Numerical Evaluation of Energy Extraction, CO2-Rock Interactions, and Carbon Sequestration in Enhanced Geothermal System (EGS) with Supercritical CO2 as Working Fluid

Abstract

Recently, geothermal development in enhanced geothermal system (EGS) has been considered using supercritical CO2 as a heat transmission fluid instead of water. It is indispensable to understand the CO2-fluid-rock interactions in EGS reservoirs to evaluate the performance of energy extraction, geological CO2 sequestration, and CO2 leakage risk with supercritical CO2 instead of water as a working fluid. The objective of this work is to evaluate the effects of chemical interactions between supercritical CO2 and reservoir rocks on the energy extraction, carbon sequestration, and CO2 leakage risk assessment. We employ a simple 3-D conceptual model with a generic 5-spot well pattern to simulate the heat, flow, geochemical interactions between CO2 and rocks at high temperature and pressure of EGS reservoirs using ECO2H module of TOUGH2 code and TOUGHREACT model. We also evaluate the effects of CO2-rock interactions on the energy extraction, geological CO2 sequestration, and CO2 leakage risk with CO2 as a heat transmission fluid instead of water for EGS reservoirs. The simulated results shows the larger energy extraction, increasing cumulative net CO2 storage with time, and carbonate mineral precipitations, demonstrating that supercritical CO2 as a working fluid instead of water was favorable for EGS reservoirs on the geological CO2 sequestration and enhanced energy extraction.