Using a Flexible, Expandable Sealant System to Prevent Microannulus Formation in a Gas Well: A Case History

Abstract

Abstract Long-term zonal isolation of gas reservoirs is a difficult problem. This paper summarizes the implementation and evaluation of a new sealant system designed to overcome this problem by preventing formation of a microannulus across the gas zone. A case history of its use in a well in the United Arab Emirates demonstrates the successful application of the flexible, expandable sealant material to prevent microannulus and maintain cement sheath integrity in the production casing section. In one well, a conventional cement slurry formulation was used for the 9 5/8-in. section. The section was then tested to 3,000 psi pressure. Cement-bond logs showed clear deterioration of cement sheath quality behind the casing. A similar result for upcoming casing sections was a concern, so the sealant was redesigned to accommodate downhole stresses across the interval. The new design, which was used in the 7- in. liner section in the same well, enabled mechanical and expansion properties to be engineered to withstand downhole stresses and minimize the debonding effect. After successful isolation in the first well, the flexible, expandable sealant material was established as standard practice in similar wells.