Abstract: The side tracking system includes a window mill having a full diameter cutting surface and a reduced diameter tapered cutting surface and a whipstock having a ramp engaging the reduced diameter cutting surface. The materials of the whipstock have a first cutablity and the materials of the casing have a second cutability. The reduced diameter cutting surface contacts the whipstock ramp at a first contact area and the full diameter cutting surface contacts the wall of the casing at a second contact area. As weight is applied to the mill, there is a first contact stress at the first contact area and a second contact stress at the second contact area. A cutability ratio is the first cutability divided by the second cutability and a contact stress ratio is the first contact stress divided by the second contact stress. The mill cuts the casing rather than the whipstock by maintaining the product of the cutability ratio and the contact stress ratio less than one.

Abstract: The invention provides a backreaming tool for expanding a pilot bore produced by a drill string, comprising a pneumatic perCussion hammer (1) in combination with a drill string, the drill string being rotatable and reversible through the pilot bore to effect backreaming by the pneumatic perCussion hammer. The pneumatic percussion hammer is longitudinally adjustable relative to the drill string. The arrangement is such that the compressed air supply to the working cylinder of the hammer is cut off when the hammer is longitudinally close to the end of the drill string, then restored as the hammer becomes more distant from the drill string.

Abstract: A downhole tool that functions as an underreamer, or alternatively, as a stabilizer in an underreamed borehole. The tool includes one or more moveable arms disposed within a body having a flowbore therethrough in fluid communication with the wellbore annulus. The tool alternates between collapsed and expanded positions in response to differential fluid pressure between the flowbore and the wellbore annulus. In one embodiment, the tool moves automatically in response to differential pressure. In a second embodiment, the tool must be selectively actuated before it is moveable. When the tool expands, the arms are preferably translated axially upwardly, while simultaneously being extended radially outwardly from the body. The expanded tool diameter is adjustable at the surface without changing components. The arms may include borehole engaging pads that comprise cutting structures or wear structures or both, depending upon the function of the tool.

Abstract: A bore hole opener for enlarging a bore hole includes a longitudinal body, a duct for drilling fluid, formed longitudinally in the body, having a fluid passage cross-section of inside radius i, and at least two hole-opening arms, borne by the body, which have an active part equipped with cutting mechanisms, which are arranged therein in such a way that they can slide between a position of rest in the body and an active position partially out of the body, and which are guided and supported for this purpose in the body over a distance g and which, in the active position, project from the body by a length o, in which the values of i, g and o are chosen to simultaneously satisfy the conditions i+g+o S;

Abstract: A back reaming tool is disclosed which includes a tool body adapted to be coupled to a drill string, and at least one roller cone rotatably mounted to a leg and having cutting elements disposed thereon. The leg is removably coupled to the tool body. The at least one roller cone is open at only one axial end thereof.

Abstract: The present invention provides a reamer (100) having at least one journal body (110) and at least one toroidal cutter body (116). The toroidal cutter body (116) has a maximum diameter (MD), an outer perimeter (OP) and a plurality of cutting elements (112, 145, 149) on the cutting surface (118). The toroidal cutter body is rotatably attached to the journal (110). When in the installed position, the axis of rotation (RA) of the at least one toroidal cutter body (116) intersects the longitudinal axis of the drill string at an acute angle.

Abstract: Provided is a bore hole underreamer in a terrestrial formation, intended in particular for oil drilling. The underreamer has a hollow body and at least two cylindrical bores. The bores are provided through an external wall of the body and have axes that are transverse to a longitudinal axis of the body. The bores are distributed over the circumference of the hollow body and each bore contains a cylindrical widening arm. Each arm has a bladed cutting end disposed on the outside of the body that slides between active and inactive positions. Another end of each arm is disposed inside the body and receives fluid pressure for pushing the arm into the active position. The underreamer includes a locking member for locking the arms in their inactive position when the locking member is immobilised in the body in a releasable fashion in a locking position.

Abstract: The hole-opener is designed so that it can be disassembled in the field to replace worn cones or to enlarge the effective diameter of the tool. It comprises: a tubular drive sub, which connects at its front end with a rotating drill string which is being pulled along a pilot hole; a sleeve which slides over the rear portion of the drive sub; and a retainer sub which is connected with the rear end of the drive sub. The drive sub has external protruding bars which engage slots formed in the forward end of the sleeve, for limiting forward movement of the sleeve and locking the drive sub and sleeve together so that they rotate as a unit. The retainer sub has a radial shoulder which abuts the rear end of the sleeve to lock it in place. The retainer sub also transmits axial pull from the drive sub to the sleeve. The sleeve carries rotary cutting elements which are pulled and rotated to cut formation and enlarge the pilot hole.

