[Music] the wire line core barrel consists of three basic components the inner tube assembly which consists of the inner tube and the head assembly the outer tube assembly and the overshot the purpose of the inner tube is to store the core sample during drilling to prevent rotation of the inner tube the head assembly is equipped with a set of ball bearings the drilling fluid is flushed via the locking and adapter coupling through the space between the inner and outer tube passing through the inner tube gap the inner tube gap can be adjusted using a threaded
spindle and a lock nut in the head assembly for example in soft and friable formations the gap needs to be smaller to prevent the drilling fluid from flushing away the core sample when the inner tube is full it pushes against the shutoff valve and stops the flow this will increase the drilling fluid pressure and it is a signal to stop drilling and replace the inner tube the core lifter case and the core spring are used to capture and break the core in hard competent rock you need a lifting force of two to three tons to
break a b size core thanks to the compressor spring the outer tube and the drill string can move upwards until the inner tube rests against the shoulder inside the drill bit the braking force is then transferred to the drill bit in the outer tube to retrieve the inner tube assembly there are two types of overshots surface and underground the underground overshot is equipped with a packing and can be pumped into flat or upwards directed drill holes the surface overshot falls down the hole by gravity and is sent down to release the inner tube when the
overshot assembly has released the latches from the locking coupling the inner tube assembly can be hoisted to the surface to release the core sample from the inner tube the driller sometimes needs to tap on it with a rubber hammer this can deteriorate a soft core sample to prevent that a triple tube core barrel can be used which means there is an extra inner tube inside the normal inner tube this can be pumped out and then opened in two halves to collect the soft core sample while emptying the core sample a second inner tube assembly can
be reinstalled the inner tube assembly is fully installed when the landing shoulder lands on the landing ring inside the outer tube and then latches against the lower end of the locking coupling without proper latching the inner tube is loose and will be pushed up the drill string while drilling to secure a proper latching most wire line systems are therefore equipped with a landing indicator you
