Gas injection process is one of the most effective techniques for enhanced oil recovery. The injection gas is mostly dependent on the reservoir temperature, pressure, oil composition, and economic factors. Therefore the oil recovery varied according to different injection gas. Furthermore, it is proved that lower interfacial tension (IFT) between injected gas and reservoir fluid results in more oil recovery. In this work, a set of vanishing interfacial tension (VIT) was designed and manufactured by our research group. The VIT experimental apparatus and the experimental methods were proved reliable by comparing the experimental IFT values with the data from references. We investigated the effect of temperature and injection gas composition on the equilibrium IFT between CO2 and simulated oil fluids at different pressures. The results show that the slope of the fitted line between IFT and pressure declines with the rising of temperature for the same injection gas. The IFT values declines with the rising of CO2 mole percents for a same reservoir temperature. Also the minimum miscible pressure (MMP) can be measured by the VIT technique. The effect of temperature and injection gas composition on the CO2 miscibility were discussed. The results show that the MMPs decline with the rising of CO2 mole percents. Besides, a new model is proposed and applied to predict pure CO2-oil MMP. A total of 41 datapoints from this work and literatures were used to train and test the new correlations. The new correlation calculated MMP with average absolute relative deviation(AARD) of 5.85% and the maximum absolute relative deviation(MARD) 23.02%. The AARD and MARD of the testing set are 3.22%, 6.31%, respectively.

Temperature and injection gas composition influence on CO2 miscibility by interfacial tension measurement

249th National Meeting (2015)

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