Diffusion Coefficients Of Carbon Dioxide In Oil-Saturated Porous Media At High Pressure And Temperature

The global warming and greenhouse effect caused by the emission of carbon dioxide (CO2) have had a huge impact on human activities. For facing the increasingly serious environmental problems and meeting the growing demand for energy, launching overall and deep research to the greenhouse gas emissions and energy efficient is of great theoretical value and realistic meaning. CO2 flooding as one of the most attractive and effective ways to enhance oil recovery (EOR) that not only can achieve long-term sequestration of CO2 but also solves the shortage of global petroleum resources, with a good prospect of application. When CO2 is injected for the purpose of enhanced oil recovery, the oil recovery efficiency of CO2 depends largely on CO2 dissolved in the oil and the dissolved after the change of oil properties. Molecular diffusion coefficient is a key factor to determine the rate of mass transfer between the CO2 and oil phase under reservoir condition. Therefore, an in-depth research on diffusion mechanism in a CO2-EOR process is essential to enable CO2-EOR that is effective and low-cost, yielding significant economic and social benefits.In this work, the improved gas-liquid diffusion model combined with pressure decay method are developed to measure the effective molecular diffusion coefficients of carbon dioxide in oil-saturated porous. This method not only consider the effect of tortuous path of the porous media but also handle the target fluids at high pressure and temperature conditions, which is more near to gas injection process for the CO2 floods, the results can provide a theoretical basis for the application and design of oil recovery.The effective diffusion coefficients of carbon dioxide in oil-saturated porous media were measured over the temperature range of 20-80 ??initial pressure range of 15-30Mpa and tortuosity range of 1.87-5.39. The comparison of the diffusivities in porous core with and without taking into account the effect of tortuous path demonstrates significant discrepancy, which can leads to a great deviation in the calculated diffusivities; The effects of tortuosity, temperature and initial pressure on the diffusion coefficient of the CO2 in the diesel oil are also discussed. The results indicate that the calculated diffusivity decreases with the increasing of tortuosity, the existence of the porous media induced fluids move along tortuous paths rather than straight lines; The diffusivity increases with the increasing of temperature and the increment is increasing, the diffusivity increases steadily with increasing of initial pressure but the increment is diminishing, for the high pressure conditions, the gas diffusivity in oil-saturated porous had less affected by the pressure, but with the properties of the gas-liquid itself.