The Darajat Geothermal Field, Indonesia, After 24 Years of Production

Abstract

The Darajat Geothermal Field is currently the largest vapor-dominated geothermal resource in Indonesia, with an installed power generation capacity of 271 MWe. Through vigilant resource management, the Darajat Field has performed relatively well since commercial operations started in 1994, averaging about 90% net capacity factor annually. As with many other geothermal fields in commercial operation for many years, Darajat has experienced a number of resource management challenges, including marginal recharge, injection breakthrough, wellbore scaling, and pressure decline. Continued commercial production at Darajat will lead to lower reservoir pressure and, potentially, invite more marginal recharge into the reservoir. Currently, wells experiencing scaling at Darajat mostly correlate with where marginal recharge has been identified, so more frequent wellbore scaling may occur in the future. Another anticipated resource issue that may affect the field’s performance in the future is reservoir dry-out, although an appropriate injection management strategy is expected to mitigate its effects. Moving all condensate injection from the central area of the field to deep injection at the northeastern margin of the field has arrested cooling in the central area. Meanwhile, geochemical signatures indicate that reservoir condensation is occurring in the northern area of the field. By continuing to leverage lessons learned to further improve processes and proactively addressing field management issues as they may arise, it is believed that the Darajat field can continue to operate at its maximum installed capacity until the end of the current contract, in 2037.