Enhanced Geothermal Systems (EGS): The Future Energy-Road Ahead
Hot permeable rocks are essential elements of geothermal production. Hydrothermal systems consisting of naturally fractured or porous geological formations have been commercially utilized to date, and technologies are steadily developing to enhance the permeability of enhanced geothermal systems. Hydraulic stimulation, or hydraulic fracturing, is widely adopted in geothermal reservoirs. Besides water-based fracturing fluids, supercritical carbon dioxide has been proposed for reservoir stimulation considering favorable fluid properties. Chemical stimulation, or injection of acids, has also been shown to enhance reservoir permeability by dissolving minerals. Thermal stimulation or injection of cold water into a geothermal reservoir further results in the initiation and propagation of thermally induced fractures along mineral boundaries and weaker mineral constituents. When simulating a geothermal reservoir, it is crucial to understand the hydro-thermo-mechanical and chemically coupled effects. Furthermore, maintaining fracture connectivity via appropriate techniques, including promoting self-propping mechanisms, is essential to enhancing reservoir production.
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