind of transfer temperature and wellbore that works and we know there's Limited

opportunity for that but as people are mentioning these other opportunities that they're chasing like i say we'll be interested in the research but i struggle with some of the physics yeah chris you're not alone in that but i also would like to move on from that maybe i shouldn't have raised it so emphatically to start with um just looking at other things so so andy as you see i i'm particularly passionate about uh what you can do uh super with The supracritical fluids because of the higher uh uh uh thermal capacities and other another features

of course i mean is that can we tempt you to look at that with you i think i think that's a very interesting problem i'll i certainly will um sort of go and have a look at that because i think that's i mean changing the fluid phase and understanding how that impacts the flow the flow I mean i guess in these systems they'll have water as the original host fluid and then it's looking at how the co2 migrates through that and acts as a sort of heat transfer um i mean i've looked at some of

the heat transfer effects for ccs itself where you know as you're injecting co2 for co2 storage you generate you can generate depending on the temperature of the input you may actually generate a a cold Zone right it may be cold and it comes in you may actually generate a cold zone around the injection well and then the co2 warms up and that can change the viscosity and the density of the co2 substantially so it may well be that near the injection well in co2 projects and it depends on the properties inside the injection well and

what you know what your surface Pressures are but it may well be that near the injection well the co2 current is actually quite a bit because it's more viscous it may actually be quite a lot deeper and so it may be able to overcome capillary thresholds into into layers above whereas further away that may not be the case and so you can actually get sort of thermally induced um flow patterns of the co2 plumes which um it's it's sort of quite an Interesting effect but i didn't look at that in the context of then recovering

the co2 for heat recovery so yeah so i think there's some interesting questions there i'll have a look at that yeah yeah i mean there's a if there's a paper or two outlining some of the concepts it'd be very interesting to see that i'm going to put you in touch with a couple of guys after this when we're offline um who are looking at this now they're also looking at some Extraordinary things you can do with the uh um with with co2 and rather than moving uh uh hot fluids out the world or whether you

can do anything in situ but we move on to that another time actually john might mention it um we have uh come to half past six and although i'm conscious that there are a number of issues we could continue talking about andy i would i would like to on behalf of our audience thank you enormously uh for Showing your time and the analysis that you've done it's been really riveting and i'm very pleased and you've put so many things in perspective for me certainly that i hadn't really managed to capture in my mind before about

all the the competing issues uh related to what looks like quite a simple process on the surface thank you very much um so uh for Everybody else i think um uh probably we ought to have a bit of a comfort break um i proposed to restrict that to 20 minutes which means that we'd reconvene 1850. the other thing i'd say for those of you who don't want to come for break unmute your microphones please and network remotely just just throw out points and comments and start talking we have we have had an emphatic rejection of

attempting to meet Physically at imperial college for example although that's of course only for people based in the uk but i do want to try and see what i can find another way to encourage people to to network and get to know each other uh in the in the in this this virtual environment anyway i'm going to sign off for 20 minutes and have to come for break myself and then i will be back again a few minutes before 10 to 7 uk time that's uh utc 0 and when john john clegg will give his

presentation again andy thank you very much indeed then okay um um um hmm long time [Music] uh degrees can you hear me now oh sorry um so we have only one resume for a geoscientist so really unless i mean i i look it are they on the same folder all of them yeah i know i yes i looked yesterday again and i've Seen only one uh i'll contact ryan again and ask uh if he has some somewhere else yeah i i wanted to talk to rob about it i mean he he's a master student which

is good but uh he's going laura sorry we can all hear you laura uh john john can you uh come off muse i can see You i i'm off for you and hopefully you can see me as well i certainly can and uh you could perhaps you could uh see if you can upload your first presentation slide let me see if i could do that hopefully you can see us slide fantastic thank you john okay i'm going to uh well i'll give it a minute because i think some i did say that we start at

ten two so just before That and i'll just check there's no um yeah no problem uh interesting fun from greg walker did you read that if working volcanics remember to look for helium if it air is a success and we still don't have liquid nitrogen superconductors then we would need more helium it's interesting craig are you actually here great since we've got one minute It's looking at uh i mean how much helium there is um near to volcanics compared with how much heating there is already in in with big oil and gas fields or gas

fields especially you look around the world if you look into east siberia north part of east siberia some of the fields there have got 15 helium and they are uh trillions of cubic meters and so it's More about getting bringing the helium to market uh than they're being uh not in not sufficient hedium to um uh to to power all that fusion um so but are you not talking to us sir craig where have you gone maybe you're not here maybe you've gone um okay i digress so john uh your talk geothermal well construction that

scale challenges and opportunities the introduction and development of Novel world construction techniques transformed the unconventional oil and gas industry in the last two decades the opportunity exists to transfer transfer these techniques to an emerging unconventional geothermal industry challenges exist not least in the form of high temperatures and difficult formations but challenges lead to opportunities and this talk explores how oil and gas might be able to apply some of its skills and Experience to geothermal to the benefit of both industries john clegg has spent more than three decades introducing new technologies for well construction in the

oil and gas industry working for companies such as schlumberger nov ultratara and weatherford and always operating at the junction of market needs and emerging technical capabilities he is now dividing his time between Writing consulting and building a new company probably pronounced hefi energy but i will correct it on that where he works as its chief technology officer john is also active in sbe and is chair of the upstream oil and gas committee for imeki institution mechanical engineers uk john the floor is yours thank you tim and uh hello everybody just sound checked him am i

coming through clearly can you hear me good Good okay so uh yeah thanks for the introduction um it it's really nice to be able to wear multiple hats and as tim said i'm kind of dividing my time between two passions of mine at the moment one of which is drilling technology and seeing the migration potential migration of drilling technology from oil and gas Into geothermal and the other one is innovation and the creation of value which can be but doesn't have to be through through technology and you can see there's two websites on the slide

here and those websites kind of define those two um the two interests that that i have if you like so i'm going to talk about technologies and their applications uh through the Talk so i thought i'd start maybe just break the ice loosen things up a bit um by talking about some interesting historical uh technological um developments which have relevance to geothermal and hopefully i'll explain why as i go through it and uh let's see if i can advance this slide yep um i'm gonna start by talking about Telephones uh probably to many people's surprise

but 146 years ago this month in february 1876 a lawyer representing a guy called alicia gray filed a patent caveat uh at the u.s patent office for a telephone a patent caveat has disappeared from the um from the landscape but it's been replaced recently by something very similar which is a provisional patent application it's Like a patent application without claims and that was on the 14th of february 1876 which is the same day that alexander graham bell's lawyer filed a patent application at the same office for a similar device and um things were moved remarkably

quickly in those days because only three weeks later the house patent was granted imagine getting a patent granted in three weeks these days and of course history's got him down as the inventor Um but it was kind of unusual and intriguing that two people should file a patent for the same item on the same day and about 100 years ago in 1922 there was a couple called william ogden and dorothy thomas they produced an article in a journal called political science quarterly where they found 148 cases of apparently independent simultaneous scientific Discoveries or inventions in

