Numerical Study on CO2-Brine-Rock Interaction of Enhanced Geothermal Systems with CO2 as Heat Transmission Fluid

Enhanced Geothermal Systems (EGS) with CO2 instead of water as heat transmission fluid is an attractive concept for both geothermal resources development and CO2 geological sequestration. Previous studies show that CO2 has lots of favorable properties as heat transmission fluid and also can offer geologic storage of CO2 as an ancillary benefit. However, after CO2 injection into geological formations, chemical reaction between brine and rock can change chemical characteristics of saline and properties of rock such as porosity and permeability. Is this advantage or disadvantage for EGS operating? To answer this question, we have performed chemically reactive transport modeling to investigate fluid-rock interactions and CO2 mineral carbonation of Enhanced Geothermal Systems (EGS) site at Desert Peak (Nevada) operated with CO2. The simulation results show that (1) injection CO2 can create a core zone fulfilled with CO2 as main working domain for EGS, and (2) CO2 storage can induced self-enhancing alteration of EGS.