Development and Evaluation of Preformed Particle Gels for Preferential Fluid Flow Control in Geothermal Reservoirs

Enhanced Geothermal Systems (EGS) represent cutting-edge technologies designed to harness clean energy from the Earth's crust. However, the presence of short-circuits in certain geothermal reservoirs poses a significant threat to their sustained viability as reliable sources of clean energy. This issue arises when cold fluids injected into the reservoirs quickly traverse fractures with large apertures and directly communicate between injection and production wells without acquiring sufficient heat from the rock matrix. Effective control of flow dynamics outside the wellbore and within the reservoir is crucial to mitigate undesirable flow patterns. Polymer gels, proven successful in managing preferential flow in oil and gas reservoirs, could be adapted for controlling flow in geothermal reservoirs. Nonetheless, the absence of hydrogel products capable of withstanding the harsh conditions of geothermal reservoirs (>150 °C) for extended periods has been a limiting factor. in response, our recent efforts have led to the development of innovative high-temperature resistant preformed particle gels (HT-PPG) specifically designed for this purpose. This study provides a comprehensive overview of our research advancements, encompassing the creation of a series of innovative particle gel products. We explore their swelling behavior, rheology, thermal stability, and plugging efficiency to fractures, highlighting their applicability in geothermal contexts, even under elevated temperatures. These products are adaptable for reservoirs with preferential fluid flow paths which have temperatures ranging from 20 to 200 °C (the reservoir could have higher temperature) and can be customized with controllable sizes ranging from micrometers to a few millimeters. Our developed products feature controllable swelling times and demonstrate commendable long-term hydrolytic thermal stability, maintaining their effectiveness for over three months. Additionally, we have designed a micromodel to observe the swelling kinetics and transport mechanisms of a representative particle gel. Furthermore, we employ numerical simulation to model particle gel injection and assess blocking performance. overall, the HT-PPG developed in this work emerges as a reliable solution for controlling preferential fluid flow in geothermal reservoirs, addressing a critical challenge in the quest for sustainable and efficient geothermal energy extraction.