Prevention of surface annular casing pressure (SCP/SAP) in the B-annulus

Abstract

The annulus between the 9⅝″ and the 13⅜″ casing strings within a Norwegian field development had historically exhibited pressure build-up at surface on many wells. It had been determined that the source of the pressure was a gas-charged formation just below the 13⅜″ shoe. Eliminating surface annular pressure (SAP) was a priority along with easy barrier verification for the lifetime of the well. To eliminate the SAP several methods had been trialled over the years, including single-stage cementing, ECPs, and liner tie-back solutions—all of which had failed to resolve the problem. Meanwhile, a hydraulically expanded steel annular barrier had been successfully deployed by the operator for zonal isolation in a number of wells across various reservoir sections. It was proposed that the same technology be used as an alternative solution to eliminate the SAP. To be utilised as a primary well barrier, the solution had to pass a number of significant criteria. It was carefully reviewed by the operator’s well integrity team to ensure that the system complied with their own company standards and the Norsok D10 guidelines. Verification of the annular barrier as the primary barrier was achieved by the application of surface pressure down the 13⅜″ by 9⅝″ annulus; pressure equivalent to the fracture gradient of the formation below the 13⅜″ shoe plus a 1,030 psi surplus. This installation marks the first time that something other than cement has been installed in a well completion as a primary barrier.