Multi-Cycle Deliverability Analysis of Underground Gas Storage Considering Stress Sensitivity

The cyclic injection production operations in underground gas storage (UGS) facilities lead to alternating changes in effective stress, resulting in irreversible permeability damage and productivity decline. To accurately evaluate the long-term operational performance of UGS, a damage factor m was introduced to modify the stress sensitivity model. A productivity equation incorporating stress sensitivity effects was subsequently established. Utilizing experimental data on the seepage capacity of reservoir rocks from the X UGS facility and well test data from the XC1 well, this study analyzed variations in the maximum gas injection capacity during multi-cycle injection operations. The results demonstrate that the modified model provides a significantly superior fit compared to classical models. The damage factor m exhibits a power-law decreasing trend with increasing cycle, declining from 0.95 in the first cycle to 0.62 in the fifth cycle during the production phase. Concurrently, the maximum injection capacity decreased from 1027.35 × 104 m3/d in the first cycle to 797.62 × 104 m3/d in the fifth cycle, representing a cumulative decline of 22.4%. The rate of decline decelerated markedly after the third cycle, with the annual attenuation rate dropping from 9.7% to 3%, indicating that plastic deformation tends to stabilize. The proposed model effectively captures the hysteresis and cycle-dependent permeability evolution in UGS reservoirs. The findings of this research offer valuable insights for guiding UGS production operations and optimizing production allocation strategies.