Low-salinity water flooding in Middle East offshore carbonate reservoirs: Adaptation to reservoir characteristics and dynamic recovery mechanisms

This study uses nuclear magnetic resonance and microscopic seepage experiments to investigate dynamic changes in oil–water interface properties during low-salinity water flooding at the pore and core scales. Unlike static measurements, dynamic experiments capture continuous changes in key parameters, such as the increasing contact angle, interfacial curvature, and decreasing capillary force during low-salinity flooding. This study quantitatively analyzes the dynamic coupling mechanisms between oil–water interface properties and the mobilization of residual oil. The experiments demonstrate that low-salinity water has a more significant impact on enhancing the recovery of crude oil with high polar component content. In the dynamic flooding process, the increase in wettability angle and curvature shows that low-salinity water reduces the resistance to crude oil migration. The water flow, in combination with crude oil, forms oil–water micro-dispersions that promote the migration of residual oil in small pores, where high-polarity crude oil exhibits greater sensitivity to wettability alterations. The increase in injection rate enhances the shear detachment effect, further improving oil recovery, with low polar component crude oil being more sensitive to this effect. The contribution of dynamic wettability changes to the recovery factor in low salinity waterflooding is an order of magnitude greater than the interfacial tension effect, making it the primary influencing factor for improving recovery. Although this study is constrained by laboratory conditions, the results provide valuable theoretical support and experimental evidence for optimizing low-salinity waterflooding strategies and evaluating crude oil type adaptability in offshore carbonate reservoirs.