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Comprehensive Laboratory Measurements of the Hydraulic and Electrical Conductivities of Electrically Conductive Proppant-Supported Fractures Under Enhanced Geothermal System Conditions
Shuo WANG, Parisa BAZAZI, Jennifer MISKIMINS, Carlos TORRES-VERDIN, and Cheng CHEN
[Stevens Institute of Technology, USA]
Hydraulic fracturing with proppants in enhanced geothermal systems (EGS) improves reservoir permeability, thereby enhancing the efficiency and economic viability of geothermal energy recovery. Accurate fracture diagnostics remain critical for the long-term success of EGS projects. Borehole electromagnetic measurements using electrically-conductive (EC) proppants and fluids provide a promising approach for mapping fractures and proppant distribution. To evaluate the effect of using EC proppants under EGS conditions, we conducted comprehensive measurements of the hydraulic and electrical conductivities of EC proppant-supported fractures under stress and temperature conditions typical of the Utah-FORGE EGS. EC proppants of 30/50-mesh and 40/70-mesh sizes were placed in the space between two Sierra White granite slabs and then subjected to confining stresses up to 10,000 psi and the temperature of 230 °C. Hydraulic conductivity of the EC proppant-supported fracture, defined as the product of fracture permeability and fracture width, was measured under various confining stresses and proppant concentrations. The proppant concentration is defined as the proppant mass per unit fracture-face area. The results revealed non-monotonic dependence of the fracture hydraulic conductivity on the proppant concentration. These findings indicate that significant fracture hydraulic conductivity can be achieved using a partial-monolayer proppant pack in granite fractures, underscoring the potential for reducing material costs. Measurements under dry conditions show that EC proppant-supported fractures exhibit increasing electrical conductivity with confining stress due to enhanced interparticle contacts. It establishes a for electrical conductivity of EC proppant-supported fractures, which serves as a reference for subsequent measurements under brine-saturated conditions. These comprehensive laboratory testing data highlight the potential of using EC proppants in field-scale EGS fracture diagnostics.
Topic: Enhanced Geothermal Systems