Stochastic techno-economic analysis of CO2-circulated geothermal energy production in a closed reservoir system

Many wells become abandoned with the depletion of oil and gas reservoirs, and low-enthalpy geothermal energy could be extracted from these abandoned wells. CO ₂ has been proposed and studied as the working fluid for mining such geothermal energy sources, owing to its favorable thermodynamic properties. The objective of this study is to develop an uncertainty-based simulation-optimization approach to analyze the techno-economic feasibility of CO ₂-circulated geothermal production in a closed reservoir system. In doing so, we address the particular geothermal reservoir conditions found in North Oman`s foreland basin where several large oil/gas fields are located. The geothermal reservoir conditions in this area can be characterized by inclined and thin layers, partially to fully fault-blocked, and relatively homogeneous and low permeable formations. Such conditions have not been investigated in the context of CO ₂-circulated geothermal production. Another key novelty of this work is to analyze a triplet horizontal well placement designed particularly for such thinly-bedded fully-closed reservoirs. The main building blocks of the proposed methodology are the application of a non-isothermal, multi-phase, multi-component numerical reservoir simulator, a neural network-based metamodel, Monte Carlo simulations, and genetic algorithm. The findings suggest the proposed well pattern is technically feasible and economically viable to harvest low-enthalpy geothermal energy from the type of depleted reservoirs found in North Oman region.