Centralized Bi-Center Reamer and Method of Use

Abstract

This apparatus provides an underreamer and a reamer or hole opener to enlarge an existing pilot hole thereby permitting further operation to be carried out in a well bore. The underreamer can be inserted down a well bore in the unexpanded condition and, since the radius of the eccentrically mounted cutters of the reamer or hole opener added to the radius of the unexpanded underreamer equals the pass through diameter (the inner diameter of the restriction), the entire assembly or apparatus can be inserted to the position requiring enlarging. The underreamer is expanded to engage the adjacent wall of the well bore and stabilize the reamer as it enlarges the hole. Since movement resulting from the lateral forces are restrained by the centralizer/underreamer as well as the bullnose or smaller pilot hole drill bit, the bi-center reamer can readily open the well bore to the desired diameter without lateral deviation.

1 . An apparatus for enlarging a bore hole comprising:
 a selectively-engageable underreaming centralizer to engage a well bore on a proximal portion of a bottom hole assembly; and,   one or more rolling cutter cones mounted eccentrically on a distal reamer portion of the bottom hole assembly such that the outer diameter of the reamer portion is smaller than the inner diameter of a passage through which the apparatus passes on a distal portion of the bottom hole assembly.   
     
     
         2 . The apparatus of  claim 1  wherein the selectively-engageable underreaming centralizer provides hard-facing on a face of a plurality of well bore engaging arms. 
     
     
         3 . The apparatus of  claim 1  wherein the selectively-engageable underreaming centralizer provides one or more rolling cutter cones for engaging the well bore. 
     
     
         4 . (canceled) 
     
     
         5 . (canceled) 
     
     
         6 . The apparatus of  claim 1  wherein the underreaming centralizer and the eccentric roller cone portion of the bottom hole assembly are on two tubular bodies connected together. 
     
     
         7 . The apparatus of  claim 1  wherein the underreaming centralizer and the eccentric roller cone portion of the bottom hole assembly are fabricated on an integral body. 
     
     
         8 . The apparatus of  claim 1  additionally providing a bit connected to the distal eccentric roller cone portion of the bottom hole assembly. 
     
     
         9 . The apparatus of  claim 1  additionally providing a bull-nose plug connected to the distal eccentric roller cone portion of the bottom hole assembly. 
     
     
         10 . A method for enlarging a pilot bore hole comprising:
 inserting a underreaming centralizer and an eccentric roller cone assembly apparatus in a zone to be enlarged while keeping the underreaming centralizer arms from deployment;   opening the underreaming centralizer arms by increasing hydraulic pressure to thereby engage the eccentric roller cone assembly into engagement with a section of the pilot bore hole and centralize and stabilize the roller cone assembly as it engages the bore hole; and,   rotating the underreaming centralizer and eccentric roller cone assembly combination to enlarge the pilot bore hole.   
     
     
         11 . The method of  claim 10  further comprising rotating the bottom hole assembly while increasing pump pressure on the underreaming centralizer to fully extend the underreaming centralizer arms to engage the well bore before advancing the underreaming centralizer and eccentric roller cone assembly in the well bore.