Friction reduction device for drill pipe

Abstract

A device to couple to a rotatable drill pipe to control pressure of a drilling system is disclosed. The device includes an inner surface to wrap around a portion of a rotatable drill pipe and having an inner diameter. A first tapered portion is opposite a second tapered portion, with a middle portion therebetween including an outer diameter greater than the inner diameter. The first and second tapered portions each taper from the outer surface to the inner surface. The middle portion, the first tapered portion, and the second tapered portion form an outer surface to sealingly pass through a seal element of a controlled-pressure drilling system. At least a portion of the outer surface corresponding to the middle portion includes a low-friction material.

What is claimed is: 
     
         1 . A device to couple to a rotatable drill pipe to control pressure of a drilling system, the device comprising:
 an inner surface to wrap around a portion of a rotatable drill pipe and having an inner diameter; and   a first tapered portion opposite a second tapered portion, with a middle portion therebetween comprising an outer diameter greater than the inner diameter;   wherein:
 the first and second tapered portions each taper from the outer surface to the inner surface; 
 the middle portion, the first tapered portion, and the second tapered portion form an outer surface to sealingly pass through a seal element of a controlled-pressure drilling system; and 
 at least a portion of the outer surface corresponding to the middle portion comprises a low-friction material. 
   
     
     
         2 . The device of  claim 1 , wherein the middle portion forms an outer cylindrical surface portion. 
     
     
         3 . The device of  claim 1 , wherein the middle portion forms an outer surface portion that is parallel to the inner surface. 
     
     
         4 . The device of  claim 1 , wherein the low-friction material is Teflon. 
     
     
         5 . The device of  claim 1 , wherein the middle portion forms an outer surface portion having a single radius, and the first and second tapered portions each comprise an outer frusto-conical surface portion. 
     
     
         6 . The device of  claim 1 , wherein the outer surface comprises a low-friction material. 
     
     
         7 . A reduced-friction rotatable tubular system for a controlled-pressure drilling system, comprising:
 a drill pipe to be disposed in a wellbore and having an inside diameter;   a rotatable tubular extending through at least a portion of the drill pipe and having an outside diameter;   a friction reduction device disposed around a portion of the rotatable tubular, wherein the friction reduction device comprises:
 an inner surface having an inner diameter; and 
 a first tapered portion opposite a second tapered portion, with a middle portion therebetween comprising an outer diameter greater than the inner diameter; 
 wherein the middle portion, the first tapered portion, and the second tapered portion form an outer surface to sealingly pass through a seal element of a controlled-pressure drilling system; and 
 wherein at least a portion of the outer surface corresponding to the middle portion comprises a low-friction material. 
   
     
     
         8 . The reduced-friction rotatable tubular system of  claim 7 , wherein the friction reduction device prevents the rotatable tubular from contacting the drill pipe. 
     
     
         9 . The reduced-friction rotatable tubular system of  claim 7 , wherein the first and second tapered portions each taper from the outer surface to the inner surface of the friction reduction device. 
     
     
         10 . The reduced-friction rotatable tubular system of  claim 7 , wherein the middle portion forms an outer cylindrical surface portion. 
     
     
         11 . The reduced-friction rotatable tubular system of  claim 7 , wherein the middle portion forms an outer surface portion that is parallel to the inner surface. 
     
     
         12 . The reduced-friction rotatable tubular system of  claim 7 , wherein the low-friction material is Teflon. 
     
     
         13 . The reduced-friction rotatable tubular system of  claim 7 , wherein the middle portion forms an outer surface portion having a single radius, and the first and second tapered portions each comprise an outer frusto-conical surface portion. 
     
     
         14 . The reduced-friction rotatable tubular system of  claim 7 , wherein the outer surface comprises a low-friction material. 
     
     
         15 . A method of reducing friction in a controlled-pressure drilling system, the method comprising:
 disposing a drill pipe in a wellbore, the drill pipe having an inside diameter;   extending a rotatable tubular through at least a portion of the drill pipe, the rotatable tubular having an outside diameter;   coupling a friction reduction device to a portion of the rotatable tubular, wherein the friction reduction device comprises:
 an inner surface having an inner diameter; and 
 a first tapered portion opposite a second tapered portion, with a middle portion therebetween comprising an outer diameter greater than the inner diameter; 
 wherein the middle portion, the first tapered portion, and the second tapered portion form an outer surface to sealingly pass through a seal element of a controlled-pressure drilling system; and 
 wherein at least a portion of the outer surface corresponding to the middle portion comprises a low-friction material.