Comparative study on heat extraction performance of geothermal reservoirs with presupposed shapes and permeability heterogeneity in the stimulated reservoir volume

Abstract

The stimulated reservoir volume (SRV) is critical to the heat extraction from an enhanced geothermal system (EGS). Being different from previous simple cube-shape SRV, this study proposes a new shape SRV with heterogeneous permeability to evaluate the heat extraction performance of an EGS. First, the new shape SRV is generated based on the location and density of microseismic events during multi-stage hydraulic fracturing. Other two SRVs with simple cube or complex shape but same volume are generated for comparison. Second, a fractal permeability is developed for the heterogeneous SRV domain. Third, a thermal-hydraulic (TH) coupling model is implemented for the heat transfer and water flow in these three SRVs. Finally, the EGS performances of these three SRVs with a stimulated volume of 0.405 km 3 are comparatively evaluated through numerical simulations. Numerical simulations reveal that the EGS with cube-shape SRV overestimates both output temperature and energy extraction. The heterogeneous permeability in the SRV domain leads to a dramatic increase of reservoir impedance. This reduces energy extraction efficiency and breakthrough time, thus shortening the lifetime of the EGS system. • A new shape SRV with heterogeneous permeability in HDR reservoir is proposed. • An evaluation system for EGS is established based on a TH coupling model. • EGS performance of the three presupposed SRVs is comparatively analyzed. • The feasibility of a megawatt EGS power plant in Gonghe Basin is discussed.