1611 sunspots were discovered by galileo fabricia china and harriet all in the same year and in 1850 centrifugal pumps were invented by apollo gwyn and bessemer all apparently independently and you wouldn't really expect that to happen randomly but it actually happens quite a lot and if you study innovation it's kind of interesting to figure out why why does Simultaneous invention happen so much and the reason is that after a long time of dormancy these new ideas emerge from apparently unrelated sources and i think that's happening at the moment to an extent in geothermal energy especially

with some of the the new unconventional geothermal systems that i'll talk about but it's also important for those ideas to emerge at the right time and i'll stick with the telephone theme for a moment and I found this on the internet and i had to do a lot of searching before i convinced myself it was real and uh it was syndicated through a lot of different newspapers but this does actually appear to have been in the boston globe in 1953 um president of uh one of the um sort of u.s telephone companies guy called mark

sullivan saying one day you'll be able to carry a Telephone around it won't be connected to the wall by a wire it might be like a watch it might not have a dial users might be able to see each other if they want as they talk and it might even translate from one language to another he's just described the smartphone that i carry around with me every day and uh this was um nearly 60 years ago um but of course it didn't happen 60 Years ago and the reason why it didn't happen 60 years ago

is because there was a lot of technology that you need to create a smartphone you know miniature cameras high resolution screens miniaturized electronics battery technology uh apis um interestingly cellular network was already available in 1953 it just wasn't used very much but the point is that unless ideas come Out at the right time they're kind of useless and about 12 years ago a guy called stephen johnson wrote a book where good ideas come from and he talked about the context of what he called the adjacent possible where there's always new layers of scientific discovery and

innovation that are just around the corner and you discover them one at a time like peeling Back the layers of an onion and as you reveal the next layer new technologies and new inventions become possible but of course until you peel back that layer they're not possible so timing is everything that's why the smartphone wasn't developed and marketed in 1953 and that's also why technologies tend to emerge at the same time as each other because these possible technologies enabling technologies emerge and uh and Mean that it can all happen so one lesson from what stephen

johnson wrote and what these other guys discovered is don't listen to people who say oh we tried that before 10 years ago we tried it 20 years ago and i think those arguments are particularly relevant to some of the things we're trying to do at the moment to scale geothermal energy there are things that May not work 10 years ago if you tried them then but might work now if you try them now and i and hopefully i'll explain over the course of the next hour or so what i mean by some of that one

final bit of technology before we move into drilling and geothermal is um is bicycles um so i guess i'm gonna say cycles um because they had one two or even three wheels Where they started to appear in the early 19th century and there were lots of different designs and you can see a couple of designs here that were done for very good reasons but weren't necessarily uh successful it took about 70 years but after about 70 years of bicycle production the industry settled on the bicycles that we see today they have a diamond frame they

have rear-wheel drive they Normally have gears front wheel steering two wheels and you know you might get hybrids racing bikes mountain bikes but they all follow the same kind of basic topology they don't look as different as these guys did and i think that's kind of the stage we're at with some of the new ideas for unconventional geothermal wells at the moment there are lots of different ideas around some of them might succeed some Of them might not but everything at the moment is being done in good faith and for very good reasons there were

very good reasons behind the designs of the two bicycles that you could see on the screen today i suspect one of the things and we'll get into this a bit later one of the things that's going to determine which uh Geothermal applications are successful is the laws of physics and that was probably something that did for these guys as well i mean the other law of gravity for example is going to work against you if you try and stop quickly on the penny farthing on the left so keep these concepts in mind as we discuss

innovation in the context of geothermal and i'm going to move now into talking about oil and gas and Everyone thought george mitchell was crazy when he started to experiment with the extraction of gas from the barnett shale um trying to get gas from source rock rather than from more conventional reservoirs like sandstone or limestone reservoirs but using a combination of horizontal drilling and fracking he was able to get gas from places where people didn't believe it could be economically extracted I was fortunate enough to live and work in fort worth texas about a little over

10 years ago and i actually took this photograph from my office window and at the time if you drove around fort worth it was not at all unusual to see drilling rigs next to freeways as the case of this one adjacent to residential housing estates uh you know close to retail centers or Industrial sites there were rigs everywhere drilling the barnett for um for gas and what made it possible was a combination of two new technologies horizontal well the new technology of horizontal drilling and maybe the slightly more mature technology of hydraulic fracturing but bringing

those technologies together changed the game and allowed the exploitation of unconventional resources In the united states and before horizontal drilling was made possible in other markets in other parts of the world unconventional boom probably wouldn't have been able to happen so again it's a bit it's about timing of having technologies available at the right time and um there have been remarkable increases in productivity and remarkable reductions in the cost of drilling Unconventional wells uh since uh the early part of this century when uh when people started when george mitchell was looking at his first twelves

and you see significant improvements uh in um first month production and uh there are equivalently uh dramatic and impressive reductions in the the cost of drilling sections so was unconventional drilling a big Success well to answer the question on the screen how much money's been made from uh shale if you read this book which is a really good book uh the author was co-author of uh the smartest guys in the room the enron story um the answer is well actually none and what the author argues is that it wasn't cash flow that drove the shell

Boom it was all about investment capital and it could be argued that a lot of people made a lot of money from it and an equivalent number of people lost an equivalent amount of money and that the overall um profit from shale uh was um probably about the same as the cumulative profit from the airline industry over the last hundred or so years which is about zero there's been as much loss as the house Uh has been made now there are other reasons uh for drilling for shale uh for oil and gas from shale um

there's some geopolitical reasons which are particularly relevant as we all keep half an eye on the news and what's going on in europe at the moment but perhaps for Geothermal and for unconventional geothermal development we'd like a business model which is a bit more sustainable and economics which are a bit more sustainable than than was maybe the case for some of the unconventional oil and gas developments so what horizontal drilling and hydraulic fracturing have to do with geothermal well potentially quite a lot and i'm going to explain now what i mean by unconventional geothermal and

Andy showed some of these systems uh in his talk earlier and you might even recognize some of the images so this is an enhanced geothermal system this is a system that could be drilled in hot dry rock where there is no natural fracture system which has uh water in it hot water in it that you can uh that you can mine or extract uh and so you drill a couple of wells uh Not necessarily vertical wells um which effectively you could call an injector and a producer you frank between them you flow through the artificial

fractures and the fluid picks up heat as it goes in this image from left to right and you return hot fluid to the surface and then you can generate electricity or you can create heat from from that it basically creates its own Permeability there's also a whole host of different advanced geothermal systems and these are basically closed loop systems where the working fluid doesn't have to come into contact with the formation these could be completely cased or completely lined and they might never that the working fluid that goes around the cycle and through the power

station might never actually see the rock that it's picking Up her heat from and there was a um andy talked briefly about um the one of these systems from uh ever and the image on the left is cartoony kind of similar to eva's concept um you see there are many other ways of doing it uh and there are um if you like um single well systems which we where you have a um a well it's kind of A u shape or a v shape or something returns to the surface and also uh coaxial systems in

a single well where you might uh flow down the inside of a piece of insulated pipe and have the return uh at the outside pros and cons um for uh both sets of systems as we uh uh and there is also the potential for hybrids where you could have a Closed-loop system which is whose performance is enhanced by the leveraging existing natural fractures or by creating artificial fractures and as with the case of the bicycles lots of different ideas lots of good ideas they've all been done for very good very well thought out reasons and

we don't know yet which one of them is going to Prevail but probably one or two will and what's occurred to me looking at them is that whichever ones prevail are going to need a fairly sophisticated level of well construction um none of these systems is going to work very well just by punching holes in the ground and hoping that we find some heat we're probably going to need things like directional drilling measurements in Some cases hydraulic stimulation or fracking and it's likely to be the most economically viable systems that that are going to prevail

and one of our missions i think when we're thinking about drilling and measurements and well construction which is my interest is to make sure that we minimize the cost And maximize the productivity as much as we can through the world construction process [Music] i think and others agree you can you can find a number of articles in the literature that agree that longer laterals in oil and gas tend to lead to a larger exposure of hydrocarbons And because of heat transfer longer laterals and we had friendly earlier in response to one of the questions about

the economics of closed-loop systems a larger surface area to get heat from the formation into the fluid is going to favor more exposure at high temperature and that is likely to lead to horizontal wells why horizontal wells because However hard you try i think there are going to be limitations temperature limitations of drilling measurement completions production equipment that you put into the well and so that if you have anything other than just a blind well punched into the ground that's going to put a a lower limit in terms of depth on what you can do

because temperature increases with depth as a result of the thermal gradient Once you've established that if you have a a lot of wellbore which is exposed to the formation uh you want to have it exposed to formation which is as high temperature as possible so that means that a lateral is likely to be favored over a vertical well simply because the the the net heat you're going to get from the same length of well is is going to be greater and i think that's what the authors of this Particular reference were getting at and we're

getting much better at drilling horizontal wells uh in oil and gas um in steve rasafos wrote an article just this month in jpt um and he quoted rice dad 2014 300 rigs uh drilled by 20 million feet less than 20 million feet of laterals seven years later fewer rigs drilled More than double that footage so we've got much much better and much much faster and of course fast uh generally means cheap uh in terms of uh of drilling wells and interestingly a lot of people are drilling sort of three mile fifteen thousand foot uh laterals

