Abstract: A reaming tool for use in a wellbore has an elongated tubular body with an outer surface. There are at least first and second reamer sections formed on the tubular body, with the first and second reamer sections (i) being positioned circumferentially opposite one another, and (ii) each having at least two blades. The first reamer section includes at least one rounded dome insert and a majority of cutting tooth inserts, while the second reamer section includes a majority of rounded dome inserts.

Abstract: Embodiments disclosed herein are directed to tilting pad bearing assemblies and bearing apparatuses using the same. As will be discussed in more detail below, the tilting pad bearing assemblies include a plurality of tilting pads. The tilting pads include at least one or more first tilting pads and one or more second tilting pads. Each of the first tilting pads includes a first superhard bearing surface having a first material. Each of the second tilting pads includes a second bearing surface having a second material. The first material includes a superhard material and the second material includes a material that is different than the first material.

Abstract: A hybrid bit includes an earth-boring element and a percussion element. The earth-boring element and the percussion element are coaxially arranged, with the earth-boring element surrounding the percussion element. A reciprocating member of the percussion element may oscillate in a manner that enables a bottom end of the reciprocating member to repeatedly protrude from a bottom end of the earth-boring element and to be repeatedly withdrawn. A configuration of the earth-boring element may enable it to drill into and remove some materials from an earth formation, while the percussion element may enable the hybrid bit to drill into and remove difficult-to-drill materials, including abrasive materials and/or materials with high compressive forces, such as chert.

Abstract: A method facilitates transmission of electric signals across well components which move relative to each other in a wellbore environment. The method utilizes well components which are movably, e.g. rotatably, coupled to each other via one or more conductive bearings. Each conductive bearing has a conductive rolling element which enables relative movement, e.g. rotation, between the well components while simultaneously facilitating transmission of electric signals through the bearing. The method also involves coupling portions of the bearing to each of the well components, and those bearing portions may be connected with electric leads to enable flow of electric signals through the bearing during operation of the system downhole.

Abstract: Embodiments relate to tilting superhard bearing element bearing assemblies and apparatuses. The disclosed assemblies/apparatuses may be employed in downhole motors of a subterranean drilling system or other mechanical systems. In an embodiment, a bearing assembly may include a support ring and a plurality of superhard bearing elements each of which is tilted and/or tiltably secured relative to the support ring and distributed circumferentially about an axis. Each of the superhard bearing elements includes a bearing surface and a base portion. The base portion of the at least one of the superhard bearing elements may include a tilting feature configured to allow the at least one of the superhard bearing elements to be tiltable about a tilt axis. The bearing assembly includes retaining features that secure the superhard bearing elements to the support ring.

Abstract: In one aspect, an apparatus for use in a wellbore is disclosed that in one non-limiting embodiment may include a drive system coupled to a drill bit by a drive sub for drilling a wellbore, wherein the drive system has an associated bend for directional drilling of the wellbore, and a reamer driven by the drive sub, wherein the reamer reams a ledge formed at a transition from a larger diameter wellbore to a smaller diameter of the wellbore during directional drilling of the wellbore.

Abstract: A hydraulic tool includes a rotor rotatably disposed within a stator. At least an inner portion of the stator and/or at least an outer portion of the rotor is configured to be installed in a drill string in either of two inverted orientations along a longitudinal axis of the hydraulic tool. The rotor is configured to rotate within the stator in either of the two orientations. A method includes disposing a rotor within a cavity defined by a stator, passing a fluid through the stator to rotate the rotor, and reversing the stator or the rotor. A drilling system includes a fluid source, a hydraulic tool, a drive shaft operatively associated with the rotor of the hydraulic tool, and a drill bit operatively associated with the drive shaft.

Abstract: A method of manufacturing coated components, e.g., for use in downhole drilling, which may limit, during the manufacturing process, the formation of microfissures and other performance-inhibiting characteristics in the abrasion resistant coating. The method may include applying an abrasion resistant coating composition to a substrate. The abrasion resistant coating composition and at least the surface of the substrate may be heated to effect metallurgical bonding of the abrasion resistant coating composition with the substrate. The substrate may then be austempered under process conditions selected to limit the volume of expansion of the substrate during austempering to less than about 0.8%.

