Experimental Determination of Minimum Miscibility Pressure (MMP) by Gas/Oil IFT Measurements for a Gas Injection EOR Project

Abstract

Abstract Reliable knowledge of minimum miscibility pressure (MMP) plays a key role in the design and implementation of any miscible gas injection enhanced oil recovery (EOR) project. Various theoretical methods but few experimental methods are available for confidently determining the MMP at reservoir conditions using actual reservoir fluids. The present experimental study reports on the determination of minimum miscibility pressure (MMP) for recombined live oil with 99.9% pure CO2 at reservoir temperature using the vanishing interfacial tension (VIT) technique. VIT technique relies on the measurements of gas/oil interfacial tension (IFT) at several pressures and reservoir temperature. MMP is then obtained by extrapolation of the measured data to zero interfacial tension. In the present study, IFT between two recombined live oil samples and CO2 was measured at reservoir temperature of 289°F and at several pressures above the bubble point pressure of 2593 psia using the pendant drop method and the capillary rise technique. The pressure was then increased in steps to approach a near zero gas/oil IFT condition. The MMP that corresponds to the pressure of zero IFT was obtained by extrapolating the measured values of gas/oil IFT to zero on IFT versus pressure plot. Such extrapolation yielded MMPs of 3533 psia and 3543 psia for the two recombined live oil samples. This study was conducted to aid in the implementation of a proposed miscible CO2 flood in a newly discovered oil field in Mississippi by comparing the results of an independently conducted equation-of-state (EOS) modeling study based on vanishing tie-line method. Measured VIT-MMP was slightly lower (~4%) compared to the EOS-estimated dispersion-free MMP (3685 psia). This experimental study reinforces the use of VIT technique as a robust experimental method for determining the MMP and its possible use to validate the EOS models for using them in compositional simulation studies.