In-situ stress simulation and integrity evaluation of underground gas storage: A case study of the Xiangguosi underground gas storage, Sichuan, SW China

Abstract

To ensure the national demand for gas supply and peak shaving, a project of capacity expansion is proposed for the Xiangguosi underground gas storage (UGS). A geologic integrity evaluation is urgently needed to optimize the upper operating pressure and ensure the long-term safe operation. Thus, based on the geological, seismic, well logging, and dynamic monitoring data as well as the indoor core experimental data, 3D static and 4D geomechanical models were established for this UGS. Some geomechanical characteristics of the geological body were analyzed. The stability of the caprock, base, and fault under different reservoir pressure was individually simulated and evaluated as well. The results show that, both the caprock of the Liangshan Formation and the base of the Hanjiadian Formation may produce a little formation deformation during the operation; the five reservoir-controlling faults have no risk of fault activation during the early UGS operation under current stress conditions, and their sealing performance is good; when the reservoir pressure is higher than the original formation pressure of 6 MPa, the integrity of the Xiangguosi UGS is at risk of instability. This research accurately and quantitatively evaluate the operation safety of the Xiangguosi UGS under the influence of dynamic stress field, which has important guiding significance for the optimization of its operation plan.

Keywords

• xiangguosi
• underground gas storage
• 4d geomechanical model
• stress-strain simulation
• geologic integrity of gas storage