Abstract: A method to provide support within a wellbore includes underreaming a section of the wellbore at a depth spanning a layer of an unstable formation. The method also includes deploying a bistable structure within the wellbore at the depth of the layer of the unstable formation. Additionally, the method includes actuating an expandable packer within the bistable structure to expand the bistable structure in a radially outward direction from a longitudinal axis of the bistable structure. The bistable structure is in contact with walls of the underreamed section of the wellbore upon expanding in the radially outward direction.

Abstract: Implementations of the present invention include a core barrel assembly including external fluid pathways extending generally axially long the outer surface of the core barrel assembly. The one or more external fluid pathways can allow for increased fluid flow around a latch mechanism. The increased fluid flow around the latch mechanism can allow the core barrel assembly to travel faster within the drill string, can allow drilling fluid to pass by the latch mechanism when engaged. Implementations of the present invention also include drilling systems including external fluid pathways, and methods of retrieving a core sample using such drilling systems.

Abstract: A core barrel assembly having a driven latch mechanism that can lock the core barrel assembly axially and rotationally relative to a drill string. The driven latch mechanism can include a plurality of wedge members positioned on a plurality of driving surfaces. Rotation of the drill string can cause the plurality of wedge members to wedge between an inner diameter of the drill string and the plurality of driving surfaces, thereby rotationally locking the core barrel assembly relative to the drill string. Drilling systems including the driven latch mechanism and methods of using the driven latch mechanism are also described.

Abstract: A latch body for use in a drilling head assembly including a fluid control subassembly, a check valve element, and/or a hollow spindle. A distal end portion of the latch body includes a port section that defines a chamber for receiving the check valve element and promoting movement of the check valve element between a blocking position and an open position. The hollow spindle of the fluid control subassembly is operatively coupled to the chamber of the port section and supports the check valve element in the blocking position. A proximal end portion of the latch body supports the fluid control subassembly of the drilling head assembly in an operative position. The latch body includes male protrusions extending inwardly toward and spaced from a longitudinal axis of the latch body. A plurality of channels extend radially outwardly from the longitudinal axis of the latch body, spanning between adjacent male protrusions.

Abstract: A locking mechanism for locking an insertable device relative to an outer tube of a ground drill comprises at least one latch, which is arranged to releasably retain the insertable device in a substantially fixed axial position relative to the outer tube. The locking mechanism comprises a cam and a cam follower, which are arranged to control a radial position of the latch. The locking system may be used in a ground drill system.

Abstract: An underreamer for well drilling comprises pivotally extendible roller cutters that extend slightly beyond the diameter of the pilot drill bit but are retained in their retracted position by the casing. Upon encountering an obstruction, the underreamer is pushed out of the casing, allowing the outer edges of the cutters to contact the obstruction. Continued downward pressure of the drill stem causes the roller arms to pivot outward to a fully extended position in which the cutters enlarge the hole to a diameter larger than the casing by rotation of the drilling stem. The advance of the casing relative to the underreamer forces the cutters to retract into the casing.

Abstract: An under reamer for expanding a borehole through an earthen formation is taught. The under reamer includes: a mandrel including an end for connection into a drill string and an opposite end and a housing including an inner bore, telescopically disposed over the mandrel and axially moveable relative to the mandrel but rotationally moveable with the mandrel. A plurality of under reamer arms are carried on the housing, the under reamer arms are formed as blocks including cutter-supporting portions in which poly-crystalline diamond compact cutters are mounted. The under reamer arms are moveable by driving the housing axially over the mandrel between a retracted position extending into the bore of the housing and an expanded position wherein the under reamers arms are pivoted out of the housing inner bore and supported therebehind by the mandrel such that the cutter-supporting portions are exposed for use to enlarge a borehole.

Abstract: A bore hole underreamer is provided having a hollow body with a longitudinal axis, which has an external wall, at least two cylindrical bores provided through the external wall and whose axes are transverse to the longitudinal axis. Each of the bores have a cylindrical widening arm for widening the hole, which is arranged in the bore like a hydraulic piston, so as to be able to slide therein between an active position and an inactive position. The underreamer has a locking member which can occupy a locking position in which this member locks the arms in their inactive position, and which, when it is released, can leave the locking position under a thrust from at least one of the arms subjected to the pressure capable of pushing the arm into its active position.

Abstract: An underreamer includes a mounting member and a plurality of cutter arms. Means pivotally mounts the cutter arms on the mounting member. Overridable means is operable for holding the cutter arms relatively outward in an underreaming position. The overriding means is operable to allow the cutter arms to move relatively inward upon forces on the cutter arms above a predetermined level.