Integrity Issues for Underground Gas Storage Wells

Underground gas storage (UGS) well integrity presents significant challenges for environmental safety and operational reliability, particularly in aging infrastructure. This comprehensive review synthesizes the current understanding of zonal isolation issues in UGS wells, analyzing mechanical failures, thermal cycling effects, and chemical degradation mechanisms that compromise wellbore integrity. Through analysis of field data from global UGS facilities, we identify that 55% of well component failures occur in casings and 32.5% in wellheads, with corrosion and human intervention as primary causes. Laboratory studies reveal that conventional cement formulations show limited effectiveness under cyclic loading conditions, radial stress increases linearly from 17 MPa to 24 MPa during operational cycles, which can lead to the formation of micro-annuli at cement interfaces. Our analysis of thermal cycling effects demonstrates that cement sheaths in sandstone formations exhibit significant degradation after 20 cycles, while shale formations show better stability. Field observations indicate that reducing plug length from 200 m to 100 m increases leakage rates by approximately 60%, highlighting the critical relationship between cement barrier design and containment effectiveness. We evaluate emerging solutions, including nano-enhanced cement and shape-memory polymers, finding variable field performance despite promising laboratory results, particularly in high-salinity environments. The study presents a novel risk-based approach for optimizing cement barrier designs, considering reservoir characteristics, gas properties, and operational conditions. These findings provide crucial insights for improving UGS well integrity, particularly for those wells that were not originally planned for gas storage.