Insights from Unplanned Outcomes in Laboratory DFIT Experiments for Utah FORGE Stimulation and Stress Analysis

Abstract

Understanding the in-situ stress in the subsurface is crucial for many scientific and engineering activities, including the development of Enhanced Geothermal Systems (EGS). A common technique for determining the minimum principal stress is to interpret the pressure transient during a small-scale hydraulic fracturing test. A few hydraulic fracturing stress measurements have been conducted at Utah FORGE, and some results have shown discrepancies and posed challenges in interpretation. To address these issues, we conducted a series of controlled laboratory DFIT experiments, specifically tailored to the geothermal context of Utah FORGE (Ye & Ghassemi, 2023, 2024). Unlike previous studies, here we describe a set of laboratory DFIT experiments with unexpected results, and use them to elucidate the operational and interpretative aspects of hydraulic fracturing stress measurements in high-temperature and naturally fractured geothermal reservoirs. Specifically, we explore the effects of near-wellbore tortuosity, non-planar fracture geometry, injection rate, and cooling on the accuracy of hydraulic fracture stress measurements, aiming to enhance stress measurement accuracy and data interpretation at Utah FORGE and other geothermal reservoirs.