High Temperature Back Pressure Valve

Abstract

A back pressure valve for sealing a wellbore. The back pressure valve has a cylindrical body with threads designed to engage threads in the opening of a tubing hanger within the wellbore. The back pressure valve also has a metal sealing surface. When the threads of the back pressure valve engage the threads in the opening of the tubing hanger, the metal sealing surface of the valve seals against the metal of the tubing hanger, forming a metal to metal seal.

What is claimed is: 
     
         1 . A back pressure valve for sealing a wellbore, the back pressure valve designed for installation in a tubing hanger at a. wellhead, the tubing hanger having an upper end and a lower end, and defining an opening having a threaded portion and walls that taper outwardly from a smaller diameter at a downward position toward the lower end to a larger diameter at an upward position toward the upper end, the back pressure valve comprising:
 a substantially cylindrical body having a threaded portion configured to engage the threaded portion of the tubing hanger when the valve enters the opening defined by the tubing hanger; and   a tapered metal sealing surface on the cylindrical body configured to contact the tapered walls of the opening in the tubing hanger when the threaded portion of the valve is engaged with the threaded portion of the opening so as to form a seal between the valve and the tubing hanger.   
     
     
         2 . The back pressure valve of  claim 1 , wherein the tapered metal sealing surface is tapered at an angle of from 3 to 10 degrees. 
     
     
         3 . The back pressure valve of  claim 1 , further comprising:
 internal threads configured for engagement with an installation tool, and through which the installation tool can provide a torque to the cylindrical body to engage the threads of the cylindrical body with the threads of the opening in the tubing hanger until a seal is formed between the tapered metal sealing surface of the cylindrical body and the walls of the opening in the tubing hanger.   
     
     
         4 . The back pressure valve of  claim 1 , further comprising:
 a sealing groove that circumscribes the cylindrical body and bisects the tapered metal sealing surface.   
     
     
         5 . The back pressure valve of  claim 1 , further comprising:
 a poppet valve having a poppet valve flange and movably contained within the cylindrical body, the poppet valve having an open position and a closed position;   wherein when the poppet valve is in the open position, the poppet valve flange is substantially disengaged from the cylindrical body so that fluid can pass between the poppet valve flange and the cylindrical body, and when the poppet valve is in the closed position, the poppet valve flange forms a seal between the poppet valve flange and the cylindrical body to prohibit fluid from passing between the poppet valve flange and the cylindrical body.   
     
     
         6 . The back pressure valve of  claim 5 , further comprising:
 a spring surrounding at least a portion of the poppet valve and biased to urge the poppet valve flange into sealed contact with the cylindrical body.   
     
     
         7 . The back pressure valve of  claim 5 , wherein the cylindrical body is composed of metal, and the poppet valve flange is composed of metal, so that when the poppet valve is in a closed position, the cylindrical body and the poppet valve flange form a metal to metal seal. 
     
     
         8 . A wellhead assembly including a back pressure valve comprising:
 a tubing hanger mounted to a wellhead and defining an opening having walls, the walls of the opening tapering outwardly from a smaller diameter within the tubing hanger to a larger diameter at the top end thereof; and   a back pressure valve having a substantially cylindrical body and a tapered metal sealing surface;   wherein the substantially cylindrical body is configured to releasably engage the walls of the opening when the back pressure valve is inserted into the opening; and   wherein the tapered metal sealing surface of the back pressure valve seals against the tapered walls of the opening when the cylindrical body engages the walls of the opening   
     
     
         9 . The wellhead assembly of  claim 8 , wherein the opening of the tubing hanger has a threaded portion and the substantially cylindrical body has a threaded portion, and wherein the threaded portions of the opening and the cylindrical body are configured for releasable engagement when the cylindrical body is inserted into the opening. 
     
     
         10 . The wellhead assembly of  claim 8 , wherein the tapered metal sealing surface of the back pressure valve is tapered at an angle of from 3 to 10 degrees. 
     
     
         11 . The wellhead assembly of  claim 9 , wherein the back pressure valve further comprises:
 internal threads configured for engagement with an installation tool, and through which the installation tool can provide a torque to the cylindrical body to engage the threads of the cylindrical body with the threads of the opening in the tubing hanger until a seal is formed between the tapered metal sealing surface of the cylindrical body and the walls of the opening in the tubing hanger.   
     
     
         12 . The wellhead assembly of  claim 8 , wherein the back pressure has a sealing groove that circumscribes the cylindrical body and bisects the tapered metal sealing surface. 
     
     
         13 . The wellhead assembly of  claim 8 , wherein the back pressure valve further comprises:
 a poppet valve having a poppet valve flange and movably contained within the cylindrical body, the poppet valve having an open position and a closed position;   wherein when the poppet valve is in the open position, the poppet valve flange is substantially disengaged from the cylindrical body so that fluid can pass between the poppet valve flange and the cylindrical body, and when the poppet valve is in the closed position, the poppet valve flange forms a seal between the poppet valve flange and cylindrical body to prohibit fluid from passing between the poppet valve flange and the cylindrical body.   
     
     
         14 . The wellhead assembly of  claim 13 , wherein the back pressure valve further comprises:
 a spring surrounding at least a portion of the poppet valve and biased to urge the at least one poppet valve flange into sealed contact with the cylindrical body.   
     
     
         15 . The wellhead assembly of  claim 13 , wherein the cylindrical body is composed of metal, and the at least one poppet valve flange is composed of metal, so that when the poppet valve is in a closed position, the cylindrical body and the poppet valve flange form a metal to metal seal. 
     
     
         16 . A method of sealing a well with a back pressure valve having metal sealing surfaces while removing a pressure control adapter and installing a production tree, the method comprising:
 inserting the back pressure valve into the wellhead through the pressure control adapter so that the metal sealing surfaces of the back pressure valve sealingly engage metal surfaces of the wellhead;   removing the pressure control adapter from the wellhead;   installing the production tree on the wellhead; and   removing the hack pressure valve from the wellhead.   
     
     
         17 . The method of  claim 16 , further comprising:
 providing a tubing hanger in the wellbore defining an opening with threaded surfaces;   providing threads on at least a portion of the surface of the back pressure valve; and   energizing the metal sealing surfaces of the back pressure valve by engaging the back pressure valve with an installation tool that provides torque to the back pressure valve so that the threaded surfaces of the opening engage with the threaded surfaces of the hack pressure valve.