Expandable reamers for enlarging a borehole in a subterranean formation include a tubular body, at least one curved blade track carried by the tubular body, and at least one blade engaged with the at least one blade track and configured to slide along the curved blade track along a curved path between a first retracted blade position and a second expanded blade position. To form such an expandable reamer, a tubular body having at least one curved blade track carried by the tubular body may be formed, and at least one blade may be engaged with the blade track. The blade and blade track may be configured such that the blade slides along the blade track along a curved path between a retracted position and an expanded position. Such expandable reamers may be used to enlarge boreholes in subterranean formations.

Expandable reamers for enlarging a borehole in a subterranean formation include a tubular body, at least one curved blade track carried by the tubular body, and at least one blade engaged with the at least one blade track and configured to slide along the curved blade track along a curved path between a first retracted blade position and a second expanded blade position. To form such an expandable reamer, a tubular body having at least one curved blade track carried by the tubular body may be formed, and at least one blade may be engaged with the blade track. The blade and blade track may be configured such that the blade slides along the blade track along a curved path between a retracted position and an expanded position. Such expandable reamers may be used to enlarge boreholes in subterranean formations.

A downhole tool configured to enlarge a borehole may include at least one blade extending laterally from a central portion of the tool. The one or more blades may each include a gage portion, and cutting elements comprising substantially circular cutting faces may be affixed to each of the one or more blades. Each of the one or more cutting elements may include a cutting edge comprising an arcuate peripheral cutting face portion for contacting the borehole. Cutting faces of at least one cutting element on a gage portion of the at least one blade may exhibit a cutting face back rake angle greater than a cutting face back rake angle of cutting elements on at least one other portion of the at least one blade.

A downhole tool configured to enlarge a borehole may include at least one blade extending laterally from a central portion of the tool. The one or more blades may each include a gage portion, and cutting elements comprising substantially circular cutting faces may be affixed to each of the one or more blades. Each of the one or more cutting elements may include a cutting edge comprising an arcuate peripheral cutting face portion for contacting the borehole. Cutting faces of at least one cutting element on a gage portion of the at least one blade may exhibit a cutting face back rake angle greater than a cutting face back rake angle of cutting elements on at least one other portion of the at least one blade.

A drilling tool of the present invention includes: a casing pipe; a ring bit having a larger diameter and disposed coaxially on a tip side of the casing pipe; and a pilot bit inserted into the ring bit through the inside of the casing pipe. An outer peripheral part at a tip of the pilot bit is provided with a bit head which is extended when rotated in a tool rotation direction during drilling. The ring bit is provided with a part to be engaged that is engaged with the extended bit head in the tool rotation direction, and a first abutting part capable of abutting against the extended bit head in a direction of an axis.

A drilling machine for a wellbore is provided. The drilling machine may include a dynamic lateral pad that is movable between an extended and retracted position. In the extended position, the pad moves the drill bit in a direction for drilling. The drilling machine may include a dynamic lateral cutter that is movable between an extended and retracted position. In at least the extended position, the cutter engages the wellbore and removes formation. The drilling machine may include a monolithic or integral drill bit/drive shaft to reduce the distance between a positive displacement motor and a distal end of the monolithic or integral drill bit/drive shaft. The drilling machine may include separate cutting structures that have different rotational speeds and can further utilize the integral drill bit/drift shaft and/or a bent housing that generates an off-axis rotation which helps optimize the formation removal in the center area of the wellbore.

A drilling machine for a wellbore is provided. The drilling machine may include a dynamic lateral pad that is movable between an extended and retracted position. In the extended position, the pad moves the drill bit in a direction for drilling. The drilling machine may include a dynamic lateral cutter that is movable between an extended and retracted position. In at least the extended position, the cutter engages the wellbore and removes formation. The drilling machine may include a monolithic or integral drill bit/drive shaft to reduce the distance between a positive displacement motor and a distal end of the monolithic or integral drill bit/drive shaft. The drilling machine may include separate cutting structures that have different rotational speeds and can further utilize the integral drill bit/drift shaft and/or a bent housing that generates an off-axis rotation which helps optimize the formation removal in the center area of the wellbore.

An apparatus is positioned within a wellbore in a subterranean formation. The apparatus includes a housing, a guide shaft, a follower, multiple underreamer blades, and a hydraulic chamber. The housing defines a track including multiple catch points. The guide shaft is disposed within the housing. The follower protrudes radially outward form the guide shaft and is received by the track. The follower and the track are cooperatively configured to restrict movement of the guide shaft relative to the housing. A rate of flow to the guide shaft is adjusted to adjust a relative position of the guide shaft with respect to the housing until the follower is located at one of the catch points. A pressure within the hydraulic chamber is adjusted to adjust a level of radially outward protrusion of the underreamer blades. The underreamer blades are rotated to cut into the subterranean formation.

Expandable tools for use in subterranean boreholes may include a body defining a fluid flow path extending through the body. A valve piston may be located within the fluid flow path of the body, the valve piston configured to move longitudinally within the body responsive to drilling fluid flowing through the fluid flow path above a threshold pressure. The valve piston may include a nozzle defining an opening at an end of the valve piston. A status indicator may be located within the flow path of the body, the status indicator being fixed relative to the body. The status indicator may be positioned and shaped to alter a cross-sectional area of the opening of the nozzle by at least partially entering the nozzle responsive to the valve piston moving longitudinally within the body.

A reaming tool for enlarging an underground borehole comprises a plurality of cutter assemblies distributed azimuthally around a longitudinal axis of the tool, wherein each cutter assembly includes a supporting structure bearing a sequence of cutters which have hard surfaces exposed and facing in a direction of rotation of the tool. The outer surface of the support structure on each cutter assembly includes zones which each face towards an end of the assembly and is configured such that as it extends circumferentially relative to the tool axis in the direction opposite to rotation of the tool, it also extends away from an end of the assembly.