Abstract: A reaming bit designed to operate with low torque fluctuation when driven with a turbine at speeds in the order of 300-600 RPM and above features a profile that is arcuate from the gauge dimension to the nose area or alternatively has a blunt straight taper section but with a ratio of profile length (PL) to bit size (BS) of under 0.75. The blades extend into a concave cone and the cutting structure continues along the blades towards the center. The blades have a step near the gauge section to increase the exposure of the blade cutting structure. An array of protrusions are disposed parallel to and behind the cutting structure to increase high speed stability and adjacent the blade step transition to protect outer casing on run in.

Abstract: A turbodrill having a housing having a bore extending at least partially therethrough, a rotatable shaft disposed in the housing bore and rotatable relative to the housing, the housing, the housing bore and the rotatable shaft having a common longitudinal axis; and a plurality of turbine blades disposed at least partially within the housing bore, at least one turbine blade of the plurality of turbine blades including a first blade profile disposed at a first point along a blade span and a second blade profile disposed at a second point along the blade span, the second blade profile differing from the first blade profile.

Abstract: A housing, mandrel and bearing assembly positionable in a wellbore includes a torque transmission member adapted to connect to a source of rotational torque (e.g. a downhole motor power output) and a tubular mandrel adapted to connect to a drill bit. A lower tubular housing is adapted to contain a lower bearing and catch sleeve assembly. The catch assembly is adapted to retain the mandrel in the lower housing if the mandrel breaks. An upper tubular housing contains an upper bearing and is adapted to connect to a housing of the downhole motor. A method of assembling the downhole housing, mandrel and bearing assembly is disclosed.

Abstract: A drilling system includes a magnetic coupling and an oscillation absorber. The magnetic coupling has a rotor that rotates about an axis of rotation. The oscillation absorber is in operable communication with the magnetic coupling and includes an outer layer coupled to a separator layer of the magnetic coupling to form an enclosed area. An absorber shaft of the oscillation absorber is at least partially within the enclosed area and is coupled to the rotor. The absorber further includes an outer mover arranged such that rotation of the absorber shaft causes the outer mover to rotate due to interaction of inner absorber shaft magnets and outer mover magnets.

Abstract: A drilling tool assembly may include a housing, a piston disposed in the housing, and a clutch assembly coupled to the housing and the piston. The clutch assembly may be configured to facilitate rotation of the piston relative to the housing. A cutting assembly may be coupled to the piston in a manner that it is rotatable relative to the piston. A method of forming a wellbore may include positioning a drilling tool in the wellbore, the drilling tool comprising a housing, a piston, a clutch assembly, and a drill head. The method may further include reciprocating the piston axially within the housing, rotating the piston relative to the housing the clutch assembly, rotating the drill head relative to the housing and the piston, and forming the wellbore.

Abstract: A downhole stabiliser (5), such as a drill motor stabiliser, comprises at least one reaming means and/or reinforcing means (10). The present invention also relates to an assembly (30), such as a downhole drilling assembly (31), comprising at least one such stabiliser (5) and/or a drill bit (40,41) comprising a gauge bit (42) at or near a drilling end (45) thereof, and a connection means (46) for connecting the drill bit (40,41) to a drill motor assembly (60), wherein the drill bit gauge (42) comprises a substantially cylindrical portion having a length less than or equal to approximately 1.0 times the nominal bit diameter. The present invention also relates to a novel locking mechanism (80), such as a lock and key mechanism, to allow locking of a shaft (70?), e.g. a motor drive shaft (71?), through or together with a stabiliser (5?).

Abstract: A downhole stabiliser (5), such as a drill motor stabiliser, comprises at least one reaming means and/or reinforcing means (10). The present invention also relates to an assembly (30), such as a downhole drilling assembly (31), comprising at least one such stabiliser (5) and/or a drill bit (40,41) comprising a gauge bit (42) at or near a drilling end (45) thereof, and a connection means (46) for connecting the drill bit (40,41) to a drill motor assembly (60), wherein the drill bit gauge (42) comprises a substantially cylindrical portion having a length less than or equal to approximately 1.0 times the nominal bit diameter. The present invention also relates to a novel locking mechanism (80), such as a lock and key mechanism, to allow locking of a shaft (70?), e.g. a motor drive shaft (71?), through or together with a stabiliser (5?).

