Sofyan, Akhmad; Ermanda, Muhammad Bobi; Aka, Hari Sumantri
Polytechnic of Energy and Mineral "Akamigas", Indonesia
A geothermal field will be declining in productivity so it is necessary to plan a make-up well drilling program for production sustainability. The purpose of this research is to determine the field decline rate, plan the needs of the make-up well program, also analyze and evaluate the project economics of the make-up well program in the geothermal field studied. The method used is decline curve analysis, analysis of available steam to find out minimum steam requirements, analysis of loss of opportunity to find out the number of lost costs as drilling costs, analysis of the make-up well needs to determine the type of configuration, number of wells, and the time required, as well as project economic analysis to determine financial feasibility. The results of research analysis on the vapor-dominated X field found a decline rate in one year is 8,31%, the minimum steam requirement to generate 59,88 MWe electricity is 389 tonnes per hour, and the opportunity costs equal to drilling costs of 3 wells. The type of well used is the standard hole with a total requirement of 12 wells for 20 years at intervals of 3-5 years per agenda. For economic analysis, each scenario based on the drilling success ratio shows a positive NPV and IRR more than 16%. From the overall results of the analysis, it can be concluded that the make-up well planning program in the geothermal X field is an economically acceptable and feasible project.