Abstract: A hole opener including a tool body having upper and lower ends. The upper and lower ends may be coupled to adjacent drilling tools. At least two blades are formed on the tool body and are arranged so that the hole opener is positioned concentric with a wellbore, and cutting elements are located on the blades. The at least two blades and the cutting elements are arranged to increase a diameter of a previously drilled wellbore.

Abstract: A drilling apparatus for earth boring operations is of the type having cutter blades mounted on a support body at the lower end of a drill string and includes a novel arrangement of fluid bore sections for delivering fluid under pressure into fluid discharge passages in each of the blades and a bifurcated pivotal mounting portion on the body which enables the bore sections to supply fluid to the cutter blades through a ball joint on the pivotal axis. Modified forms of invention are specifically designed for cutter blades which are intended to perform reaming operations but include the fluid delivery system as well as an extended delivery system for delivering fluid under pressure to other tools in the drill string.

Abstract: An expandable reamer shoe is provided for use with expandable casing in a borehole. The reamer shoe has a number of reaming members in the form of blades which remain closed against the body of the shoe when inserted through casing, and can then be expanded to underream below the casing. Additionally, the expandable reamer shoe is made substantially of a drillable material so that the borehole can be extended beyond the point reached by the expandable reamer shoe.

Abstract: A reaming tool which includes a body having reaming blades affixed thereto at azimuthally spaced apart locations around a circumference of the body is shown and described. The reaming blades each have at least one cutter attached thereto at selected positions and orientations on each of the blades to minimize a net lateral force developed by the reaming tool. The tool includes a pilot hole conditioning section having a plurality of azimuthally spaced apart pilot blades affixed to the body longitudinally ahead of the reaming blades.

Abstract: A method and apparatus for milling a window in a downhole structure, such as a casing or a liner, includes a mandrel that supports milling elements arranged in a predetermined pattern. In one example, the milling elements are arranged in one or more continuous channels each having a generally helical pattern. The milling elements are able to cut the window in the downhole structure substantially continuously to the desired size.

Abstract: Disclosed are an expandable well bore reamer and method utilizing a pair of reaming blades pivotally mounted on a central support member, each blade having an inner and an outer mounting arm positioned on opposite sides of such central support member with a movable cam with cam members to push against the inner mounting arm of each blade to pivot the reaming blades outward to an open position.

Abstract: A reamer shoe (1) for mounting on a tubing string has a reaming area (5) supporting a plurality of discrete reaming members (6) typically formed as simple geometrical shapes. The reaming members provide complete circumferential coverage of the shoe body (2) but the individual reaming members are non-continuous and do not fully extend either longitudinally along or circumferentially around the reaming area on the shoe body. The invention therefore provides a reamer shoe for reaming a bore in preparation for receiving casing, which is effective on rotation or reciprocation, regardless of direction or speed.

Abstract: An expandable reaming tool including at least two reamer pads connected to a tool body. The reamer pads are adapted to be displaced between a retracted position and an expanded position. At least one spiral blade is formed on at least one reamer pad. A plurality of cutting elements are disposed on the at least one spiral blade.

Abstract: A reamer tool which is capable of removing paraffin scale, ice, salt, calcium, cement, barium and other accumulations from the inside surfaces of oil well pump tubing and casing, which reamer tool may include a housing for suspension in the well tubing or casing; a shaft slidably mounted in the housing for attachment to an impact device; shaft threads provided on the shaft; a lock nut threadibly mounted on the shaft for removably engaging the housing; and a reset spring provided in the housing between the housing and the end of the shaft. Displacement of the shaft in the housing causes the lock nut to engage the housing, and the lock nut rotates on the shaft threads and rotates the housing such that the housing rotates in the well bore or casing and removes the solid blockages from the well bore or casing.

Abstract: The drilling assembly includes an eccentric adjustable diameter blade stabilizer having a housing with a fixed stabilizer blade and a pair of adjustable stabilizer blades. The adjustable stabilizer blades are housed within openings in the stabilizer housing and have inclined surfaces which engage ramps on the housing for camming the blades radially upon their movement axially. The adjustable blades are operatively connected to an extender piston on one end for extending the blades and a return spring at the other end for contracting the blades. The eccentric stabilizer also includes one or more flow tubes through which drilling fluids pass that apply a differential pressure across the stabilizer housing to actuate the extender pistons to move the adjustable stabilizer blades axially upstream to their extended position. The eccentric stabilizer is mounted on a bi-center bit which has an eccentric reamer section and a pilot bit.

