Sustainable development of the Kamojang geothermal field

Geothermal electricity production in Indonesia began with the operation of a 0.25 MWe pilot project in Kamojang geothermal field, in 1978. Commercial operation started in 1983, with the commissioning of the 30 MWe Unit-1 power plant. In 1987, an additional capacity of 110 MWe was provided by the Unit-2 and Unit-3 power plants. The addition of the 60 MWe Unit-4 power plant in 2008 increased the total generating capacity to 200 MWe. The 27 years of commercial operation have led to a slight decline in reservoir pressure and temperature within the active production sector. The most recent significant change in the field conditions and performance occurred following the 2008 increase in generating capacity from 140 to 200 MWe. The production decline of individual wells has been relatively low, at an average of 3%/yr. However, the increased rate of steam withdrawal might negatively affect long-term sustainability of energy production at Kamojang unless suitable field management strategies are implemented. In order to stabilize the steam flow, it has been necessary to drill about three make-up wells every 2–3 years. The unbalanced mass extraction, where less than 30% of the produced steam mass can be injected, is a serious concern for long-term reservoir management in Kamojang. The field operator (Pertamina) plans to increase the Kamojang generating capacity from 200 to 230 MWe (Unit 5) and optimize the long-term performance of the Kamojang geothermal resource. The response of the reservoir during the previous three decades is being used to guide reservoir development for the planned increase in production capacity.