Investigating the Phase Behavior of Viscoelastic Surfactant with Squalene and Crude Oil Systems at High Temperature

Studying phase behavior at high temperatures is always a challenge due to the risk of evaporation and losing fluid volume; however, we achieved it with our novel device with a high-pressure high-temperature (HPHT) cell, capable of reaching 300 °C without losing any fluid volume. Phase behavior has been investigated for viscoelastic surfactant (VES)/crude oil system and VES/squalene system to explore the effect of salinity, concentration, and temperature on the volume fraction phases and the solubilization ratios. The crude oil system is to mimic the real case in the oil field, while the squalene system is considered a reference model oil with known composition and properties. The results showed that in VES/crude oil system, the emulsion volume decreases with increase in salinity and surfactant concentration, while the temperature has a mixed effect on the emulsion volume, which decreased with increase in the temperature to its minimum volume at 90 °C and then increased again with increase in the temperature above 90 °C. Equal solubilization for each set was achieved at 75% Seawater (SW) salinity, 1.2% VES concentration, and approximately in the temperature range of 60 °C to 150 °C. In VES/squalene system, the lowest emulsion value was recorded for every set at 50% SW salinity, 90 °C temperature, and 1.25% VES concentration. Also, equal solubilization for each set was achieved at 0.5% and 1.25% VES concentration, and 90 °C temperature. However, no equal solubilization was noted for the salinity set. In both sets, no lower emulsion phase was noticed, it is either the middle phase or upper phase.