THM coupled numerical analysis on the geothermal energy storage & extraction in porous fractured reservoir

This paper presents the numerical investigation of the geological thermal energy storage (GeoTES) by considering well configuration, discrete fracture network (DFN), and mechanical effect. After validated against field experiments, the MOOSE framework was used to simulate the GeoTES with geological properties from the Weber/Tensleep formation. Mono-well, doublets with different well distance, 5-spot with and without discrete fracture network, and 5-spot with and without mechanical deformation were modeled based on annual injection-storage-extraction-rest cycle for over 10 years. Each period in a cycle lasts for one season, and the same amount of water was injected and extracted within each year. Results show that: (1) the highest recovery efficiency 37% is yielded from the mono-well and the 5-spot without DFN, suggesting that extracting thermal energy directly from the injection well is the best practice; (2) the presence of DFN yield less recovery efficiency, and the pore pressure continues to build-up; (3) thermal expansion and mechanical volumetric strain increase upon three months of injection can only increase the formation permeability about 3% at maximum, indicating the influence the mechanical behavior is negligible for the investigated GeoTES. Future work towards a detailed reservoir model with consideration of chemical reaction is undergoing.