Can Lowering the Injection Brine Salinity Further Increase Oil Recovery by Surfactant Injection under Otherwise Similar Conditions?

Abstract

It is well-established that injecting water with significantly lower salinity than the formation water salinity may give increased oil recovery. Although less well studied, the observed low-salinity effect has drawn attention to possible benefits from combining low-salinity water with traditional enhanced oil recovery techniques, such as surfactant, polymer, alkali, etc., to make the overall recovery process more efficient. Surfactant injection, for example, reduces the interfacial tension (IFT) between the injected surfactant solution and the oil, thus mobilizing capillary trapped oil and/or reducing the tendency for capillary trapping. The majority of literature on the topic of low salinity and surfactant flooding primarily addresses one or the other. This study, however, compares the combined effect of reduction in IFT and low-salinity conditions to the effect of a sole reduction in IFT on oil recovery in intermediate-wet Berea sandstone cores. We find that reductions in residual oil saturation, at similar capillary numbers and phase behavior conditions, are higher for the low-salinity surfactant injection experiments compared to regular surfactant injection experiments. This strongly indicates that there is a combined effect of IFT reduction and low salinity on recovery compared to that from a reduction in IFT alone.

Nanofluids of Kaolinite and Silica in Low Saline Seawater (LowSal) with and without Surfactant: Interfacial Tension and Wettability Alteration of Oil–Water–Rock System for Low Salinity-Enhanced Oil Recovery

“…The potential combination of low salinity water and surfactant flooding can obtain a maximum possible benefit over traditional techniques to make LSWI-EOR more efficient, and such a process is known as a hybrid method. LSWI, along with a surfactant, helps lower the IFT of the oil–brine system to certain minima, thus reducing the tendency of capillary trapping and mobilizing trapped capillary oil to the production well. − Tichelkamp et al investigated the impact of surfactants on the IFT of a crude oil (light, heavy)–brine system at a low salinity condition. They observed that the IFT of the light crude oil–brine system achieved ultralow IFT in the presence of surfactant dioctyl sodium sulfosuccinate (AOT).…”

Low Salinity Polymer Flooding: Effect on Polymer Rheology, Injectivity, Retention, and Oil Recovery Efficiency

“…Due to the growing interest in low salinity water flooding, it has already drawn interest for possible synergies with other traditional EOR techniques like surfactants, alkalines, etc. The synergism between low salinity water flooding and surfactant flooding has already been studied by researchers. − Although these studies were reported to obtain a benefit from low salinity surfactant synergy, according to most literature, the low salinity water flooding mechanism works in a very similar fashion to the surfactant flooding mechanism. Both of these methods are intended to increase the microscopic displacement efficiency via wettability alteration, oil–water interfacial tension reduction, and formation of a microemulsion.…”

A Synergy between Controlled Salinity Brine and Biosurfactant Flooding for Improved Oil Recovery: An Experimental Investigation Based on Zeta Potential and Interfacial Tension Measurements

“…Other studies have explored the EOR potential via combining low salinity brine with chemical surfactant injection in the bid to increase oil production and their results show better recovery with combined process than applying either of the techniques alone [19][20][21]. Addition of surfactants has also been shown to be efficient in decreasing oil-brine interfacial tension and altering of rock surface wetness [22][23][24].…”