EMEPMI and PETRONAS have recently concluded major simulation studies on the application of immiscible Water Alternating Gas (WAG) injection to enhance oil recovery for Tapis and Guntong fields, the two largest waterflooded fields operated by ExxonMobil in Malaysia. Both fields have been under waterflood operation for more than 25 years with about 40% original-oil-in-place (OOIP) recovered to-date.

Evaluations of immiscible WAG injection process application at Tapis and Guntong fields were carried out using full-field reservoir simulation models. The scope of the evaluation work included: a) assessment of additional recovery from enhancing waterflood operations, b) assessment of recovery uplift from WAG injection, c) WAG pattern and WAG ratio optimization, d) optimal WAG operating parameters and reservoir management strategy, and e) integrating production and injection well operating conditions with facilities process design.

The Tapis WAG evaluation study has supported ExxonMobil's plans to implement a WAG project at Tapis. The study has matured to the point of providing the subsurface design basis for the Project. The Guntong study has provided an initial assessment of WAG potential used for the conceptual WAG development and early project planning.

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