Effect of Asphaltene content on Gas-Oil interfacial mention

CO2 injection was proved to be an effective method for enhanced oil recovery; Injected gas might have negative effect on oil flow in the reservoir as a result of asphaltene deposition and pore throat blockage during the process. The gas injection process may be miscible or immiscible, depends on temperature, injection gas, properties of reservoir fluids and pressure. Maximum sweep efficiency is expected in miscible displacement process, which occurs above the minimum miscible pressure (MMP) while the other factors are constant. Zero surface tension represents the Miscibility.The pendant drop technique has been recently developed to measure the interfacial tension (IFT) between the injected gas phase and the reservoir oil at different pressures and reservoir temperature. In this paper, mutual interactions between each of two different synthetic oils and CO2 are experimentally studied. Tow synthetic oils consist of 1.3 gr asphaltene and 3 gr asphaltene was used. First, a series of saturation tests are conducted to determine the onset pressure of asphaltene precipitation for each synthetic oil-CO2 system. Second, the equilibrium interfacial tension (IFT) between each sample and CO2 is measured as a function of the equilibrium pressure. It is found that the determined onset pressure is higher if the synthetic oil is heavier. It is also found that the onset pressure is a function of composition and asphaltene content.