Fixed cutter drill bit for abrasive applications

Abstract

The invention provides a fixed cutter drill bit for drilling through unconsolidated, highly abrasive formations. The bit includes a bit body having a cutting face and a side portion. The bit body comprising carbide matrix material. A plurality of blades azimuthally spaced about the cutting face and a plurality of cutters disposed along the blades. At least one gage pad is disposed along a side of the bit body and includes wear resistant gage elements formed of a material more wear resistant than the matrix material forming a portion of the gage pad. The wear resistant elements have a rounded surface and are embedded in gage pad material proximal a leading edge of the gage pad to provide a rounded wear-resistant edge or surface proximal the leading edge.

1 . A drill bit for drilling through an earth formation comprising:
 a bit body having a cutting face and a side portion, the bit body comprising carbide matrix material; and   a plurality of blades azimuthally spaced about the cutting face;   wherein at least one of the plurality of blades is configured such that at least a portion of said blade has a wider blade base than a blade top in the axial direction and at least a portion of the surface of said blade top comprises an ultrahard material impregnated therein.   
     
     
         2 . The drill bit of  claim 1 , wherein said blade increases in thickness in a radial direction away from the center of the bit body. 
     
     
         3 . The drill bit of  claim 1 , wherein each of the plurality of blades is configured along a portion thereof to have a wider blade base than a blade top. 
     
     
         4 . The drill bit of  claim 1 , wherein said portion of said blade has a blade front face angle or a blade back face angle greater than about 5°. 
     
     
         5 . The drill bit of  claim 1 , wherein said portion of said blade has a blade front face angle or a blade back face angle in the range of from about 5° to about 10°. 
     
     
         6 . The drill bit of  claim 4 , wherein said portion of said blade has a blade front or back face radius of curvature of least about 0.375 inches. 
     
     
         7 . The drill bit of  claim 1 , wherein said portion of said blade has a blade front or back face radius of curvature of least about 0.375 inches. 
     
     
         8 . The drill bit of  claim 1 , wherein the bit body further comprises at least one gage pad disposed along a side of the bit body and at least a portion of the bit body or at least one gage pad is coated with ultrahard material or comprises ultrahard material embedded in a surface thereof. 
     
     
         9 . The drill bit of  claim 1 , where the ultrahard material comprises diamond grit impregnated in the blade surface. 
     
     
         10 . The drill bit of  claim 9 , wherein the ultrahard material further comprises surface set diamonds embedded in the blade tops. 
     
     
         11 . The drill bit of  claim 10 , wherein the ultrahard material comprises diamond grit having a grain size of at least about 700 μm or more and natural diamond having a grain size in the range of from about 1 mm to about 3 mm. 
     
     
         12 . The drill bit of  claim 1 , wherein the ultrahard material comprises diamond grit having a grain size of at least about 700 μm or more. 
     
     
         13 . The drill bit of  claim 1 , wherein the ultrahard material comprises diamond grit having a grain size of at least about 850 μm or more. 
     
     
         14 . The drill bit of  claim 1 , wherein the ultrahard material comprises polycrystalline diamond. 
     
     
         15 . The drill bit of  claim 1 , wherein said blade further comprises a first matrix material and a second matrix material wherein the first matrix material has a different wear resistance that the second matrix material. 
     
     
         16 . The drill bit of  claim 1 , wherein the matrix material comprises tungsten carbide powder having an average grain size of about 60 μm or less formed with a metallic binder. 
     
     
         17 . The drill bit of  claim 1 , wherein the matrix material comprises a matrix powder including at least about 40% by weight tungsten carbide having an average particle size of between about 0.2 and 30 μm formed with a metallic binder. 
     
     
         18 . The drill bit of  claim 1 , wherein the matrix material comprises cast carbide in an amount of at least about 40% or more by weight. 
     
     
         19 . The drill bit of  claim 1 , wherein the drill bit further comprises a plurality of cutters disposed along at least one of the plurality of blades. 
     
     
         20 . The drill bit of  claim 19 , wherein selected cutters have a back rake angle of at least about 20°. 
     
     
         21 . The drill bit of  claim 20 , wherein selected cutters have a back rake angle is at least about 30°. 
     
     
         22 . The drill bit of  claim 21 , where the cutters increase in back rake angle from around 20° to about 30° or more along a profile of the bit toward gage. 
     
     
         23 . The drill bit of  claim 19 , wherein cutters proximal a gage region of the bit have a back rake angle greater than the back rake angle of cutters near a center of the bit. 
     
     
         24 . The drill bit of  claim 19 , wherein selected ones of the cutters have a side rake angle of greater than 0° degrees. 
     
     
         25 . The drill bit of  claim 19 , wherein the cutters on the bit are arranged in a short parabolic cutting profile. 
     
     
         26 . The drill bit of  claim 19 , wherein the cutters are positioned to minimize an imbalance force on the bit or a difference in work rate between cutters on the bit. 
     
     
         27 . The drill bit of  claim 19 , wherein cutters along a blade are arranged to form a helix angle of less than 5°. 
     
     
         28 . The drill bit of  claim 27 , wherein cutters along the blade are arranged to form a helix angle of 2° or less. 
     
     
         29 . The drill bit of  claim 19 , wherein at least one of the cutters comprises a bevel about a top periphery thereof, and wherein the bevel has width of at least about 0.012 inches and is at an angle of around 45° from a side surface of the cutter. 
     
     
         30 . The drill bit of  claim 19 , wherein a space between front faces of a majority of adjacent cutters on the cutting face is about 0.04 inches or less. 
     
