Characterization of the Effectiveness of Fluid/Fluid and Rock/Fluid Interactions in the Success of Low Salinity Water Flooding: Pore Scale CFD Simulation

Document Type : Research Paper

Authors

1 Department of Chemical and Petroleum Engineering

2 Petroleum Engineering, Department of Chemical and Petroleum Engineering, Tehran, Iran

10.22078/pr.2025.5610.3489

Abstract

The effect of fluid/fluid and rock/fluid mechanisms on the amount of oil recovery in low salinity water flooding has not been well understood. Also, reservoir and field conditions such as the initial wettability of the reservoir, hysteresis and the effect of the injection sequence have rarely been investigated. Therefore, the present study, using the computational fluid dynamics method, first investigates the effect of initial wettability and hysteresis on the displacement efficiency of saline water in a porous network. Then, it analyzes the contribution of wettability alteration and variation of interfacial tension mechanisms on the final oil recovery in tertiary low salinity water injection. According to the results, as the initial wettability goes towards more water-wet condition (with an optimal value of 30°), low salinity water is able to sweep a larger area of the porous media. Also, the presence of hysteresis leads to superior performance of secondary injection low salinity compared to its tertiary injection in all final wettability states for the studied porous media. The difference is largest in the case of final contact angle of 60°. In order to investigate the contribution of the water/oil interfacial tension (IFT) variation and wettability alteration mechanisms, the tertiary low salinity water injection (after the secondary high salinity injection) was simulated in three different normalized salinities (relative to high salinity water) of 0.7, 0.1 and 0.01. In the absence of fluid/fluid mechanisms, salinity reduction will lead to improved oil production. In the absence of rock/fluid mechanisms, the best case for the IFT trend with salinity is the parabolic trend (not decreasing IFT with decreasing salinity). Finally, this study shows that rock/fluid and fluid/fluid mechanisms are synergistic regardless of the trend of changes in interfacial tension. In addition, the effect of IFT alone on improving oil recovery is one order (ten times) less than the effect of wettability alteration. However, based on the synergistic effect, the simultaneous interactions of these two mechanisms are significantly higher than individual performance of each mechanism.

Keywords

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References

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Journal of Petroleum Research
Volume 35, 1404-3 - Serial Number 142
September and October 2025
Pages 104-121

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