Numerical Investigation of Energy Extraction from a Depleted Oil Geothermal Reservoir

Abstract

With the rising global energy demand, the consumption of fossil fuels is increasing substantially. It requires a parallel focus on other energy sources. The extraction of geothermal energy from depleted oil reservoirs with a high geothermal gradient is a promising alternative energy resource. The present work examines the potential of thermal energy extraction from a depleted oil geothermal reservoir via a permeable fault that acts as a primary fluid flow path. Initially, a conceptual model is defined for a depleted oil reservoir with injection and production wells. Then, a coupled numerical model is developed for heat transfer and fluid flow in the porous medium. The performance of thermal energy extraction from these reservoirs is affected by various operational parameters such as injection temperature and injection mass flowrate. The influence of each parameter on temperature and power generation at the extraction well is determined by performing parametric study. Then, a multiobjective optimization analysis is performed using the Analytic Hierarchy Process (AHP) considering different conflicting objective functions to select the best operational scheme. The evaluation criteria include maximizing average power, heat extraction, geothermal life and thermal breakthrough and minimizing the flow impedance in reservoir. Finally, the best optimal parameters are determined based on the comprehensive score of each case. A comparative evaluation is also conducted between the optimal and base cases to highlight the improvement in thermal performance. The present study provides a reliable approach for optimal field development of a geothermal system in a depleted oil reservoir.