A novel semi-analytical monitoring model for multi-horizontal well system in large-scale underground natural gas storage: Methodology and case study

Abstract

Carbon neutrality necessitates cleaner and more efficient use of fossil fuels. The storage of substantial amounts of energy in porous subsurfaces, such as underground natural gas storage (UGS), which is regarded the only long-term energy storage solution, is one of the promising technologies. Appropriate monitoring mechanisms are necessary for the security of UGS with a correctly configured injection-withdrawal capacity. In this research, a semi-analytical model of multi-horizontal well systems is presented and used to large-scale underground natural gas storage. The Laplace transform and Stehfest numerical inversion are used in UGS to solve the radial diffusion equation. We used the line source function and the pressure superposition principle to find a solution for a multi-horizontal well system. To illustrate the reliability of the suggested method, a numerical verification was performed. In UGS, pressure behavior at various phases identifies several types of flow regions, including wellbore storage effect stage, skin effect stage, early radial flow stage, linear flow stage, transitional flow stage, and late radial flow stage. Continuous gas injection and withdrawal from offset wells might result in pressure behavior with rising or dropping features when compared to a single well model. The evaluated permeability is 0.68 mD, the well spacing is 502 m, and the initial pressure is 27.28 MPa, according to field data from China's largest Hutubi UGS. The maximum injection and withdrawal capacities for wells with and without interference with wells are 9.46 × 105 and 1.1 × 106 m3/d/MPa, respectively, according to the productivity index. By continually injecting gas from offsetting wells, the target well's potential gas withdrawal capacity is raised by 16.2 %.