Abstract: A driveshaft assembly for a downhole motor including a driveshaft having a longitudinal axis, first and second ends, and a convex spherical bearing surface disposed at the first end configured to transfer axial loads. The assembly also includes a connection lug disposed at the driveshaft first end, extending circumferentially between first and second ends, and including a recess in the first end of the lug, the recess comprising a concave cylindrical surface concentrically disposed about a pivot axis oriented orthogonal to the longitudinal axis. The assembly also includes a torque transfer key disposed within the recess and having a central axis radially spaced from the pivot axis, a convex cylindrical surface concentrically disposed about the pivot axis, and a planar surface. The convex cylindrical surface of the key slidingly engages the concave cylindrical surface of the recess; and the pivot axis intersects the key.

Abstract: The subject matter of this specification can be embodied in, among other things, a method that includes a downhole rotational lock mechanism including a tubular housing having a longitudinal bore with an internal wall. A driving gear is disposed in the longitudinal bore of the tubular housing and has a peripheral edge secured to the internal wall of the longitudinal bore of the tubular housing. The driving gear has an upper portion including a plurality of gear teeth arranged around a central longitudinal bore through the driving gear. A driven gear is movably disposed in the longitudinal bore of the tubular housing, and has a central longitudinal bore and a lower portion including a plurality of gear teeth. An output drive shaft is disposed longitudinally in the longitudinal bore of the tubular housing and in the longitudinal bore of the driven gear.

Abstract: A drilling apparatus comprised of a multiplicity of subassemblies for drilling an open-hole extension from within an existing cased borehole located in a geological formation for the production of oil and gas. In one embodiment, one subassembly includes a motor located within a cased section of the borehole that rotates a drill pipe segment attached to a rotary drill bit in the open-hole to drill the open-hole extension of the well. In another embodiment, a shroud encloses the motor located within the cased portion of the well that is used to control the mud flow to and from the bit in the open-hole during the drilling process.

Abstract: A threaded sleeve stabilizer spans an upper stator connection in a mud driven drilling motor used for borehole drilling. A number of collets are loaded in compression between the stator and the housing of the motor, and are held in compression by a threaded connection.

Abstract: A drilling apparatus including a drill collar forming part of a primary drilling assembly and having an outward opening groove in the side thereof, and a secondary drilling assembly. The secondary drilling assembly includes a tubular drill string connected at one end to the drill collar, a drilling motor mounted in the drill string, and a drill bit mounted at the other end of the drill string and connected to the drilling motor. The secondary drilling assembly is mounted in the drill collar so as to be movable between a first position in which the drill bit is seated in the groove, and a second position in which the bit projects laterally from the groove in the side of the drill collar.

Abstract: A downhole activation system within a tubular. The system includes an axially movable mover. A first magnet attached to the mover. The first magnet axially movable with the mover. A second magnet separated from the first magnet. The second magnet magnetically repulsed by the first magnet. A biasing device urging the second magnet towards the first magnet; wherein movement of the first magnet via the mover towards the second magnet moves the second magnet in a direction against the biasing device. Also included is a method of activating an activatable member in a downhole tubular.

Abstract: A downhole motor assembly including a housing, a power section with a stator and a rotor contained within the housing, a proximal drive assembly connected with a proximal rotor end, a distal drive assembly connected with a distal rotor end, a proximal thrust bearing arranged between the housing and the proximal drive assembly, a distal thrust bearing arranged between the housing and the distal drive assembly, and an axial load decoupling device in the distal drive assembly located longitudinally between the distal rotor end and the distal thrust bearing, for separating axial loads imposed on the proximal thrust bearing from axial loads imposed on the distal thrust bearing.

Abstract: A bottom hole assembly has a drill bit that is driven by a downhole turbine. The turbine speed is reduced by cycloidal gearing that requires no temperature sensitive seals when operating temperatures in some applications exceed 350 degrees F. The output shaft of the cycloidal gear reducer goes through a bearing before connection to the drill bit or associated reamer. The motive fluid can be the drilling mud. The bit can be driven at desired speeds such as 50-300 RPM while the speed reduction ratio can be in the order of 10 to 1 or more. This drive assembly can replace Moineau type downhole motor drivers that have temperature limitations due to use of rubber in the stators.

Abstract: Rotational locking mechanisms for drill string assemblies, bottom hole assemblies, and drilling motors are presented herein. A fluid-driven motor assembly is disclosed for use in a drill string to drill a borehole in an earth formation. The drill string includes a drill pipe and a drill bit. The motor assembly includes a housing that is configured to operatively connect to the drill pipe of the drill string to receive drilling fluid therefrom. A stator, which is disposed within the housing, is configured to rotate at a stator speed. A rotor is disposed within the stator and coupled to the drill bit. The rotor is configured to rotate at a rotor speed. The motor assembly also includes a rotational locking assembly operatively coupled to the rotor and the housing. The rotational locking assembly is configured to prevent the stator speed of the stator from exceeding the rotor speed of the rotor.

