Three-Dimensional Thermoporoelastic Modeling of Hydrofracturing and Fluid Circulation in Hot Dry Rock

Geothermal energy, featured as a renewable low-carbon energy resource, exhibits great potential in mitigating global warming. However, efficient mining of geothermal energy from hot dry rock remains challenging due to the lack of a thermoporoelastic modeling approach that allows for integrated simulation of hydrofracturing and fluid circulation, and poor understanding of the mechanisms of hydraulic stimulations. To conquer these challenges, we propose an advanced modeling approach, which enables us to deal with the interplay between fluid transport, heat transfer, rock deformation, and three-dimensional fractures' growth and interaction. Based on the thermoporoelastic model, a refined investigation is performed to determine the hydrofracturing and fluid circulation processes, using data collected from the EGS Collab Experiment 1. This meso-scale testbed involves creating major hydraulic fractures, accompanied by numerous secondary hydroshearing fractures, hydraulically connecting two horizontal wellbores to build a fluid circulation system. All wellbores in the testbed were heavily instrumented with monitoring devices, offering high-quality data to properly constrain the geomechanical model. Our study provides insights into: (a) how the EGS Collab testbed responds to propagating fractures with strong stress shadowing and long-term injection of chilled water; (b) why the parallel pattern of two hydraulic fractures with a distance much smaller than the fracture dimension forms during multi-staged hydraulic stimulations; and (c) what the mechanisms are that determine hydrofracturing performance. Overall, this work not only contributes to a novel modeling approach for integrated simulation of hydrofracturing and fluid circulation, but advances our understanding of creating enhanced geothermal systems with interconnected fracture networks.