GEOCHEMICAL MODELING OF WATER-ROCK-PROPPANT INTERACTIONS

Enhanced geothermal system (EGS) reservoir fracture creation and management may require the use of proppants to maintain fracture conductivity. The most commonly used proppants, which remain in hydraulically created fractures to keep them open, include silica sand, ceramic, and sintered bauxite. In geothermal systems, proppant will need to withstand high temperatures, acidified fluids, acid treatments, and cleanouts while maintaining the porosity and permeability of the fracture. Geochemical modeling of water-rock-proppant interactions was conducted in conjunction with static experiments to extrapolate experimental observations to the reservoir scale. PHREEQC was used to examine the chemical stability of silica and bauxite proppants in equilibrium with fluids of varying composition. TOUGHREACT was used to model one dimensional flow of these fluids through a granite reservoir with fractures filled with silica or bauxite proppant. The modeled results indicate that under certain conditions, proppant can either dissolve or act as a nucleation site for mineral precipitates.

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