Effects of the spatial heterogeneity in reservoir parameters on the heat extraction performance forecast based on a 3D thermo-hydro-mechanical coupled model: A case study at the Zhacang geothermal field in the Guide basin, northeastern Tibetan plateau

Abstract

Geothermal extraction assessment is of considerable importance for the reservoir operation management. Based on the data of the high-temperature reservoir of the Zhacang geothermal field in the Guide basin, northeastern Tibetan plateau, this study explores the effects of the heterogeneity in the reservoir parameters on the assessment of the reservoir extraction ability via a 3D thermo-hydro-mechanical (THM) fully coupled model and compares the prediction discrepancies between the heterogeneous reservoir models with the constant and stress-dependent permeability. Modeling results show that the variance of the specific heat capacity has a negligible impact on the reservoir performance, whereas the changes in the correlation length can result to relatively apparent difference in both the outlet temperature and effective electric power rate. Compared with the specific heat capacity, the spatial heterogeneity in permeability has greater significant effect on the reservoir performance, which may be related to the occurrence of the preferential flow with the increasing variance and correlation length of the permeability. The prediction difference of the reservoir performance emphasizes the great importance of the stress-dependent reservoir permeability in a THM coupled reservoir numerical model to accurately assess the extraction ability of a geothermal reservoir concerned.