Waterflooding is the most widely applied improved oil recovery technique. Recently, there has been growing interest in the chemistry and ionic composition of the injected water. Low-salinity waterflooding (LSWF) is a relatively recent enhanced oil recovery technique that has the ability to alter the crude oil/brine/rock interactions and improve oil recovery in both clastics and carbonates. In this paper, the increase in the recovery factor during LSWF was modeled based on the exchange of divalent cations (Ca²⁺ and Mg²⁺) between the aqueous phase and the carbonate rock surface. Numerical simulations were performed using laboratory coreflood data, and oil recovery and pressure drop from experimental works were successfully history matched. The ion exchange equivalent fractions, effluent ions concentrations, changes in mineral moles, and pH have also been examined. Besides, an investigation of multi-component ionic exchange as a mechanism responsible for wettability alteration during LSWF in heterogeneous low-permeability carbonate cores is presented. The results show that wettability alteration is responsible for the increase in oil recovery during LSWF, as reflected by the shift in the crossover points of the relative permeability curves. A sensitivity study done on many key parameters (e.g., timing of LSWF injection, injection rate and temperature) and the mechanistic modeling method revealed that they all have huge effects on the process.

注水是应用最广泛的改进采油技术。最近，人们对注入水的化学和离子组成越来越感兴趣。低盐度注水（LSWF）是一种相对较新的增强型采油技术，具有改变原油/盐水/岩石相互作用并改善碎屑岩和碳酸盐岩中采油率的能力。在本文中，基于二价阳离子（Ca ²⁺和Mg ²⁺）在水相和碳酸盐岩表面之间。使用实验室岩心驱油数据进行了数值模拟，并成功地对实验工作中的采油量和压降进行了历史匹配。还检查了离子交换当量馏分，流出离子浓度，矿物摩尔的变化和pH。此外，提出了一种多组分离子交换的研究机制，该机制是造成低渗透碳酸盐岩心非均质渗流过程中润湿性改变的机理。结果表明，相对渗透率曲线交叉点的变化反映出，润湿性改变是导致LSWF采油量增加的原因。对许多关键参数（例如，LSWF注射时间，