Effect of Simple Polar Compounds and Salinity on Interfacial Tension and Wettability of Rock/Oil/Brine System

Abstract

The objective of this study was to investigate the effect of polar compounds and salinity on the interfacial tension and wettability characteristics of rock/oil/brine systems. Crude oil and core samples from Safaniya formation iIt<Saudi Arabia were used in the study. The concentration of polar compounds in the crude oil was varied by adding different amounts of oleic acid and octadecylamine to the crude oil. Results showed that, the interfacial tension between crude oil and brine was lowered to a minimum value when oleic acid concentration of (J.O28 gm-mole/lit. and brine salinity of 40,000 ppm NaCI were used. In case of using octadecylamine, the optimum salinity for obtaining the minimum interfacial tension lies between 4,000 and 10,000 ppm NaCI. The studied rock/oil/brine system is water-wet when oleic acid concentrations of 0.007 and 0.0105 gm-mole/lit were used for brine salinities of 10,000 and 0.0 ppm NaCl, respectively. The existence of octadecylamine in oil and sodium chloride in water reverses the system wettability from oil-wet to water-wet.