Selem Ahmed M, Agenet Nicolas, Blunt Martin J, Bijeljic Branko
Department of Earth Science and Engineering, Imperial College London, SW7 2AZ London, United Kingdom.
TotalEnergies, Pau, France.
J Colloid Interface Sci. 2022 Dec 15;628(Pt A):486-498. doi: 10.1016/j.jcis.2022.06.063. Epub 2022 Jun 18.
The wettability change from oil-wet towards more water-wet conditions by injecting diluted brine can improve oil recovery from reservoir rocks, known as low salinity waterflooding. We investigated the underlying pore-scale mechanisms of this process to determine if improved recovery was associated with a change in local contact angle, and if additional displacement was facilitated by the formation of micro-dispersions of water in oil and water film swelling.
X-ray imaging and high-pressure and temperature flow apparatus were used to investigate and compare high and low salinity waterflooding in a carbonate rock sample. The sample was placed in contact with crude oil to obtain an initial wetting state found in hydrocarbon reservoirs. High salinity brine was then injected at increasing flow rates followed by low salinity brine injection using the same procedure.
Development of water micro-droplets within the oil phase and detachment of oil layers from the rock surface were observed after low salinity waterflooding. During high salinity waterflooding, contact angles showed insignificant changes from the initial value of 115°, while the mean curvature and local capillary pressure values remained negative, consistent with oil-wet conditions. However, with low salinity, the decrease in contact angle to 102° and the shift in the mean curvature and capillary pressure to positive values indicate a wettability change. Overall, our analysis captured the in situ mechanisms and processes associated with the low salinity effect and ultimate increase in oil recovery.
通过注入稀释盐水使润湿性从油湿向更亲水的条件转变，可以提高储层岩石的原油采收率，即所谓的低盐度水驱。我们研究了这一过程潜在的孔隙尺度机制，以确定采收率的提高是否与局部接触角的变化有关，以及油中水分散体的形成和水膜膨胀是否促进了额外的驱替。
使用X射线成像以及高温高压流动装置来研究和比较碳酸盐岩样品中的高盐度和低盐度水驱。将该样品与原油接触，以获得在油气藏中发现的初始润湿状态。然后以递增的流速注入高盐度盐水，接着采用相同的步骤注入低盐度盐水。
低盐度水驱后，观察到油相中形成了水微滴，并且油层从岩石表面脱离。在高盐度水驱过程中，接触角与115°的初始值相比变化不明显，而平均曲率和局部毛细管压力值仍为负值，这与油湿条件一致。然而，对于低盐度情况，接触角减小至102°，平均曲率和毛细管压力转变为正值，这表明润湿性发生了变化。总体而言，我们的分析揭示了与低盐度效应以及原油采收率最终提高相关的原位机制和过程。
