Downhole cutting tools having rolling cutters with non-planar cutting surfaces

Abstract

A cutting tool may include a tool body having a plurality of blades extending radially therefrom; each of the plurality of blades having a plurality of cutter pockets formed therein; and at least one rotatable cutting element having a cutting table with a convex cutting surface mounted in at least one of the plurality of cutter pockets, wherein the at least one rotatable cutting element is mounted in a nose or shoulder region of the at least one of the plurality of blades.

What is claimed: 
     
         1 . A cutting tool comprising:
 a tool body having a plurality of blades extending radially therefrom;   each of the plurality of blades having a plurality of cutter pockets formed therein; and   at least one rotatable cutting element having a cutting table with a convex cutting surface mounted in at least one of the plurality of cutter pockets, wherein the at least one rotatable cutting element is mounted in a nose or shoulder region of the at least one of the plurality of blades.   
     
     
         2 . The cutting tool of  claim 1 , wherein the convex cutting surface is a convex region extending radially from the center of the cutting element a distance, after which the cutting surface surrounding the convex region transitions to form a concave rim. 
     
     
         3 . The cutting tool of  claim 1 , wherein the convex cutting table has a ratio of extension at apex to cutting table base diameter ranging from 0.015 to 0.21. 
     
     
         4 . The cutting tool of  claim 3 , wherein the convex cutting table has a ratio of extension at apex to cutting table base diameter ranging from 0.025 to 0.065. 
     
     
         5 . The cutting tool of  claim 1 , further comprising a plurality of rotatable cutting elements mounted in the shoulder region of at least one of the plurality of blades. 
     
     
         6 . The cutting tool of  claim 5 , wherein the plurality of rotatable cutting elements mounted in the shoulder region have a cutting table with a planar and/or non-planar cutting surface disposed on a substrate, wherein a portion of the substrate has a reduced diameter that is disposed within a sleeve. 
     
     
         7 . The cutting tool of  claim 5 , wherein the plurality of rotatable cutting elements located in the nose region have a portion of the substrate extending above the sleeve that is greater than the portion of the substrate extending above the sleeve for rotatable cutting elements located in the shoulder region. 
     
     
         8 . The cutting tool of  claim 1 , further comprising a plurality of non-rotatable cutting elements mounted on at least one of the plurality of blades. 
     
     
         9 . A cutting tool comprising:
 a tool body having a plurality of blades extending radially therefrom;   each of the plurality of blades having a plurality of cutter pockets formed therein; and   at least one rotatable cutting element having a cutting table with a concave cutting surface mounted in at least one of the plurality of cutter pockets, wherein the at least one rotatable cutting element is mounted in the shoulder of the at least one of the plurality of blades.   
     
     
         10 . The cutting tool of  claim 9 , further comprising a plurality of rotatable cutting elements mounted in the nose region of at least one of the plurality of blades. 
     
     
         11 . The cutting tool of  claim 10 , wherein the plurality of rotatable cutting elements mounted in the nose region have a planar and/or non-planar cutting surface. 
     
     
         12 . The cutting tool of  claim 10 , wherein the plurality of rotatable cutting elements mounted in the nose region have a cutting table with a convex cutting surface disposed on a substrate, wherein a portion of the substrate has a reduced diameter that is disposed within a sleeve. 
     
     
         13 . The cutting tool of  claim 12 , wherein the cutting table with a convex cutting surface has a ratio of extension at apex to cutting table base diameter ranging from 0.015 to 0.21. 
     
     
         14 . The cutting tool of  claim 13 , wherein the cutting table with a convex cutting surface has a ratio of extension at apex to cutting table base diameter ranging from 0.025 to 0.065. 
     
     
         15 . The cutting tool of  claim 10 , wherein the plurality of rotatable cutting elements located in the nose region have a portion of the substrate extending above the sleeve that is greater than the portion of the substrate extending above the sleeve for the rotatable cutting elements located in the shoulder region. 
     
     
         16 . A cutting tool comprising:
 a tool body having a plurality of blades extending radially therefrom; and   a plurality of rotatable cutting elements, wherein the plurality of rotatable cutting elements have differing cutting surface geometries based on their radial position along the plurality of blades.   
     
     
         17 . The cutting tool of  claim 16 , wherein the plurality of rotatable cutting elements are located in the nose and shoulder region of the blades. 
     
     
         18 . The cutting tool of  claim 17 , wherein the rotatable cutting elements in the nose have a convex cutting surface geometry while the rotatable cutting elements in the shoulder have a concave cutting surface geometry. 
     
     
         19 . The cutting tool of  claim 17 , wherein the rotatable cutting elements in the nose have a concave cutting surface geometry while the rotatable cutting elements in the shoulder have a convex cutting surface geometry. 
     
     
         20 . The cutting tool of  claim 17 , wherein the plurality of rotatable cutting elements located in the nose region have a thicker substrate layer supporting the cutting surface than the rotatable cutting elements located in the shoulder region.