Drill bits and methods for forming curved portions of a borehole

Abstract

Drill bits and methods for forming a curved portion of a borehole include a first plurality of cutting elements, such as tungsten carbide inserts, positioned at the outer or perimeter region of a bit face and oriented to bore in a direction generally perpendicular to the bit face. A second plurality of cutting elements, such as polycrystalline diamond compact cutters, are positioned at the inner region of the bit face and oriented to bore in a direction generally parallel to the bit face. When forming a curved portion of a borehole, the first plurality of cutting elements engage the formation to allow the drill bit to reorient at sharper angles than conventional methods for forming a curve, while when forming a linear portion of a borehole, the second plurality of cutting elements engage the formation to provide stability to the drill bit and a rapid rate of penetration.

What is claimed is: 
     
         1 . A drill bit adapted for forming a curved portion of a borehole, the drill bit comprising:
 a body having a first end and a second end;   a shank disposed at the first end of the body, wherein the shank is adapted for attachment to a drill string, a downhole component, or combinations thereof;   a bit face disposed at the second end of the body, wherein the bit face comprises a perimeter region and an interior region, and wherein the interior region comprises a recessed conical portion for contacting a formation to provide stability to the drill bit;   a plurality of tungsten carbide inserts disposed in the perimeter region, wherein the plurality of tungsten carbide inserts define a leading edge oriented to bore into the formation in a direction generally perpendicular to the bit face; and   a plurality of polycrystalline diamond compact cutting elements disposed in the interior region, wherein the plurality of polycrystalline diamond compact cutting elements are oriented to bore into the formation in a direction generally parallel to the bit face, wherein the plurality of tungsten carbide inserts are adapted to engage the formation to form a curved region of a borehole, and wherein the plurality of polycrystalline diamond compact cutting elements are adapted to engage the formation to form a linear region of the borehole.   
     
     
         2 . The drill bit of  claim 1 , wherein the recessed conical portion comprises a height of four inches or less. 
     
     
         3 . The drill bit of  claim 1 , wherein the recessed conical portion comprises a height of four inches or greater. 
     
     
         4 . The drill bit of  claim 1 , wherein the plurality of polycrystalline diamond compact cutting elements forms a first cut in the formation having a first dimension, and wherein the plurality of tungsten carbide inserts forms a second cut in the formation having a second dimension less than the first dimension for facilitating boring of the drill bit along a curved path. 
     
     
         5 . The drill bit of  claim 1 , wherein the body comprises an overall length of five inches or less. 
     
     
         6 . The drill bit of  claim 1 , wherein the bit face comprises a plurality of blades extending therefrom, wherein the plurality of polycrystalline diamond compact cutting elements are positioned along an inner portion of the plurality of blades, and wherein the plurality of tungsten carbide inserts are positioned along an outer portion of the plurality of blades, between individual blades of the plurality of blades, or combinations thereof. 
     
     
         7 . The drill bit of  claim 1 , further comprising a port positioned at a center of the bit face for washing the plurality of tungsten carbide inserts, the plurality of polycrystalline diamond compact cutting elements, or combinations thereof. 
     
     
         8 . A method for forming a borehole, the method comprising the steps of:
 providing a drill bit into a borehole, wherein the drill bit comprises a bit face having a first plurality of cutters disposed on an outer portion thereof to define a leading edge and a second plurality of cutters disposed on an inner portion thereof; and   forming a curved portion of the borehole by using the first plurality of cutters to bore through a formation in a direction generally perpendicular to the bit face while urging the drill bit along a curved path.   
     
     
         9 . The method of  claim 8 , further comprising the step of forming a linear portion of the borehole by using the second plurality of cutters to bore through a formation in a direction generally parallel to the bit face while urging the drill bit along a linear path. 
     
     
         10 . The method of  claim 9 , wherein the inner portion of the bit face comprises a recessed cone, a recessed dome, or combinations thereof, and wherein the step of forming the linear portion of the borehole comprises stabilizing the drill bit by moving the drill bit such that a portion of the formation enters the recessed cone, recessed dome, or combinations thereof to contact the bit face. 
     
     
         11 . The method of  claim 9 , wherein the first plurality of cutters comprise a plurality of tungsten carbide inserts, wherein the second plurality of cutters comprise a plurality of polycrystalline diamond compact cutting elements, wherein the step of forming the curved portion of the borehole comprises removing portions of the formation with the first plurality of cutters that comprise a dimension less than that of portions of the formation removed using the second plurality of cutters to facilitate movement of the drill bit along the curved path. 
     
     
         12 . The method of  claim 8 , wherein the step of forming the curved portion of the borehole comprises providing the curved portion with an angular rate of changing ranging from eight degrees to thirty five degrees per one hundred feet of length. 
     
     
         13 . A drill bit comprising:
 a bit face having an outer portion and an inner portion;   a first plurality of cutters disposed on the outer portion, wherein the first plurality of cutters are oriented to bore into a formation in a direction generally perpendicular to the bit face; and   a second plurality of cutters disposed on the inner portion, wherein the second plurality of cutters are oriented to bore into a formation in a direction generally parallel to the bit face, wherein the first plurality of cutters are adapted to engage the formation to form a curved region of a borehole, and wherein the second plurality of cutters are adapted to engage the formation to form a linear region of the borehole.   
     
     
         14 . The drill bit of  claim 13 , wherein the inner portion comprises a recessed region having a height of four inches or less. 
     
     
         15 . The drill bit of  claim 13 , wherein the inner portion comprises a recessed region having a height of four inches or greater. 
     
     
         16 . The drill bit of  claim 13 , wherein the first plurality of cutters comprises a plurality of tungsten carbide inserts that define a leading edge that contacts the formation prior to the second plurality of cutters, wherein the leading edge adapted to crush the formation when forming a curved region of the borehole. 
     
     
         17 . The drill bit of  claim 16 , wherein the second plurality of cutters comprise a plurality of polycrystalline diamond compact cutting elements adapted to cut the formation. 
     
     
         18 . The drill bit of  claim 13 , further comprising a port positioned at a center of the bit face for washing the first plurality of cutters, the second plurality of cutters, or combinations thereof. 
     
     
         19 . The drill bit of  claim 17 , wherein the plurality of polycrystalline diamond compact cutting elements forms a first cut in the formation having a first dimension, and wherein the plurality of tungsten carbide inserts forms a second cut in the formation having a second dimension less than the first dimension for facilitating boring of the drill bit along a curved path. 
     
     
         20 . The drill bit of  claim 13 , wherein the drill bit comprises an overall length of five inches or less. 
     
     
         21 . The drill bit of  claim 13 , wherein the bit face comprises a plurality of blades extending therefrom, wherein the second plurality of cutters are positioned along an inner portion of the plurality of blades, and wherein the first plurality of cutters are positioned along an outer portion of the plurality of blades, between individual blades of the plurality of blades, or combinations thereof.