Analytical/Streamline Simulations for Enhanced Geothermal Systems

Natural geothermal energy sites are rare, so future expansion of geothermal energy resources is likely to require injecting water in enhanced geothermal systems (EGS) to produce heat from reservoirs. Many prospective geothermal reservoirs exhibit strongly advective, fracture-dominated flow through impermeable crystalline rock, which is challenging to model with traditional 3D reservoir simulators. This work presents a prototype streamline simulator for heat and fluid flow directly on fracture networks. Novel analytical solutions for one-dimensional heat and water movement are developed on the finite domain between the injection and production wells. Transverse diffusive heat loss is approximated using the Lauwerier approximation. The form of the resulting solution is an infinite sine series. Streamlines are generated using particle tracking for a fractured network. Solutions to the analytical model with parameters representative of EGS are mapped onto the streamlines to create a rapid, approximate solution for the 3D fracture simulation. Finally, the streamline simulation results are favorably compared to a 3D simulation with explicitly meshed fractures and 3D simulations with upscaled fractures using the equivalent continuum porous media (ECPM) approach. This abstract is SAND2025-09466A. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This work was funded by the SNL Laboratory-Directed Research & Development Exploratory Express program. This poster is SAND2025-15123C.