Interfacial behavior of complex hydrocarbon fluids at elevated pressures and temperatures

Document Type

Conference Proceeding

Publication Date

12-1-2005

Abstract

Unlike all the physical properties of the bulk fluid phases, interfacial tension (IFT) is unique in the sense that it relates to the interface between the two immiscible fluid phases. Hence, interfacial tension between the fluid phases can be used to infer a great deal of information about solubility, miscibility and mass transfer interactions between the two bulk fluid phases in contact. However, all these multitude of roles played by interfacial tension in fluid-fluid phase behavior interactions have not been well recognized. Miscible gas injection displacement processes are widely employed in petroleum industry to minimize the capillary trapping for significant oil recovery enhancements. The mass transfer interactions between the injected gas and reservoir crude oil at reservoir pressures and temperatures modify the fluid phase compositions for miscibility development. Recently a new technique of vanishing interfacial tension (VIT) has been developed utilizing the concept of zero IFT at miscibility for miscibility determination in gas-oil systems. In this paper, we examine the utility of interfacial tension to characterize miscibility and mass transfer mechanisms using complex hydrocarbon fluids at elevated pressures and temperatures. The interfacial tension measurements were carried out using the standard gas-oil systems of known phase behavior characteristics; CO2 against n-decane at 37.8 oC, and CO2 against an oil mixture consisting of 25 mole% n-C1+ 30 mole% n-C4+ 45 mole% n-C10 at 71.1 oC. The well-known capillary rise technique has been adapted and successfully used in this study for IFT measurements at elevated pressures and temperatures. Our previously developed mechanistic model has been utilized to characterize the mass transfer mechanisms from the measured IFT data. For CO2/n-decane system at 37.8 oC, the minimum miscibility pressure (MMP) determined using the VIT technique (7.9 MPa) matched well with the reported MMPs by slim-tube (8.2-8.6 MPa) and rising-bubble techniques (8.8 MPa). For CO2/n-C1+ n-C4+ n-C10 system at 71.1 oC, the VIT technique resulted in an MMP value of 12.2 MPa, which is in good agreement with the published values of slim-tube and phase diagram measurements (11.7 MPa) and analytical model predictions (11.7 MPa). The mechanistic model results indicate that the vaporization of components from the oil to the gas phase is the governing mass transfer mechanism occurring between the fluid phases of both the gas-oil systems studied. Thus, this paper discusses the multiple roles of interfacial tension with supporting experimental data obtained at elevated pressures and temperatures and emphasizes the need to recognize interfacial tension as a good phase behavior indicator in fluid-fluid phase equilibria for more efficient use of this fundamental property in several other applications. © 2005 IEEE.

Publication Source (Journal or Book title)

Proceedings - 2005 International Conference on MEMS, NANO and Smart Systems, ICMENS 2005

First Page

173

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