Integrated Diagnostics for Interpreting the Efficiency of the Utah FORGE Enhanced Geothermal System

Abstract

We present results from a one-week circulation test at the Utah FORGE site following the installation of coiled-tubing deployed fiber optic cables in the 16B producer. A comprehensive suite of diagnostics was applied to evaluate flow pathways and reservoir response. A spinner injection log suggested that injection was limited to three heelward stages, while fiber optic distributed sensing revealed three to four primary inflow zones in the producer. Thermal signatures during pressure buildup indicated possible crossflow behavior and provided evidence for a dominant connection point between the wells. Chemical tracer tests, including a freshwater negative tracer test, inform the circulation volume between the wells. We present efforts to use the tracer data to estimate the effective heat exchange area between the wells. Production efficiency increased steadily from 25% to 65% during the test. Bottomhole pressure and temperature measurements provided supporting constraints on reservoir conditions. Collectively, these diagnostics demonstrate the utility of fiber optics and complementary tools for characterizing fluid circulation and reservoir behavior in enhanced geothermal systems.