Impact of spatially correlated heterogeneity and boundary on techno-economic performance of CO2-circulated geothermal harvest

Abstract

Depleted oil/gas reservoirs are excellent candidates to apply CO2 Plume Geothermal (CPG) production, a promising CO2 storage and utilization technique. However, most oil/gas reservoirs are separated into geological blocks by faults, and the impact of boundary conditions and formation heterogeneity on CPG performance is still challenging. This study evaluates a CPG system's optimal configuration with various heterogeneous formations and boundaries. Six CPG scenarios with spatially correlated heterogeneous porosity, permeability, and open/close lateral boundaries are designed and simulated. For each scenario, well space and injection overpressure are sampled in their ranges to generate a suite of CPG models. Net present values (NPV) are calculated from the simulation results and used as the objective function. A meta-model-based optimization framework is developed to find the optimal well space and overpressure to maximize NPV for each scenario. The comparative analyses between the six scenarios find that high heterogeneity variance and long geologic continuity in the flow direction cause an early breakthrough. Long well space can enhance NPV, but no longer if it is larger than the correlation length in the flow direction. CO2 storage and electricity revenues are essential to profit for a closed system, but CO2 storage income is the primary source of profit in an open system.