Estimating Thermal Breakthrough at Utah-FORGE from a Thermo-Hydraulic Fracture Model Calibrated to Circulation Data

Abstract

The Utah Frontier Observatory for Research in Geothermal Energy (FORGE) conducted a 30-day commercial-scale circulation test in August 2024 between wells 16A(78)-32 and 16B(78)-32. During this test, field data were collected, including injection pressure, spinner log measurements of mass flow near each injection perforation, tracer injection and recovery, and mass injection and recovery rates. A discrete fracture network (DFN) of the FORGE site was developed using microseismic data from hydraulic stimulation and circulation tests, core samples, strain gauge measurements, and inferred fracture connectivity derived from flow and pressure responses. In this study, a multi-component thermal-hydraulic simulation of the DFN was calibrated to match the observed field data and used to predict thermal breakthrough behavior. The DFN is modeled as a set of 2D fractures embedded in a 3D domain, with fracture permeabilities dependent on their aperture and flow rate. A linear relationship between mass flow rate and fracture aperture calibrated to the circulation test data is used to parameterize the DFNs based on spinner log data. Using the calibrated parameters, thermal-hydraulic simulations were performed to model a 180-day circulation test and estimate the time to thermal breakthrough.