Hydraulic inner barrel in a drill string coring tool

Abstract

An axial bore is defined throughout the hydraulic lift inner barrel. This axial bore is communicated with the interior of the inner tube thereby allowing the interior of the inner tube to be flushed prior to initiation of the coring operation. When the coring operation is begun, flow of drilling fluid to the interior of the inner tube is prevented by allowing a ball dropped within the drill string to seat within a plug through which the communicating axial bore is defined. Once the flow of drilling fluid to the interior of the inner tube is stopped, the coring operation can begin. After the coring operation is completed, a second ball is dropped and allowed to seat within an inner mandrel through which the axial bore of the coring tool is also defined. Once the axial bore of the inner mandrel is closed, drilling fluid is forced into an expansion chamber within a telescopic piston disposed circumferentially outside of the inner mandrel. The piston is connected to the inner tube. Diversion of drilling fluid into the expansion chamber causes the piston to be longitudinally displaced upward with respect to the inner mandrel, and hence with respect to the outer tube of the drill string. The inner tube is thus similarly lifted within the drill string, thereby activating core catchers or any other downhole mechanism coupled directly or indirectly to the inner tube.