Abstract

Low salinity water flooding is an approach used during the EOR process to alter the surface wettability the IFT reduction. However, implementation of this method in shaly sandstone layers has not been totally successful due to the presence of clays and its active interaction with salt ions. In this study, attempts are made to evaluate the effect of ions on the surface wettability of shale rocks and the IFT of brine/oil. For this purpose, NaCl and MgCl₂ were considered as two very common salts used in many studies. The results obtained indicated that in the low salinity water range, decreasing the concentration of monovalent ions changes the wettability of shale from neutral wet to weakly water wet where the contact angle reaches 63° in the 1000 ppm NaCl solution. On the other hand, decreasing the divalent concentration initially increases and then decreases the contact angle in the crude oil-brine-shale rock system, inducing an oil wet system in place. It was found that a favorable wettability is achieved when the concentration of NaCl and MgCl₂ in the solution reaches 1000 ppm and 8000 ppm respectively. This could be due to several phenomena including the “salt in” effect. In addition, time appears to be an important factor in the shale wettability alteration and a significant contact angle reduction was observed over time. IFT was also sensitive to the salt ion concentration and reached its lowest value once the concentration of NaCl and MgCl₂ in the solution decreased by 49.46% and 32.04% respectively.

摘要

低盐度水驱是在 EOR 过程中使用的一种方法，用于改变表面润湿性，减少 IFT。然而，由于粘土的存在及其与盐离子的积极相互作用，这种方法在页岩砂岩层中的实施并未完全成功。在这项研究中，试图评估离子对页岩岩石表面润湿性和盐水/石油 IFT 的影响。为此，NaCl 和 MgCl ₂被认为是许多研究中使用的两种非常常见的盐。结果表明，在低盐度水范围内，降低单价离子浓度使页岩的润湿性由中性湿润变为弱水湿润，在 1000 ppm NaCl 溶液中接触角达到 63°。另一方面，降低二价浓度在原油-盐水-页岩系统中先增加然后减小接触角，在适当的位置诱导油湿系统。结果表明，当 NaCl 和 MgCl ₂的浓度达到在溶液中分别达到 1000 ppm 和 8000 ppm。这可能是由于多种现象造成的，包括“盐入”效应。此外，时间似乎是页岩润湿性改变的一个重要因素，并且随着时间的推移观察到接触角显着降低。IFT 对盐离子浓度也很敏感，当溶液中 NaCl 和 MgCl ₂的浓度分别下降 49.46% 和 32.04% 时，IFT 达到最低值。