Unstable Asphaltene is major concern in oil reservoir under CO2 Water alternating Gas injection due to its unrecoverable damage to reservoir and expensive treatments for production system. Therefore, the effective strategy to control Asphaltene precipitation should be the part of reservoir management. Dealing unstable Asphaltene in Malaysian reservoir was divided into three main parts that were evaluating Asphaltene colloidal stability, Asphaltene Prediction and Asphaltene prevention.

Solid Detection System was used to measure the stability and onset pressure of crude oil under reservoir conditions with different amount of gas injections. Various PVT experiments were performed in the laboratory using the PVT cell. PVT data obtained from PVT cell is then fitted with the reliable equation of state (EOS) to generate the Asphaltene phase envelopes.

An inhibitor design program was initiated and four inhibitors, Inhibitor A, Inhibitor B, Inhibitor C and Inhibitor D were selected to evaluate their performance in neutral, acidic and basic environment. Titration Test was performed to evaluate the inhibitor efficiency. Inhibitor B in acidic environment was then selected as efficient inhibitor to inject in situ to control Asphaltene precipitation with injection gas.

Using this strategy, Asphaltene precipitation is expected to be minimized which will keep the reservoir undamaged and will save large amount of remedial cost.

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