Abstract: In one embodiment, a casing bit drive assembly may be used with a casing drilling system. The casing bit drive assembly may include one or more of the following: a retrievable drilling motor; a decoupled casing sub; a releasable coupling between the motor and casing bit; a releasable coupling between the motor and casing; a cement diverter; and a casing bit.

Abstract: An impulse-type underground supercharged jet drilling method and device is provided. The impulse-type underground supercharged jet drilling method uses up and down vibrations of a drill string or weight on bit variation during the drilling process, so that an upper joint connected to the drill string drives a housing and a supercharging cylinder block to move up and down relative to a supercharging piston, while the supercharging piston, a high pressure line, and a drive shaft disposed outside the high pressure line make a reciprocally retractable movement relative to the housing. As a result, some working fluid entering the supercharging cylinder block is intermittently supercharged, and discharged from a high pressure fluid passage disposed in the supercharging piston and the high pressure line. The present disclosure can effectively perform an underground supercharging to parts of the drilling fluid, thus improving the rock breaking efficiency and the drilling speed.

Abstract: Embodiments of the invention relate to tilting pad bearing assemblies and apparatuses. The disclosed tilting pad bearing assemblies and apparatuses may be employed in downhole motors of a subterranean drilling system or other mechanical systems. In an embodiment, a bearing assembly or apparatus includes a support ring and a plurality of tilting pads. Each tilting pad is tilted and/or tiltably secured relative to the support ring. In some embodiments, one or more of the tilting pads include a plurality of superhard bearing segments assembled to form a superhard bearing surface. One or more seams may be positioned between adjacent superhard bearing segments of the superhard bearing segments. In other embodiments, one or more of the tilting pads may include at least one or only one superhard bearing segment, such as a polycrystalline diamond bearing segment.

Abstract: Various embodiments relate to bearing assemblies configured to enable removal and replacement of superhard bearing elements, and bearing apparatuses that may utilize such bearing assemblies. The disclosed bearing assemblies may be used in a number of applications, such as downhole motors in subterranean drilling systems, directional drilling systems, roller-cone drill bits, and many other applications. In an embodiment, a bearing assembly includes a support ring and a retention ring assembled with the support ring. The bearing assembly further includes a plurality of superhard bearing elements. The retention ring and at least a number of the superhard bearing element are collectively configured to restrict displacement of the at least a number of the superhard bearing elements.

Abstract: The rotary percussive device includes a casing forming a support, a striking mechanism equipped with a longitudinal body, rotatably mounted in the casing along the axis of the body, including a cylinder extending along the axis of the body, a striking piston slidingly mounted inside the cylinder and intended to strike a shank coupled to a drill rod, and a distribution device arranged to control an alternating movement of the striking piston along the axis of the body, and a motor arranged to drive the body of the striking mechanism in rotation along an axis of rotation substantially coinciding with the axis of the body. The striking mechanism includes a closing lid mounted on the body and arranged to close one of the ends of the body, the closing lid being coupled in rotation to an output shaft of the motor and at least partially including the distribution device.

Abstract: The invention being designed in this application relates to a radial drilling method. Boreholes are placed into oil and gas formations to provide openings for the removal of the product. Oil and gas wells extend to different depths and downhole well conditions. The radial system has been designed to accommodate the well conditions and to jet or drill different oil and gas formation. The radial system provides a mill/bit which is rotated from a downhole motor or a surface swivel. The mill ports, the steel casing, and the bit extend outward into the formation forming a borehole to a predetermined length. The borehole is provided without an entrance radius into the formation. Several radial holes can be provided considering a one trip event.

Abstract: The present invention discloses a cutting tool integrated in a drillstring for enlarging a borehole, where the cutting tool at least comprises: one or more side mills (12, 13, 14) arranged along the axis of said drillstring in a reamer housing (11), where the side mills (12, 13,14) are adapted to be rotated relative to the tool housing (11) by individual driving means. The self driven rotational side mills may be dome shaped cones where expand radially out of the reamer housing (11), or may be a special non-circular dome shaped cones where rotates without expanding.

