Experimental Study and Modeling of Gravity Drainage during WAG Process in Fractured Carbonate Rocks

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The experimental study and modeling of gravity drainage during Water Alternative Gas Injection, WAG process, in carbonate rock for one of the Iranian off-shore reservoir at lab-scale were carried out. The mechanism of gravity drainage during the WAG process, and its contribution to the oil recovery in the fractured carbonate reservoirs were also studied. In the WAG process alternatively gas is injected during the process and gravity drainage could be happened. Changes in the block dimensions, rock properties, oil properties, gas properties, and fractures properties and their effect on the amount of oil recovered during the gravity drainage mechanism were studied. It would be worth mentioning that Methane, as major constituent of natural gas, was used as injection fluids within the experiments. Also carbonate rock was used as block sample in the physical model within the experiments. The results obtained from the experiments were compared with those obtained from the simulation and the comparison confirmed fair agreement between the results. It was found out that from 1 to 6 percent of oil can be recovered by gravity drainage during WAG process.