Hybrid bit with roller cones and discs

Abstract

A hybrid drill bit includes a bit body having a central bit body axis, a roller cone at an end of the bit body and rotatably coupled to the bit body about a roller cone axis, and a disc at the end of the bit body and rotatably coupled to the bit body about a disc axis. The roller cone axis extends toward the central bit body axis. The disc axis is transverse to a radial of the central bit body axis through a center of the disc, and the disc includes a plurality of disc cutters.

What is claimed is: 
     
         1 . A hybrid drill bit, comprising:
 a bit body defining a central bit body axis;   a roller cone at an end of the bit body and rotatably coupled to the bit body about a roller cone axis, the roller cone axis extending toward the central bit body axis; and   a disc at the end of the bit body and rotatably coupled to the bit body about a disc axis;
 where the disc axis is transverse to a radial of the central bit body axis through a center of the disc; and 
 where the disc comprises a plurality of disc cutters. 
   
     
     
         2 . The hybrid drill bit of  claim 1 , further comprising:
 a first arm coupled to the bit body extending generally along the central bit body axis and beyond the end of the bit body, where the disc is rotatably coupled to the first arm; and   a second arm coupled to the bit body extending generally along the central bit body axis and beyond the end of the bit body, where the roller cone is rotatably coupled to the second arm.   
     
     
         3 . The hybrid drill bit of  claim 1 , where the roller cone axis intersects the central bit body axis. 
     
     
         4 . The hybrid drill bit of  claim 1 , where the roller cone axis is non-radial from the central bit body axis. 
     
     
         5 . The hybrid drill bit of  claim 4 , where the shortest distance between the central bit body axis and the roller cone axis is less than 9/16 inches. 
     
     
         6 . The hybrid drill bit of  claim 1 , where the roller cone comprises a cone body and a plurality of cutting teeth disposed on the cone body. 
     
     
         7 . The hybrid drill bit of  claim 6 , where the cutting teeth of the roller cone comprise milled steel teeth with a hardface metal coating. 
     
     
         8 . The hybrid drill bit of  claim 6 , where the plurality of disc cutters on the disc extend further from the end of the bit body than the plurality of cutting teeth on the roller cone. 
     
     
         9 . The hybrid drill bit of  claim 6 , where the plurality of cutting teeth on the roller cone extend further from the end of the bit body than the plurality of disc cutters on the disc. 
     
     
         10 . The hybrid drill bit of  claim 1 , where the disc comprises a disc body and a generally ring-shaped cutting row radially disposed about the disc body; and
 where the plurality of disc cutters are disposed along the generally ring-shaped cutting row.   
     
     
         11 . The hybrid drill bit of  claim 10 , where each disc cutter in the plurality of disc cutters comprises a cylindrical cutter body with a cutter axis through a center of the cylindrical cutter body and a flat cutter face at an end of the cylindrical body; and
 where the cutter axis is transverse to a radial from the center of the disc to the center of the cylindrical cutter body.   
     
     
         12 . The hybrid drill bit of  claim 1 , comprising a plurality of roller cones and a plurality of discs. 
     
     
         13 . The hybrid drill bit of  claim 12 , where each disc of the plurality of discs has a different disc axis offset, S, and a different disc center offset, L, from the central bit body axis; and
 where each disc axis of the plurality of discs is at a different angle β from the central bit body axis, where the angle β is the angle of the respective rotational axis from the central bit body axis.   
     
     
         14 . A well drilling system, comprising:
 a well head;   a drill string connected to the well head;   a hybrid drill bit connected to the drill string, the hybrid drill bit comprising:
 a bit body defining a central bit body axis; 
 a roller cone at an end of the bit body and rotatably coupled to the bit body about a roller cone axis, the roller cone axis extending toward the central bit body axis; and 
 a disc at the end of the bit body and rotatably coupled to the bit body about a disc axis, the disc axis extending away from the central bit body axis. 
   
     
     
         15 . The well drilling system of  claim 14 , where the hybrid drill bit further comprises:
 a first arm coupled to the bit body extending generally along the central bit body axis and beyond the end of the bit body, where the disc is rotatably coupled to the first arm; and   a second arm coupled to the bit body extending generally along the central bit body axis and beyond the end of the bit body, where the roller cone is rotatably coupled to the second arm.   
     
     
         16 . The well drilling system of  claim 14 , where the roller cone comprises a cone body and a plurality of cutting teeth disposed on the cone body;
 where the disc comprises a disc body and a generally ring-shaped cutting row radially disposed about the disc body; and   where the generally ring-shaped cutting row includes a plurality of disc cutters disposed along the cutting row.   
     
     
         17 . A method of cutting a formation in a wellbore, the method comprising:
 rotating a drill bit in a formation in a wellbore;   crushing or cracking the formation in a rotating action using a roller cone on the drill bit; and   scraping the formation in a shearing action using disc cutters on a disc on the drill bit, the disc configured to rotate.   
     
     
         18 . The method of  claim 17 , where crushing or cracking the formation in a rotating action using a roller cone comprises prefracturing the formation using the roller cone, where the roller cone is deeper into the formation than the disc cutters of the disc; and
 where scraping the formation in a shearing action using disc cutters on a disc comprises scraping prefractured cuttings of formation.   
     
     
         19 . The method of  claim 17 , where scraping the formation in a shearing action using disc cutters on a disc on the drill bit further comprises rotating the disc about a disc axis such that the disc cutters cycle about the disc axis.