Pore scale release and transport of oil by low salinity water

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Low salinity waterflooding has been shown to increase oil recovery both on the core and field scale in many but not all sandstones. Macro-scale observations suggest that changing the water salinity alters the wetting state of the rock, usually making it more water-wet. However, as yet there are no systematic pore scale observations of how this wettability alteration alters the pore scale distribution of oil and water and thus improves oil recoveryIn this work, X-ray micro-CT scanning is used to image low salinity water flooding experiments. The change in fluid distribution within the pores is monitored along with the wetting state of the sample, characterised using several measures - in situ contact angle, fluid-fluid interfacial curvature, and fluid-solid fractional wetting. These are then used to interpret the observed changes in water and oil distribution low salinity waterflooding, providing valuable insight into the oil recovery mechanisms. More generally, this work provides insight into pore scale observations of wetting state, the betterment of which is crucial in improving our understanding of a range of important areas including carbon sequestration, remediation of contaminated aquifers, and subsurface hydrogen storage