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Yuichi Sugai Postdoctoral fellow (Kyushu University, Dept. of Earth Resources Eng., Japan) (Visit period: July 21, 2008 - Sept. 30, 2008) "Measurement of Swelling of Crude Oil in Porous Media due to Carbon Dioxide Dissolution" In CO2 EOR, injected carbon dioxide dissolves in crude oil and oil swelling is caused by the carbon dioxide dissolution. Some of residual oil can become movable and be recovered by oil swelling in reservoir. Moreover, relative permeability of oil can be improved by increase of oil saturation due to oil swelling. Therefore, oil swelling is an important phenomenon to consider in CO2 EOR. According to our previous studies, it is shown that not only partial pressure of carbon dioxide but also oil saturation influence the solubility of carbon dioxide in oil in porous media. Contact area between oil and carbon dioxide should differ depending on difference of oil saturation in porous media, that is, the contact area is important in consideration of the solubility and the oil swelling. The relationship between oil swelling and contact area between oil and carbon dioxide is estimated in this study. Oil and carbon dioxide were injected into a coin-shape pressure cell and oil swelling was observed under a microscope. Specific contact area (cm2/g-oil) was regulated by regulating the amount of injecting oil into the cell. As a result, expansion of 3 % of initial oil volume was observed in case of minimum specific contact area (1.87 cm2/g-oil) and expansion of 8 % of initial oil volume was observed in case of maximum specific contact area (6.86 cm2/g-oil) even at a low pressure (10 psi). Both swelling speed and swelling rate increased with specific contact area. Oil swelling at higher pressure is measured using the pressure cell and that in porous media is measured using a micromodel recently. .jpg)
An example of the oil swelling due to carbon dioxide dissolution at different time steps for two different contact (specific surface) areas.
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