Star Energy signed a farm-in agreement in November 2004 to acquire a 50% working interest in the Banyumas PSC. The contract area covers 4,000 square km and is located in southern Central Java, some 50 km northwest of the 350,000 BOPD Cilacap refinery, and within 100 km of West Java's gas pipeline infrastructure. The contract, currently in exploration phase, was signed in 2001 and is valid for 30 years upon discovery of commercial oil or gas.

The conventional thinking was that there is no deep hydrocarbon potential in the small young basins of Central Java. As a result, the Banyumas block had only been lightly explored.

After careful appraisal of the surface geology, Star geologists realized that the rocks at the surface were actually much older, and indicated far better reservoir potential, than had been previously thought. Coupled with numerous surface seeps of oil and gas in the area, and non-commercial gas finds from previous drilling, the evidence suggested an opportunity to find commercial quantities of hydrocarbons significantly deeper than previously thought.