Thermal-Hydraulic-Mechanical (THM) Modeling of Fluid Flow and Heat/Tracer Transport Between Injection and Production Wells at the Utah FORGE Site



Key Words:

FORGE, numerical modeling, THM, sustainability


Stanford Geothermal Workshop




Enhanced Geothermal Systems



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2174 KB

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The Frontier Observatory for Research in Geothermal Energy (FORGE) site is a multi-year initiative funded by the U.S. Department of Energy for enhanced geothermal system research and development. The site is located on the margin of the Great Basin near the town of Milford, Utah. Modeling and simulation is playing a critical role FORGE, being considered as a general scientific discovery tool to elucidate behavior of enhanced geothermal systems and as a deterministic (or stochastic) tool to plan and predict specific project activities. In this analysis, we use the FALCON simulator to study mid-term flow and transport (6 month) in the enhanced geothermal system (EGS) reservoir focusing on the breakthrough times for injected tracers and thermal fronts, in an effort to provide input on injection-production well spacing that can ensure reliable and sustainable heat recovery from the geothermal reservoir over the testing timeframe of the FORGE program. A 3-dimensional Thermal-Hydraulic Mechanical (THM) reservoir model that encompasses the zones that were stimulated in Well 16A(78)-32, consisting of a 2.16e8 m3 volume using grid cells that range from 2 to 100m has been developed for the analysis. For selected cases, the reservoir model is coupled to a 1-dimensional thermal hydraulics simulation of non-isothermal fluid through Well 16A(78)-32, including perforations emplaced during the stimulation process. The combined simulation examines pressure and temperature changes (along with associated fluid property changes) in the well bore, partitions spatially and temporally varying flow exiting the well and entering the geothermal reservoir by examining the pressure difference between the perforated zones in the well and the surrounding formation and the reservoir along with the reservoir permeability, and assigns three point sources in the reservoir model that correspond to the three stimulation zones in the well. Spatial and temporal evolution of the fractured permeability in the reservoir resulting from injecting cold fluid (50oC) into the initially hot reservoir (~220oC) results in both poro-elastic and thermo-elastic evolution of the reservoir. For this simulation, the location of the production well was situated directly above the injection well, vertically offset by three distances (75m, 100m and 125m) to examine tracer the thermal breakthrough times. An open hole completion of Well 16B was simulated using the formulation by Peaceman, where the spatial variability of flow along the well bore could be evaluated. The extraction behavior shows an interesting response to the pressure and temperature evolution in the reservoir

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