Ma Wenguo, Yuan Wenhang, Wang Peng, Liu Xuan, Wang Yueqi
Key Laboratory for Enhanced Oil & Gas Recovery of the Ministry of Education, Northeast Petroleum University, Daqing 163318, Heilongjiang, China.
Daqing Oil Field Co. Ltd., Daqing 163453, Heilongjiang, China.
ACS Omega. 2024 Dec 3;9(50):49377-49386. doi: 10.1021/acsomega.4c06758. eCollection 2024 Dec 17.
In alkali/surfactant/polymer (ASP) flooding systems, alkalis react with clay minerals such as Illite, montmorillonite, and kaolinite, leading to reservoir damage and impacting oil recovery rates. Therefore, studying the dissolution effects of strong alkalis on clay minerals is crucial for improving oil recovery. This study uses Illite as a representative clay mineral and employs the ReaxFF reactive force field and molecular dynamics simulations to model its dissolution in NaOH solution. We investigated the diffusion coefficients of metal cations in Illite and their interactions with hydroxide ions at various NaOH concentrations. The study also explores the evolution of dissolution products and protonation characteristics during the dissolution of Illite. By calculating the changes in ionic energy throughout the dissolution process, we analyzed variations in ionic reactivity within the system. Simulation results show that as the NaOH concentration increases, metal cations in Illite form stable chemical bonds with hydroxide ions, creating highly aggregated clusters with strong ionic interactions that hinder migration. Consequently, the diffusion coefficients of metal cations gradually decrease. During the reaction, water dissociates to produce hydrogen ions and hydroxide ions. Ion exchange occurs between the solution cations and Illite cations. Illite cations gradually precipitate and form metal hydroxides by combining with hydroxide ions under electrostatic forces. Protonation propagates from the surface to the internal structure during the reaction. Moreover, the degree of protonation increases with higher NaOH concentrations. Changes in the average ionic energy before and after the reaction indicate that K exhibits the highest reactivity. Intermediate silicate products are unstable in NaOH solution, with some Si ions showing higher energy and stronger reactivity.
在碱/表面活性剂/聚合物（ASP）驱油体系中，碱与伊利石、蒙脱石和高岭石等粘土矿物发生反应，导致储层损害并影响原油采收率。因此，研究强碱对粘土矿物的溶解作用对于提高原油采收率至关重要。本研究以伊利石作为代表性粘土矿物，采用ReaxFF反应力场和分子动力学模拟来模拟其在氢氧化钠溶液中的溶解过程。我们研究了不同氢氧化钠浓度下伊利石中金属阳离子的扩散系数及其与氢氧根离子的相互作用。该研究还探讨了伊利石溶解过程中溶解产物的演变和质子化特征。通过计算整个溶解过程中离子能量的变化，我们分析了体系内离子反应性的变化。模拟结果表明，随着氢氧化钠浓度的增加，伊利石中的金属阳离子与氢氧根离子形成稳定的化学键，形成具有强离子相互作用的高度聚集簇，阻碍迁移。因此，金属阳离子的扩散系数逐渐降低。反应过程中，水离解产生氢离子和氢氧根离子。溶液阳离子与伊利石阳离子之间发生离子交换。伊利石阳离子逐渐沉淀，并在静电力作用下与氢氧根离子结合形成金属氢氧化物。反应过程中质子化从表面向内部结构传播。此外，氢氧化钠浓度越高，质子化程度越高。反应前后平均离子能量的变化表明钾的反应性最高。中间硅酸盐产物在氢氧化钠溶液中不稳定，一些硅离子表现出较高的能量和较强的反应性。
