Geo-mechanical evaluation of a proposed gas storage in aquifer anticline trap with deep fault

This paper investigates the feasibility of a proposed underground gas storage facility. Based on S gas storage, a large-scale 2D hydromechanical coupling FEA model is established to explore the geo-mechanical properties of S gas storage under a multi-cycle alternating injection and production and validated by the interference logging test. To account for the damage development of fault damage area under the influence of seepage-stress coupling, the soil adopts the Mohr–Coulomb constitutive assumption. Additionally, a zero-thickness cohesive element is proposed as a mechanical model to simulate the fault gouge. The mechanical parameters of zero-thickness cohesive elements are verified by a ring shear test and a preliminary FE model. Thereafter, another refined conceptual finite element (FE) model considering the fault damage area, fault core, water-containing damaged area, overburden damaged area, and the contact model between different damaged areas of the fault and the fault core is developed and validated. The simulation results demonstrate that the initial seal ability of the caprock and faults remains intact. Specifically, (i) the maximum caprock and ground displacements are 8.5 cm and 5.4 cm, respectively. (ii) The most significant slip distance is 0.125 mm, indicating that, leakage under the action of multi-period alternating injection–production, the S aquifer structure had no fault activation and caprock. (iii) The risk of fault activation is higher for high-angle faults compared to low-angle faults. Low-angle faults are more susceptible to shear slip. Providing a scientific reference for the feasibility study of gas storage.