Pore scale release and transport of oil by low salinity water

在许多砂岩中，低矿化度水驱可以提高岩心和油田的采收率，但并不是所有砂岩都可以。宏观尺度的观察表明，改变水的盐度会改变岩石的湿润状态，通常会使岩石更加湿润。然而，到目前为止，还没有系统的孔隙尺度观察到这种润湿性改变如何改变油水的孔隙尺度分布，从而提高石油采收率。孔隙内流体分布的变化与样品的润湿状态一起被监测，使用几种测量方法来表征——原位接触角、流体-流体界面曲率和流体-固体分数润湿。然后使用这些数据来解释观察到的水和油分布变化，为低矿化度水驱提供了有价值的采油机制。更一般地说，这项工作提供了对湿润状态的孔隙尺度观测的见解，这对于提高我们对一系列重要领域的理解至关重要，包括碳封存，污染含水层的修复和地下氢储存

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