As enhanced geothermal systems (EGS) continue to gain attention, the ability to engineer and quantify fracture connectivity becomes increasingly important. A critical aspect of this process is understanding proppant placement within fractures, as it directly impacts hydraulic conductivity and guides decisions on (a) where to best intersect fractures for optimal flow paths, or (b) which well completion technique needs to be implemented. Current methods of fracture detection, such as microseismic monitoring or proppant tracers often cannot uniquely resolve proppant distribution far from the borehole, thereby introducing high uncertainty when determining which fracture regions are hydraulically conductive. In this study, we advance the application of triaxial borehole electromagnetic (EM) measurements for detecting and imaging propped fracture geometry in geothermal fields as an alternative/addition to the current fracture detection and appraisal methods to reduce uncertainty. As a preliminary study, we performed numerical simulation of EM measurements in the presence of fractures for both open- and cased-hole completions. Fracture geometries were simulated using ResFrac, providing realistic representations of stimulated areas, and then modeled in COMSOL to evaluate the synthetic triaxial borehole EM response of fractures injected with electrically conductive proppant. Simulation results indicate that borehole instruments with spacings of 100 m, operated at low frequencies (100 Hz), are required to detect the full extent of stimulated fractures. For fracture imaging, a combined strategy is recommended: Long-spacing, low-frequency measurements provide information on the overall extent of proppant-filled fractures, while short-spacing, higher-frequency measurements yield more precise information on fracture locations and type along the borehole. These findings support the development of new inversion methods for imaging the propped fracture geometry, enabling more accurate analysis of fracture connectivity in the field and ultimately improving the ability to ensure robust hydraulic communication between injector and producer wells in EGS.

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