In meeting the challenge to improve oil recovery through implementation of IOR techniques, Dulang field was selected to study the possibility of CO2 injection as a potential recovery method. Dulang was chosen as the candidate because of the complete suite of information on this field and the availability of CO2 source within Dulang and nearby fields. The work focused on characterizing the oil and oil - CO2 interactions that was performed through phase behavior studies, vaporization test and displacement tests.

Studies conducted indicates that at the reservoir temperature of 215°F, CO2 injection would not be able to achieve miscibility with the crude oil at the current reservoir pressure, or even if the pressure is increased to the initial reservoir pressure. Equation-of-State (EOS) model also shows that the Multiple Contact Miscibility Pressure (MCMP) for CO2 and produced hydrocarbon gas is 3230 psig and 3340 psig respectively. This pressure is significantly higher than the initial reservoir pressure of 1800 psig.

Vaporization of Dulang crude by pure CO2 and the CO2-rich produced gas was studied. The laboratory study suggests significant vaporization of 15% of the stock tank oil with pure CO2. However, based on Equation of State, the vaporization ranges from 2 - 5 % with produced gas at operating reservoir pressure of 1400 - 1800 psig.

In view of the above, the potential recovery process is an immiscible process using produced gas containing high CO2 for cost optimization. In addition, the water alternating gas (WAG) process may improve mobility control and sweep efficiency. Detail studies involving WAG Composite Core, G & G Modeling and Numerical Simulation are currently on-going for identified location of a pilot project.

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