as opposed to the ten thousand foot laterals that we previously saw because they are seen i think partly for reasons analogous to what i described on The previous slide they seem to be uh more capital efficient and uh provide better returns on investment but we do have uh because we like to impose artificial restrictions on ourselves and uh lease lines quite often uh dictate that you can't drill anything more than a a two mile lateral we thought it would be useful to see are we in the right ballpark in terms of How much energy we

can extract from a geothermal well compared with an unconventional u.s land well so um if you run the numbers unconventional u.s wells will produce uh in their lifetime between half a million and three-quarters of a million barrels and that's equivalent to approximately a thousand gigawatt hours from a well um there's a lot of literature that suggests that ags and egs wells can Deliver in the region of eight megawatts per well sometimes it's higher and sometimes it's lower and what that means is that it will take 16 years for a geothermal well to produce the same

amount of energy as an unconventional oil and gas well but the geothermal world could produce for a lot longer decades more potentially it may not decline i'll come back to this in a minute but it may not decline in the same way as the oil or The gas well does and that longer time scale from an economic perspective is a bit of a blessing and a bit of a curse it's great that you can produce for so long but how many people want to invest in something which is not going to pay back for uh

like sort of 20 30 years [Music] not many i mean people want to get rapid return on investments and that could be a potential barrier The questions are can we actually get eight megawatts from a single well and the question that i guess comes more to what i'm interested is can we actually drill that well for five million dollars or is it going to cost us 50 million or can we do it for cheaper than a uh an unconventional oil and gas well so that leads to a question of how complex does the well need

to be And in order to answer that it's worth thinking about some of the drivers for what is going to potentially cause us problems i mean we had a couple of questions and a few comments in andy's lecture about what are the issues with the thermal performance of uh closed-loop geothermal wells and enhanced geothermal systems um i'm not a reservoir expert and i'm Not a thermal expert i'm here to talk about drilling which i'll do in a minute but i thought it'd be useful just to touch on these as long as you're kind with the

questions and recognize that this i'm getting slightly out of my area of expertise but um there are potentially issues in the vertical i borrowed this from a website of a company called icarus energy And their argument here is that in the in the vertical what we have to do is to provide as much thermal insulation as possible between the well and the formation particularly because you're likely to pass through aquifers before you get the heat back to the surface and they'll be delighted to take all the heat from you before it gets to surface And

so that means maybe thinking differently about cement where you place it how you use it and also the properties of it and so some kind of thermal insulation around the the od of the well in the lateral we've got the opposite problem uh if we do use uh cement we don't want it to be um uh thermally can uh sort of thermally insulating so the cement then has to Have a high thermal conductivity uh in order to be able to get uh heat from the uh the formation and uh into the well and neither of

those problems appears to be insurmountable uh they you know there's application there's material science there's going to be a lot of engineering but it should be possible to build wells where we've got high thermal conductivity in the lateral and lower thermal conductivity in the vertical then it gets a bit more tricky [Music] this is a as you can see i'm not going to read all this out you can see from the font and the quality of the reproduction that this document was produced a few years ago uh this actually talks about the hot dry rock

geothermal work that was done i think andy referred to it at the beginning of his talk in uh in cornwall in the 1980s And these guys saw what you might expect which is a decline in performance temperature performance over a year production period when we're taking heat out of a hot dry rot well and the reason for that is that unfortunately rock doesn't have very good thermal Conductivity it was explained to me a year or so ago by a friend of mine who said the thermal conductivity of rock varies between rocks that the kind of

rocks we're going to be drilling here by a factor of two so it's either bad or it's really bad like doubly bad um that there is no highly thermally conductive rock and what happens is if you imagine we've got this set of concentric rings here if you Imagine the central one is the borehole and you're pulling heat out of the rock in the borehole uh rock for heat from radioactive decay in the adjacent formation or from the center of the earth or from wherever is trying to get back into that borehole of course to balance

things and to replenish it but the closer you get to the borehole the smaller the cross-sectional area has to flow through so it finds it harder and Harder as you get closer and closer these guys i recommend you take a look at this paper because they will explain it a lot better than i do but they recognize this and their recommended solution is what they call a thermal soak method where you drill a number of wells and you produce from them uh individually so um this particular case uh they're flowing through well s which is

in the center of This image they're taking heat from the formation around it and you can see that there's not much heat flow it's getting kind of depleted but there are two adjacent wells uh well r and well t which are where the the formation is um effectively being reheated and the fluid in the wellbore which is not flowing is also being reheated as the the temperature and the formation recovers they have solutions where they propose Effectively a a set of laterals it looks a bit like this uh where you're producing heat from the uh

from the red one and where you are allowing the blue ones to uh recover and it's likely that the number's not going to be three um i think they've modeled i think they've got a good idea of how many wells you'll need but they for understandable reasons they haven't published that yet but This drives us towards not only horizontal wells but also multilaterals and also because you're trying to manage flow of heat into each of the individual wells while another one is producing it also starts to uh set constraints over how close together you drill

them uh sort of the the spacing between them uh their relative positions and so on if you project back from this into the egs systems where you frank between Wells earlier on if you're fracking between wells in order to create a flow path you're also going to want to have a good idea of how close they are together if they're too close together then you're not going to get enough surface area in the fractures if they're too far apart then the fractures might miss or only partially hit the target well and so there's going to

be an optimum position And so what i'm suggesting is that for many of the solutions we're looking at and some of it is explicit in those images i showed you earlier and some of it more implicit uh there's going to be a requirement to draw wells that maybe look a bit like our oil and gas wells that we draw for unconventionals where you have sets of laterals and they could be parallel Laterals uh they might be uh multilaterals where if you point them you know north south east west and points of the compass you get

better heat recovery um but you could finish up with wells that look very much like the wells that we drill in unconventional oil and gas and if they do look like this it's kind of good news because uh it means that uh drilling the same well Over and over again as we discovered in the us means that you can dramatically reduce the cost of drilling as well so factory drilling or cookie cutter drilling whatever you want to call it uh by drilling every well pretty much the same you could take huge amounts out of the

cost over um over years as you as you learn how to do it and as you optimize performance and i'll come back and talk a bit more about optimization Later on what that means is that and kind of as tim alluded to in his introduction there is a tremendous amount of opportunity for oil and gas companies who position themselves in high temperature high pressure drilling directional drilling um they potentially will own the future and if you go elsewhere let's get this moved on There we go uh if you look elsewhere look at larry fink black

rock his 22 22 letters ceos he's predicting that unicorns aren't going to be tech companies anymore they're going to be sustainable scalable innovators and startups that help the world to decarbonize the kind of companies that are going to develop the kind of technology that are going to enable the sorts of things that i've talked about Over the last few minutes and that andy was uh talking about earlier so a good time to get into this business and for reasons i'll explain the oil and gas business is very very well placed to take advantage and to

to help to be at the leading edge of uh developing these these new technologies and i'm going to quote eric van ort from a uh sp paper he published last year Um deep geothermal is currently where wind and solar were about 20 years ago and i agree with him i believe it could well follow the same cost trajectory if you look at the cost trajectory of wind and solar cost reductions over the last 10 to 20 years have been dramatic and i think geothermal could follow the same route and is a compelling Place for all

of us in the owner gas industry to uh become involved so it's a big prize um how does world construction help well i've talked about thermal efficiency a bit i've talked about economics a bit i've talked about things that i don't profess to be a global expert in i talked a bit about innovation and the creation of value and the remainder of The talk isn't going to be about thermal efficiency or economics it's going to be about the techniques and the knowledge that we might be able to transfer from oil and gas to geothermal and

and help us to enable that industry and become a part of it and also some of the things that we might still have to learn uh i'm going to talk about how we actually drill the wells um How we stimulate them how we create film paths underground how we build surface infrastructure they're the subjects of similarly long talks there's not enough time and my knowledge is not sufficient to be able to talk about those in detail this evening but i can talk about how we drill the wells and so that's where the rest of the

talk is going to go that was if you like a very long introduction um there's a couple of big challenges And the first challenge um i've actually here called it uh hpht high pressure high temperature drilling um i think it's more temperature than pressure i'll explain why in a moment but there are various definitions of exactly where hpht starts um this image was taken from schlumberger and they took about 150 celsius 10 000 psi as being their kind of hp ht limit If you look at api they talk about 177 celsius and 15 000 psi

in the same kind of ballpark slightly different numbers geothermal can be deeper and hotter than the oil and gas wells that we're used to drilling so it could be the pressure and temperature become more extreme well if you look at where geothermal wells have been drilled compared with some of Our most extreme oil and gas wells what you can see is that the geothermal whales they're identified as these red triangles and they're kind of clustered around the top left you don't see pressures like the pressures that we see in the oil and gas industry but

you see significantly higher temperatures the iddp wells up to 450 degrees celsius a whole cluster of wells in the 200 to 250 degrees celsius Area we need to go deep um this is the um a map of the temperature gradient in the us from smu uh to get above 200 celsius we may need to go down to about seven and a half kilometers um on here you can see the existing geothermal area in northern california uh you can also see the higher temperature oil and gas plates that we have in the eagleford And the haynesville

uh down in the um the the southern part of you know across texas and louisiana and when you get to 10 kilometers a lot of places open up and you get some very high temperatures uh accessible to drill now many years ago i learned how to scuba dive and one of the things that was set in my mind when i was diving is that uh one bar pressure one atmosphere is 10 Meters of water you need to readily be able to recall facts like that when you're calculating what's going on when you're diving so at

