Tubular Coupling Assembly With Modified Buttress Thread

Abstract

Tubular coupling assembly with modified buttress thread includes a coupling member to couple two pin connections. The coupling member includes an outer surface and an inner surface opposite the outer surface, which can seal to surfaces of the two pin connections. The inner surface includes a first tapered axial portion extending from a first end of the coupling member towards a center of the coupling member. The inner surface includes a second tapered axial portion extending from a second end of the coupling member towards the center of the coupling member. The coupling member includes a shoulder portion connecting the first tapered axial portion and the second tapered axial portion. Regions of the shoulder portion that connect to the first tapered axial portion and to the second tapered axial portion have respective concave shapes to couple to respective convex shapes on each of the two pin connections.

1 . A coupling member configured to couple two pin connections, the coupling member comprising:
 an outer surface;   an inner surface opposite the outer surface, the inner surface configured to seal to surfaces of the two pin connections, the inner surface comprising:
 a first tapered axial portion extending from a first end of the coupling member towards a center of the coupling member, 
 a second tapered axial portion extending from a second end of the coupling member towards the center of the coupling member, and 
 a shoulder portion connecting the first tapered axial portion and the second tapered axial portion, wherein regions of the shoulder portion that connect to the first tapered axial portion and to the second tapered axial portion have respective concave shapes configured to couple to respective convex shapes on each of the two pin connections. 
   
     
     
         2 . The coupling member of  claim 1 , wherein the inner surface is configured to form a metal-to-metal seal with the surfaces of the two pin connections. 
     
     
         3 . The coupling member of  claim 1 , wherein each of the first tapered axial portion and the second tapered axial portion comprises a respective pocket configured to accommodate excessive dope applied when the coupling member is coupled to the two pin connections. 
     
     
         4 . The coupling member of  claim 1 , wherein the first tapered axial portion and the second tapered axial portion comprise respective buttress threads to couple to respective complimentary buttress threads of the two pin connections. 
     
     
         5 . The coupling member of  claim 1 , wherein the shoulder portion is made of a metal. 
     
     
         6 . The coupling member of  claim 1 , further comprising a sealing element made of a polymeric or elastomeric material, wherein the coupling member comprises a seal ring groove configured to receive the sealing element. 
     
     
         7 . The coupling member of  claim 6 , wherein the sealing element encapsulates a metallic strip. 
     
     
         8 . The coupling member of  claim 6 , wherein the polymeric or elastomeric material does not swell in a presence of water. 
     
     
         9 . The coupling member of  claim 6 , wherein the sealing element has an inverted trapezoidal shape. 
     
     
         10 . The coupling member of  claim 6 , wherein the seal ring groove is formed in the shoulder portion of the coupling member. 
     
     
         11 . A wellbore completion comprising:
 a mill end tubular comprising an end;   a field end tubular comprising an end; and   a coupling member configured to couple the mill end tubular and the field end tubular, the coupling member comprising:
 an outer surface; 
 an inner surface opposite the outer surface, the inner surface configured to seal to end of the mill end tubular and the end of the field end tubular, the inner surface comprising:
 a first tapered axial portion extending from a first end of the coupling member towards a center of the coupling member, 
 a second tapered axial portion extending from a second end of the coupling member towards the center of the coupling member, and 
 a shoulder portion connecting the first tapered axial portion and the second tapered axial portion, wherein regions of the shoulder portion that connect to the first tapered axial portion and to the second tapered axial portion have respective concave shapes configured to couple to respective convex shapes on the end of the mill end tubular and the end of the field end tubular. 
 
   
     
     
         12 . The coupling member of  claim 11 , wherein the first tapered axial portion and the second tapered axial portion comprise respective buttress threads to couple to respective complimentary buttress threads of the two pin connections. 
     
     
         13 . The coupling member of  claim 11 , wherein the shoulder portion is made of a metal. 
     
     
         14 . The coupling member of  claim 11 , further comprising a sealing element made of a polymeric or elastomeric material, wherein the coupling member comprises a seal ring groove configured to receive the sealing element. 
     
     
         15 . The coupling member of  claim 14 , wherein the sealing element encapsulates a metallic strip.