Drilling on gauge sub

Abstract

A drilling on gauge sub including a tubular housing having a first end, a second end and an exterior surface. Coupling means are positioned at both the first end and the second end of the tubular housing to couple the tubular housing to other components of a drill string. At least three cavities are provided in the exterior surface of the tubular housing. Each of the cavities having a first end and a second end. Reamer cutters are secured within each of the at least three cavities. The reamer cutters including cutters mounted on rotatably mounted rollers.

1 . A drilling on gauge sub, comprising: 
 a tubular housing having a first end, a second end and an exterior surface;    coupling means at both the first end and the second end of the tubular housing to couple the tubular housing to other components of a drill string;    at least three cavities in the exterior surface of the tubular housing, each of the cavities having a first end and a second end;    reamer cutters positioned in each of the at least three cavities, the reamer cutters including cutters mounted on rotatably mounted rollers.    
   
   
       2 . The drilling on gauge sub as defined in  claim 1 , wherein the reamer cutters are in the form of replaceable modules detachably secured in the cavities by fasteners.  
   
   
       3 . The drilling on gauge sub as defined in  claim 2 , wherein 
 an undercut locking groove is positioned at the first end of each of the cavities;    each reamer cutter module having a first end and a second end, the first end the each reamer cutter module having a projecting tongue adapted to engage the locking groove of one of the cavities;    detachable fasteners securing the second end of each of the reamer cutter modules within the second end of one of the cavities so that the projecting tongue of each reamer cutter module remains locked in engagement with the locking groove, each reamer cutter module being replaceable by detaching the fastener and withdrawing the projecting tongue from the locking groove.    
   
   
       4 . The drilling on gauge sub as defined in  claim 1 , wherein the rollers are cylindrical rollers oriented substantially parallel to the longitudinal axis of the tubular housing.  
   
   
       5 . The drilling on gauge sub as defined in  claim 4 , wherein carbide spacers are positioned at each end of the cylindrical rollers to serve as wear surfaces and transmit axial loads.  
   
   
       6 . The drilling on gauge sub as defined in  claim 3 , wherein the detachable fasteners are bolts which engage threaded apertures in the tubular housing.  
   
   
       7 . The drilling on gauge sub as defined in  claim 6 , wherein a debris cover is positioned over each of the bolts, the debris cover being adapted to shield the bolt from debris.  
   
   
       8 . The drilling on gauge sub as defined in  claim 7 , wherein each debris cover is held in place by spring pins.  
   
   
       9 . The drilling on gauge sub as defined in  claim 1 , wherein the rollers rotate on radial bearings.  
   
   
       10 . The drilling on gauge sub as defined in  claim 9 , wherein the radial bearings are positioned within a lubricant filled bearing chamber with seals being positioned at each end of the bearing chamber to contain lubricant.  
   
   
       11 . The drilling on gauge sub as defined in  claim 10 , wherein a lubricant supply passage communicates with the bearing chamber, a piston being positioned in the lubricant supply passage, the piston having a first face and a second face, the first face engaging lubricant contained within the lubricant supply passage, the second face being exposed to pressure from drilling fluids, such the pressure; exerted upon the second face of the piston causes the piston to move in the lubricant supply passage with the first face of the piston urging lubricant into the bearing chamber.  
   
   
       12 . A drilling on gauge sub, comprising: 
 a tubular housing having a first end, a second end and an exterior surface;    a first coupling at the first end and a second coupling at the second end of the tubular housing, the first coupling and the second coupling being adapted to couple the tubular housing to other components of a drill string;    more than two cavities in the exterior surface of the tubular housing, each of the cavities having a first end and a second end, an undercut locking groove being positioned at the first end of each of the cavities;    replaceable reamer cutter modules detachably positioned in the cavities, each reamer cutter module having a first end and a second end, the first end the each reamer cutter module having a projecting tongue adapted to engage the locking groove of one of the cavities, detachable fasteners securing the second end of each of the reamer cutter modules within the second end of one of the cavities so that the projecting tongue of each reamer cutter module remains locked in engagement with the locking groove, each reamer cutter module being replaceable by detaching the fastener and withdrawing the projecting tongue from the locking groove, each reamer cutter module including rotatably mounted cylindrical rollers which rotate on radial bearings and are oriented substantially parallel to the longitudinal axis of the tubular housing, cutters projecting from and being spaced around the outer circumference of the rollers;    the radial bearings being positioned within a lubricant filled bearing chamber with seals being positioned at each end of the bearing chamber to contain lubricant; and    a lubricant supply passage communicates with the bearing chamber, a piston being positioned in the lubricant supply passage, the piston having a first face and a second face, the first face engaging lubricant contained within the lubricant supply passage, the second face being exposed to pressure from drilling fluids, such the pressure; exerted upon the second face of the piston causes the piston to move in the lubricant supply passage with the first face of the piston urging lubricant into the bearing chamber.    
   
   
       13 . The drilling on gauge sub as defined in  claim 12 , wherein carbide spacers are positioned at each end of the cylindrical rollers to serve as wear surfaces and transmit axial loads.  
   
   
       14 . The drilling on gauge sub as defined in  claim 12 , wherein the detachable fasteners are bolts which engage threaded apertures in the tubular housing.  
   
   
       15 . The drilling on gauge sub as defined in  claim 14 , wherein a debris cover is positioned over each of the bolts, the debris cover being adapted to shield the bolt from debris.  
   
   
       16 . The drilling on gauge sub as defined in  claim 15 , wherein each debris cover is held in place by spring pins.  
   
   
       17 . A method of drilling on gauge with a downhole drilling motor assembly, comprising the steps of: 
 securing a drilling on gauge sub having rollers on which are secured cutters adjacent to a drill bit end of the downhole drilling motor assembly; and    using the cutters to ream the hole, while the rollers concurrently guide the movement of the drilling motor assembly and reduce friction with the hole.