10 kilometers if it's water we're at a thousand bar or uh 14 700 psi below 15 000 psi often at those depths there's no need to worry about well control and uh ingress of high pressure fluids so you don't necessarily need to use very highly Dense fluids and so maybe it is more high temperature than high pressure that we that we need to worry about um this is um original source here as you can see it's gone through a few it's been recycled a few times but the original source being the international geothermal association uh

they put egs and what they call dclgs deep closed loop geothermal systems we can call our Um advanced geothermal systems have a loop and stuff like that um those things require their high enthalpy they require 200 celsius and above and they're down at depths of you know sort of three kilometers down you saw on the last slide or all the way down to 10. and that implies an operating range above 200 celsius and up to about uh 150 Megapascal sorry about the uh the mixture of units here but generally higher temperature but not the extreme

pressures that we see in extreme hp ht wells baker hughes just published their geothermal golden decade document you can find out i'm sure on their website and they claim in that document that three wells on a 400 celsius project Will produce more geothermal electrical power than 40 wells at 200 celsius obviously while using fewer resources as well so there is tremendous drive and i think tremendous opportunity in looking at higher temperatures so i think there will be pressure on us as an industry to develop solutions for uh higher and uh and higher temperatures uh maybe

not 400 celsius straight away but certainly higher than we can do at The moment because i compiled a list when i was researching this i compiled a list of all of the conversion commercial oil and gas mwd directional drilling tools that are rated above 200 degrees celsius and this is the list there's basically nothing that our industry has which we currently rate above this temperature there are mwd and lwd tools that have been used briefly above 200 celsius but not very Far above but there's nothing which is commercial nothing mainstream there's nothing you could go

out and rent from a service company and drill a 210 or 225 or 250 celsius well with at the moment there has been development of uh mud motors and the high-temperature mud motor is it's basically uh a mud motor with uh no elastomeric material in the stator um It requires a very very accurate machining of both the uh the rotor and the stator um you see um that the sp paper on the left has uh looked in some detail at uh both the design and also the field testing of such a thing and uh you

see some images i got from a uh commercial uh website on the uh on the right to give you a bit more of a flavor of what these things might look like The absence of elastomer means that they're likely to be able to operate at a higher temperature but the elastomer is there for a reason in mud motors it helps to process uh sort of sand and other solids and get them through the motor helps to provide a seal helps to prevent wear and those are all challenges that will have to be addressed using these

using these devices and i'll come back And mention that again in just a minute in a couple of slides time the the sp paper on the left was talking about aiming for a 50-hour life uh to give you some context in terms of uh the development that will be required uh to uh to maybe successful but i think they potentially have a big part to play drilling mud um water-based muds can lose viscosity at high temperatures and so as we get to higher temperatures all Base mods are often preferred but they're less environmentally friendly so

you know that if we're trying to produce a greener form of energy using oil based materials may be not ideal and importantly they also have a lower heat capacity because one of the things that our drilling mud can be helpful with is taking heat away from the various tools that we have as weird running uh the well Um come back to that in a moment but lower heat capacity is is not a great thing and there is a requirement for a pathway to higher temperature water-based mods there's a few references talking about water-based and all-based

mods that are on the slide here and if you can't write down quick enough i i think there will be a recording so i'm sure you'll be able to get them from the recording Um but it might be uh the the authors of the uh paper talking about the um [Music] the the metal motor high temperature motor and uh their um 50 hour life we're also suggesting that lubricants uh the addition of lubricants to draining mud could be needed to compensate for the lack of elastomers and to allow us to extend the wear of those

things like metal to metal uh pdms so what that means Is that our drilling fluids could get quite complicated uh in the future but our rigs might get quite complicated too um i talked a moment ago about the role of drilling fluid in taking heat away from components down hole and um it kind of stands to reason that the cold colder the mud is when you put it Into the well the um the the more heat it's going to be capable of taking away from uh downhole drilling and measurement equipment as as it drills surface

mud cooling um was used as long ago as 1990s to uh use um pdm and mwd or at least eight sort of fairly rudimentary measurements uh while drilling to control trajectory in temperatures as high as 350 celsius So the industry's been there with uh mwd and underlying motors at high temperature by using uh surface mud cooling and more recently [Music] there are examples from saudi arabia showing how surface mud coolers were able to reduce downhill temperatures below the failure temperatures of tools and extend the the life of equipment downhole And most recently um uh well

utah forge well it was drilled is effective like an experimental geothermal well uh drilled in the united states uh claimed significant benefit from the the use of uh modulus and there's a few references the the cases i just referred to are in the references on the screen you can use circulation of mud to pull heat away from drilling a measurement tools down hole But if you stop circulating to make a connection the temperature can fairly rapidly increase and cause significant damage and uh there is a as a reference i haven't got on the slide actually

uh sp paper i'll um i'll provide it after the talk uh which talks about how quickly uh the um temperature can increase and how quickly damage can be done But we do have continuous circulation systems uh that can help prevent this there's a couple of references on the screen that talk about uh continuous circulation they've already been used on geothermal wells in indonesia to allow higher flow rates and the continued use of high levels of lcm er in in another case but they are a potential solution to allowing us to Keep the temperature of equipment

downhill below the reservoir temperature and allow us to extend the ability of drilling geothermal wells just just a little bit more so i've talked about a few potential solutions to the issue of temperature there's a big challenge to solve with temperature which i'm going to return to later in the talk and that is how we actually build tools to Survive the downhill environment or all i've talked about in the last few minutes is mitigation really and i'll come back to that later but there is another drilling challenge and uh the other drilling challenge is really

the formations that uh that we're going to be drilling um i was brought up in the southwest of england and so i was lucky enough to get school Geography trips and geology trips to places like dartmoor and the image on the screen here is one of the tours on dartmoor and for those of you who haven't been there or don't know it it's characterized by a lot of granite outcrops called tours uh and then you know as you can see in the background nice gently sloping moorland that uh goes down between them and you can

you can expend a lot of Calories by walking between them because you're forever going downhill and uh and uphill so i went there on a school field trip sometime in the 1970s and we're still on the top of one of these and uh my geography teacher said do you notice anything about these tours so well they're gray kind of a bit pointy um you know they're they're all quite high He said well they're all the same height and if you look across top all the tools are all kind of they're not the same height but

kind of similar height to each other and the way it was explained to me is that um these granite intrusions were present in sedimentary formations during the ice age the glaciers came and scraped everything flat and since then Uh the sedimentary formations around have been washed away to create these nice slopes that you can see in the background but the tours that they're made of pretty tough stuff and they didn't move uh and so it is tough stuff uh it's hard to drill much harder to drill than the formations around it and it's gonna require

a different approach to drilling and a different way of thinking about things and so a second Challenge after temperature is the need to be able to reliably drill tough abrasive highly fractured formations which by the way are likely to have a much higher coefficient of friction than the rocks where we're used to drilling we're much more used to drilling sedimentary rocks at lower temperatures and uh also by the way the wells are likely to be bigger Just to make things a bit more difficult and again i think andy mentioned in his talk earlier about the

