Analysis of the 2024 Circulation Tests at Utah FORGE and the Response of Fiber Optic Sensing Data

Abstract

The 2024 circulation tests at the Utah FORGE site demonstrated a significant improvement in reservoir conductivity and fluid recovery following commercial-scale hydraulic stimulation. A nine-hour circulation test conducted in April 2024 was followed by a one-month test from August to September 2024. The results confirmed that hydraulic stimulation with proppant effectively enhanced permeability, leading to a substantial increase in production rate—from 7 gpm (0.17bpm) in 2023 to 378 gpm (9.0 bpm) in 2024—with a wellhead temperature of 385°F. This study investigates the behavior of the reservoir using the wellhead data (e.g., injection pressure, injection rate, production pressure, production rate, production temperature), downhole PT gauge, and the fiber optic sensing data. During the one-month circulation test, the injectivity (injection rate over pressure) gradually increased as the circulation continued. The injectivity increase could be due to the thermal cooling effect. The strain rate change pattern interpreted from the fiber optic cable corresponds to sudden flow of hotter water, as confirmed by the surface temperature gauge. The results highlight the benefits of proppant-supported fractures and the potential for sustained commercial geothermal energy production at Utah FORGE. These findings underscore the importance of continued circulation testing and advanced monitoring techniques for optimizing Enhanced Geothermal Systems (EGS) performance.