(64e) Evaluation of Ultra-High Temperature Resistant Preformed Particle Gels for Geothermal Preferential Fluid Flow Control

In recent years, to reduce carbon emissions, more and more attention has been focused on utilizing indigenous, renewable energies, such as solar, tidal and geothermal energy. Geothermal energy as a cost-effective green energy has been deployed to provide electricity worldwide for more than 100 years. The principle of generating geothermal energy is to inject cold water into the deep subsurface geothermal reservoir through the injection well, where temperatures are high enough for power generation (150~200 ^oC), and the injected cold water is recovered as steam or hot water through the production well. The extracted heat can be used for power generation. However, natural or unwanted fractures generated during drilling and hydraulic fracturing could cause fast and excessive cold water production and reduce the heat exchanging time between the cold water and the geothermal reservoirs, which significantly deteriorates the heat extraction efficiency. Currently, there are no hydrogel products available to meet the harsh conditions of geothermal reservoirs. This work systemically evaluates a novel high-temperature resistant preformed water-swellable particle gel system (HT-PPG) for controlling the fluid and heat flow through fracture networks in the geothermal reservoirs. We assessed the effect of variables like temperature, pH, and salinity on swelling behavior, gel strength, long-term thermal stability and plugging efficiency of this novel HT-PPG. The dried gel particle can swell to over 20 times its original volume, and the fully swelled particle gel's elastic modulus can reach over 800 Pa. Additionally, the HT-PPG showed excellent long-term hydrolytic thermal stability. No syneresis was observed during the three months exposure at 175 ^oC. HT-PPG described in this work is a promising product for controlling the fluid and heat flow in fractures containing geothermal reservoirs.