Device and method for mitigating annular pressure buildup in a wellbore casing annulus

Abstract

A device and method are provided for mitigating annular pressure buildup in a wellbore casing annulus of an oil or gas well. The device includes a tubular member including an outer side, a chamber secured around the outer side, the chamber having at least one flexible portion for varying the internal volume of the chamber, at least one reservoir capable of supplying a gas, and a pressure compensator connecting the reservoir and the chamber. The reservoir is able to feed the chamber volume with the gas via the pressure compensator.

1 . A device for mitigating annular pressure buildup in a wellbore casing annulus of an oil or gas well, comprising:
 a tubular member comprising an outer side,   a chamber secured around said outer side,   said chamber having at least one flexible portion for varying the internal volume of the chamber,   at least one reservoir capable of supplying a gas,   a pressure compensator connecting said at least one reservoir and said chamber, and   wherein said at least one reservoir is able to feed said chamber with said gas via the pressure compensator.   
     
     
         2 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said chamber comprises an envelope disposed around said outer side, said outer side and said envelope forming said chamber, and wherein said envelope comprises said at least one flexible portion. 
     
     
         3 . A device for mitigating annular pressure buildup according to  claim 2 , wherein said envelope includes a first flange and a second flange, said flanges being arranged at a distance from one another along said tubular member, and wherein said flexible portion is an elastic membrane that is disposed radially around said outer side, that extends axially along the tubular member and that is fastened at its axial extremities to said two flanges. 
     
     
         4 . A device for mitigating annular pressure buildup according to  claim 3 , wherein said elastic membrane is configured to produce a uniform rise or decrease of said chamber volume. 
     
     
         5 . A device for mitigating annular pressure buildup according to  claim 3 , wherein said elastic membrane is transversally or longitudinally lobe-shaped. 
     
     
         6 . A device for mitigating annular pressure buildup according to  claim 3 , wherein said flanges and said elastic membrane are made of steel. 
     
     
         7 . A device for mitigating annular pressure buildup according to  claim 3 , wherein said tubular member comprises reinforcement and holding means fastening said elastic membrane. 
     
     
         8 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said chamber includes at least one tube, wherein said tube comprises said at least one flexible portion. 
     
     
         9 . A device for mitigating annular pressure buildup according to  claim 8 , wherein said one or more tubes are straight tubes arranged parallel to said tubular member or tubes wound around said tubular member. 
     
     
         10 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said pressure compensator allows gas to flow from said at least one reservoir to said chamber when said external pressure increases. 
     
     
         11 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said pressure compensator is an air pressure regulator adapted to high pressure. 
     
     
         12 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said reservoir is selected from bottles, cylinders or any other recipients suitable for containing gas under pressure. 
     
     
         13 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said at least one reservoir is a cryogenic storage dewar. 
     
     
         14 . A device for mitigating annular pressure buildup according to  claim 1 , wherein said chamber comprises a burst disk to vent supply gas when the pressure prevailing in the chamber exceeds a predetermined limit. 
     
     
         15 . A device for mitigating annular pressure buildup according to  claim 1 , wherein the said tubular member is a casing tube. 
     
     
         16 . A method of mitigating pressure buildup within a wellbore casing annulus of an oil or gas well, wherein said method comprises:
 providing at the ground level a device for mitigating annular pressure buildup according to  claim 1 ,   lowering said device in the wellbore,   letting said pressure compensator allow flow of said gas from the at least one reservoir into the chamber, so as to at least partially compensate an increase of external pressure due to the lowering of said device.   
     
     
         17 . A method according to  claim 16 , comprising filling said reservoir with said gas in pressurized form or in liquid form, before lowering said device in the wellbore. 
     
     
         18 . A method according to  claim 17 , wherein said gas is inert gas, such as nitrogen. 
     
     
         19 . A method according to  claim 16 , further comprising filling said reservoir with a gas generator capable of producing said gas, before lowering said device in the wellbore. 
     
     
         20 . A method according to  claim 19 , wherein said gas generator is a propellant and wherein said gas is produced by said propellant. 
     
     
         21 . A method according to  claim 16 , further comprising adjusting the pressure prevailing in said chamber to a value substantially equal to ground level pressure before lowering said device in the wellbore. 
     
     
         22 . A method according to  claim 16 , wherein said pressure compensator lets said gas flow from the at least one reservoir to the chamber when the external pressure is above a specified pressure. 
     
     
         23 . A method according to  claim 16 , wherein said flexible portion deforms when the pressure difference between the external pressure and the pressure inside said chamber exceeds a specified value.