Abstract: An expandable reamer apparatus and methods for reaming a borehole, wherein a laterally movable blade carried by a tubular body may be selectively positioned at an inward position and an expanded position. The laterally movable blade, held inwardly by blade-biasing elements, may be forced outwardly by drilling fluid selectively allowed to communicate therewith by way of an actuation sleeve disposed within the tubular body. Alternatively, a separation element may transmit force or pressure from the drilling fluid to the movable blade. Further, a chamber in communication with the movable blade may be pressurized by way of a downhole turbine or pump. A ridged seal wiper, compensator, movable bearing pad, fixed bearing pad preceding the movable blade, or adjustable spacer element to alter expanded blade position may be included within the expandable reamer. In addition, a drilling fluid pressure response indicating an operational characteristic of the expandable reamer may be generated.

Abstract: Exemplary methods, systems and components disclosed herein provide propagation of light signals from an external source to a borehole mining mole which includes an optical/electric transducer configured to provide propulsive power for the borehole mining mole and its associated mineral prospecting tools. Some embodiments include one or more umbilicals connected from a remote source location to an onboard reel incorporated with the borehole mining mole. The umbilicals are spooled outwardly or inwardly from the onboard reel during traverse of the borehole mining mole along a path in an earthen environment.

Abstract: A turbine for use in a downhole drill string including an elongated casing defining an interior and a plurality of motor units in the interior. Each motor unit has a rotor and a stator. A torque transmission couplings connects each of the plurality of motor units to the drill string. The torque transmission couplings having flexible linkages. As a result, the power section has tight tolerances for the clearance at the tips of the rotors because the motor units are relatively stiff. The flexing normally obtained by bending the rotor shaft is accomplished and absorbed in the flexible linkages.

Abstract: A system and method are disclosed for drilling a well and obtaining a downhole core sample. A drilling rig includes a pivotal mast. The mast supports an injector thereon with an injector axis offset with respect to the central axis of the mast when the drilling rig is handling threaded tubular. The mast also supports a drive unit. A drilling assembly includes coil tubing, the injector, and a bottomhole assembly including a percussion tool suspended in the well from the coil tubing. A coring assembly includes a threaded tubular string and the drive unit supported on the mast for rotating the threaded string and the coring bottomhole assembly while the injector is spaced from the axis of the mast.

Abstract: Embodiments of the invention relate to a bearing assembly including at least one superhard bearing element having at least one bearing registration feature configured to facilitate orientating of a curved, pre-machined bearing surface thereof with respect to a bearing body, methods of fabricating such bearing assemblies, and bearing apparatuses incorporating such bearing assemblies. Subterranean drilling systems incorporating such bearing assemblies are also disclosed.

Abstract: A method of prolonging the life of a PDC cutter having a substantially cylindrical shape centered about a rotational axis, and an apparatus for multi-axis modulation of a PDC cutter, the method including imparting linear modulation to the cutter in at least one direction and imparting rotary modulation to the cutter about the rotational axis, the rotary modulation being synchronized with, and facilitated by, the linear modulation.

Abstract: In an aspect, a drilling motor is provided that in one embodiment includes a stator and a rotor configured to be disposed in the stator, wherein the rotor includes a lobe member having an elastically deformable surface configured to provide an interference seal between the stator and the rotor.

Abstract: In an embodiment, a bearing apparatus comprises a first bearing assembly including a plurality of circumferentially-spaced first bearing elements each of which includes a first bearing surface. The bearing apparatus further includes a second bearing assembly including a plurality of circumferentially-spaced second bearing elements each of which includes a second bearing surface oriented to engage the first bearing surfaces of the first bearing assembly during operation. At least one of the second bearing elements may be circumferentially spaced from an adjacent one of the second bearing elements by a lateral spacing greater than a lateral dimension of the at least one of the second bearing elements.

Abstract: Drilling tool (1) for drilling a well downhole where fluid is surrounding the tool and where the tool has a housing (15) and is connected to an electrical conducting means, such as a wireline. The drilling tool has a drilling head (2) and a fluid cleaner (3) for removal of elements, such as debris and formation pieces, from the fluid while drilling downhole. The fluid cleaner has a chamber (4) and a filter (5) within the chamber for separation of the elements from the fluid. The tool further comprises a pump (8) for pumping the fluid into the chamber through an inlet (11) in the drilling head (2) and through the filter before entering the well again. Furthermore, the tool comprises a driving unit for driving the pump and the drilling head.

