Pre-feasibility Study of Condensing Wellhead Generating Unit Utilization in Partially Vapor Dominated System

Abstract

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. Then, 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 full factorial experimental design with Monte Carlo simulation to calculate and design the 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 and Specific Steam Consumption (SSC) are 6.1, 7.9, 9.9 MWe and 1.85, 1.89, 1.93 kg/s/MWe respectively. Based on the economic evaluation, the P10, P50, and P90 of Internal Rate of Return (IRR) and Net Present Value (NPV) are 12%, 16%, 21% and 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.