importance of surface area a larger diameter well is going to give you more surface area and also allow you to get more fluid volume and with its attendant heat capacity to be able to pull heat away from the formation as you draw so they're going to be larger diameter petrol wiki seems to like to talk in millimeters so Between 219 and 340 millimeters that's about eight and a half to thirteen and three eighths in inches okay um fractures means the potential for losses um if we're drilling enhanced geothermal wells in particular if we're looking to

leverage the natural fractures once we've drilled them then a Lot of circulation material is probably not going to be a good idea so egs wheels in particular are going to be less suited to that and so we may have to fall back on techniques like um air drilling or foam drilling or we can use uh things like mud cap drilling where although we do lose fluid to the formation we're losing fluid which is going to be uh less expensive than the uh the drilling mud that we're going to be using to um To drill the

well um [Music] mud cap drilling or pressurized mud cap drilling it's effectively a specialized form of uh mpd um and often used for the avoidance of losses and there's a few references on the screen that will explain it to you if you want to go into a bit more detail Um but mud isn't always used to drill geothermal wells foam or air can also be used but even if you use mud uh the coefficient of friction with the igneous rocks tends to be higher than it is with um sedimentary rocks there are references that will

teach you that stuck pipe can be a significant issue In uh some geothermal wells um because of the high coefficient of friction you can get very high levels of of torque and drag and the combination of torque and drag and the potential for stuck pipe and the potential for longer and deeper directional profiles um means that well block quality is likely to be of very high importance and the smoothness of the wellbore its rigocity and its Tortuosity i was i did a distinguished lecturer tour a couple of years ago when i was talking about the

importance of wellbore quality and tortuosity to oil and gas wells and i think it's likely to be doubly important for geothermal wells because of issues with friction and because of the the risks of torque and drag and getting stuck now how do we actually drill these wells uh There is a lot of excitement and rightly so about a lot of different ways of um of of drilling um igneous formations there's a company quase elegy recently uh rose uh sorry raised um 40 million dollars in funding to develop millimeter wave running um there's plasma drilling uh

which is being developed in the uk and in slovakia And uh one of the finalists at last year's pivot 2021 new ventures competition was looking at using ballistics as you can see in the picture on the left and these are all really attracting interest um but um i've admitted the um the name of the company because i don't want to make any Commercial points don't want to embarrass anybody but it was interesting that one new drilling technique was recently compared in an investment article to nuclear fusion um now i told you earlier i was at

school in the 1970s which meant i went to university at the very beginning of the 1980s and in 1981 or maybe 82 i went to columbine Oxfordshire where they had the thing called the joint european taurus and this was a nuclear fusion reactor that was going to produce energy in the next 20 or 30 years and the last time i checked it's still a nuclear fusion reactor and it's still going to be producing energy in the next 20 or 30 years so i kind of hope that these new drilling technologies aren't the nuclear fusion of

geothermal i hope they don't take as long as 20 or 30 Years to develop but i fall back on eric van orton a very good paper that he wrote last year where he talked about this is the list of these new drilling techniques uh impulse drilling spallation drilling impact drilling millimeter wave laser plasma and he pointed out that there was a 1968 report that looked at novel drilling techniques That basically talked about all of that stuff and so it was being developed in the 1960s and it's still being developed so it may be reasonable to

assume that it might not be commercial in the next few years and i'm not sure that it needs to be because here is um a couple of images from a paper about the utah forge experience And the use of pdc bits drilling uh hard formations and particularly drilling igneous formations and granites and one of the things that's impressed me over the last uh decade or so is the ability of the pdc manufacturers to make their products drill formations that we would just have thought were impossible to drill with this kind of technology even a few

years before they they Achieved it and they've been able to push these products further and further and harder and harder to the extent that the you can see the afv for the utah forge well it was drilled almost twice as fast as uh was expected um partly because the use of pdc bits partly because of the use of sort of other oil and gas trading technologies partly because of sort of drilling optimization And this is the results of a very recent um drilling optimization uh campaign in the philippines uh the cost of drilling an entire

section uh what was discovered in this and there will be an sp paper about this i'm told um sometime in the next 12 months so i'll be able to show more information then but what i've been told about this is that It requires things like forensics study of the applications optimization of the drilling process optimization of the bha the bit design and everything just the same as if we're drilling uh conventional sedimentary formations but the rules are different uh the rules for bit design are different the rules for uh drilling parameters is different and and

so we're learning how to do it all over again but as you can see in a Six world program here we're learning pretty quickly we've almost cut the cost per foot of the section the entire section you know sort of um sort of shoot a shoe uh by 50 by more than 40 in this particular case uh there was a um the following section apparently a smaller hole size the results are even better but uh i'm not able to show you those yet but there is Tremendous potential from just using the same technology as we've

been using to drill oil and gas wells so we may not need to get that esoteric in terms of of what we choose to use and what we develop and the other big issue i have to mention this with geothermal is sour service and particularly if you're running hydrothermal wells if you get any exposure to hot fluids in the Formation you can get calcium iron sodium ions carbon dioxide h2s hydrochloric acid ammonia all of these things can be present and when you combine those with the higher temperatures we're likely to see we're going to have

some significant materials challenges and some significant design challenges for the tools that we decide to put down there the rules just like we draw a bit the Rules are going to be different um still going to follow the laws of physics they're still going to you know sort of fit with the chemistry that we understand but we're going to have to think very differently about how we design things uh not that we can't do it because we know how to handle these problems in our industry we understand sour service we understand the impact of things

like h2s and temperature we just need to make sure that we apply Everything we know i'm just going to jump back because it's something i forgot to mention the other thing that was very noticeable apparently from this particular study not just an improvement in rop but also an improvement in whole quality and tortuosity which is not all together surprising but i've just forgotten to mention it it's important in the context of what i was saying earlier We can actually use drilling optimization techniques to improve hold quality as well as improving rop and given the nature

of the formations we're drilling the high coefficient friction that potential for torque and dragon stockpile that's going to be very important so we have apologies for not mentioning that before so how we're going to drill these Horizontal wells and um if anybody saw my dl talk about world ball quality you won't be surprised that i think that rotary steerable systems will have a a part in this because they will allow us to get the world placement the accuracy of world placement the the the laterals which are parallel to each other that you may need for

a number of the potential solutions we saw Earlier uh the tortuosity and rigocity uh requirements uh from drilling these um the these heart of formations and they are actually starting to be used uh this is a geothermal installation which is being drilled in hamburg in germany uh it's about three and a half thousand uh meters that's about ten thousand feet per tvd and my understanding is that Rotary steerable conventional oil and gas rotary stoval is actually being used to uh to draw these wells or will be used to drill these wells and this is the

kind of tool that we think we're going to need to drill those geothermal wells you note the integration of a rotary steerable system and an nwd tool together and there's a couple of reasons for that one Of them is cost but the more important one is risk because there's a lot of duplication between rotary steerable and mwd electronics they both have dni sensors they both have processors memory uh you know a whole bunch of things that are similar and so by building a single tool you reduce the number of sensors you reduce the number of

electronic components you reduce the number of electrical connections and so on And that's really where the risk is going to be we will be able to figure out how to build uh high temperature steering heads i mean rotary steerable systems they all have metal seals in them in these days anyway so there's you know no issues with elastomers limits and fits might have to change material selection might have to be carefully thought about coefficients of expansion but a good engineer will know how to do all of that stuff Um we have to be able to

prove that we can make uh downhole electronics and sensors work above 200 celsius and potentially significantly beyond the 200 celsius and that's where all our challenges are and that's why if you go back to the slide i showed earlier there are currently no commercial 200c plus drilling so mwd or lwd tools and the reason is that Plastic packaged electronics just won't get there um the the traditional approach which has been spectacularly successful i have to say in oil and gas drilling tools has been to take existing commercial plastic package components and just push them and

push them and push them and i can remember when it was a big deal to get from 120 celsius to 150 celsius And now 150 is pretty standard a lot of people will operate 175 or even 185 and um i don't know i guess i'm going to grossly oversimplify it you buy a bunch of electronic components uh you put them in an oven and you see which ones survive and then you use those and it's a lot more complicated than that but a combination of screening and selection Enables you to sort out the weak ones

