Drill bit for horizontal directional drilling

Abstract

A bit body for a drill bit for horizontal directional drilling includes a pair of legs and a small wedge member disposed between the pair of legs. A roller cone is rotatably mounted to each bearing shaft extending from a respective leg. The roller cones support full coverage cutting structures. A center jet nozzle is configured to direct drilling fluid between the pair of roller cones. A stabilizer member maintains an upright drilling position of the drill bit within the borehole.

What is claimed is: 
     
         1 . An earth boring drill bit, comprising:
 a bit body comprising a pair of legs and a small wedge member disposed between the pair of legs;   a pair of roller cones each rotatably mounted to a bearing shaft extending from a respective leg, the roller cones supporting full coverage cutting structures; and   a center jet nozzle configured to direct drilling fluid between the pair of roller cones.   
     
     
         2 . The drill bit of  claim 1 , wherein the bit body further comprises a large wedge member disposed between the pair of legs circumferentially opposite the small wedge member. 
     
     
         3 . The drill bit of  claim 2 , further comprising a stabilizer member extending from the large wedge member and being configured to maintain a drilling orientation of the drill bit within a borehole. 
     
     
         4 . The drill bit of  claim 3  wherein the drilling fluid nozzle directs drilling fluid at an angle away from the stabilizer member. 
     
     
         5 . The drill bit of  claim 3  wherein the stabilizer member includes a wear resistant element configured to protect an outer surface of the stabilizer member. 
     
     
         6 . The drill bit of  claim 5  wherein the wear resistant element comprises a layer of hardfacing material applied to a portion of the outer surface of the stabilizer member. 
     
     
         7 . The drill bit of  claim 5  wherein the wear resistant element comprises a plurality of generally cylindrical inserts. 
     
     
         8 . The drill bit of  claim 7  wherein the plurality of generally cylindrical inserts includes tungsten carbide inserts. 
     
     
         9 . The drill bit of  claim 1  wherein the center jet nozzle is angled to direct drilling fluid to fluidly erode a formation at a transitional zone between a sidewall and a bottom of a borehole. 
     
     
         10 . The drill bit of  claim 1  wherein the pair of legs comprises a pair of steel forgings. 
     
     
         11 . The drill bit of  claim 1  wherein each one of the pair of legs is a leg of a conventional three cone roller cone bit. 
     
     
         12 . The drill bit of  claim 1  wherein the drill bit is a bi-cone bit. 
     
     
         13 . The drill bit of  claim 1  wherein an included angle of the small wedge member is 20°-30°. 
     
     
         14 . The drill bit of  claim 13  wherein the bit body further comprises a large wedge member disposed between the pair of legs circumferentially opposite the small wedge member, an included angle of the large wedge member being approximately 120° minus the included angle of the small wedge member. 
     
     
         15 . The drill bit of  claim 13  wherein the included angle of the small wedge member is approximately 20°. 
     
     
         16 . The drill bit of  claim 1  wherein the small wedge member includes a cavity, the cavity defining a portion of a central plenum of the drill bit. 
     
     
         17 . A bi-cone earth boring bit for horizontal directional drilling, comprising
 a pair of legs separated by a first wedge member disposed on one side and separated by a second wedge member disposed on a second side, the first wedge member having an included angle greater than an included angle of the second wedge member;   a bearing shaft extending from each leg;   a roller cone rotatably mounted to each bearing shaft, the roller cones supporting a plurality of cutters configured to fully cut a borehole bottom; and   a stabilizer member extending from the large wedge member.   
     
     
         18 . The bi-cone earth boring bit of  claim 17 , further comprising:
 a center jet nozzle disposed proximate a center of the bi-cone earth boring bit and configured to a direct drilling fluid between the roller cones and toward a transitional zone between a borehole sidewall and the borehole bottom.   
     
     
         19 . The bi-cone earth boring bit of  claim 17 , further comprising:
 an extended nozzle extending between the roller cones and having a nozzle orifice and defining an exit plane, the nozzle orifice having a diameter; and   wherein the exit plane is configured to be disposed a distance above the borehole bottom, the distance being less than seven times the diameter of the nozzle orifice.   
     
     
         20 . The bi-cone earth boring bit of  claim 17  wherein the included angle of the second wedge member is 20°-30° and the included angle of the first wedge member is approximately 120° minus the included angle of the second wedge member. 
     
     
         21 . A horizontal directional drilling drill bit, comprising:
 a pair of legs separated by a first wedge member disposed on one side and separated by a second wedge member disposed on a second side, the first wedge member having an included angle greater than an included angle of the second wedge member;   a plurality of roller cones, each roller cone coupled to a respective one of the pair of legs;   a stabilizer member extending from the first wedge member, the stabilizer member supporting hardfacing material or wear resistant inserts or both; and   a drilling fluid nozzle configured to direct drilling fluid to fluidly erode a formation at a transitional zone between a borehole sidewall and a borehole bottom.   
     
     
         22 . The drill bit of  claim 21  wherein the drilling fluid nozzle is an extended nozzle extending between the roller cones and having a nozzle orifice and defining an exit plane, the nozzle orifice having a diameter; and
 wherein the exit plane is configured to be disposed a distance above the borehole bottom, the distance being less than seven times the diameter of the nozzle orifice. 
 
     
     
         23 . The drill bit of  claim 22  wherein the distance is between one and four inches. 
     
     
         24 . The drill bit of  claim 21  wherein the drilling fluid nozzle is a center jet nozzle disposed proximate a rotational axis of the drill bit and being configured to direct drilling fluid between the roller cones.