Abstract: A method for forming a drill bit body is disclosed which comprises infiltrating powdered tungsten carbide with a binder alloy in a mold. The mold has therein at least one displacement adapted to form a mounting pad for a cutting element. The displacement comprises a substantially cylindrical body having a diameter selected to substantially conform to a radius of the cutting element and a projection adapted to form a relief groove under a position of a diamond table in the cutting element when the cutting element is mounted on the pad. The width of the relief groove is selected so that the relief groove extends back from an outer surface of the bit body at least about 40 percent of that portion of a thickness of the diamond table which does not extend past the outer surface.

Abstract: A variety of large diameter PDC cutters for use in drill bits are disclosed. Specifically, various PDC cutters having a diameter between 19.0 mm and 25.0 mm are disclosed. The various PDC cutters disclosed include an elliptical PDC cutter, wherein a major diameter of the elliptical cutter is selected from a range of 19.0 mm to 25.0 mm, a circular PDC cutter, wherein a diameter of the circular cutter falls between 19.0 mm and 25.0 mm, and a non-planar substrate cutter, wherein a diameter of the non-planar cutter falls between 19.0 mm and 25.0 mm. Additionally, the thickness of the diamond table is increased as compared to prior art PDC cutters. The increase in diamond table thickness results in improved durability and performance.

Abstract: A method for forming a drill bit body is disclosed which comprises infiltrating powdered tungsten carbide with a binder alloy in a mold. The mold has therein at least one displacement adapted to form a mounting pad for a cutting element. The displacement comprises a substantially cylindrical body having a diameter selected to substantially conform to a radius of the cutting element and a projection adapted to form a relief groove under a position of a diamond table in the cutting element when the cutting element is mounted on the pad. The width of the relief groove is selected so that the relief groove extends back from an outer surface of the bit body at least about 40 percent of that portion of a thickness of the diamond table which does not extend past the outer surface.

Abstract: A novel drill bit includes a cutting reamer portion that cuts to gage diameter, and a pilot portion that cuts to a radius about 50%-80% of the reamer portion. The pilot portion extends downward from the reamer portion to create a distinct cutting area including pilot. The torque and weight on bit is evenly distributed between said pilot portion and said reamer portion of said drill bit by iterative adjustment of criteria such as backrake, siderake, cutter height, cutter size, and blade spacing.

Abstract: A drill bit including improved gage pads is particularly adapted for side cutting a borehole wall. In a preferred embodiment, the drill bit gage pads alternate between an active gage pad with a cutting surface portion and a non-active gage pad with a wear-resistant surface. Gage pad cutting elements placed on a first active gage pad cooperate with gage pad cutting elements placed on other active gage pads. What results is a contiguous series of overlapping cutting elements suitable to cut the borehole wall. Non-active gage pads are preferably placed between the active cutting gage pads. These non-active gage pads have a wear-resistant surface (such as steel or diamond insert) that extends to the gage diameter. These non-active gage pads help to maintain borehole size and prevent undue torque being placed on the drill bit.

Abstract: A novel drill bit includes a cutting reamer portion that cuts to gage diameter, and a pilot portion that cuts to a radius about 50%-80% of the reamer portion. The pilot portion extends downward from the reamer portion to create a distinct cutting area including pilot. The torque and weight on bit is evenly distributed between said pilot portion and said reamer portion of said drill bit by iterative adjustment of criteria such as backrake, siderake, cutter height, cutter size, and blade spacing.

Abstract: A drill bit is disclosed which includes a bit body having a plurality of blades thereon. The blades have a plurality of cutting elements affixed thereon at selected positions. The cutting elements are disposed into at least two groups. A first one of the groups has at least 60 percent of the cutting elements therein disposed at a first mean backrake angle. A second group has at least 60 percent of the cutting elements therein disposed at a second mean backrake angle. The second backrake angle is at least about fifteen degrees more than the first backrake angle. A bottom hole coverage of the cutting elements in the second group is at least about eighty percent.

