Dulang oil field, an anticline classtic reservoirs with areal extended about 330sq.km in offshore Peninsular Malaysia Basin was discovered in 1981 with water depth of 76m and total STOIIP around 1BSTB (Figure 1). The field was on production since 1991 with cumulative production (as at Jan 2010) around 21% of STOIIP. Immiscible Water-Alternating Gas (IWAG) EOR injection has been identified to be implemented which can enhance the oil recovery further. A Pilot injection project was carried out in sub-block area of the main reservoirs for a period of four (4) years. Full field injection plan has been formulated and has moved-up to execution phase.

Monitoring the flood front movement by IWAG injection becomes a major challenge in this project especially with wide well spacing and high reservoir heterogeneity where "fingering" effect is prone to occur. This paper will describe the application of time-lapse (4D) seismic in the full field IWAG to monitor the flood front movement through times.

A feasibility study was carried out to investigate the detectability and repeatability between two seismic vintages in order to understand the uncertainty. Factors contribute to the chances of success (COS) of the project also being identified. The result shows that through simulation prediction, a cumulative acoustic impedance of 6% to 8% can be observed after two years IWAG injection cycles. Also being described in this paper are the planning of the full field project right from technology identification, screening study, feasibility study and finally the full field implementation.

This information’s are valuable to the industry especially to enhance oil recovery projects where full scope of formulizing the 4D seismic application being evaluated in order to enhance the surveillance and monitoring programme hence ensure the success of the EOR projects.

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