Development and Application of a Casing Annulus Pressure Relief Device for Better Wellbore Integrity in Deepwater Wells

A kind of casing annulus pressure relief device with high precision rupture disk as the core part was developed to solve the problem of annular pressure buildup problems which can cause casing collapse and rupture during deepwater oil and gas production.It makes use of the characteristics of rupture disk material to release the annulus expansion fluid instantaneous and eliminate the potential risk caused by the increase of the annulus pressure.The rupture disk assembly body is manufactured with stainless steel SS316,and burst disk is manufactured from nicochrome NS312,which incorporate a conventional domed inward type structure design with a maximum design rupture pressure level of 36.6 MPa.The rupture disk casing sub design has a double hole pressure relief to prevent failure.Laboratory tests demonstrate that the rupture disk maintains structure integrity,has high temperature resistance and good aging stability with 0.80 times of designed rupture pressure for the engineering requirement.The actual test rupture pressure complies with the design requirement of manufacturing deviation of ±3.0%.With the increasing of test fluid temperature,the test rupture pressure would slightly decrease,with the total change volume less than 5.0% and lower than rupture pressure tolerance,meeting field application requirements.The casing annulus pressure relief device achieved success in field applications in 3 deepwater wells in one eastern block of the South China Sea,and no downhole accidents have occurred up to now that were caused by annular pressure buildup problems.The research showed that the casing annular pressure relief device achieved the anticipated annular pressure management objectives and could ensure the wellbore safety.