Abstract: A drilling sub assembly adapted to be coupled between a drill bit of a drilling rig and a drill pipe, the drilling sub assembling including a turbine unit directly coupled to the drill bit via a mandrel, such that passage of a drilling fluid through the drilling sub assembly rotates the turbine unit which in turn directly rotates the drill bit coupled thereto. The present invention further relates to a baffle for controlling and reducing debris present within a drilling fluid used in combination with the drilling sub assembly.

Abstract: A jetting nozzle for forming boreholes or for cleaning out other tubular formations has a vibration-inducing mechanism that maximizing penetration rates and expands the diameter of the boreholes. The vibration-inducing mechanism can be an internal turbine responsive to the flow of pressurized jetting fluid through the nozzle. The nozzle has forward openings defining a voraxial spray pattern for the forward-directed jetting portion of the fluid exiting the nozzle. The nozzle can also have a pointed end that is adapted to penetrate the formation. The vibration also reduces friction between the fluid supply hose and the borehole being jetted through the formation by the nozzle. A system for forming boreholes with the jetting nozzle and a method of forming boreholes is also disclosed.

Abstract: A bottom hole assembly has a drill bit that is driven by a downhole turbine. The turbine speed is reduced by cycloidal gearing that requires no temperature sensitive seals when operating temperatures in some applications exceed 350 degrees F. The output shaft of the cycloidal gear reducer goes through a bearing before connection to the drill bit or associated reamer. The motive fluid can be the drilling mud. The bit can be driven at desired speeds such as 50-300 RPM while the speed reduction ratio can be in the order of 10 to 1 or more. This drive assembly can replace Moineau type downhole motor drivers that have temperature limitations due to use of rubber in the stators.

Abstract: A moving cavity motor or pump, such as a mud motor, comprising: a rotor, a stator, and one or more apparatus for constraining (i.e., controlling or limiting) the movement of the rotor relative to the stator.

Abstract: A borehole cutting assembly for directional cutting in a borehole, the assembly comprising an input pipe and a cutting head rotatably mounted on the input pipe such that the orientation of the cutting head relative to the input pipe can be altered to determine the direction of cutting of the borehole. A cutting tool and cutting tool motor are mounted on the cutting head to enable the cutting tool to be rotatably driven relative to the cutting head so that when the cutting tool is loaded in use the cutting head is subject to a tool reaction torque that acts to rotate the cutting head to change the orientation of the cutting head. The cutting head is rotatably mounted on the input pipe by a controlled torque coupling comprising a progressive cavity pump having a rotor and a stator each provided with drive formations arranged to define a fluid flow cavity therebetween. Rotation of the rotor relative to the stator forces fluid flow through the cavity to counteract the tool reaction torque.

Abstract: The present invention relates to systems and methods for controlling downhole motors. One aspect of the invention provides a valve-controlled downhole motor including: a downhole motor and a spool valve. The downhole motor includes a sealed chamber having a first port and a second port, a stator received within the sealed chamber, and a rotor received within the stator. The spool valve includes a barrel and a spool received within the barrel. The barrel includes an inlet port, an exhaust port, a first feed port, a second feed port, a first return port, and a second return port. The inlet port is located in proximity to the first feed port and second port. The exhaust port is located in proximity to the first return port and the second return port. The spool includes a first gland and a second gland.

Abstract: There is provided a system and method for having multiple movable isolation zones within a borehole, to provide for zones having predetermined properties, such as pressure, flow or optical properties. These movable isolation zones provide advantages in downhole activities, such as, laser cutting and laser drilling to advance a borehole.

Abstract: A steerable system comprises a fluid powered motor 10 having a rotor 16 and a stator 18, and a bias arrangement having a plurality of bias pads 34 connected to the stator 18 so as to be rotatable therewith, the bias pads 34 being moveable to allow the application of a side load to the steerable system.

Abstract: A downhole tool string, comprising a tool string bore and a drill bit located at the bottom of the tool string. The drill bit comprises a body intermediate a shank and a working surface. The working surface may comprise a substantially coaxial rotationally isolated jack element with a portion of the jack element extending out of an opening formed in the working surface to engage a subterranean formation. The tool string may comprise a driving mechanism adapted to rotate the jack. The clutch assembly disposed within the tool string bore may comprise a first end in communication with the jack element and second end in communication with the driving mechanism.

Abstract: A steerable system comprises a fluid powered motor 10 having a rotor 16 and a stator 18, and a bias arrangement having a plurality of bias pads 34 connected to the stator 18 so as to be rotatable therewith, the bias pads 34 being moveable to allow the application of a side load to the steerable system.