CRUDE OIL/BRINE INTERFACIAL TENSIONS

Interfacial tension (IFT) between crude oil and brine is an important variable in water/oil and water/oil/gas displacements. IFT influences capillary pressure, capillary number, adhesion tension, and the dimensionless time for imbibition. Despite its importance, there is little data available and even less data that can be related to key crude oil chemical properties such as acid and base number. In this paper we present the results of a study of interfacial tensions for 41 wellcharacterized stock-tank crude oil samples. Transient IFTs measured by the pendant drop technique were monitored as a function of time. The effects of salinity and pH (over the range from 3 to 10) have been investigated and correlations observed between IFT and an oil’s acid number, base number, and amount of asphaltenes. This extensive data set will be of use to core analysts when they compare capillary pressures measured with different fluid pairs or design core floods with model fluids, and in many other applications. It can also be used to examine mechanistic explanations for the magnitude of IFT between a crude oil and brine.