Hybrid bit with blades and discs

Abstract

A hybrid drill bit includes a bit body having a central bit body axis at a center of the bit body, a blade on the bit body extending from an end of the bit body, and a roller disc rotatably coupled to the bit body about the end of the bit body to rotate on a roller disc axis. The roller disc axis extends toward the central bit body axis, and the blade includes a plurality of fixed cutting elements.

What is claimed is: 
     
         1 . A hybrid drill bit, comprising:
 a bit body defining a central bit body axis;   a blade on the bit body extending from an end of the bit body, the blade comprising a plurality of fixed cutting elements; and   a roller disc rotatably coupled to the bit body about the end of the bit body to rotate on a roller disc axis, the roller disc axis extending toward the central bit body axis.   
     
     
         2 . The hybrid drill bit of  claim 1 , comprising an arm coupled to the bit body extending generally along the central bit body axis and beyond the end of the bit body; and
 where the roller disc is rotatably coupled to the arm.   
     
     
         3 . The hybrid drill bit of  claim 1 , where the roller disc axis of the roller disc intersects the central bit body axis. 
     
     
         4 . The hybrid drill bit of  claim 1 , where the roller disc axis of the roller disc is non-radial from the central bit body axis. 
     
     
         5 . The hybrid drill bit of  claim 4 , where a shortest distance S between the central bit body axis and the roller disc axis is less than 0.5 inches. 
     
     
         6 . The hybrid drill bit of  claim 1 , where the roller disc comprises a disc body and a generally ring-shaped cutting row radially disposed about the disc body; and
 where the roller disc comprises only one cutting row.   
     
     
         7 . The hybrid drill bit of  claim 6 , where the cutting row defines a rotational plane through the center of the cutting row, the rotational plane being normal to the roller disc axis;
 where the rotational plane of the roller disc is generally perpendicular to a periphery of a corresponding bit profile; and   where a center of the roller disc is the intersection of the roller disc axis and the rotational plane.   
     
     
         8 . The hybrid drill bit of  claim 7 , where the roller disc is in a shoulder zone of the bit profile. 
     
     
         9 . The hybrid drill bit of  claim 1 , comprising a plurality of roller discs and a plurality of blades. 
     
     
         10 . The hybrid drill bit of  claim 9 , where each disc of the plurality of roller discs is a different distance L from the central bit body axis, where the distance L is a shortest distance between a center of the respective roller disc and the central bit body axis. 
     
     
         11 . The hybrid drill bit of  claim 9 , where the plurality of roller discs are not in a cone zone of a corresponding bit profile. 
     
     
         12 . The hybrid drill bit of  claim 9 , where each roller 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 roller disc axis from the central bit body axis. 
     
     
         13 . The hybrid drill bit of  claim 9 , where the plurality of blades are more radially inward than the plurality of discs with respect to the central bit body axis of the bit body. 
     
     
         14 . The hybrid drill bit of  claim 7 , where the cutting row of the roller disc extends further from the end of the bit body than the fixed cutting elements of the blade. 
     
     
         15 . 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 having a central bit body axis at a center of the bit body; 
 a blade on the bit body extending from an end of the bit body, the blade comprising a plurality of fixed cutting elements; and 
 a roller disc rotatably coupled to the bit body about the end of the bit body to rotate on a roller disc axis, the roller disc axis extending toward the central bit body axis. 
   
     
     
         16 . The well drilling system of  claim 15 , where the hybrid drill bit further comprises:
 an arm coupled to the bit body extending generally along the central bit body axis and beyond the end of the bit body; and   where the roller disc is rotatably coupled to the arm.   
     
     
         17 . The well drilling system of  claim 15 , where the roller disc comprises a disc body and a generally ring-shaped cutting row radially disposed about the disc body; and
 where the roller disc comprises only one cutting row.   
     
     
         18 . 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 disc on the drill bit; and   scraping the formation in a shearing action using fixed cutting elements on a blade on the drill bit.   
     
     
         19 . The method of  claim 18 , where crushing or cracking the formation in a rotating action using a roller disc comprises prefracturing the formation using the roller disc, where the roller disc is deeper into the formation than the fixed cutting elements of the blade; and
 where scraping the formation in a shearing action using fixed cutting elements on a blade comprises scraping prefractured cuttings of formation.   
     
     
         20 . The method of  claim 18 , where crushing or cracking the formation in a rotating action using a roller disc on the drill bit comprises a roller disc configured to roll against the formation with small shear.