2013a. Analysis of operational strategies for utilizing CO2 for geothermal energy production

Geothermal energy production can be limited by insufficient working fluid and pressure depletion, whereas geologic CO2 storage (GCS) can be limited by overpressure, which may drive CO2 leakage and cause induced seismicity. Integration of these complementary systems can realize synergy, enhancing the viability of each system. While most research on CO2-based geothermal systems has emphasized using CO2 as a heat-transfer working fluid, it is possible to also use CO2 as a supplemental pressure-support fluid to generate artesian pressures at the CO2 and brine producers. A well pattern consisting of a minimum of four concentric rings of horizontal producers and injectors is proposed to conserve pressure from the injection process, minimize loss of CO2, control the lateral extent of overpressure, and segregate the CO2 and brine production zones. We present simulations of this approach for an idealized reservoir model, consisting of a relatively permeable sedimentary formation, confined by two impermeable confining units. Consideration of more realistic (heterogeneous) geologic settings and wellbore flow effects will be necessary to more rigorously evaluate the potential economic advantages of this approach