and uh allows you to use the the stronger ones as you're building uh tools but you run up against diminishing returns and the difficulty becomes uh asymptotic as you get closer and closer to uh 200 celsius and if you get to the point where i don't know 40 or 50 of your tools are failing screening when you get to 200 celsius How many are going to be on the ragged edge by the time they go down hole and uh don't you really need 100 of your tools to be passing screening at that point don't you

need everything to work reliably at that point in order to be able to push on and get to 220 230 or whatever that'd be much better and so how do you do it and our industry has come up with a couple Of ways of doing it um over the last uh decade or so um this one uh subject of an sp paper which also spoke about the um the the the full uh the high temperature downhill motor i showed you uh earlier one of those images and this is a 300 celsius mwd tool that operates

in a 300 celsius environment That uses a combination of water evaporation and absorption to keep the electronics at maximum temperature of 175c for about 100 hours so basically you're taking heat out by evaporating the water now when you run out of water you run out of cooling capacities and you gotta have to get out the hole pretty quickly after that um it might last for about 100 hours which is not quite as long as you need but it's In the ballpark um it could well work my instinct all the way through my career with innovation

and product development has been to make things as simple as possible and as easy to repair as possible and there's certainly more complexity in this than there is in a standard 175 celsius tool the other way is and this is actually from a A paper from a company that's made a 200 celsius lwd tool it's not rated above 200 celsius but it is rated to 200 celsius and this was achieved basically by a ground up redesign of all of the electronics where the plastic packaging was all thrown away and dies were created either based on

the components that were being replaced or Application specific dice and uh different packaging different materials um used to uh put these boards together i have actually seen this one work up to about 210 celsius on one occasion there are other tools that are related to similar temperatures but i have experience with this one and have seen it succeed at high temperatures so this gives us a clue about a way to go which is maybe not trying to use those Plastic package components and maybe not trying to build 175 celsius boards but building a board that

could look very different to what we've seen before but which will still operate at higher temperatures now luckily we're not the only people trying to do this um we've got a lot of help from adjacent industries uh this is uh an artist's impression of what the surface of venus Might look like um i've had conversations with uh jet propulsion laboratory in pasadena about work that they are doing to try and develop electronics that would work on what's going to be a fairly short-lived venus rover and their specification i think is for the electronics to work

at 480 celsius for 500 hours which is kind of mind-blowing from the Perspective of what we've just been talking about and the electronics that we're used to in this industry but that's what nasa is going to have to do now we're not going to take nasa's electronics and put it into downhill tools anytime soon but there is the potential for a long-term technology transfer there but the space and the aerospace industries are looking at higher temperatures For components um for example um it's better to have sensors and um measurement and monitoring control electronics closer to

the combustion chamber on a gas turbine engine than in a uh a cool box uh some distance away on the outside and so there is pressure to increase the temperature capability of the electronics which is used in Places like that and 225 celsius seems to be a kind of magic number in terms of the potential availability of technologies that could be imported into oil and gas and leverage and so there is the potential for us in the not too distant future you know the very close foreseeable future to get from below 200 to up to

about 225 and then maybe use technologies more like the ones that nasa are looking at To a springboard to maybe to 300 maybe maybe even beyond you do that by building things in a very different way um multichip modules um are microchips that have um basically a very different structure i think one definition is uh silicon's a substrate density higher than 30 percent we would probably use different materials maybe use silicon carbide or even diamond instead of silicon Uh one of the great things about mcm's as well as their potential for temperature resistance is the

fact that you can build them so that they have a very low aspect ratio they're very light and they're very short and close to the board compared with more conventional uh techniques and if you think about drilling in things like granite and the potential for increased levels of shock and vibration at temperature then having stuff which is uh squatter And shorter could be a big help in terms of in terms of reliability and the other thing is taking heat away from the electronics and getting heat from the electronics and even in ambient temperatures uh electronics

can get pretty warm you know listen to the fan the next time it goes off on your laptop and put your hand over the processor and you know put your hand on the side of your iphone after you've been using it For a while and you'll see how hot electronics can get it's very very capable of doing it just by itself and the use of esoteric materials to take heat away from the components and ultimately get it to the cooling effect of the running mud flowing past it is potentially another big part of the solution

we have um a few examples here uh that the Right-hand image is actually some of the work that nasa's doing on their uh venus lander electronics and we can see very high temperature packing and the mcm's multitude modules on the on the screen here just to give you examples of the kind of things that we might be looking at and so we go back to the oni and remember the layers of the onion and the need for those enabling technologies to be available at the right time I think if we look at the down downhole

electronics that we're going to need to give us the intelligent tools that we need to put these wells in the right place and maximize their value progress in other industries means that and progress in materials technology means that the layers of the onion that we need to be able to develop this high temperature stuff for geothermal are just on the point of being revealed or have just been revealed so we're not Like the guys in the telephone company in 1953 who are dreaming about smartphones we can actually see the layer of the onion that's been

pulled back to give us the the technologies that we're going to uh to need to go ahead so as an industry i think this is something that we can do and if people say to you we tried this 10 years ago and it didn't work it's because that layer of the onion Really wasn't visible 10 years ago whereas now i think it is so then thinking about thermal decline i'm going to conclude in a minute but those multilaterals where it was necessary to switch between the legs well how are you going to do that and

if you have the ability to create high temperature electronics and to put automation downhole at high temperatures you're going to have systems that can Monitor the reservoir and potentially switch autonomously between legs to absolutely optimize uh production heat production and therefore electricity generation from the from the downhill environment so once we discover and once we create the downhole processors sensors memory comms atd converters all of the things that we need is not just going to allow drilling and Measurements it's going to allow us to do logging intelligent completions and the production monitoring the production optimization

i just i just spoke about so to conclude new technologies transformed and scaled unconventional oil and gas horizontal drilling and that had taken years itself to develop hydraulic fracturing that had also taken decades itself to develop If we take our expertise in oil and gas and we take the new technologies that are available to us and we combine that with decades of experience because you know as a planet we've got decades of experience of drilling geothermal wells it's just that some of the people involved in drilling the wells and some of the people involved in

the technology as i've talked about haven't always talked to each other as much as they should Have done in the past they had no need to no they do if we put all that stuff together i think we can scale geothermal to previously unimagined heights and on that positive note i'm going to stop i'm going to thank you many of the references uh that are in the presentation and many more are in an sp paper that i've uh co-authored with um colleague steve grace that's going to be Presented at the drilling conference in galveston in

just under a month's time so some of the references that you'll see in here and some others as well you'll find in that paper so thank you for your time and uh tim i'd leave it to you how you want to yeah handle questions fantastic john thank you so much very very interesting well We've a few people have written in the uh in the chat box so i'll just read these out so muhammad hilard says do you think mud cooler or even high flow rate will be helpful for drilling deep geothermal whales beyond five kilometers

uh the short answer is yes uh there is a slightly longer answer and that is that um for you know mud mud cooling will Definitely help on the surface uh i mentioned that in one of the slides high flow rates will help because uh one of the strategies we'll use to help these tools to survive is pulling as much heat as possible out of them using the uh the drilling mud that also that comes back to a point about thermal capacity of the mud and the difference between oil based and water-based muds and why it's

going to be important to develop water based mods But high flow rates you know the higher flow rate uh the more heat potentially all of things being equal the more heat you're going to be taking away the reason i said there's a long version of the answer is um high flow rates requires big pumps uh and uh mod chiller has implications for the design of the rig as well so um at the moment there should be no shortage of rigs Capable of doing this there may be competition from oil and gas drilling at the moment

given the prices of those commodities but in the long term uh it may need um additional sort of high power high capacity particularly high flow rate rigs to be to be built these rigs will be drilling deeper as well so and they're drilling larger whole sections so we'll probably need to have a generation of um you know pretty high-end land rigs to uh To to do this that's a good point i mean you know you said can we do this for five million dollars and then you're you're heaping everything onto it so you say you're

going to be using i don't know what the completion is going to be nine and five eighths or something like that or seven inch you know and the amount of rock you're moving and just the size of the equipment and the rigs surely that's Going to just push your uh your well costs uh above your five your five million dollars yeah i know the size of the rig and the scale of the uh the the scale of the um operation is a concern and i haven't got calculations i could show you now to to indicate

