f Optimization of Waterflood and Plan for EOR Stage on Rantau Structure in North Sumatera Indonesia

Rantau structure is located in north Sumatra basin of Indonesia, divided into 11 compartment and has 580.25 MMbbl remaining oil in place. start produced in 1929. Peak primary oil production occurred in 1969 with 31,711 bopd. The secondary stage has been started with injecting water since 1984 with peripheral pattern and successful increasing oil production from secondary recovery until 5,500 bopd in 1988 from the previous condition 2,550 bopd in 1984 with source of water injection from sea water, this poor water injection quality directly impact problems for injection wells (plugging) and declining oil production until 2300 bopd in 1997. EOR division Pertamina EP planned for pilot water flood on 3 potential layers and EOR stage on layers and blocks that in 1984 already impact by water injection. Kick off pilot water flood had been done in January 2010 with irregular 5-spot pattern and successful increase reservoir pressure and oil production until 400-500 bopd (after 3-4 months injected) from 2 producer wells form the previous condition 20 bopd. From the prediction with reservoir simulation additional reserve form full-scale water flood in 3 potential layers (600, 400, 770 & 800) can get maximum 11.65 MMbbl and additional reserve from chemical flood 6.83 MMbbl (layer 600).