Modeling and Laboratory Study of Carbonated Water Flooding

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Carbonated Water Flooding (CWF) is an enhanced oil recovery (EOR) method where an oil reservoir is flooded with water containing dissolved CO2. It is being considered as a promising EOR (Enhanced Oil Recovery) method for maturing light and heavy oil fields. A numerical and experimental study of the CWF was conducted, focusing on the underlying physical phenomena. In MATLAB, a numerical model describing a 1D CWF process was formulated assuming immiscible conditions. Modeling predictions have shown that in this simulator the oil swelling accounts for an increased oil production, together with a reduced residual oil saturation. This reduced residual oil saturation is the consequence of a reduced interfacial tension. However, the effect of this reduced residual oil saturation should be studied thoroughly. In addition to the numerical model, core-flood experiments have been performed using Bentheimer sandstone and n-hexadecane to validate the model predictions. It was found that injecting water containing 3.7% CO2 of the total mass of the aqueous phase reduces the residual oil saturation from pure water flooding to about 12.8. The experiment is performed with periods of injection and no injection, where an experiment with continuous injection would have provided more information about oil banking. The results of the experiment have been used to validate the model. From this validation it is deducted that either the residual oil saturation is reduced if the CO2 content in the oil phase is increased or there are errors in both the experiments and simulations. The mechanisms occurring during CWF are described (oil swelling, viscosity reduction, changing densities, solubility, changes in residual oil saturation).