Reamer roller cone bit with stepped reamer cutter profile

Abstract

A bottom hole assembly including a pilot bit for initially forming an unconfined inner sidewall of a wellbore and a reamer tool above the pilot bit and comprising a first cutter ring to expand the unconfined inner sidewall, and a second cutter ring located above and outwardly of the first cutter ring to expand the unconfined inner sidewall as expanded by the first cutter ring. The reamer tool may further comprise a third cutter ring located above and outwardly of the second cutter ring to expand the unconfined inner sidewall as expanded by the second cutter ring. The first cutter ring may be located on a first roller cone, the second cutter ring may be located on a second roller cone, and the third cutter ring may be located on a third roller cone.

1 . A reamer tool for expanding a wellbore in an earth formation, the reamer tool comprising:
 a first roller cone having a first cutter ring configured to expand an unconfined inner sidewall of the wellbore; and   a second roller cone having a second cutter ring located above and outwardly of the first cutter ring and configured to expand the unconfined inner sidewall of the wellbore as expanded by the first cutter ring.   
     
     
         2 . The reamer tool as set forth in  claim 1 , further comprising a third roller cone having a third cutter ring located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring. 
     
     
         3 . The reamer tool as set forth in  claim 2 , further comprising a fourth cutter ring located on the first roller cone above and outwardly of the third cutter ring and configured to expand the unconfined inner sidewall as expanded by the third cutter ring. 
     
     
         4 . The reamer tool as set forth in  claim 3 , further comprising a fifth cutter ring located on the second roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fourth cutter ring. 
     
     
         5 . The reamer tool as set forth in  claim 4 , further comprising a sixth cutter ring located on the third roller cone above and outwardly of the fifth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fifth cutter ring. 
     
     
         6 . A bottom hole assembly comprising:
 a pilot bit for initially forming an unconfined inner sidewall of a wellbore; and   a reamer tool above the pilot bit, the reamer tool including
 a first cutter ring configured to expand the unconfined inner sidewall of the wellbore, 
 a second cutter ring located above and outwardly of the first cutter ring and configured to expand the unconfined inner sidewall as expanded by the first cutter ring, and 
 a third cutter ring located above and outwardly of the second cutter ring and configured to expand the unconfined inner sidewall as expanded by the second cutter ring. 
   
     
     
         7 . The bottom hole assembly as set forth in  claim 6 , the reamer tool further comprising first, second and third roller cones. 
     
     
         8 . The bottom hole assembly as set forth in  claim 7 , wherein the first cutter ring is located on the first roller cone, the second cutter ring located on the second roller cone, and the third cutter ring is located on the third roller cone. 
     
     
         9 . The bottom hole assembly as set forth in  claim 8 , further comprising
 a fourth cutter ring located on the first roller cone above and outwardly of the third cutter ring and configured to expand the unconfined inner sidewall as expanded by the third cutter ring;   a fifth cutter ring located on the second roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fourth cutter ring; and   a sixth cutter ring located on the third roller cone above and outwardly of the fourth cutter ring and configured to expand the unconfined inner sidewall as expanded by the fifth cutter ring.   
     
     
         10 . The bottom hole assembly as set forth in  claim 9 , wherein each roller cone includes at least three cutter rows, wherein successive cutter rows are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the wellbore outwardly. 
     
     
         11 . The bottom hole assembly as set forth in  claim 9 , wherein the wellbore is defined by an unconfined inner sidewall and successive cutter rows are located above and outwardly of previous cutter rows such that each cutter row engages the wellbore in such a manner as to incrementally expand the unconfined inner sidewall outwardly. 
     
     
         12 . A method of expanding a wellbore using a reamer tool comprising a plurality of cutter rows mounted on a plurality of roller cones, the method comprising the steps of:
 engaging, with a first cutter row on a first roller cone, an unconfined inner sidewall of the wellbore, thereby expanding the wellbore outwardly; and   engaging, with a second cutter row located on a second roller cone above and outwardly of the first cutter row, the unconfined inner sidewall of the wellbore as expanded by the first cutter row, thereby further expanding the wellbore outwardly.   
     
     
         13 . The method as set forth in  claim 12 , further including the step of engaging, with a third cutter row located on a third roller cone above and outwardly of the second cutter row, the unconfined inner sidewall of the wellbore as expanded by the second cutter row, thereby further expanding the wellbore outwardly. 
     
     
         14 . The method as set forth in  claim 13 , further including the steps of
 engaging, with a fourth cutter row located on the first roller cone above and outwardly of the third cutter row, the unconfined inner sidewall of the wellbore as expanded by the third cutter row;   engaging, with a fifth cutter row located on the second roller cone above and outwardly of the fourth cutter row, the unconfined inner sidewall of the wellbore as expanded by the fourth cutter row; and   engaging, with a sixth cutter row located on the third roller cone above and outwardly of the fifth cutter row, the unconfined inner sidewall of the wellbore as expanded by the fifth cutter row.   
     
     
         15 . The method as set forth in  claim 12 , wherein the reamer expands the wellbore outwardly from the unconfined inner sidewall of the wellbore and the reamer tool is lowered in the wellbore. 
     
     
         16 . The method as set forth in  claim 12 , wherein the wellbore is defined by an initial inner sidewall formed by a pilot bit below the reamer tool, a first step formed by the first cutter row adjacent the initial inner sidewall, a second step formed by the second cutter row above and outward of the first step, and a final inner sidewall formed by the reamer tool.