     
         31 . The drill bit of  claim 30 , wherein at least some of the cutters positioned on the blades have an exposed substrate length of about 9 mm or less. 
     
     
         32 . The drill bit of  claim 19 , wherein at least some of the cutters have a diameter of at least about 19 mm. 
     
     
         33 . The drill bit of  claim 19 , wherein the cutter extent from the corresponding blade front face is less than or equal to about 0.06 inches. 
     
     
         34 . The drill bit of  claim 33 , wherein a majority of the cutters are arranged substantially flush with blade front faces. 
     
     
         35 . The drill bit of  claim 1 , wherein the bit comprises less than 8 blades. 
     
     
         36 . The drill bit of  claim 19 , wherein at least one of the cutters comprise a table of ultrahard material integrally formed with a carbide substrate comprising tungsten carbide particles formed with a metallic binder, and the substrate comprises a binder content of 12% by weight or less, a hardness of at least about 90 Ra, and a tungsten carbide content of at least about 88% by weight. 
     
     
         37 . The drill bit of  claim 36 , wherein the substrate has an average carbide particle size of about 3 microns or less. 
     
     
         38 . The drill bit of  claim 36 , wherein the substrate further comprises ultrahard particles impregnated in the substrate. 
     
     
         39 . The drill bit of  claim 36 , wherein a coating is disposed on at least a portion of the substrate and the coating comprises the ultrahard particles. 
     
     
         40 . The drill bit of  claim 19 , wherein at least one of the cutters comprises a polycrystalline diamond body bonded to a substrate and the polycrystalline diamond body is partially or entirely thermally stable. 
     
     
         41 . The drill bit of  claim 1 , wherein the drill bit further comprises at least one gage pad disposed along a side of the bit body having a circumferential width of at least about 2 inches or is arranged to provide a total gage pad with about the periphery of the bit body greater than or equal to about 30% of the circumference of the bit. 
     
     
         42 . The drill bit according to  claim 1 , wherein the drill bit further comprises at least one gage pad disposed along a side of the bit body and a plurality of rounded wear-resistant elements are aligned along a surface of the at least one gage pad proximal a leading edge or a trailing edge to provide rounded wear resistant protection. 
     
     
         43 . The drill bit of  claim 42 , wherein the wear resistant elements comprise elements selected from the group consisting essentially of thermally stable polycrystalline diamond elements, polycrystalline diamond elements, and grit hot-pressed inserts. 
     
     
         44 . The drill bit of  claim 42 , wherein a plurality of wear resistant elements are additionally disposed along a surface of the gage pad between the leading and trailing edges and comprise diamond enhanced inserts or TSP elements having diameters of at least about 13 mm. 
     
     
         45 . The drill bit of  claim 44 , wherein diamond enhanced inserts cover at least about 20% of the surface area of the gage pad. 
     
     
         46 . The drill bit of  claim 44 , wherein wear resistant elements cover at least about 50% of the outer surface of the gage pad. 
     
     
         47 . The drill bit of  claim 45 , wherein the diamond enhanced inserts have substrate lengths of at least about 13 mm and at least a portion of the substrate is embedded in the gage pad. 
     
     
         48 . The drill bit of  claim 42 , wherein the wear resistant elements are positioned proximal the leading edge and arranged to provide a wear resistant barrier along the leading edge that spans at least 75% of the gage pad length. 
     
     
         49 . The drill bit of  claim 42 , wherein the wear resistant elements are axially aligned along their longitudinal axes forming a rounded, substantially continuous and wear-resistant portion of the gage pad. 
     
     
         50 . The drill bit of  claim 42 , wherein wear resistant elements are also disposed proximal a bottom edge and a top edge of the gage pad. 
     
     
         51 . The drill bit of  claim 1 , wherein the drill bit further comprises at least one gage pad disposed along a side of the bit body, and wherein the at least one gage pad is slanted at an angle with respect to the longitudinal axis of the bit. 
     
     
         52 . The drill bit according to  claim 1 , wherein at least one back-reaming element is positioned along a surface of the bit to back-ream formation in a path of the bit when the bit is pulled from a wellbore. 
     
     
         53 . The drill bit of  claim 1 , wherein the drill bit comprises a plurality of heel surfaces each having at least one back reaming element disposed along the heel surface. 
     
     
         54 . The drill bit of  claim 53 , wherein the back reaming elements comprise PDC cutters having a diameter of at least about 13 mm. 
     
     
         55 . The drill bit of  claim 1 , further comprising fluid ports disposed in the bit body and oriented to direct fluid towards a center of a corresponding fluid channel or away from a corresponding blade front face. 
     
     
         56 . The drill bit of  claim 1 , further comprising a plurality of fluid ports generally disposed between the blades wherein a number of fluid ports is greater than the number of blades. 
     
     
         57 . The drill bit of  claim 1 , wherein the drill bit further comprises a fluid port and the fluid port comprises a diffuser nozzle. 
     
     
         58 . The drill bit of  claim 1 , wherein a coating of ultrahard material is applied to a portion of the bit body by chemical vapor deposition. 
     
     
         59 . A method for drilling an earth formation, comprising:
 Providing a drill bit according to  claim 1 ; and   rotating the drill bit to form a wellbore.   
     
     
         60 . A method of manufacturing a drill bit comprising:
 forming a bit body having a cutting face and a side portion, the bit body comprising carbide matrix material; and   forming a plurality of blades azimuthally spaced about the cutting face;   wherein at least one of the plurality of blades is configured such that at least a portion of said blade has a wider blade base than a blade top in the axial direction and at least a portion of the surface of said blade top comprises an ultrahard material impregnated therein.