Multiscale Characterization of Thermo-Hydro-Chemical Interactions Between Proppants and Fluids in Low-Temperature EGS Conditions

Bruce Mutume (), Ali Ettehadi, B. Dulani Dhanapala, Terry Palisch and Mileva Radonjic ()
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Bruce Mutume: Hydraulic Barrier Material and Geomimicry Laboratory, School of Chemical Engineering, Oklahoma State University, 420 Engineering North, Stillwater, OK 74078, USA
Ali Ettehadi: Hydraulic Barrier Material and Geomimicry Laboratory, School of Chemical Engineering, Oklahoma State University, 420 Engineering North, Stillwater, OK 74078, USA
B. Dulani Dhanapala: ATRC Imaging Suite, College of Engineering, Architecture, and Technology, Oklahoma State University, 420 Engineering North, Stillwater, OK 74078, USA
Terry Palisch: CARBO Ceramics Inc., 5050 Westway Park Blvd, Houston, TX 77041, USA
Mileva Radonjic: Hydraulic Barrier Material and Geomimicry Laboratory, School of Chemical Engineering, Oklahoma State University, 420 Engineering North, Stillwater, OK 74078, USA

Energies, 2025, vol. 18, issue 15, 1-24

Abstract: Enhanced Geothermal Systems (EGS) require thermochemically stable proppant materials capable of sustaining fracture conductivity under harsh subsurface conditions. This study systematically investigates the response of commercial proppants to coupled thermo-hydro-chemical (THC) effects, focusing on chemical stability and microstructural evolution. Four proppant types were evaluated: an ultra-low-density ceramic (ULD), a resin-coated sand (RCS), and two quartz-based silica sands. Experiments were conducted under simulated EGS conditions at 130 °C with daily thermal cycling over a 25-day period, using diluted site-specific Utah FORGE geothermal fluids. Static batch reactions were followed by comprehensive multi-modal characterization, including scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and micro-computed tomography (micro-CT). Proppants were tested in both granular and powdered forms to evaluate surface area effects and potential long-term reactivity. Results indicate that ULD proppants experienced notable resin degradation and secondary mineral precipitation within internal pore networks, evidenced by a 30.4% reduction in intragranular porosity (from CT analysis) and diminished amorphous peaks in the XRD spectra. RCS proppants exhibited a significant loss of surface carbon content from 72.98% to 53.05%, consistent with resin breakdown observed via SEM imaging. While the quartz-based sand proppants remained morphologically intact at the macro-scale, SEM-EDS revealed localized surface alteration and mineral precipitation. The brown sand proppant, in particular, showed the most extensive surface precipitation, with a 15.2% increase in newly detected mineral phases. These findings advance understanding of proppant–fluid interactions under low-temperature EGS conditions and underscore the importance of selecting proppants based on thermo-chemical compatibility. The results also highlight the need for continued development of chemically resilient proppant formulations tailored for long-term geothermal applications.

Keywords: proppant stability; enhanced geothermal systems; EGS hydraulic fracturing; thermal cycling; Utah FORGE; fluid-solid interactions (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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