Corrosion resistant system for pipe connections

Abstract

A corrosion resistant system comprises a connection assembly disposed to concatenate two riser pipes above ground in a wellhead toolstring. The connection assembly includes an o-ring housing interposed between the riser pipes. An anode assembly, also positioned above ground in the wellhead toolstring, includes at least one sacrificial anode acting as a corrosion inhibitor for at least one wellhead tool in the wellhead toolstring. The riser pipes are made of metals having pitting resistance equivalent numbers designated as PREN1 and PREN 2 respectively, and the o-ring housing is made of a metal having a pitting resistance equivalent number designated as PRENH. Both [PRENH-PREN1] and [PRENH-PREN 2] are in a range between about −5 and +∞. An optional isolator assembly may isolate at least one wellhead tool in the wellhead toolstring electrically from a downhole portion of the wellhead toolstring.

We claim: 
     
         1 . A wellhead corrosion resistant system, comprising:
 a connection assembly disposed to concatenate a first riser pipe to a second riser pipe above ground in a wellhead toolstring;   the connection assembly including an o-ring housing such that the o-ring housing is disposed to be interposed between the first riser pipe and the second riser pipe when the connection assembly concatenates the first riser pipe to the second riser pipe;   an anode assembly including at least one sacrificial anode, wherein the at least one sacrificial anode acts as a corrosion inhibitor for at least one wellhead tool in the wellhead toolstring when the anode assembly is also positioned above ground in the wellhead toolstring;   wherein the first riser pipe has a first riser internal surface, the o-ring housing has a housing internal surface and the second riser pipe has a second internal surface, wherein the first riser internal surface, the housing internal surface and the second riser internal surface are contiguous when the connection assembly concatenates the first riser pipe to the second riser pipe;   wherein the first riser internal surface presents a metal having a pitting resistance equivalent number designated as PREN1;   wherein the second riser internal surface presents a metal having a pitting resistance equivalent number designated as PREN2;   wherein the housing internal surface presents a metal having a pitting resistance equivalent number designated as PRENH;   wherein [PRENH-PREN1] is in a range between about −5 and +∞; and   wherein [PRENH-PREN2] is in a range between about −5 and +∞.   
     
     
         2 . The wellhead corrosion resistant system of  claim 1 , in which the first riser internal surface presents a metal selected from the group consisting of:
 (a) 28 Chrome;   (b) Inconel 718;   (c) L80; and   (d) P110.   
     
     
         3 . The wellhead corrosion resistant system of  claim 1 , in which the second riser internal surface presents a metal selected from the group consisting of:
 (a) 28 Chrome;   (b) Inconel 718;   (c) L80; and   (d) P110.   
     
     
         4 . The wellhead corrosion resistant system of  claim 1 , in which the housing internal surface presents a metal selected from the group consisting of:
 (a) 28 Chrome;   (b) Inconel 718;   (c) L80; and   (d) P110.   
     
     
         5 . The wellhead corrosion resistant system of  claim 1 , in which at least one sacrificial anode are a zinc-aluminum alloy. 
     
     
         6 . The wellhead corrosion resistant system of  claim 1 , in which the connection assembly further includes a male union and a female union, wherein connection of the male union to the female union enables the o-ring housing to be interposed between the first riser pipe and the second riser pipe when the connection assembly concatenates the first riser pipe to the second riser pipe. 
     
     
         7 . The wellhead corrosion resistant system of  claim 6 , in which the connection assembly further includes a nut, wherein threading of the nut over the female union enables connection of the male union to the female union. 
     
     
         8 . The wellhead corrosion resistant system of  claim 1 , in which the anode assembly is a first anode assembly, and in which the wellhead corrosion resistant system further includes a second anode assembly, wherein the second anode assembly disposed to be positioned also above ground in the wellhead toolstring such that at least one wellhead tool in the wellhead toolstring is interposed between the first anode assembly and the second anode assembly. 
     
     
         9 . The wellhead corrosion resistant system of  claim 1 , in which the anode assembly further includes a removable internal anode housing to which at least one of the sacrificial anodes is secured, wherein the anode housing also includes a plurality of slots, wherein the slots are configured to encourage fluid flow around the anode housing. 
     
