Numerical simulation–based optimization of an integrated framework for the efficient development and sustainable utilization of geothermal resources: Application to the Bedugul geothermal field

Abstract

Geothermal energy is a crucial renewable resource that can generate large power continuously but requires integrated and accurate assessments of its development and utilization for long-term and sustainable exploitation. Accordingly, this study develops an assessment framework considering all the influential factors for power generation: the potential capacity; silica scaling; type of power generation system; and temporal changes in the pressure, temperature, and fluid saturation in the reservoir. The applicability and effectiveness of the proposed method are demonstrated via a case study of the Bedugul geothermal two-phase system on Bali Island, Indonesia, using a calibrated numerical model and a stochastic resource assessment. The numerical model is a combination of wellbore, silica scaling, and thermodynamic power generation models. On the basis of the wellbore model by the Hagedorn and Brown pressure drop correlation, the calculated means of the production capacity and enthalpy from the liquid reservoir are 39.0 kg/s and 1340 kJ/kg, respectively. Using double-flash and flash-binary power generation systems over an exploitation period with a two-phase reservoir temperature of 260 °C, a reinjection temperature of 130 °C, and a silica scaling model, the predicted production from the liquid reservoir can sustain a power generation of 60 MWe, which is equivalent to 70 % of the power potential, according to a stochastic resource assessment using the Plackett–Burman design. The double-flash system is found to generate 1.0 MWe more power (a 1.6 % increase relative to the baseline capacity) than the flash-binary system using pentane as working fluid and to extend the lifetime of the make-up wells by 2.5 years. Consequently, it is vital, at an early stage of development, to understand the nature and properties of reservoirs and the thermodynamics of power generation systems via comprehensive research and reliable and accurate assessments of the power production capacity.