SPE-203766-MS
A Case of Achieving Sustainable Annular Sealing in a Deepwater Marginal Nigerian Field
The industry has been relying on cement as primary method for annular sealing. The initial evaluation considers a formation integrity test and a cement bond log. This shows good results in 85% of the cases and cement squeeze is the main remediation method. The ultimate measure of the sealing performance is production: more than 50% of the wells have sustained casing pressure in the B-annulus or are producing in degraded mode. Additional solutions are required to improve the sustainability of the industry.
The present paper discusses a case history in a marginal well in Nigerian deepwater. Primary cement evaluation was successful, in line with the industry statistic of 85% successful cases. However, production started with 60% Basic Sediments and Water (BS&W) and after six months of production, the well was shut-in due to excessive gas production. The investigation identified that the target Turonian oil sand was separated by thin shales from bottom water and gas cap.