Prediction of live reservoir fluid interfacial tension from dead oil measurements

Abstract

The interfacial tension (IFT) between crude oil and water governs the multiphase flow in porous media and is therefore of paramount importance for understanding reservoir behavior. IFT data is commonly, but inadequately, acquired at ambient conditions using samples of dead oil, because live crude oil samples are limited in availability and measurements under high pressure and temperature conditions are complex. In this study, ten live crude oil samples were used to establish the first correlation allowing to predict live crude oil interfacial tension based on dead oil IFT values and conventional PVT data. IFT experiments were executed for all samples at different pressure and temperature conditions. A common trend of IFT increase from the dead oil at ambient to the live oil at reservoir conditions was noted in the experiments. Based on the measured data, a correlation was established to predict live oil IFT at reservoir conditions from dead oil IFT at ambient condition, using dead oil viscosity and molecular weight, as well as gas to oil ratio and fluid densities as input parameters. The correlation showed a strong coefficient of determination (R2 = 0.98) and was validated using three additional live crude oils from different fields. The IFT values at reservoir conditions were well predicted with average errors below 5%.