Hydraulic lift inner barrel in a drill string coring tool

Abstract

An automatically operable hydraulic lift inner barrel is devised to lift the inner tube of the core barrel on a drill string. An inner mandrel is axially disposed within the outer tube of the coring tool. An outer piston which is selectively locked to the inner mandrel is telescopically and concentrically disposed about the inner mandrel. Fluid is selectively diverted from the outer tube into the inner mandrel and inside the outer piston. An inner locking piston within the inner mandrel responds to the hydraulic pressure to unlock the outer piston from the inner mandrel. The outer piston is then longitudinally displaced by the hydraulic pressure thereby lifting the inner tube which is connected to it. After the outer piston has moved a predetermined distance, the hydraulic pressure supplied to the inner mandrel and inside the outer piston reaches a second predetermined magnitude. Burst disks are then blown thereby relieving the hydraulic pressure within the outer piston inner mandrel. The inner locking piston reassumes its initial position thereby locking the inner mandrel once again to the outer piston which is now in an extended position. Therefore, an inner tube within a coring tool can be selectively lifted, moved a predetermined longitudinal distance with respect to the outer tube, and then locked into position all in an automatic operation initiation by the initial diversion of hydraulic fluid to the inner mandrel and outer piston.