Camco International (uk) Limited

Camco Drilling Group Limited

Camco International, Inc.

Camco Drilling Group Limited of Hycalog

Camco Drilling Group Ltd. of Hycalog

Andrew D Murdock

Alex Newton

Malcolm Roy Taylor

John M Fuller

Douglas Bruce Caraway

John M Clegg

Steven Taylor

David Truax

Stephen Martin Evans

Nigel Dennis Griffin

Brian P Jarvis

Dean Travers Watson

Daniel J Sarik

Clive Jarvis

Steve Barton

David John Jelley

Haydn Lamb

Michael Barnes

John Deane

Michael Tomczak

Alex Nexton

A drill bit for drilling a borehole, the drill bit comprising a bit body having an axis of rotation , a leading face, a plurality of blades upstanding from the leading face, at least one of the blades terminating 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, the gauge surface terminating at an end thereof remote from the blade at a junction with a gauge pad end wall , wherein the gauge pad carries a single cutter having a face and a cutting edge located radially inward of the gauge surface , and wherein 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

Cutting structure for earth boring drill bits

A method of predicting the walk rate of a design of rotary drag-type drill bit of the kind where the leading face of the bit body is formed with a central depression, or cone, comprises the steps of: calculating the cone volume V.sub.cone of the bit; calculating that ratio ##EQU1## of the total torque generated by the cutters on the bit which is attributable to those cutters which are mounted in said cone; calculating a Walk Factor ##EQU2## and then determining the predicted walk rate W of the bit from a graph, or other database, relating previously established values of F for other drill bits to the respective walk rates W for those drill bits.

Method of determining characteristics of a rotary drag-type drill bit

A method of determining wear characteristics of a rotary drag-type drill bit comprises the steps of: determining the location and shape of a datum profile for the cutters on the bit body: determining the location and shape of a reference profile located inwardly of the datum profile; and ascertaining the volume of superhard material in the cutters between the datum profile and the reference profile. The volume of superhard material in the cutters at discrete radial locations is then plotted against the radial distance of the material from the axis of rotation of the bit body. The predicted wear rate WR.sub.r of superhard material at radius r is also calculated as a function of the volume and the predicted wear rate is plotted against r. The type and location of the cutters may then be modified, if necessary, to give a wear rate which is substantially constant across the radius of the drill bit.

Formation engaging elements are moveably mounted onto a drill bit. Such elements may be used to protect other rigidly mounted formation engaging elements from impacts that occur during use of the drill bit, or they may be used to alter the aggressiveness of the drill bit when used in directional drilling operations.

Rotary drill bit having moveable formation-engaging members

A torque transmitting device for use with a rotary drill bit connected to a drill collar, comprises a first member connected to the drill collar, a second member connected to the drill bit, and coupling means connecting the two members together for rotation about a common central axis. The coupling means permits limited relative rotation between the members about the axis, but provides a resistance to rotation of the first member relative to the second member in a forward drilling direction which is greater than its resistance to relative rotation in the reverse direction. The comparatively lower resistance to rotation in the reverse direction prevents momentary reverse rotation of the drill collar, due for example to torsional oscillations, being transmitted to the drill. bit. This reduces the likelihood of damage to the cutters on the drill bit, which might otherwise result from such momentary reverse rotation of the bit.

Torque transmitting device for rotary drill bits

A rotary drill bit for use in drilling holes in subsurface formations comprises a bit body having a leading face and a gauge region, a number of blades formed on the leading face of the bit and extending outwardly away from the axis of the bit so as to define between the blades a number of fluid channels leading towards the gauge region, a number of cutting elements mounted side-by-side along each blade, and a number of nozzles in the bit body for supplying drilling fluid to the fluid channels for cleaning and cooling the cutting elements. In each of the fluid channels, adjacent the gauge region, is an opening into an enclosed passage which passes internally through the bit body to an outlet which, in use, communicates with the annulus between the drill string and the wall of the borehole being drilled. The gauge region of the drill bit comprises a substantially continuous bearing surface which extends around the whole of the gauge region.

Rotary drill bits

A drill bit comprises a main body part having a shank for connection to a drill string, an end face, an internal passage for supplying drilling fluid to the end face, a number of blades extending from the end face outwardly and longitudinally of the central axis of rotation of the bit, and a number of cutters mounted on each said blade. Each blade comprises a central metal core at least partly surrounded by solid infiltrated matrix material. A method of manufacturing such a drill bit includes the steps of forming a main body part from metal, applying to the outer surface of the main body part a coating layer of wax which liquefies at elevated temperature, applying to the coated body part mold-forming material to provide a self-supporting mold surrounding the coated body part, and raising the temperature of the body and surrounding mold sufficiently to liquefy the coating material. The liquefied coating is then drained from the mold, and the cavities left by the coating material are packed with powdered matrix material, which is then infiltrated with a binder alloy at elevated temperature to form a solid infiltrated matrix layer, on the bit body part, corresponding to the layer of wax previously applied.