Abstract: A drill bit for drilling a borehole having a bit body with an axis of rotation, a leading face, and a plurality of blades upstanding from the leading face. At least one of the blades terminates in a gauge pad having a gauge surface arranged, in use, to face a wall of the borehole. The gauge surface being devoid of cutting elements and terminating at an end remote from the blade at a junction with a gauge pad end wall. The gauge pad carries a cutter having a face and a cutting edge located radially inward of the gauge surface, and the junction of the gauge surface and the gauge pad end wall crosses, radially, between the face of the cutter and the wall of the borehole. The gauge surface may be a substantially continuous surface, and may have at least one additional cutter located angularly between two adjacent blades of the drill bit.

Abstract: A drill bit for drilling a borehole, the drill bit comprising a bit body 10 having an axis of rotation 12, a leading face, a plurality of blades 26 upstanding from the leading face, at least one of the blades terminating in a gauge pad 28 having a gauge surface 29 arranged, in use, to face a wall 30 of the borehole 32, the gauge surface 29 being devoid of cutting elements, the gauge surface 29 terminating at an end thereof remote from the blade at a junction 58 with a gauge pad end wall 56, wherein the gauge pad 28 carries a single cutter 62 having a face 64 and a cutting edge 65 located radially inward of the gauge surface 29, and wherein the junction 58 of the gauge surface 29 and the gauge pad end wall 56 crosses, radially, between the face 64 of the cutter 62 and the wall 30 of the borehole 32.

Abstract: A reaming tool is disclosed which includes a body having reaming blades affixed thereto at azimuthally spaced apart locations around a circumference of the body. The reaming blades each have at least one cutter attached thereto at selected positions and orientations on each of the blades to minimize a net lateral force developed by the reaming tool. The tool includes a pilot hole conditioning section comprising a plurality of azimuthally spaced apart pilot blades affixed to the body longitudinally ahead of the reaming blades.

Abstract: A drag type casing mill/drill bit for down hole milling of a casing window and lateral drilling of a bore hole in an earth formation comprises a bit body adapted to be rotated in a defined direction. The bit body includes an operating end face having a plurality of radially extending blades formed as a part of the operating end face of the bit body. A plurality of primary cutting elements are individually mounted in pockets in one of the plurality of blades. In addition, a plurality of secondary ridge structures are mounted to each of the plurality of blades interspersed with the plurality of primary cutting elements in a pattern such that as the bit body rotates the secondary ridge structures contact the casing or the earth formation thereby protecting the primary cutting elements and allowing continuous substantially smooth casing milling and earth formation drilling.

Abstract: A drill bit for use in horizontal boring includes a bit body with a central axis of rotation including a forwardmost pilot section, a reaming section rearwardly of the pilot section including a forwardly inclined arcuate steering surface and a plurality of gauge cutting teeth disposed rearwardly of the pilot section in opposed relationship to the inclined steering section, the gauge teeth extending farther from the central axis in a radial direction than the steering section such the arcuate steering section lies entirely within a circular profile corresponding to the path of the gauge teeth when the bit is rotated 360° and a coupling section at a rear end portion of the body configured for attachments to an adjacent component of the drill sting.

Abstract: A back reaming tool is disclosed which includes a tool body adapted to be coupled to a drill string, and at least one roller cone rotatably mounted to a leg and having cutting elements disposed thereon. The leg is removably coupled to the tool body. The at least one roller cone is open at only one axial end thereof.

Abstract: A downhole reaming tool is disclosed having radially extendible cutting blades extended by hydraulic pressure directed into the tool to force an inner tubular body having protrusions thereon with tapered sides forward against the walls of mating recesses defined in such radially extendible cutting blades to extend the blades.

Abstract: A hole opener and method for using same which allows for a greater number of cone utters to be attached to the hole opener. The support structure provided by the present invention uses a barrel which is attached to the drill stem to effectively increase the diameter of the drill stem so that additional cutters may be attached to the hole opener. Using the barrel structure, the structural integrity of the tool is not compromised, and a strong support structure for the cutters is provided. The cone cutters may be removable from the barrel. The removable structure is provided by placing a bolt inside the segments which is used to mate the segment with a pocket attached to the barrel. This results in a very versatile tool in that the same boring head may be used for boring various types of materials. The barrel structure of the present invention also provides a means for trapping cones inside the barrel to prevent the cone cutters from being left inside the hole.