where i think that the cost is going to go But what i am heartened by is the way that we were able to reduce the cost of uh drilling unconventional wells because one part of the equation is the rig rate but the other part is the number of days yeah and although there'll be people on the call now who are sniggering because they've heard me advocate in the past that we shouldn't prioritize penetration rate above all else because it can have very adverse effects on completions and production But if we do learn how to safely

drill these wells much faster by using things like rotary steerable systems by understanding how to use pdc bits there may be cases for combinations of pdc bit technology and some of the um the more esoteric technologies as i talked about earlier on you know pdc bits with um sort of you know particle drilling and stuff like that we could if we can significantly increase the Speed at which we can drill these wells accurately we reduce the number of days and uh that goes a long way to mitigating the uh the equipment we're going to need

in the higher rig rate and and also if we if we're drilling them as um on pads so you know we're doing multilaterals and stuff like that um you've got the rig on location and so that that makes the process more efficient as Well a couple of questions i'll read out uh so from philip ball hi john that's you uh do you know what happened to the centef tool used in the d scramble project and then phillip gives us the the link to a paper in development of a novel logging tool for 450 centigrade geothermal

wells i say hi philip and the answer is no i don't but uh what i'm going to do is capture the link from the chat before The uh okay yeah it's the yeah so he's given the reference to that okay so uh john dewatt uh um from says that utah ford shows significant rigosity of the world ball after they improve the drilling rop so essentially through removing limiters what tools or processes do you see to deliver a low regard well paul though gusty world war good good question yeah and um Well john a good question

and i know i've talked to john about this i think i even quoted john uh on this topic in the uh in the dale talk about the importance of uh regaste and tortuosity um and i i don't want to contradict myself i don't want to contradict something i said earlier it's not just about Drinking the world faster uh i think what they did utah forge was remarkable in terms of proving uh rop they didn't have access to all the tools that they needed they weren't able to use stuff like rss which can significantly improve rigorosity

and i think as i said when i was looking at those data from the philippines one of the things that was learned in that process is that the The limiters and the um the application characteristics are very different to the ones that you get when you're drilling sedimentary rocks so i think the answer to that question is a better understanding of what's good and what's bad when you're drilling uh igneous formations i don't think we fully understand that yet but i think stuff like it to some extent utah forge and to some Extent the philippines

work and other examples as well uh will show us the way and will allow us to get a low regards to world war um with still high higher rop but one of the messages i put out in that bl talk is that single biggest change you can make is use a rotary steerable system and uh you'll get a much smoother world ball um and you heard me talk at length earlier About the importance of that okay uh so jesse jacoby has changed the subject not substantially let's not forget about the application of artificial intelligence whereby

oil and gas has excelled we can tap from the experience to and apply the same to geothermal yeah i i think so and i i think drilling optimization might be one area of doing that um and I think machine learning for stuff like production optimization um especially with the challenges associated with production from closed loop wells could be another great opportunity and uh richard dawe formerly from imperial college and now i believe retired very great talk what sort of area needs to be drilled to get a decent heat output for power generation temperature volume of

rock develops and Water output what sort of pumps are needed to get the water to surface so quite a few questions there you might look yourself to uh pick up pick them all up and answer them quite a few questions yeah um the the the diameter of the uh production world ball tends to be larger in geothermal than it is in oil and gas wells i mean whereas in oil and gas Wells we'd often be excuse me producing from six and eight six and a half inch or maybe eight and a half or eight three

quarter eight and three eighths um in geothermal it seems to start at about eight and a half eight inch rates and i'll go up to twelve and a quarter thirteen and a half thirteen three eighths that kind of uh so so the wells are I guess on average the worlds are about twice as big in terms of uh in terms of diameter uh then we start to talk about laterals uh there is a um there's got to be an optimal lateral length which is a function of the flow through the uh through the lateral but

also things like the heat transfer from the rock and the amount of time it takes to Recover and i there's still work being done on that uh one of the references in the paper the bolander references is a good place to look and get an idea of how that of how that kind of trade-off might might take place um pumps to get the water to the surface um good question and i don't actually know the answer potentially big ones Um but uh there could be some um there could be some benefit that comes across from

uh convection but uh i i think i i don't know how big those um pumps are going to be but uh potentially see you've got a long length of uh of pipe to get fluid through so potentially uh quite a lot of power in the pump okay so eric uh or Eureka mercado says do you have any experience in using turbo drills or turbines in geothermal drilling i believe they have a temperature limit around 250 centigrade yeah that's a very good point and personally no but i think they might have been used at utah forge

um you you can build directional turbines um i mean a downhill turbine will drive um The bit in just the same way as a downhill uh motor well uh you you may maybe you'll put a gearbox on the bottom of the turbine to get a more closer to a normal drilling speed but it could you can always think of it as a black box replacement uh they do have a higher temperature limit than uh pdm's and i believe that they can't say this for certain i believe That they were used at utah forge on the

subject of which so john de watts come to us back with some factual information about the utah forge they use pdc bits which went from 15 feet per hour to 60 feet to 100 feet the last step using a change in drilling fluid so that's just information for everybody yeah thanks john good information and good point yeah uh about the uh about the drilling fluid okay uh there's only any other questions Or comments that people want to uh put in it can be as i said in the previous talk you know tangential you don't have

to anymore stick to the subject you can uh talk about things that uh occur to you as a result of hearing this talk or anything to talk does anybody want to adventure any such opinion um mark mark anderson says john utah forge was a vertical well how will rss help uh good question rss can help in Vertical wells by reducing tortuosity um and i've seen i don't want to get into a pitch for rss here but i've seen examples in um the central united states where vertical sections 12 and quarter inch vertical sections have been

reduced from taking you know 10 20 30 days to drill down to just a few days by uh by using rotary steerables and by avoiding the kind of crooked hole issues That you might get there but i think rss is going to be more important if as i believe we're likely to use to drill laterals and uh john's point is a good one i think forge did have a deviated section um i i think it had a tangent section um after the vertical and peter you have your hand up and you're actually i'm on mute

so go ahead And hopefully you can hear me yes so john thank you for that um just how soon or how long do you think it will be before the drilling techniques that you're aware often are are coming down the line will actually be good enough to to make deep drilling economical that there's a there's a number of questions in there the the first one is About how soon could these drilling techniques be available and i mean uh i don't want to be too commercial tim said earlier on that uh i'm we have our own

company that's developing some of these techniques and we're hoping that we'll have something within two or three years so it's in uh you know between now and the middle of the the decade So the the technology availability could be fairly quick the issue is that it's enabling technology and um so nobody's going to drill these wells until they're convinced that the technology exists to allow you to do it so there's a bit of a chicken and egg situation there but There appear to be plenty of people who are interested in high temperature drilling and measurement

systems and who are interested in drilling either directional or um horizontal wells i've talked to you'll be surprised to talk to a lot of the companies who are looking at unconventional geothermal wells and the the message it's not exactly the same for everybody but There's a very consistent thread that runs through it which is yeah when this technology exists we'll use it but um that the for enabling technology the take-up time is uh you know you're not going to see it used all over the world in the first year but we would uh expect to

see technology available to do some of this stuff within uh two to three years Uh john the what yeah john thanks for the presentation very good um my question comes back to all the novel drilling technologies so laser and plasma and yeah as eric pointed out they were around in the 70s for sure and some of these entities have managed to secure more and more research funding to keep on doing research but some of the ones i've looked at on a geothermal project They didn't actually have an appreciation of the means to take the power

to the bottom of the hole they just imagined they would drill on coil or something like that and then they didn't have an imagination of how they were going to circulate fluids to control the wellbore at the same time as drilling with those those uh technologies what are your thoughts about those technologies are they just going to be pie in the sky or Is one of them actually going to break through my my feeling and i i i don't want to make a a kind of a too much of a personal journey through this john

but i agree with a lot of what you said there and i think um these technologies have been around for a while they are very cool and very exciting and they are attracting a lot of funding and what i'm going to say is a Generalization so it's not necessarily true of all of these um sort of technologies before somebody uh sort of uh jumps in and um starts yelling at me but there are cases where conveyance is going to be a challenge that hasn't really been addressed uh there is one i've seen where they talk

