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Zeolite-Tagged Propped Fractures Under Utah FORGE EGS: Use of Mineral Breakdown and Chemical Transport to Identify Fracture Conductivity in API19D Modified Experiment
Bruce MUTUME, Ali ETTEHADI, Seokjhin KIM, Wenming DONG, Christine EHLIG-ECONOMIDES, Mileva RADONJIC
[Oklahoma State University, USA]
Optimized heat mining from deep, impermeable, hot rocks relies on fluid flow through hydraulic fracture networks. Identifying evidence of optimized, short-circuit-free circulation within the fractured reservoir is crucial for reservoir optimization. Given the high temperatures, mineral stability studies suggest natural zeolites, which form during hydrothermal alteration, as ideal candidates. In this preliminary study, we tested engineered zeolites (with a fixed chemical composition) as particulate tracers in simulated fracture networks. These zeolites were blended with quartz sand proppants, and their behavior was compared to that of quartz sand alone. The sand pack was placed between granitoid platens from Utah FORGE drilled core and subjected to coupled thermo-hydro-mechanical-chemical (THMC) conditions with deionized water flow for 150 hours. Four engineered zeolite types (CBV-10A, CBV-500, CBV-28014, and CP-814E) were mixed in equal proportion (25 wt %) and used to replace 20 wt % of the 50-gram sand proppant. Post-flow characterization of the solids utilized XRD, SEM-EDS, and TEM-EDS, while effluent was analyzed by ICP-MS. The XRD analyses of the post-flow solids confirmed the complete displacement of the engineered zeolite mixture from the sand pack, indicating a structural breakdown under geothermal conditions. TEM-EDS analysis of dried fluid-derived powders supported this dissolution, as solid particles were primarily composed of Si, Ca, K, S, Cl, and O. Furthermore, the ICP-MS data from the effluent chemical analysis showed enhanced aluminosilicate mobilization, with approximately 1.28 times higher dissolved Si and 1.26 times higher dissolved Al relative to control runs. In addition, K, Mg, Ca appear to have similar trend in identified concentrations that are not yet fully understood. While compositional overlap complicates precise elemental attribution, these results demonstrate the feasibility of zeolite tagging as a reactive tracer method, but do not support the use of these specific zeolite particles for particulate transport monitoring. A second set of experiments is now utilizing the natural zeolite Mordenite, a thermally stable option, to monitor particulate transport. Further work is warranted to optimize zeolite selection for thermal stability suitable as field-scale tagging materials for fracture flow.
Topic: FORGE