Fang Hongxu, Yue Xiaokun, Wang Lu, Liu Sen, Zhang Huili, Feng Fei, Gao Xue, Wang Zhaojie, Wei Shuxian, Lu Xiaoqing, Liu Siyuan, Lyu Weifeng
School of Materials Science and Engineering, China University of Petroleum, Qingdao 266580, China.
College of Science, China University of Petroleum, Qingdao 266580, China.
Langmuir. 2024 Dec 31;40(52):27645-27658. doi: 10.1021/acs.langmuir.4c04211. Epub 2024 Dec 18.
The wettability of shale is an important factor affecting oil and gas extraction, and conventional experimental methods are difficult to study at the nanoscale. Moreover, most existing studies are qualitatively based on the wettability of rock surfaces with little consideration for their impact on the CO-EOR. This study employs molecular dynamics simulation methods to conduct an in-depth analysis of the role of rock surface wettability in the CO-enhanced oil recovery (EOR) process. The research findings indicate that as the surface hydroxyl content increases, the adsorption affinity for CO is enhanced, with the selectivity increasing exponentially from 0.74 in the strongly oleophilic wetting (SOW) pore to 3.62 in the strong hydrophilic wetting (SHW) pore. Additionally, variations in wettability result in different types of CO displacement. As oil wettability decreases, the contact interface between CO and oil changes from a convex to a concave shape. Moreover, different types of wettability result in different dynamic contact angle changes over time, which significantly impacts various displacement stages. A comprehensive comparison shows that pores exhibiting oil-wet characteristics reduce the efficiency of the CO-EOR. Finally, the investigation explored the influence of pore structure on oil displacement efficiency. In double pores, when the larger pores exhibit hydrophobic characteristics, they further accelerate the displacement speed of the smaller pores. In connected pores, the presence of notch speeds up the displacement effect within the smaller pores, reducing the impact of wettability on displacement efficiency. This study deeply analyzes the role of shale surface wettability in the CO-EOR process, revealing the impact of wettability on the CO adsorption affinity, fluid displacement, oil displacement efficiency, and flow characteristics of shale oil, providing an important theoretical basis for optimizing the CO-EOR process by adjusting wettability.
页岩的润湿性是影响油气开采的一个重要因素，而传统实验方法难以在纳米尺度上进行研究。此外，大多数现有研究在定性上基于岩石表面的润湿性，很少考虑其对二氧化碳强化采油（CO-EOR）的影响。本研究采用分子动力学模拟方法，深入分析岩石表面润湿性在CO强化采油（EOR）过程中的作用。研究结果表明，随着表面羟基含量的增加，对CO的吸附亲和力增强，选择性从强亲油润湿性（SOW）孔隙中的0.74呈指数增长至强亲水润湿性（SHW）孔隙中的3.62。此外，润湿性的变化导致不同类型的CO驱替。随着油润湿性降低，CO与油之间的接触界面从凸形变为凹形。而且，不同类型的润湿性导致动态接触角随时间发生不同变化，这对各个驱替阶段有显著影响。综合比较表明，具有油湿特性的孔隙会降低CO-EOR的效率。最后，该研究探讨了孔隙结构对驱油效率的影响。在双孔隙中，当较大孔隙呈现疏水特性时，它们会进一步加快较小孔隙的驱替速度。在连通孔隙中，缺口的存在加快了较小孔隙内的驱替效果，降低了润湿性对驱替效率的影响。本研究深入分析了页岩表面润湿性在CO-EOR过程中的作用，揭示了润湿性对CO吸附亲和力、流体驱替、驱油效率和页岩油流动特性的影响，为通过调节润湿性优化CO-EOR过程提供了重要的理论依据。