Abstract: A reamer for drilling a hole having a diameter larger than a pass through diameter in one aspect includes a body having reaming blades affixed at azimuthally spaced apart locations. These blades have cutters attached at selected positions. An outermost surface of each blade conforms to a radially least extensive one, from a longitudinal axis of the reamer, of a pass through and a drill circle, The drill circle is substantially coaxial with the axis. The pass-through circle is axially offset from the drill circle and defines a section wherein the pass-through circle extends from the axis past the drill circle, so that cutters disposed on the reaming blades in the section drill at full drill diameter, while avoiding wall contact at the pass-through diameter. In another aspect, the reamer includes a pilot hole conditioning section including azimuthally spaced apart blades affixed to the body longitudinally ahead of the reaming blades.

Abstract: A reaming tool for enlarging an earth bore in a subsurface formation in which a sub is connected to a lower end of a drill string and elongated cutter blades are pivotally secured to a lower end of the body which have cutter elements preferably in the form of rotatable cutter disks along their leading edges and a fluid delivery hose leads into fluid passages in each of the cutter blades to supply fluid under pressure to a series of fluid discharge nozzles associated with the cutter elements.

Abstract: A drill bit assembly for earth boring operations in which a sub is connected to a lower end of a drill string and elongated cutter blades are pivotally secured to a lower end of the body which have cutter elements preferably in the form of rotatable cutter disks along their leading edges and a fluid delivery hose leads into fluid passages in each of the cutter blades to supply fluid under pressure to a series of fluid discharge nozzles associated with the cutter disks.

Abstract: A rotary drag bit suitable for directional drilling. The bit includes a bit body from which extend radially-oriented blades carrying PDC cutters. The blades extend to primary gage pads, above which secondary gage pads are either longitudinally spaced or rotationally spaced, or both, defining a gap or discontinuity between the primary and secondary gage pads through which drilling fluid from adjacent junk slots may communicate laterally or circumferentially. Longitudinally leading edges of the secondary gage pads carry cutters for smoothing the sidewall of the borehole. The cutters are preferably configured and oriented so as to provide a relatively aggressive cutting edge to the formation in both longitudinal and rotational directions of bit movement, the cutting edges lying adjacent cutting surfaces preferably disposed at negative rake angles to the formation material of the borehole wall for enhanced durability.

Abstract: A method is disclosed comprising the steps of locating, on a surface of a downhole component, a plurality of thermally stable polycrystalline diamond (TSP) bearing elements, and then applying to the surface a settable facing material which bonds to the surface between the bearing elements and embraces the elements to hold them in place. A method in which bearing elements each comprising a body of TSP at least partly surrounded by a layer of less hard material are secured to the surface by welding or brazing part of the surface of each bearing element which comprises said less hard material to said component is also described.

Abstract: A rock drilling tool includes a pilot bit screw threaded into a front end of a drill rod. A reamer is mounted on the outside of the pilot bit. The reamer includes a central opening having a front portion and a rear portion. The front portion is connected to the pilot bit, and the rear portion constitutes a stiffening sleeve which extends around the outside of the drill rod.

Abstract: A rotary drill bit suitable for directional drilling. The bit includes a bit body from which extend legs carrying rotatable cutters. The body carries primary gage pads, above which secondary gage pads may be either longitudinally spaced or rotationally spaced, or both. Longitudinally leading edges of the gage pads may carry cutting structure for smoothing the sidewall of the borehole. Cutting structure may likewise be disposed on the trailing ends of the gage pads to provide an up-drill capability to facilitate removal of the bit from the borehole. The gage pads provide enhanced bit stability and reduced side cutting tendencies, as well as reducing lateral loading on the rotatable cutters and associated bearing structure and seals. The invention also has utility in bits not specifically designed for directional drilling.

Abstract: A drill pipe having a length of conduit having a first diameter, a first and a second end portion, where each end portion has a second diameter greater than the first diameter. An enlarged portion is located between and spaced from the first and second end portions, where the enlarged portion comprises a central section which has a third diameter greater than the first diameter. The central section has a substantially smooth external surface, and two end sections, one end section at either end of the central section, which vary in diameter between the first and the third diameter. One of the end sections has a spiral formation thereon.

