Sustainability of geothermal development strategy using a numerical reservoir modeling: A case study of Tompaso geothermal field

Abstract

Numerical reservoir simulation is a fundamental instrument to assess geothermal energy development strategy. This study aimed to optimize geothermal project development by integrating numerical modeling, reserve estimation, and geothermal power plant thermodynamics. Therefore, a case study for a numerical reservoir model was built based on the published data of the Tompaso field in North Sulawesi, Indonesia. The Tompaso field model was built in the TOUGH2 simulator, and the output was validated using observed data of 10 wells. The deviation of temperature and pressure models against the observed data ranged from 4.1 to 20.2 °C and 1.2–18 bar, respectively, so that the model is believed to reach the natural state condition. The natural state model was the basis for calculating the proven reserve using the dynamic deliverability method and approach of experimental design Box-Behnken 2nd order. A proxy equation generated by 27 simulations was combined with Monte Carlo simulations yielding a proven reserve of 62.2 MWe (P50) for the Tompaso field. Two development scenarios, full-scale and stepwise, were selected and simulated to determine the requirement of production, reinjection, and make-up wells for each strategy. It was found that using a stepwise development strategy can reduce the required amount of reinjection and make-up wells.