Fractured Geothermal Reservoir Performance Estimation Using Supercritical CO2

Abstract

Abstract. Geothermal energy is gaining momentum worldwide to extract sustainable and clean energy. However, deep geothermal reservoirs possess low porosity and permeability, which impose challenges in extracting subsurface heat energy. A coupled thermohydro model is formulated to investigate the cold front growth and production temperature estimation using supercritical CO2 as a geofluid to extract heat energy from a deep geothermal reservoir. Fluid properties are considered to evolve with the change in pressure and temperature. The results are obtained after verifying the present model with the analytical formulation by Lauwerier. Natural fracture orientation has been observed to influence the cold thermal front growth and production temperature. The production temperature increases up to the orientation of 60 deg of natural fracture with the hydraulic fracture. Further increment of orientation of natural fracture to 75 deg and 90 deg shows no significant change in production temperature. The production temperature at 60 deg is 1.3 and 5.05% higher than 30 deg and 15 deg at 15 years. The fracture aperture has also significantly impacted the production temperature and has been found to be larger at a lower aperture. The influence of distinct fracture apertures of hydraulic and natural fractures is evaluated, and better production temperatures are observed when the magnitude of natural fracture aperture is set higher than the hydraulic fracture aperture. A comparative study using supercritical CO2 (scCO2) and water as a geofluid is also performed and found that scCO2 outperforms water in terms of heat extraction efficiency up to the geothermal life of the reservoir.