Meshing, Multiphysics Modeling, and Field-Scale Assimilation for EGS and Geophysical Sensing

ABSTRACT: Enhanced Geothermal Systems (EGS) hold promise for abundant heat extraction from the deep subsurface, but reliably predicting fluid flow behavior through stressed and chemically reactive fracture networks over long time periods remains challenging. This study introduces a novel scheme for predictive modeling and field data assimilation. A novel automated workflow is developed to generate a high-resolution, unstructured, dual mesh that precisely captures the characteristics of hydraulic fractures, boreholes, and drift. Geomechanical processes are solved on tetrahedral cells, while thermal-flow-transport processes are solved on Voronoi cells. PFLOTRAN is employed for high-performance thermal-hydrological-mechanical-chemical-electrical (THMC-E) simulations to model reactive fracture flow, transport, heat transfer, geomechanical behavior, and electrical geophysical responses. The simulation results can be correlated with geophysical and fluid data from saline circulation tests at the 4100-level testbed (1.5 km deep) at the Sanford Underground Research Facility (SURF) in South Dakota. An analysis has been conducted to evaluate the impact of fracture conductivity on fluid flow dynamics, pressure evolution, heat transfer processes, and stress-strain responses in EGS. This study advances our understanding of coupled THMC-E processes, paving the way for increasingly accurate fluid flow predictions and rapid geophysical data assimilation for EGS reservoirs.