Does Interfacial Viscoelasticity Increase Oil Recovery at Very High Temperature and Salinity in Carbonates?

Abstract

Abstract Flooding with low salinity water (LSW) may increase oil recovery. Despite the general belief that the mechanism of LSW is governed by wettability alteration, crude oil-water interfacial viscoelasticity appears to be a more dominant oil recovery process. Our recent work using 15 crude oils from different parts of the world show that there is a strong correlation between the elasticity of the oil-brine interface and oil recovery. The elasticity of the crude oil – water interface may be tuned by a very small amount of a polymeric surfactant. In this work, we present a systematic study in four different crude oils (A, B, C, D) with different viscoelastic interfaces in different crude oil-brines. We have measured interfacial elasticity of crude-low salinity water (LSW), crude-high salinity water (HSW), and crude-high salinity water with 100 ppm polymeric surfactant (HSW-PS). The polymeric surfactant may increase the interfacial elasticity of the interface significantly. Two of the crude oils (A and C) show an increase in interface elasticity with 100 ppm PS in HSW. In the second crude oil (B), there is not much change in interface elasticity observed with HSW, LSW, and HSW-PS. With the fourth crude oil (D) we observe LSW and HSW-PS increase interface elasticity. We have conducted nine different coreflooding experiments. Six are at 50 °C, one at 90 C, and other two at 100 °C. Extra recoveries vary in the range of 8% to 20% for systems with high elasticity promoted by the addition of 100 ppm polymeric surfactant in HSW. In crude A, we observe the largest extra recovery with HSW-PS at 50°C; it is 20% higher in comparison to LSW. At 100°C, extra recovery with HSW-PS is 10%. At both temperatures, pressure drop is lower with HSW-PS than with LSW. The implication is higher injectivity besides mobilizing incremental residual oil from carbonate cores.