Influences of Reservoir Heterogeneity and Anisotropy on CO2 Sequestration and Heat Extraction for CO2-based Enhanced Geothermal System
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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 CO2 sequestration, the influences of reservoir heterogeneity and anisotropy on CO2 sequestration and heat extraction in CO2-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 CO2 sequestration and restrains heat extraction. Higher ratio between horizontal (x and y directions) and vertical permeability components enhances CO2 sequestration 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 CO2 sequestration 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 CO2 sequestration and heat extraction.
Keywordsenhanced geothermal system CO2 sequestration heat extraction reservoir heterogeneity reservoir anisotropy
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The authors would like to thank the National Natural Science Foundation of China (51478001) and the Natural Science Foundation of Anhui Province (1808085QE178) for the financial support.
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