Geological Risks Assessment and Quantification in Ulumbu Geothermal Field, East Nusa Tenggara, Indonesia

Abstract

 The Ulumbu geothermal power plant is currently operating with a total capacity of 10 MWe. However, the Ulumbu geothermal field still holds the potential for further resource utilization, with at least 40 MW available for the next
development phase. This further development carries risks of failure, making geological risk assessment and quantification crucial for calculating the success of development drilling in terms of resource risks. The method of geological risk assessment and quantification in geothermal exploration has been previously developed and applied to two fields, Galunggung and Patuha. The more frequently this method is applied to other geothermal fields, the more valid it becomes, considering that each geothermal field has its unique characteristics in terms of geothermal play type and resource conditions. This paper applies the geological risk assessment and quantification method to the Ulumbu geothermal field under two conditions: pre-drilling (3G data before 1992) and post-drilling (1996 drilling data and the latest 3G data). The results show that the pre-drilling condition exhibits a higher geological risk compared to the post-drilling condition