Structural Well Integrity – Surface Casing Corrosion Management Strategy North Sea Experience

Abstract

Abstract Structural Well Integrity is an emerging area in Well Integrity Management in the oil and gas Industry. A key component that ensures the structural integrity for wells is the surface casing. However, over the years little or nothing has been done to address corrosion problems of the surface casing. Though a number of reports have been completed that analysed the casing failures with recommendations for monitoring and maintenance of affected wells, surface casing corrosion has remained an issue with many operators globally. The loss of casing wall thickness due to corrosion (Microbial, Oxygen and acid) can lead to collapse of affected wells with attendant loss of production, environment concerns from resulting spills, loss of lives, significant remediation cost and reputational damage. With recent failures of the surface casing due to corrosion and the need to extend the end of field life, a campaign was embarked on to develop an industry-acceptable management strategy. This paper discusses the integrated approach employed to understand the problem and develop management strategy. The objective of the strategy developed is to implement a management system that ensures that structural integrity of the surface casings of the operators' well portfolio is maintained in line with the well life extension requirements. Effort was made to trace the history of surface casing corrosion within North Sea; review results from surveys of the surface casing; review the calculated risks associated with structural integrity of surface casings for all sample wells; develop workflow for corrosion management; and document monitoring and mitigating measures.