Abstract: A drill bit and method of drilling employing a gage definition region on the bit to relatively gradually and incrementally increase the diameter of the borehole being drilled from a diameter that is cut by fixed face cutters or rolling cone cutters on the bit body to a larger diameter. Preferably, the diameter of the gage definition region defined by cutting structures thereon varies along a longitudinal length of the bit, being smallest nearest the leading end of the bit. In a preferred embodiment, the gage definition region includes a plurality of helically arranged cutting elements disposed around the perimeter of the gage definition region. Such a configuration of cutting elements helps to reduce the loading on, and wear of, each individual cutting element. Thus the effective life of the bit is extended by enhancing its ability to drill the borehole to the gage diameter over a longer interval than may be achieved with conventional bit designs.

Abstract: A drill bit for boring a bore hole in an earthen formation comprises: a bit body having a pin end, a cutting end and a longitudinal bit axis and including at least two legs extending from the cutting end, each of the legs including a bearing that rotatably supports a cutter cone. The bit body further includes a fluid flow system, including a flowway in said pin end that is in fluid communication with at least one exit port in the cutting end, the exit port being defined by a nozzle boss and disposed adjacent one of the legs. Each of the legs includes a leading side surface, a trailing side surface, and a center panel, and at least one of said legs is asymmetric such that its trailing side surface is larger than its leading side surface. The present bit can also include a lubricant system that has its opening in the trailing side of the leg, and can further include various wear resistant coatings and inserts on its surface.

Abstract: A rotary drag bit being suitable for directional drilling. The bit includes a bit body from which extend radially-oriented blades carrying PDC cutters. The blades extend to primary gage pads, above which secondary gage pads are either longitudinally spaced or rotationally spaced, or both, defining a gap or discontinuity between the primary and secondary gage pads through which drilling fluid from adjacent junk slots may communicate laterally or circumferentially. Longitudinally leading edges of the secondary gage pads may carry cutters for smoothing the sidewall of the borehole. The tandem primary and secondary gage pads provide enhanced bit stability and reduced side cutting tendencies. The discontinuities between the primary and secondary gage pads enhance fluid flow from the bit face to the borehole annulus above the bit, promoting formation cuttings removal. The tandem gage arrangement also has utility in conventional bits not designed specifically for directional drilling.

Abstract: The present invention is an apparatus for use in drilling operations. It uses an under-reamer having a plurality of elongated arms with cutting elements at the ends of the arms for enlarging a previously drilled borehole drilled by a drill bit. One or more stabilizers in close proximity to the under-reamer provide stability to the under-reamer and the drill bit. The stabilizer could be rotating or non-rotating; and could be positioned between the under-reamer and the drill bit, or above the under reamer or above a directional device on the drillstring. The cutting arms are selectively operable to perform the enlargement. The stabilizer may be provided with members that closely fit the size of the borehole.

Abstract: This disclosure is directed to an improved drill collar having pin and box connection in an elongate hollow member. In cross-section, the drill collar is formed of a square billet defining three rectangular corners. The fourth corner is rounded thereby reducing the weight in that area and thereby creating an eccentered center of mass and mass moment of inertia. A cutter is located along one of the edges so that the cutter scuffs against the well borehole during rotation to thereby enhance circular configuration and to reduce key seating or deviation.

Abstract: A rotary drag bit being suitable for directional drilling. The bit includes a bit body from which extend radially-oriented blades carrying PDC cutters. The blades extend to primary gage pads, above which secondary gage pads are either longitudinally spaced or rotationally spaced, or both, defining a gap or discontinuity between the primary and secondary gage pads through which drilling fluid from adjacent junk slots may communicate laterally or circumferentially. Longitudinally leading edges of the secondary gage pads carry cutters for smoothing the sidewall of the borehole. The tandem primary and secondary gage pads provide enhanced bit stability and reduced side cutting tendencies. The discontinuities between the primary and secondary gage pads enhance fluid flow from the bit face to the borehole annulus above the bit, promoting formation cuttings removal. The tandem gage arrangement also has utility in conventional bits not designed specifically for directional drilling.

Abstract: A rotary drag bit including a gage design which facilitates steerability while preventing lateral displacement of the bit and attendant ledging of the borehole wall, and reams and conditions the borehole wall as the bit advances through the formation. The bit includes an elongated gage section comprised of a plurality of circumferentially spaced gage pads, each including mutually longitudinally displaced gage pad segments of varying lateral aggressiveness, or tendency to cut formation material under application of load.