Matrix hard facing by lost wax process

A rotary drill bit, for drilling holes in subsurface formations, comprises a bit body, cutting structures mounted on the bit body, and a fluid supply system for supplying drilling fluid to the surface of the bit body, to cool and clean the cutting structures. The fluid supply system comprises a number of nozzles mounted in the bit body, a main passage in the bit body and a number of auxiliary passages leading from the main passage to the nozzles. Some or all of the passages are at least partly lined with an erosion-resistant lining material. The lining material may comprise a hard facing applied to the internal surface of a preformed passage or a rigid tube which itself defines the internal surface of the passage.

Rotary drill bit with hardfaced fluid passages and method of

A rotary drill bit for use in drilling holes in subsurface formations comprises a bit body having a leading face and a gauge region, a number of blades formed on the leading face of the bit and extending outwardly away from the axis of the bit so as to define between the blades a number of fluid channels leading towards the gauge region, a number of cutting elements mounted side-by-side along each blade, and a number of nozzles in the bit body for supplying drilling fluid to the fluid channels for cleaning and cooling the cutting elements. In at least one of the fluid channels, adjacent the gauge region, is an opening into an enclosed passage which passes internally through the bit body to an outlet which, in use, communicates with the annulus between the drill string and the wall of the borehole being drilled. The portion of the gauge region outwardly of the opening comprises a bearing surface which, in use bears against the wall of the bore hole and extends across the width of the channel.

A drill bit comprises a main body part having a shank for connection to a drill string, an end face, an internal passage for supplying drilling fluid to the end face, a number of blades extending from the end face outwardly and longitudinally of the central axis of rotation of the bit, and a number of cutters mounted on each said blade. Each blade comprises a central metal core at least partly surrounded by solid infiltrated matrix material. A method of manufacturing such a drill bit includes the steps of providing a metal mandrel having said shank and internal passage, and providing on the mandrel, so as to be supported by it, a number of blade cores each having a portion extending outwardly and longitudinally of the central axis of the mandrel, casting infiltrated matrix material around at least a part of each core and around at least a part of the mandrel to form the blades, and then removing portions of the cores so as to detach each core from support by the mandrel to leave within each blade a core which is substantially wholly supported by the surrounding matrix material.

In or relating to rotary drill bits

A rotary drill bit comprises a bit body, a shank for connection to a drill string, a plurality of cutters mounted on the bit body, and a gauge structure which extends around the bit body and, in use, engages the surrounding formation forming the sides of the borehole being drilled. At least a section of the gauge structure is rotatably mounted on the bit body so that, in use, the gauge section may remain substantially non-rotating in engagement with the formation while the bit body rotates relative to it. The external surface of the non-rotating gauge section may be formed with longitudinal grooves to permit the flow of drilling fluid past the gauge section to the annulus. Alternatively the outer surface of the gauge section may be generally cylindrical, in which case internal passages are provided through the gauge section, and/or the bit body, for the flow of drilling fluid past the gauge section to the annulus.

Rotary drill bit having a non-rotating gauge section

A rotary drill bit for drilling holes in subsurface formations comprises a bit body having a shank for connection to a drill string, a number of circumferentially spaced blades on the bit body each extending outwardly away from the central axis of rotation of the bit, a number of cutters mounted side-by-side along each blade, and a passage in the bit body for supplying drilling fluid to the surface of the bit for cleaning and cooling the cutters. The blades comprise alternating primary and secondary blades. The cutters on the primary blades are primary cutters which are located at different radial distances from the bit axis so as to define a cutting profile which, in use, covers substantially the whole of the bottom of the bore hole being drilled. At least the majority of the cutters on the secondary blades are secondary cutters each of which is located at substantially the same radial distance from the bit axis as an associated primary cutter on the preceding primary blade.

A rotary drill bit comprises a bit body having a shank for connection to a drill string, a plurality of cutters mounted on the bit body, each cutter having a cutting face, and means for supplying drilling fluid to the surface of the bit body to cool and clean the cutters. At least some of the cutters are lateral cutters located to act sideways on the formation being drilled, and the cutting faces of such lateral cutters are orientated to exhibit negative side rake and negative top rake with respect to the surface of the formation. The negative side rake angle is greater than 20.degree. and may be as much as 90.degree., and the negative top rake angle is also more than 20.degree.. A single cutter may include two cutting faces at different negative side rake angles, e.g. the cutter may comprise a generally cylindrical substrate formed at one end with two oppositely inclined surfaces meeting along a ridge, a facing table of polycrystalline diamond being bonded to the substrate surfaces and extending over the ridge.

A rotary drilling tool has a plurality of cutters mounted on the tool body and formed with cutting edges defining a cutting profile. The cutters include at least two concentric arrays of primary preform polycrystalline diamond cutters which are radially spaced so as to define an annular groove in the cutting profile, between the two arrays. The deepest part of the groove in the cutting profile is defined by secondary preform polycrystalline diamond cutters located at a radial position which is intermediate the radial positions of the two arrays of primary cutters, so that in use the secondary cutters remove the tops of annular ridges of formation left between the arrays of primary cutters.

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Stroud, United Kingdom

Andrew D Murdock