EFF ECT OF ROCK WETTABILITY ON THE MISCIBLE GAS INJECTION OF CO2 AND CH4 IN CARBONATE OIL RESERVOIRS

One of the most used EOR (Enhanced Oil Recovery) methods to improve the oil production is the miscible gas injection. Among the different factors affecting miscible gas injection’s performance which have not studied extensively is rock wettability of the reservoir. Wettability specifies how different types of fluids are distributed in the pores of the reservoir rock and thereby influences the implemented EOR. A compositional simulation study implemented here using the data belonged to one of the Iranian nonfractured carbonate oil reservoirs investigates effect of different rock wettabilities (Water wet, intermediate and oil wet) on the miscible injection of two different gases including CO2 and CH4. A three parameter EOS (Equation of State) tuned by experimental results are employed in the simulation and MMP (Minimum Miscibility Pressure) estimation processes. Resultsindicate that the recovered oil is increased by changing wettability from oil to water-wet for all injected gases with maximum oil recovery is achieved in case of miscible CO2 injection in water-wetted reservoir. Moreover, GOR (Gas Oil Ratio) is decreased generally by changing the rock wettability from oil-wetted to the water-wetted one, even though reservoir pressure drop is fairly the same for different wettability types.

Keywords:

Enhanced Oil Recovery , Miscible gas injection , Carbon dioxide , Methane , Wettability , Reservoir Simulation