Measurement of interfacial tension and spreading coefficient under reservoir conditions: experimental investigation

The variation of interfacial tension with temperature and pressure influences the transport of the fluid in a reservoir strongly. This makes the interfacial tension probably the most important of the factors that make one-third of the total oil in place (in reservoir rock) unrecoverable by gas drive or water flooding. Several models and correlations were used to predict the measured data presented here. We have studied the applicability of four of the most commonly used IFT-correlations, those of Katz et al. [AIME Technical Publications No. 1624, pp. 285-294], Hough and Stegemeier [Soc. Pet. Eng. J. (1961) 259-263], Lee and Chien [SPE/DOE 12643, Fourth Symp. on EOR, Tulsa, OK], and Pedersen et al. [Properties of oils and natural gases, Gulf Publishing Co., 1989, pp. 196-207]. The experimental results from the three binary systems as well as the recombined crude oil system have shown that the interfacial tension in the high pressure region (below saturation pressure) remains quite low despite large pressure decrements. This study was then extended to include measurements of the equilibrium interfacial tension for oil-brine, oil-gas and gas-brine at reservoir temperature and pressure over the range 250 to 3728 psia. The interfacial tensions were used to evaluate the spreading coefficient as a function of pressure at reservoir temperature. The viscosity and density of the oil and gas and brine phases were also measured over the same range of reservoir conditions. (C) 1998 Elsevier Science B.V.