     
         10 . The wellhead corrosion resistant system of  claim 1 , further comprising:
 an isolator assembly disposed to be positioned also above ground in the wellhead toolstring such that the isolator assembly isolates electrically an uphole portion of the wellhead toolstring from a downhole portion of the wellhead toolstring;   wherein the isolator assembly is configured to isolate at least one wellhead tool in the wellhead toolstring electrically from the downhole portion of the wellhead toolstring when the at least one wellhead tool in the wellhead toolstring is positioned in the uphole portion of the wellhead toolstring between the anode assembly and the isolator assembly.   
     
     
         11 . A wellhead corrosion resistant system, comprising:
 a connection assembly disposed to concatenate a first riser pipe to a second riser pipe above ground in a wellhead toolstring;   the connection assembly including an o-ring housing such that the o-ring housing is disposed to be interposed between the first riser pipe and the second riser pipe when the connection assembly concatenates the first riser pipe to the second riser pipe;   an anode assembly including at least one sacrificial anode, wherein the at least one sacrificial anode acts as a corrosion inhibitor for at least one wellhead tool in the wellhead toolstring when the anode assembly is also positioned above ground in the wellhead toolstring;   wherein the first riser pipe is made of a metal having a pitting resistance equivalent number designated as PREN1;   wherein the second riser pipe is made of a metal having a pitting resistance equivalent number designated as PREN2;   wherein the o-ring housing is made of a metal having a pitting resistance equivalent number designated as PRENH;   wherein [PRENH-PREN1] is in a range between about −5 and +∞; and   wherein [PRENH-PREN2] is in a range between about −5 and +∞.   
     
     
         12 . The wellhead corrosion resistant system of  claim 11 , in which the first riser pipe is made of a metal selected from the group consisting of:
 (a) 28 Chrome;   (b) Inconel 718;   (c) L80; and   (d) P110.   
     
     
         13 . The wellhead corrosion resistant system of  claim 11 , in which the second riser pipe is made of a metal selected from the group consisting of:
 (a) 28 Chrome;   (b) Inconel 718;   (c) L80; and   (d) P110.   
     
     
         14 . The wellhead corrosion resistant system of  claim 11 , in which the o-ring housing is made of a metal selected from the group consisting of:
 (a) 28 Chrome;   (b) Inconel 718;   (c) L80; and   (d) P110.   
     
     
         15 . The wellhead corrosion resistant system of  claim 11 , in which at least one sacrificial anode is a zinc-aluminum alloy. 
     
     
         16 . The wellhead corrosion resistant system of  claim 11 , in which the connection assembly further includes a male union and a female union, wherein connection of the male union to the female union enables the o-ring housing to be interposed between the first riser pipe and the second riser pipe when the connection assembly concatenates the first riser pipe to the second riser pipe. 
     
     
         17 . The wellhead corrosion resistant system of  claim 16 , in which the connection assembly further includes a nut, wherein threading of the nut over the female union enables connection of the male union to the female union. 
     
     
         18 . The wellhead corrosion resistant system of  claim 11 , in which the anode assembly is a first anode assembly, and in which the wellhead corrosion resistant system further includes a second anode assembly, wherein the second anode assembly disposed to be positioned also above ground in the wellhead toolstring such that at least one wellhead tool in the wellhead toolstring is interposed between the first anode assembly and the second anode assembly. 
     
     
         19 . The wellhead corrosion resistant system of  claim 11 , in which the anode assembly further includes a removable internal anode housing to which at least one of the sacrificial anodes is secured, wherein the anode housing also includes a plurality of slots, wherein the slots are configured to encourage fluid flow around the anode housing. 
     
     
         20 . The wellhead corrosion resistant system of  claim 11 , further comprising:
 an isolator assembly disposed to be positioned also above ground in the wellhead toolstring such that the isolator assembly isolates electrically an uphole portion of the wellhead toolstring from a downhole portion of the wellhead toolstring;   wherein the isolator assembly is configured to isolate at least one wellhead tool in the wellhead toolstring electrically from the downhole portion of the wellhead toolstring when the at least one wellhead tool in the wellhead toolstring is positioned in the uphole portion of the wellhead toolstring between the anode assembly and the isolator assembly.