Casing Expansion as a Promising Solution for Microannular Gas Migration

Abstract

Summary The objective of this research was to investigate the potential effect of expandable-casing technology on the cement sheath and remediation of sustained casing pressure (SCP) caused by microannular gas migration. Varying magnitudes of SCP exist in the Gulf of Mexico, where more than 80% of casing strings exhibiting SCP are production and surface casings, representing a great technical, economic, and environmental risk. Situations in which SCP is observed usually result in costly and frequently unsuccessful remediation efforts. A unique bench-scale physical model was used to simulate expansion of a previously cemented casing under field-like conditions. Experimental measurements obtained before and after low-percentage pipe expansion exhibited improvement of cement/pipe interface. Successful multirate flow-through experiments with nitrogen gas showed the effectiveness of this technique in sealing of microannular-gas-leakage pathways, providing ideal remediation of SCP immediately post-expansion; and after up to 60 days of post-expansion, the seal integrity was intact.