Abstract Low salinity water injection (LSWI) has gained great attention as a promising enhanced oil recovery (EOR) method with numerous advantages (e.g., economic and environmental aspects), compared to other conventional chemical EOR methods. For the past two decades, a number of laboratory studies have been performed by researchers to understand the main pore-scale mechanisms of oil displacement during LSWI; however, further experimental and modeling research works are required to comprehend the LSWI governing mechanisms. The focus of this paper is to investigate important aspects such as oil recovery mechanisms, wettability alteration, changes in pH of formation water, and mineral reactions (dissolution/precipitation) which occur during LSWI in sandstones and carbonates. To explore the effect of ion-exchange, a compositional model is developed with the aid of laboratory data provided by Computer Modeling Group (CMG), where Na+ and SO42− are used as interpolants to model LSWI in sandstone and carbonate cores, respectively. In this study, it is concluded that wettability change from preferentially oil-wet to more water-wet is the dominant mechanism for a considerable increase in the oil recovery in carbonate rocks. Based on the simulation runs, the amount of calcite precipitation and dissolution is found to be small in the carbonate case studied in this research work; exhibiting an insignificant impact. However, the calcite precipitation and dolomite dissolution are the central factors, affecting oil recovery during LSWI if there is a high bicarbonate content ( HCO 3 - ) , in the presence of other catalytic ions.

中文翻译：

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砂岩和碳酸盐岩低矿化度注水模拟研究：Na + 和SO 4 2 - 的影响

摘要 与其他常规化学 EOR 方法相比，低矿化度注水 (LSWI) 作为一种有前景的提高石油采收率 (EOR) 方法受到了极大的关注，具有许多优势（例如，经济和环境方面）。在过去的 20 年里，研究人员进行了许多实验室研究，以了解 LSWI 期间驱油的主要孔隙尺度机制；然而，需要进一步的实验和建模研究工作来理解 LSWI 管理机制。本文的重点是研究重要方面，例如石油采收机制、润湿性改变、地层水 pH 值的变化以及砂岩和碳酸盐岩 LSWI 期间发生的矿物反应（溶解/沉淀）。为了探索离子交换的效果，在计算机建模组 (CMG) 提供的实验室数据的帮助下开发了一个成分模型，其中 Na+ 和 SO42- 用作插值，分别模拟砂岩和碳酸盐岩心中的 LSWI。在这项研究中，得出的结论是，润湿性从优先亲油变为更亲水是碳酸盐岩中石油采收率显着增加的主要机制。根据模拟运行，发现在本研究工作中研究的碳酸盐案例中方解石沉淀和溶解的量很小；表现出微不足道的影响。然而，方解石沉淀和白云石溶解是主要因素，如果存在高碳酸氢盐含量 (HCO 3 - ) 且存在其他催化离子，则影响 LSWI 期间的石油采收率。