In this study, different scenarios of CO2 injection in dipping gas condensate and oil reservoirs are investigated through reservoir simulations. Both miscible and immiscible flooding conditions were investigated for a range of different injection gas mixtures, and geological realizations.

We find particularly interesting results for miscible flooding of gas condensate systems below dewpoint pressure. Here, dropped out condensate is the prime target for enhanced recovery projects and multi-contact miscibility could develop through the combined condensing/vaporizing mechanism.

Different patterns of permeability variation with depth in layering scenarios with dip angle showed distinct different responses on produced condensate. CO2 WAG in partially depleted gas condensate reservoirs seems to have the same value of oil recovery in early times, but ultimate recovery is different according to layering heterogeneity. In the case of pure CO2 injection, both up-dip and down-dip, it was found that homogeneous layering showed highest recovery. Here developed multicontact miscible oil-bank is able to move and sweep condensate above it easier. Applying various gas injection mixtures of CO2 and C1 combinations, the effect on ultimate recovery were studied. In this case CO2 injection is above minimum miscibility pressure (MMP) resulting in high recoveries.

CO2 WAG in dipping oil reservoir was also studied extensively, based on injection pattern, MMP values and various layering systems. CO2 WAG in scenarios with increasingly trend of permeability with depth had the highest value of recovery. This is because of prevention from early gas breakthrough in upper layers and good sweep efficiency in lower layers. Pure CO2 injection with total same injection volume showed lower recovery. This may verify that gravity in WAG water injection period is the most effective parameter in the case of down-dip WAG.

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