The figure being paid for the extra stake has not been officially revealed. However, Pertamina is understood to have paid about $20 million for the additional equity in the gas-rich block, which it purchased from its Malaysian counterpart Petronas and China's largest oil and gas company PetroChina.
Earlier this year, Petronas and PetroChina acquired Amerada Hess' 30% stake in the PSC for $164 million.
