PRE-FEASIBILITY STUDY OF WELLHEAD GENERATING UNIT UTILIZATION IN PARTIALLY VAPOR DOMINATED SYSTEM

• Main Author: Alwy Dahlan, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/40139
• Institution: Institut Teknologi Bandung

The development of geothermal fields needs 5-6 years from the first well drilled until the operation of the central power plant. Between the gap years, the wells will be shut in and will be re-opened when the power plant is ready. However, there is an alternative to utilize the wells with Wellhead Generating Unit (WGU), the small power plant which can generate the electricity as soon as the drilled productive wells completed. Therefore, the investor and developer will earn an early return on investment. The objective of this study is to decide the preferable scheme for the installed capacity of WGU with economic consideration. Correspondingly, this study uses two types of WGU, backpressure and condensing turbine. Full factorial experimental design with Monte Carlo simulation is used to calculate and design the backpressure and condensing turbine. Steam fraction, mass flow rate, turbine inlet pressure, and turbine exhaust pressure are the parameters to be analyzed in the Monte Carlo Simulation. The economic feasibility of the project is based on capital expenditure, decline curve analysis, and electricity price. The result of probability, P10, P50, and P90 of gross power output for the backpressure and condensing turbine are 3.2, 4.2, 5.2 MWe and 6.1, 7.9, 9.9 MWe respectively. Then, the P10, P50, and P90 of Specific Steam Consumption (SSC) are 3.49, 3.59, 3.70 kg/s/MWe and 1.85, 1.89, 1.93 kg/s/MWe respectively. Based on the economic evaluation, the best type of WGU is condensing turbine with the P10, P50, and P90 of Internal Rate of Return (IRR) are 12%, 16%, 21% respectively and the P10, P50, and P90 of Net Present Value (NPV) are 1.1 MUSD, 3.6 MUSD, 6.0 MUSD respectively over 30 years of WGU lifetime. This paper is the first study for designing the WGU combined with an economic study based on the technical evaluation to propose the best option to develop the field.