Effect of Oil Composition on Minimum Miscibility Pressure—Part 1: Solubility of Hydrocarbons in Dense CO2

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Abstract
Summary: This paper examines the effect of oil composition on the phase behavior of CO2/hydrocarbon mixtures and, hence, on the development of miscibility in a CO2 flood. Results of component-partitioning measurements are reported for mixtures of CO2 with five synthetic oil systems: normal alkanes, branched alkanes, naphthenes, aromatics, and a mixture of all four molecular types. The results of the experiments indicate that unsubstituted ring structures are less soluble in dense CO2 than branched or normal alkanes with the same number of carbon atoms, but that the addition of alkyl side chains to ring structures improves their solubility. Also reported are component-partitioning measurements for mixtures of CO2 with three crude oils: Rock Creek (paraffinic), Maljamar (more aromatic), and Rock Creek plus 15 wt% of a mixture of aromatic components. The experimental results suggest that of the many factors that influence extraction of hydrocarbons by dense CO2, the distribution of molecular weights present in the oil is the most important.