about there's a little cutout in the um in a schematic that says the high temperature electronics Will go here so so somebody needs to develop that high temperature electronics and yeah and in some cases uh it's difficult to understand how the the need to remove the rock from the for from the well um is is consistent with the way that it's going to be drilled Um for example if you need a clear fluid um i used are you going to be able to use a clear fluid to uh to lift the cuttings that inevitably will

be produced and get them all the way up to surface and so some of those challenges i think i'm sure there's challenges being thought about uh i guess what i'm going to say is we haven't yet seen the evidence of those challenges being addressed and my concern For that those technologies is that by the time they're ready for prime time rotary drilling and pdc bits could be so good that we're not going to need them before i uh read alfred's uh uh short note um i was actually like why are you talking john i was

scrolling through my emails because um i was uh shown as a solution to the very problem that john devart just mentioned which was a used mud so mud motors generate the power Uh and of course they take away take away the the cuttings etc but the particular the particular application was interesting although i don't i don't have any knowledge about whether it would work or not which was to um was how you use plasma drilling which is then powered by the mud motors uh to uh to to focus only on turning the granite beyond the

rock bit uh into a sandstone light substance whilst at the same time Uh not not damaging the sides of the world ball in in the in the area so you have to focus only on the area just in front of the world but just in front of the bit you break that up into into a rough rock and then you crash it with the pdcs but um i i just mentioned that there is such a thing john dewalt that's a good point and yeah that's a very good point about um if you assume that you

need about the same amount of Power to uh destroy the rock as you do with a with a conventional bit then a mod motor is going to be capable of providing that so uh yeah that yeah you know there's going to be efficiency and stuff like that but but in principle at least you're in the right order of magnitude for that to work so that's a good point yeah okay uh alfred de bourdi on sorry thank you john how has seismic data for Oil exploration been helpful for geothermal exploration you you need to address that

question to a reservoir engineer not to me because if i answered that question there's a 50 chance i would i'd mislead you um but what i will say is i i think that there's definitely going to be a place For both logging data and the data which allows us to understand the uh the nature of the subsurface and you know it might be that we're interested in different things we might not be so interested in things like um sort of porosity um or density but we might be more interested in uh fractures uh in fact

we could be very interested in the presence of fractures and faults And stuff like that uh for some of these uh systems fractures could be really helpful um faults could um scavenge you know sort of steal all of the uh all of our working fluid for example what what concerns me a bit about i mean i think either in your presentation around is they're talking about the depth that some of these wells might have to be you know five to one if you Want to get regularly to the uh the sort of 250 centigrade type

solutions um is that your you might be drilling through formations that need need to be cased off um and therefore you know just watching this this uh well go down and down and down until you're back to the you know three and a half inch um you know that that seems to be i i'm just here it keeps bugging me that to Say well yes once you get down there it might be hot dry rock but you've got to go through potentially dangerous formations shallow gas etc yeah you may do i mean uh hopefully um

a lot of it will be fairly shallow and there'll be aquifers most places where you're drilling you'll have to drill through those in case them and then also insulate yourself from them because they'll be they'll be delighted to take all the Heat off you and you know they'll that they could extract significant like charge tax as you as you flow through them um it may be that you know that we've learned how to drill for oil and gas in parts of the world where it's uh prevalent we don't have to find where the basins are

and we um That there are some countries have been sort of very blessed with those resources and others not so much um hot dry rock is going to be present pretty much anywhere it's just a question of how deep you go but it may well be that we need to understand the subsurface efficiently that we know that there aren't um sort of uh deep pockets of oil or gas or any Other or water or whatever under pressure then it gonna cause us drilling hazards as we uh as we drill so maybe we have to pick

our locations a little bit to uh to help us to resolve that or maybe we have to as you say understand how to uh control the wells and um maybe use uh maybe use case you know multiple casing strings or maybe use expandables or whatever to be able to to manage those uh situations so alfred I think as part of your answer has already just been told by john or they didn't realize he was answering your question which is uh you look for the bright spots and you don't drill anywhere near them okay any other

maybe that's it yeah that's right there's your answer already anything else that people want to uh to raise or you've really just off the wall comments you don't you don't need to uh You know have a direct comment you can you can even make a comment and not ask a question john you've just seen unmuted yourself john the war does that mean you're going to say something off the wall yeah the one thing that hasn't come up and it's probably off john's scope here is the earthquake issue so if you go and fracture granite rocks

hard metamorphic rocks we often tend to release the energy significantly and suddenly and some Projects have been stopped because of earthquakes i mean how's that going to play out john have you looked into that at all of course it's the advantage for a closed-loop system it's it is an advantage for a closed-loop system um my understanding is uh i'll give you both sides of the story there have been examples where um drilling of um enhanced geothermal Systems unconventional geothermal wells has been stopped because of induced seismicity or seismic activity there aren't very many but one

of the things that i've repeatedly seen is that the pressures used are not the same as the pressures that are used when we're um sort of fracturing uh unconventional uh wells uh in shales so um If you believe that then the amount of hydraulic energy is going to be less and then the probability of seismic activity is uh is is going to be less um induced seismicity that that's a whole you know you know if we were if we were there in person at imperial college um and we were going to be talking um sort

of uh late into the night after this i'm sure one of the Topics that will come would be um conventional and gastronomy in europe and the opposition to it because of seismicity um but maybe now contrasted against the potential of not having any gas um and you know either the cost of energy or the um the availability of energy might change our societal attitude towards that i'm Not saying that induced seismicity is a good thing just saying that maybe our tolerance might change a little bit in in the light of higher energy costs i think

it already has john because if you look at the standards to which the um the the cornwall drilling i think also a potential devon drilling um in terms of induced seismicity they were equivalent to what it is for uh quarry Blasting in terms of the tolerable the tolerable levels for uh seismicity and drilling so so you've got oil and gas whales uh which have you know this ridiculous i'm sorry i didn't be political this this very stringent um uh requirement in the uk and all in europe and then you go to a geothermal well all

of a sudden it's just equivalent of pouring rock and therefore you can use dynamite to blast it and therefore you can certainly feed it on the surface When it happens so it's already happening in the uk anyway that's a good that's a good point and i don't with a risk of deviating too much before i went to university i went to um in the summer break at school i went to nottingham university for a week to learn about coal mining and the national coal board wanted to persuade me that coal mining was the career for

me And we did a mind planning exercise and um basically you you cut a seam um and then you allow it to collapse um and what they said was you need to plan your mind because we're not allowed to um sort of uh mine under hospitals and schools in case they collapse but houses are fine yeah so you've got an industry that's allowed to Bring your house down literally compared with an industry that's not allowed to produce minor earthquakes and yeah and so there could be a realignment of our uh tolerance to seismicity yeah i'm

pretty sure it will be yeah okay any anything else that uh comes up again i like the uh i like a football comment anything that uh that you can think of that will inform the whole discussion but provide a new perspective try and try and be creative and Challenging truly somebody must be creative and challenging well payam akto has just joined us um in the closing minutes so payam would you like to give us uh anything that's uh that's creative and challenging to add to this time you've come off mute maybe not okay i want

to say thanks to alfred for his Comment geothermal all the way i love that okay uh yeah all right i think i think we're done so um thank you john uh very much indeed i i thoroughly enjoyed that um really uh an extraordinary counter through all sorts of challenging technologies um let's uh well best luck with your own company uh getting somewhere in the next three years but also for all of us i think uh That some of the things that insights you created will make us uh use geothermal in an economic way throughout the

world i wish you all uh uh good night um and one thing i would like to ask well are there any uh 40 people on the court on the call now is um if you if you want to give a talk on geothermal energy then uh please write to me um and you'll find my uh so for example chris um and mark you two perhaps would be interested in giving a Talk um and then we'll go to a global audience like these have and it's not related to the london section exclusively it'll be throughout the

world and to be part of the geothermal technical section um uh which i also uh uh host so do do write to me if you're interested you'll find my email anywhere really um certainly on all the invitations uh and uh i look forward to talking to everybody else uh in in march Um and so good night thank you john thank you all thank you yeah thanks john