Abstract: A roller cone drill bit having selected left hand walk is disclosed. The bit includes a bit body adapted to couple to a drill string, and a plurality of legs depending from the bit body. Each leg has a roller cone rotatably mounted thereon. Each cone includes a plurality of cutting elements thereon. At least one cone has a nose point of its profile displaced radially inward with respect to a nose point of the profile of the other cones. A roller cone drill bit having selected right hand walk is also disclosed. The bit include a bit body adapted to couple to a drill string, and a plurality of legs depending from the bit body. Each leg has a roller cone rotatably mounted thereon, each cone including a plurality of cutting elements thereon defining a profile. At least one cone has a nose point of the profile displaced radially outward with respect to a nose point of the profile of the other cones.

Abstract: A fixed cutter drill bit particularly suited for plastic shale drilling includes rows of cutter elements arranged so that the cutting tips of the cutters in a row are disposed at leading and lagging angular positions so as to define a serrated cutting edge. The angular position of the cutting tips of cutters in a given row may be varied by mounting cutters with different degrees of positive and negative backrake along the same blade. Preferably, within a segment of a given row, the cutters alternate between having positive backrake and negative backrake while the cutters mounted with positive backrake are more exposed to the formation material than those mounted with negative backrake. Nozzles are provided with a highly lateral orientation for efficient cleaning. The positive backrake cutter elements have a dual-radiused cutting face and are mounted so as to have a relief angle relative to the formation material.

Abstract: A drill bit is disclosed which includes a bit body having a plurality of blades thereon. The blades have a plurality of cutting elements affixed thereon at selected positions. The cutting elements are disposed into at least two groups. A first one of the groups has at least 60 percent of the cutting elements therein disposed at a first mean backrake angle. A second group has at least 60 percent of the cutting elements therein disposed at a second mean backrake angle. The second backrake angle is at least about fifteen degrees more than the first backrake angle. A bottom hole coverage of the cutting elements in the second group is at least about eighty percent.

Abstract: A variety of large diameter PDC cutters for use in drill bits are disclosed. Specifically, various PDC cutters having a diameter between 19.0 mm and 25.0 mm are disclosed. The various PDC cutters disclosed include an elliptical PDC cutter, wherein a major diameter of the elliptical cutter is selected from a range of 19.0 mm to 25.0 mm, a circular PDC cutter, wherein a diameter of the circular cutter falls between 19.0 mm and 25.0 mm, and a non-planar substrate cutter, wherein a diameter of the non-planar cutter falls between 19.0 mm and 25.0 mm. Additionally, the thickness of the diamond table is increased as compared to prior art PDC cutters. The increase in diamond table thickness results in improved durability and performance.

Abstract: A drill bit including improved gage pads is particularly adapted for side cutting a borehole wall. In a preferred embodiment, the drill bit gage pads alternate between an active gage pad with a cutting surface portion and a non-active gage pad with a wear-resistant surface. Gage pad cutting elements placed on a first active gage pad cooperate with gage pad cutting elements placed on other active gage pads. What results is a contiguous series of overlapping cutting elements suitable to cut the borehole wall. Non-active gage pads are preferably placed between the active cutting gage pads. These non-active gage pads have a wear-resistant surface (such as steel or diamond insert) that extends to the gage diameter. These non-active gage pads help to maintain borehole size and prevent undue torque being placed on the drill bit.

Abstract: A drill bit with dropping tendencies includes an active region, a passive region, a biased mass distribution, an uneven torque generation, and an imbalance force vector directed toward the middle of the active region. Cutting elements in the active region of the drill bit may be more aggressive than those in the passive region through manipulation of, e.g., backrake angle, blade length, cutter sizes, blade angles and bit profile. The imbalance force vector may be achieved by manipulation of bit geometric parameters such as cutter radial position, angular position, longitudinal position, and rake angle.

