无机盐作用下伊利石水化特性的分子模拟

伊蒙混层水化导致井壁失稳的现象相当突出，蒙脱石的水化研究较多。为研究伊利石在无机盐作用下的水化机理及膨胀特性，通过分子模拟技术建立了1M-tv和1M-cv两种在油气储层中较常见的伊利石晶体模型，并进一步通过分子动力学方法研究了伊利石层间粒子的微观分布和进入层间的无机盐阳离子的水化参数。结果表明，伊利石层间距随吸附水分子数的增大而增大，当水分子数为20时达到饱和状态； 1M-tv构型比1M-cv构型更容易发生水化膨胀； K⁺和Ca²⁺分别是一价阳离子和二价阳离子中水化数和水化半径最小的，且K⁺可以嵌入四面体片层的硅氧六元环中而难以发生离子交换，可有效阻止水分子进入伊利石晶体结构内部；实验结果很好地验证了KCl和CaCl₂对伊利石水化膨胀的抑制性。该结果对于页岩的防塌机理研究和钻井液水化抑制剂的研究具有一定的理论指导意义。

Molecular Simulation for Inorganic Salts Inhibition Mechanism on Illite Hydration

In order to study the microscopic mechanism of illite hydration expansion and the mechanism of inorganic salt inhibitors, two illite crystal models (1M-tv and 1M-cv), which are common in oil and gas reservoirs, were established through molecular simulation technology. Furthermore, molecular dynamics method was used to study the microscopic distribution of illite interlayer particles and the hydration parameters of inorganic salt cations entering the interlayer. The results show that the interlayer spacing of illite increases with the number of adsorbed water molecules. It reaches saturation when the number of molecules is 20; 1M-tv configuration is more prone to hydration expansion than 1M-cv configuration; K⁺ and Ca²⁺ are the smallest hydration numbers and hydration radius of monovalent cations and divalent cations, respectively. In addition, K⁺ can be embedded in the silicon-oxygen six-membered ring of the tetrahedral sheet, making it difficult for ion exchange to occur, which can effectively prevent water molecules from entering the inside of the illite crystal structure. The experimental results well verify the inhibition of KCl and CaCl₂ on illite hydration expansion. The results have important theoretical significance for the study of shale anti sloughing mechanism and drilling fluid hydration inhibitor.