Effect of Oil Composition on Minimum Miscibility Pressure—Part 2: Correlation

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Abstract
Summary: A new correlation for CO2 minimum miscibility pressure (MMP) is proposed and tested. The correlation is based on experimental evidence that extraction of hydrocarbons from a crude oil depends most strongly on the size of the hydrocarbon molecules. Thus, an oil rich in hydrocarbons that are efficiently extracted should show a lower MMP than a heavier oil. The only crude-oil data needed for use of the correlation are a carbon-number distribution, which can be obtained easily by chromatography. The density of CO2 at the MMP is correlated against a weighted-composition parameter. The MMP of any oil at a given temperature is estimated as the pressure required to yield that CO2 density. The effects of contaminants in CO2 can be estimated easily by calculating the pressure required to give a mixture density equal to that required for pure CO2. Correlation accuracy was tested by comparing predicted and measured MMP's for 35 oils. The proposed correlation produces MMP estimates accurate to within about 10% for most oils. Comparison of correlation predictions with those of other commonly used correlations indicates that the proposed correlation is significantly more accurate, particularly for recombined oils.