Comparison of Supercritical CO2 With Water as Geofluid in Geothermal Reservoirs With Numerical Investigation Using Fully Coupled Thermo-Hydro-Geomechanical Model

Abstract

In the present work, fully coupled dynamic thermo-hydro-mechanical (THM) model was employed to investigate the advantage and disadvantages of supercritical CO2 (SCCO2) over water as geofluids. Low-temperature zone was found in both SCCO2-enhanced geothermal system (EGS) and water-EGS systems, but spatial expansion is higher in water-EGS. Although, the spatial expansion of SCCO2 into the rock matrix will help in the geo-sequestration, the expansion of stress and strain invaded zones were identified significantly in the vicinity of fracture and injection well. SCCO2-EGS system is giving better thermal breakthrough and geothermal life conditions compared to the water-EGS system. Reservoir flow impedance (RFI) and heat power are examined, and heat power is high in the water-EGS system. Minimum RFI is found in the SCCO2-EGS system at 45 °C and 0.05 m/s. Maximum heat power for SCCO2-EGS was observed at 35 °C, 20 MPa, and 0.15 m/s. Therefore, the developed dynamic THM model is having greater ability to examine the behavior of SCCO2-EGS and water-EGS systems effectively. The variations occur in the rock matrix, and the performance indicators are dependent on the type of fluid, injection/production velocities, initial reservoir pressure, and injection temperature. The advantages of SCCO2-EGS system over the water-EGS system provide a promising result to the geothermal industry as a geofluid.