Geothermal resource risk in Indonesia : a statistical inquiry

This paper presents a statistical study of the geothermal resource risk in Indonesia, specifically, that the resource base and well productivity are adequate and that the drilling cost per well is reasonable. This paper is timely because the Government of Indonesia is now embarking on an ambitious plan to rapidly scale up geothermal power capacity and eventually achieve a longer-term target of 9,500 MW by 2025. This study relies on the resource base estimates made by the Indonesian Government-owned enterprise P.T. Pertamina (now subsidiary Pertamina Geothermal Energy, or “PGE”) for nearly 80 sites, and productivity data on 215 wells in the country in the GeothermEx archives; these wells comprise some 80 percent of the total production wells drilled in Indonesia. Such a thorough national inventory of the geothermal resource base is available from very few countries. The geothermal resource base (proved-plus-probable-plus-possible) at a given site ranges from 10 MW to 800 MW with a log-normal distribution. More than 70 percent of the known Indonesian fields have a resource base greater than 50 MW and at least half of the fields (about 40) offer a resource base of 100 MW or more.