Previously proposed models of wettability change have not been tied to the chemistry that controls wettability but instead were driven by simplistic criteria such as salinity level or concentration of an adsorbed species. Such models do not adequately predict the impact of brine compositional change and therefore cannot be used to optimize brine composition. In this work, after testing proposed models in the literature on sandstones and carbonates, we propose a mechanistic surface-complexation-based model that quantitatively describes observations for ionically treated waterfloods. To the best of our knowledge this is the first surface- complexation-based model that fully describes ionic compositional dependence observed in ionically treated waterfloods in both sandstones and carbonates. We model wettability change by directly linking wettability to brine chemistry using detailed colloidal science. Brine has charged ions that interact with polar acidic/basic components at the oil-water interface and rock surface and therefore oil/brine and rock/brine interfaces are charged and exert both Van der Waals and electrostatic forces on each other. If the net result of the forces is repulsive, the thin water film between the two interfaces is stable (i.e., the rock is water-wet) otherwise, the thin water film is unstable and the rock becomes oil-wet. Based on Hirasaki (1991), we describe a ratio of electrostatic force to Van der Waals force with a dimensionless group, called "stability number," where rock wettability is water-wet for values greater than one and oil-wet for values less than one. For sandstones, the zeta potentials of oil/brine and rock/brine interfaces become more negative/less positive by diluting or softening the brine and/or increasing pH. Similarly, for carbonates, dilution and/or sulfate enrichment of brine makes surface potentials more negative. Such brine modification can therefore be used to improve oil recovery. We implemented the improved wettability change model in a comprehensive coupled reservoir simulator, UTCOMP-IPhreeqc, in which oil/brine and rock/brine zeta potentials are modeled using the IPhreeqc surface complexation module. We take into the account total acid number (TAN) and total base number (TBN) for the oil/brine interface and we use rock surface reactions for brine/rock surface potential modeling. Surface potentials obtained from the geochemical model are used to calculate the dimensionless group controlling wettability change, which is dynamically modeled in the transport simulator. The model is validated in sandstones and carbonates by simulating an inter-well test, and several corefloods and imbibition tests reported in the literature. For sandstones, we model Kozaki (2012) and BP's Endicott trial. For simple dilution in carbonates we model experiments by Shehata et al. (2014) and Yousef et al. (2010). For enrichment with sulfate we model Zhang and Austad (2006) and for increasing total ionic strength via sodium chloride enrichment, Fathi et al. (2010a).
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机译：先前提出的润湿性变化模型尚未与控制润湿性的化学性质相关联，而是通过简单的标准如盐度水平或吸附物种浓度的驱动。这些模型不充分预测盐水成分变化的影响，因此不能用于优化盐水组合物。在这项工作中，在测试砂岩和碳酸盐中的文献中的提出模型之后，我们提出了一种基于机械表面络合的模型，其定量地描述了用于离子处理的水运的观察。据我们所知，这是第一种基于表面络合的模型，它充分描述了在砂岩和碳酸盐中的离子处理的水泡中观察到的离子组成依赖性。通过将胶体科学直接与盐水化学联系起来，我们模拟润湿性改变。盐水的离子在油 - 水界面和岩石表面的极性酸性/碱性成分中的带电，因此加入油/盐水和岩石/盐水界面，并互相施加van der WaaS和静电力。如果力的净结果是令人厌恶的，则两个界面之间的薄水膜是稳定的（即，岩石是水湿的），否则薄的水膜是不稳定的，岩石变得润湿。基于Hirasaki（1991），我们描述了静电力与van der Waals力的比率，其具有无量纲基团，称为“稳定性数”，其中岩石润湿性是水湿的值，对于大于一个的值和油湿的值小于一。对于砂岩，通过稀释或软化盐水和/或增加pH，油/盐水和岩石/盐水界面的Zeta电位变得更加负/较低的阳性。类似地，对于碳酸盐，稀释和/或硫酸盐富集盐水使表面电位变得更加阴性。因此，这种盐水改性可用于改善溢油。我们在全面的耦合储层模拟器中实施了改进的润湿性变化模型，其中油/盐水和岩石/盐水Zeta电位采用IPHREEQC表面络合模块进行了建模。我们参加了油/盐水界面的总酸数（TAN）和总基数（TBN），我们使用岩石表面反应进行盐水/岩石表面电位建模。从地球化学模型获得的表面电位用于计算控制润湿性变化的无量纲基团，其在传输模拟器中动态建模。通过模拟井间测试和文献中报告的几个Corefloods和吸收测试，在砂岩和碳酸盐中验证了该模型。对于砂岩，我们模特kozaki（2012）和BP的诺基吉特试验。在碳酸盐中简单稀释，我们通过Shehata等人的模型实验。 （2014）和Yousef等人。 （2010）。为了富含硫酸盐的富集，通过氯化钠富集，Fathi等，增加Zhang and Austad（2006）并增加总离子强度。 （2010A）。
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