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Coupled THMC Flow-Through Experiments and Decision Analysis of Proppant Performance Under Utah FORGE EGS Conditions
Bruce MUTUME, Ali ETTEHADI, Terry PALISCH, Wenming DONG
[Oklahoma State University, USA]
Thermo-hydro-mechanical-chemical (THMC) flow-through experiments were conducted to evaluate the stability of three proppant systems under Utah FORGE-representative EGS conditions. Quartz sand (FORGE 40/70), Carbolite 40/70, and Kryptosphere LD (40 mesh) were confined between granitoid platens and exposed to 2,000-6,000 psi and 200 °C in deionized water. Mineralogical, chemical, and mechanical responses were assessed using XRD, SEM-EDS, ICP-MS, and API sieve analysis, and compared with earlier thermo-chemical (TC) batch tests in Utah FORGE fluids at 220 °C. XRD shows that both ceramic proppants maintained their crystalline structure under TC and THMC loading, though with amorphous-peak changes. FORGE sand exhibited stronger feldspar-range peak modifications in FORGE fluids than in DI-water THMC tests, confirming the dominant role of fluid chemistry in dissolution pathways. SEM-EDS indicates stress-enhanced surface alteration; mainly Al-Si reactivity on ceramics and Fe removal from FORGE sand, but with limited correspondence between TC and THMC trends. ICP-MS results show that THMC conditions significantly increase dissolution relative to TC tests, with cumulative major-element release (TIRI) lowest for Kryptosphere LD (~2.6×10⁵ ppb), intermediate for FORGE sand (~2.66×10⁵ ppb), and highest for Carbolite (~3.12×10⁵ ppb). Sieve analysis reveals negligible less than 140-mesh fines for the ceramics but ~22 % fines and a high conductivity-weighted breakage index (CWBI ≈ 52-55) for FORGE sand, indicating severe mechanical degradation. A multi-criteria decision framework (AHP) integrating TIRI, CWBI, and price weighted fines most heavily (0.584), followed by price (0.281) and dissolution (0.135). Resulting scores were 0.752 (Carbolite), 0.719 (Kryptosphere LD), and 0.400 (FORGE sand), showing that mechanical integrity is the dominant factor governing performance under geothermal THMC conditions. Ceramic proppants therefore outperform sand despite higher cost. These rankings apply only to the tested materials and selected criteria; future work should incorporate additional performance metrics and expanded proppant classes.
Topic: FORGE