hi, I'm from Indonesia.
If I may, i'd like to give some comments to add some realism for the game.
The background, Sumatra, is one of the major islands in the state of Indonesia (Republic of Indonesia), located in the South East Asia.
I've asked my petroleum engineering friend, he said there's no major oil resource in West Sumatra. The oil resource (in which Exxon operated there) is located in Aceh, on the westernmost tip of the island.
The Aceh has been a place plagued by insurgents in the past. In the 80s up until 1998, when the repressive New Order regime under President Suharto decided Aceh is a Military Operation Territory (Daerah Operasi Militer/DOM), that's when things get hot real quick. The Aceh Freedom Movement (Gerakan Aceh Merdeka/GAM) gained momentum and started many attack on the Indonesian military in the region. It costs many lives, either from the military, the rebels, and civilian populations.
This insurgency ended after the Acehnese people signed a peace accord and MoU in 2005, after the Tsunami disaster at the end of 2004 struck Aceh and killed 100'000 people there. The current governor there is a former rebel, elected in a free local election.
So if you want to put a little bit realism+twist in the game, I suggest that you would set the game in Aceh instead of West Sumatra (no oil there!), maybe placing a new twist like a new rebel movement, set up by the Chinese to take over the oil control there, currently exploited by Exxon Mobil.
Just my 2 cents.