Dieng geothermal project : Risk assessment for a decision on 60 MW expansion

Abstract

Dieng is one of the prospected geothermal fields in Indonesia with an estimated field development potential of 350 MWe. Presently, one 60 MWe power plant unit has been installed and the current production is around 46 MW. Dieng geothermal power plant is owned and operated by PT Geo Dipa Energi (GeoDipa), a state-owned company. GeoDipa is implementing a phase development for the field. Unit 1 has been in operation since 1998 and now GeoDipa plans to add another 60 MWe unit. The Unit 2 project is still in feasibility stage and the feasibility study is currently being updated. In the development of Unit 2, there are risks that need to be considered before a decision can be made. Therefore, in this report, the risks associated with Unit 2 project are identified and appropriate mitigation actions are listed. The key risks have been identified to be resources and technical risks which are related to scaling and corrosion in production wells, turbines and the Fluid Collection and Reinjection System (FCRS). To mitigate scaling, methods such as hot water reinjection, pH modification, inhibitors, cold water injection and retention tank have to be studied further. Several environmental risks are also analysed and should be mitigated prior to a decision on the Unit 2 project.