Rimsza Jessica M, Kuhlman Kristopher L
Geochemistry Department, Sandia National Laboratories, Albuquerque, New Mexico 87123, United States.
Applied Systems Analysis & Research, Sandia National Laboratories, Albuquerque, New Mexico 87123, United States.
Langmuir. 2021 Nov 16;37(45):13291-13299. doi: 10.1021/acs.langmuir.1c01836. Epub 2021 Nov 3.
Elevated temperature and pressure in the earth's subsurface alters the permeability of salt formations, due to changing properties of the salt-brine interface. Molecular dynamics (MD) simulations are used to investigate the mechanisms of temperature and pressure dependence of liquid-solid interfacial tensions of NaCl, KCl, and NaCl-KCl brines in contact with (100) salt surfaces. Salt-brine dihedral angles vary between 55 and 76° across the temperature (300-450 K) and pressure range (0-150 MPa) evaluated. Temperature-dependent brine composition results in elevated dihedral angles of 65-80°, which falls above the reported salt percolation threshold of 60°. Mixed NaCl-KCl brine compositions increased this effect. Elevated temperatures excluded dissolved Na ions from the interface, causing the strong temperature dependence of the liquid-solid interfacial tension and the resulting dihedral angle. Therefore, at higher temperature, pressure, and brine concentrations Na-Cl systems may underpredict the dihedral angle. Higher dihedral angles in more realistic mixed brine systems maintain low permeability of salt formations due to changes in the structure and energetics of the salt-brine interface.
由于盐 - 盐水界面性质的变化，地球地下升高的温度和压力会改变盐层的渗透率。分子动力学（MD）模拟用于研究与（100）盐表面接触的NaCl、KCl和NaCl - KCl盐水的液 - 固界面张力对温度和压力的依赖机制。在所评估的温度范围（300 - 450 K）和压力范围（0 - 150 MPa）内，盐 - 盐水二面角在55°至76°之间变化。与温度相关的盐水成分导致二面角升高至65 - 80°，高于报道的60°的盐渗透阈值。混合的NaCl - KCl盐水成分增强了这种效应。升高的温度将溶解的Na离子排除在界面之外，导致液 - 固界面张力以及由此产生的二面角对温度有强烈的依赖性。因此，在较高温度、压力和盐水浓度下，Na - Cl系统可能会低估二面角。在更实际的混合盐水系统中较高的二面角由于盐 - 盐水界面的结构和能量变化而使盐层保持低渗透率。
