Evaluation method for fault safety and its application based on ANSYS: a case study of Baiju aquifer gas storage in Dongtai Depression, Subei Basin

Abstract

Aquifer gas storage uses porous media reservoir to store natural gas. The location of aquifer gas storage has a wide geographical range and does not depend on large salt mines or depleted oil and gas reservoirs, which is of great significance to China's natural gas strategy. Aquifer gas storage realizes periodic injection-production through natural fault blocking natural gas and cementing technology, so as to achieve the purpose of adjusting seasonal peak value. Affected by the change of injection-production pressure, faults are easy to be opened or broken during operation, leading to the leakage of natural gas stored. Therefore, it is very important to evaluate the fault safety of aquifer gas storage, but the common fault evaluation and numerical simulation methods do not involve the porous media reservoir, and the study of its expansion mechanism is insufficient, which does not satisfy the fault safety evaluation of water-bearing structure. Based on the basic characteristics of aquifer gas storage, this paper summarizes a set of complete fault safety evaluation methods by ANSYS finite element simulation and static mechanics analysis. A case study was carried out in Baiju aquifer gas storage in the Dongtai Depression of the Subei Basin. A 3D entity model of formation and fault was established. According to the initial stress equilibrium analysis and the axial compression experiments of fault rock samples, the validity of the model can be demonstrated. With displacement constraint method, the stress state of target faults at different operating pressure was simulated. The maximum value of predicted operating pressure is 29.50 MPa, and tensile failure may occur above this value.

Keywords

• ansys
• aquifer gas storage
• fault
• safety evaluation