this offers some insight on how the psc profits are calculated and may even offer insight on the value add to EEES from the investment this year and next....I don't know how and where the pessimistic -> optimistic scenarios come from. But the price of $4.50 mmscf is ballpark.
http://prezi.com/k3otielfcxi7/capital-budgeting-in-skk-migas-sengkang/