Numerical simulation study of segmented hydraulic fracturing in horizontal wells of fractured hot dry rocks, at the U.S. FORGE site

Abstract

Enhanced geothermal systems (EGS) are engineered deep rock heat exchangers that require hydraulic fracturing to create artificial heat storage and transfer heat through fissures. The technique involves a complex heat-fluid-solid (THM) coupling process. In this study, based on the Frontier Observatory for Research in Geothermal Energy (FORGE) site 16A(78)-32 horizontal well in Milford, Utah, USA, a hydraulic fracturing model for horizontal wells, distinct from traditional EGS doublet designs, was established. This model combines the three thermal-fluid-mechanical (THM) physical fields and investigates the impact of injection volume, temperature, and injection sequence on ground rock modification during horizontal well hydraulic fracturing. The results show that after 75 h of enhanced production treatment, the model predicts an increased production volume of approximately 8.3 × 10⁶ m³. Increasing the injection fluid volume stimulates shear fracturing in existing fractures, widening the area of greater production. Changing the injection sequence does not increase the volume of fractured rock. With increasing injection temperature, there is a slight decrease in the modified volume produced.