Influences of Reservoir Heterogeneity and Anisotropy on CO2 Sequestration and Heat Extraction for CO2-Based Enhanced Geothermal System

Enhanced geothermal systems(EGS) have a great potential to extract geothermal energy and have attracted much interest. In this paper, based on a 3D thermal-hydrologic model considering COsequestration, the influences of reservoir heterogeneity and anisotropy on COsequestration and heat extraction in CO-based EGS are investigated. Different heterogeneous reservoirs and homogeneous reservoir are compared, and different ratios among reservoir permeability components are compared. The results show that greater reservoir heterogeneity enhances COsequestration and restrains heat extraction. Higher ratio between horizontal(x and y directions) and vertical permeability components enhances COsequestration and heat extraction, and vertical permeability component has a little effect. With the increasing ratio between x-directional(perpendicular to the line of the injection well and the production well) and y-directional(perpendicular to x direction) reservoir permeability components(i.e. kx:ky), both COsequestration amount and steady-state heat extraction rate first increase and then decrease, and thermal breakthrough time increases, showing that there exists an optimum kx:ky, which is about 1:1. The results of this paper indicate that reservoir heterogeneity and anisotropy have important influences on COsequestration and heat extraction.