he drilling system is made up of wireline coring, PDM motor and retractable bit system.The release and the fishing part of the wireline system is linked to the PDM motor through a Suspension seal sub; the PDM motor is connected through a sub with the retractable bit; the spline shaft of which, in turn, is threaded to the coring barrel. The combined drilling system is dropped down through and hangs below the wireline drillpipe.The pressurlzed fluid is pumped through the drill string down to the drilling system; meanwhile the thrust load is applied to the drilling system through the spindle of the drill at the surface and the wireline drillpipe; so drilling and coring can be performed.When it is necessary to recover the core or replace the bit, it can be carried out simply by stopping the pump, lifting the wireline drillpipe away the hole bottom, dropping down the overshot device and fishing up the drilling system, eliminating tripping out the drilling string.The drilling system operates in such a manner: the mud pump at the surface powers the PDM motor of the drilling system, which, in turn, drives the bit of the core barrel and the extendable reamer of the retractable bit system; so that it is not necessary to rotate the drillpipe.When dropping and fishing, the bit of the retractable bit system, which comprises a four -piece finger type bit body, is in a retracted position. When drilling, operate the wireline drillpipe to extend the retractable bit to the required size ( 75mm).O. D of the drilling system is: overshot part, 59mm; O. D of PDM motor and retractable bit are 56mm. The core barrel is matched with 75mm wireline drillpipe.Bit size: Core bit: 56mm; Reamer: 55/75mm.