Abstract A central issue in the equation of state (EoS) development is to describe accurately fluid density and thus other thermodynamic properties based on it. This study attempts to investigate the density modeling of high-pressure mixtures, particularly related to reservoir fluids, by cubic and non-cubic EoS. A large density database of binary mixtures related to petroleum fluids was established and used to compare some typical cubic and non-cubic EoS, including SRK, PR, PC-SAFT, Soave-BWR, and GERG-2008. For the first four EoS, their volume translated versions were also evaluated. The evaluation results suggest that the EoS form three groups in order of accuracy: GERG-2008 as the first group, Soave-BWR and PC-SAFT in the second, and PR and SRK in the last. Volume translation is more effective for the last group but it does not change the order. A model-to-model comparison was made between SRK and PC-SAFT, and between SRK and PR for 500 binary pairs over a wide range of conditions, showing that the differences in the excess volume are usually small between different models. This observation motivated the introduction of an excess volume method, which combines two EoS in estimating the final thermodynamic properties. The evaluation of this method using the binary density database shows that it can deliver reasonable density estimates using a simple model like SRK. Its limitations were analyzed and its potential application for estimating high-pressure reservoir fluid densities was discussed.

中文翻译：

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使用立方和非立方 EoS 以及超体积法对高压混合物进行密度建模

摘要 状态方程 (EoS) 发展中的一个核心问题是准确描述流体密度，从而准确描述基于它的其他热力学特性。本研究试图通过立方和非立方 EoS 研究高压混合物的密度建模，尤其是与储层流体相关的高压混合物。建立了与石油流体相关的二元混合物大密度数据库，用于比较一些典型的立方​​和非立方 EoS，包括 SRK、PR、PC-SAFT、Soave-BWR 和 GERG-2008。对于前四个 EoS，还评估了它们的批量翻译版本。评估结果表明，EoS按照准确率分为三组：GERG-2008为第一组，Soave-BWR和PC-SAFT为第二组，PR和SRK为最后一组。卷转换对最后一组更有效，但不会更改顺序。在 SRK 和 PC-SAFT 之间以及 SRK 和 PR 之间在各种条件下对 500 个二元对进行了模型到模型的比较，表明不同模型之间的过量体积差异通常很小。这一观察促使引入了过量体积方法，该方法结合了两个 EoS 来估计最终的热力学特性。使用二进制密度数据库对该方法的评估表明，它可以使用像 SRK 这样的简单模型提供合理的密度估计。分析了其局限性，并讨论了其在估计高压储层流体密度方面的潜在应用。表明不同模型之间多余体积的差异通常很小。这一观察促使引入了过量体积方法，该方法结合了两个 EoS 来估计最终的热力学特性。使用二进制密度数据库对该方法的评估表明，它可以使用像 SRK 这样的简单模型提供合理的密度估计。分析了其局限性，并讨论了其在估计高压储层流体密度方面的潜在应用。表明不同模型之间多余体积的差异通常很小。这一观察促使引入了过量体积方法，该方法结合了两个 EoS 来估计最终的热力学特性。使用二进制密度数据库对该方法的评估表明，它可以使用像 SRK 这样的简单模型提供合理的密度估计。分析了其局限性，并讨论了其在估计高压储层流体密度方面的潜在应用。