Abstract

To promote resource efficiency and protect two significant Javanese watersheds, Unocal Geothermal of Indonesia (UGI) together with PERTAMINA has successfully installed and operated one of the world's largest geothermal water injection systems on Gunung Salak geothermal field.

The Gn. Salak geothermal field is located about 60 km south of Jakarta, West Java, at the upstream of two important river watersheds: the Cisadane and the Citarik. The Cisadane River flows to the north and provides water for households, farmlands and industries in Jakarta, Bogor and Tangerang cities. The Citarik River flows to the south through Sukabumi Regency and irrigates thousands of hectares of rice fields before it empties into the Indonesian Ocean. UGI, on behalf of PERTAMINA, operates the Gn. Salak geothermal field and supplies steam for six 55 MW power plants that feed the Java-Bali electricity grid. Three of the power plants are owned and operated by PT. PLN (Persero) and the other three are owned and operated by UGI.

The Gn. Salak geothermal field is liquid-dominated (vs. dry steam at Kamojang Field, West Java). "Flashing" (boiling) the produced fluid to steam in the surface separators, the remaining fluid (about 80% of the total fluid), is injected back into the reservoir. Volume of the injected brine is up to 11 million kg/hr, depends on the output of the power plants.

The injected fluid (called brine) has a total dissolved solids content around 15,000 ppm, typical of other large liquid-dominated geothermal fields. Brine management is critical to UGI because it helps maintain the economic life of the field, and preserves the environment as required by UGI operations philosophy and Indonesian regulations regarding surface discharge.

Since the commercial start-up of the Gn. Salak power plants, UGI has reinjected more than a billion barrels of brine. There has never been a surface brine discharge at Gn. Salak that caused damage to the local environment, rivers, or people living around the project. The Gn. Salak geothermal injection program demonstrates how an energy producer can be operated successfully within a protected forest, providing economic benefits while protecting the natural environment and local communities.