Abstract: A directional horizontal boring backreamer for enlarging an initial bore, including three equally spaced radially extending wings attach to a common axle, equally spaced around the axle, each wing including a plurality of cutters positioned along the wing for enlarging the bore, and attached to each wing is a gusset plate welded to the axle at the juncture of the wing and axle and to the wing for added bending strength to the wing. The gusset plates also including an internal passage way from the center passage of the axle to the outer edge of the wings to support and supply a series of fluid jets supplied by fluid for assistance in cutting during the backreaming operation.

Abstract: A 2-stage underreamer for use in a subterranean wellbore includes a unitary body having upper and lower blades mounted in slots formed perpendicular to each other in the body. Separate upper and lower piston assemblies are provided for driving the blades respectively from a storage configuration in which they are located substantially completely within the slots to a use position. The blades each include a steel arm having mounted thereon a base of tungsten nickel cobalt matrix in which diamond and/or tungsten carbide inserts are provided. A signal is given to the surface that the blades are in their extended position by changing the mud.

Abstract: A drilling assembly for drilling holes in subsurface formations comprises a drill bit 10, a drive unit 12 including a housing and a rotor 11 operatively coupled to the drill bit to rotate the drill bit relative to the housing, and a modulated bias unit 14 coupled to rotate with the drive unit housing and apply a lateral bias thereto in synchronism with rotation of the housing. The modulated bias unit 14 comprises one or more hydraulic actuators including members 16 which, in use, bear against the sides of the borehole, and means for modulating the pressure of fluid supplied to the actuators in synchronism with rotation of a component of the drilling assembly, and in selected angular phase relation thereto, whereby each hydraulic actuator is actuated in a selected rotational position of the component.

Abstract: A cutter for a trenchless boring apparatus includes a mount having a first end to be coupled to a free end of a drill pipe. A plurality of cutting teeth are secured to the mount with the teeth arranged in a helical pattern surrounding an axis of the mount.

Abstract: A back reamer apparatus is configured to be attached to a pipe section of a drilling rig for back reaming and compacting a pilot bore. The back reamer apparatus includes a body having a front end configured to be coupled to the pipe section, and at least three planar side walls configured to form a pyramid-shaped section which is tapered downwardly toward the front end of the body to compact the soil and form an enlarged bore upon rotation of the body by the drilling rig. The body is formed to include an internal passageway for receiving a drilling fluid. Each of the side walls is formed to include at least one aperture in communication with the passageway to permit the drilling fluid to pass through the at least one aperture formed in each side wall.

Abstract: An underreamer which may be mounted on a core drill to allow single phase underreaming or creation of a bore hole of larger diameter beneath a pilot hole. A plurality of levers are powered by a plurality of corresponding jacks which are adapted to exert pressure on the levers in order to cause them to extend beyond the periphery of the expander body. Each lever contains at least one roller-cutter rotatably mounted to the lever so that when the levers are forced outward, the roller-cutters crush rock beyond the periphery of the expander body and thus underream the bore hole.

Abstract: A reamer bit for reaming in earth formations. In one embodiment, the bit provides a plurality of levels of stems onto which may be disposed semi-spherical reamer cutters. The cutters are arranged such that they are circumscribable within a sphere. The levels of stems may include as few as two stems or several. This arrangement provides for a significantly larger cutting area which, in turn, prevents premature bit wear. As s further advantage, the bit may include several levels with roller cutters having progressively increasing diameter to provide an arrangement which subscribes to a generally triangular formation.

Abstract: A reamer bit for reaming in earth formations. In one embodiment, the reaming bit provides spherical reaming faces with replaceable cutting bit holders. The holders include cutting bits. The spherical reaming faces are not appreciably susceptible to drag during a reaming procedure and premature wear of the faces is alleviated by the provision of bits. The overall result is a substantially improved apparatus for reaming which assists in cost reductions for the process.

Abstract: An anti-whirl underreamer comprising a body configured for connection to a drillstring, at least two arms carried by the body which are extendable between a retracted position and a projected position, a movable piston and biased spring assembly for moving the arms, a plurality of cutting elements carried by one of the arms for cutting an axially extending cylindrical sidewall of the borehole within a subterranean formation and for applying a resultant radial force to the body as it rotates, and a low friction bearing region carried by another arm for transmitting the resultant radial force from the body to the sidewall of the borehole during rotation of the underreamer within the borehole. The cutting elements are positioned so that the resultant radial force developed is of sufficient magnitude and direction to substantially maintain the low friction bearing region in contact with the sidewall of the borehole as the underreamer is rotated within the borehole.