Abstract: A drill bit including improved gage pads is particularly adapted for side cutting a borehole wall. In a preferred embodiment, each gage pad preferably includes a cutting surface portion and a wear-resistant surface. Gage pad cutting elements placed on a first gage pad cutting surface portion cooperate with gage pad cutting elements on other gage pads to reduce the torque on each gage pad cutting surface. The cutting elements may be made more aggressive by the reduction of a wear-resistant surface trailing the cutting elements. The wear-resistant surface on the first gage pad is varied with the wear-resistant surface on other gage pads to yield the wear-resistant advantages of previous gage pads.

Abstract: A fixed cutter drill bit particularly suited for plastic shale drilling includes rows of cutter elements arranged so that the cutting tips of the cutters in a row are disposed at leading and lagging angular positions so as to define a serrated cutting edge. The angular position of the cutting tips of cutters in a given row may be varied by mounting cutters with different degrees of positive and negative backrake along the same blade. Preferably, within a segment of a given row, the cutters alternate between having positive backrake and negative backrake while the cutters mounted with positive backrake are more exposed to the formation material than those mounted with negative backrake. Nozzles are provided with a highly lateral orientation for efficient cleaning. The positive backrake cutter elements have a dual-radiused cutting face and are mounted so as to have a relief angle relative to the formation material.

Abstract: A supporting substrate for supporting a diamond layer on a cutting element is disclosed which has an irregular surface defining the interface between the substrate and the diamond layer. The irregularities in the surface may have varying amplitudes, varying frequencies, or both and can vary according to defined mathematical expressions. The irregularities may assume recognizable geometric forms, such as spiral, circle or wave configurations, or may be arranged in an irregular manner. The surface is constructed with or without a plane of symmetry and may have different average amplitudes and/or frequencies in different areas.

Abstract: A drill bit adapted to walk predictably during drilling is disclosed, comprising: a bit body having a longitudinal axis and a bit face having an active zone and a passive zone, and a plurality of cutters on the bit face, a first portion of said cutters being positioned in the active zone and a second portion of said cutters being positioned in the passive zone, the first portion of cutters being more aggressive than the second portion. This the difference in aggressiveness of cutters in the first and second portions is achieved by maximizing the effect of one or more of seven features of the bit. These features include: cutter size, cutter tip profile, blade relationship, cutting structure, back rake, gage pad design and balance. Application of the principles of the present invention result in a large imbalance vector being oriented toward the leading half of the active zone.

Abstract: A supporting substrate for supporting a diamond layer on a cutting element is disclosed which has an irregular surface defining the interface between the substrate and the diamond layer. The irregularities in the surface comprise closed loops that may vary in amplitude, frequency or both. The irregularities may comprise ridges or grooves or a combination of ridges and grooves.

Abstract: A polycrystalline diamond cutter having a coating of refractory material applied to the polycrystalline diamond surface increases the operational life of the cutter. The coating typically has a thickness in the range of from 0.1 to 30 .mu.m and may be made from titanium nitride, titanium carbide, titanium carbonitride, titanium aluminum carbonitride, titanium aluminum nitride, boron carbide, zirconium carbide, chromium carbide, chromium nitride, or any of the transition metals or Group IV metals combined with either silicon, aluminum, boron, carbon, nitrogen or oxygen. The coating can be applied using conventional plating or other physical or chemical deposition techniques.

Abstract: A fixed cutter drill bit includes cutter elements mounted in sets on the bit face. A cutter element set includes at least three cutters with cutting faces having at least two different curvatures. The cutter elements of the set are mounted on various blades of the bit such that, in rotated profile, the cutting profile of a larger and a smaller cutter element overlap, and such that the smaller cutter element is flanked by larger sized cutters. The bit exhibits increased stability, before and after wear has occurred. The large cutters provide for efficient shearing while the smaller cutters may provide prefracturing in certain formations.