Understanding the phase equilibria and physical-chemical characteristics of the CH–CO–HO–NaCl quaternary system is important for evaluating costs and risks for the storage of CO in depleted natural gas reservoirs as well as fluid inclusion studies. In this study, phase equilibria and thermodynamic properties of this system were investigated through the utilization of a statistical association fluid theory-based (SAFT) equation of state (EOS) at temperatures from 298 to 513 K (25–240 °C), pressures up to 600 bar (60 MPa) and concentration of NaCl up to 6 mol/kgHO. The model parameters were obtained from the fitting of available experimental data of subsystems (i.e., CH–HO, CH–CO, and CH–HO–NaCl) that were judged to be reliable and incorporation of available parameters for the subsystems (i.e., pure component, CO–HO, and CO–HO–NaCl). Using the SAFT EOS developed in this study, we predicted the solubility of (CH + CO) gas mixtures in pure HO and compared it with the available experimental data and the predicted values from four popular numerical simulators. The results indicate that our model can provide reliable predictions for the CH–CO–HO ternary system. Subsequently, we further predicted the phase equilibria and density of the CH–CO–HO–NaCl system with NaCl varying from 0 to 6 mol/kgHO. We also employed the SAFT EOS to predict the solubility of CO and CH in the water-alternating-gas process for CO-enhanced oil recovery, demonstrating good agreement with the simulation results obtained through the Peng-Robinson EOS for predicting the CO and CH solubility. These predicted thermodynamic properties and phase behaviors in the CH–CO–HO–NaCl system provide quantitative insights into the implications of CO storage in depleted oil and gas reservoirs.

中文翻译：

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CH4–CO2–H2O–NaCl 四元系统的 SAFT2 状态方程及其在枯竭气藏中 CO2 封存的应用


了解CH-CO-H2O-NaCl四元系统的相平衡和物理化学特征对于评估贫化天然气储层中CO2封存的成本和风险以及流体包裹体研究非常重要。在这项研究中，通过利用基于统计关联流体理论 (SAFT) 的状态方程 (EOS)，在 298 至 513 K (25–240 °C) 的温度、压力下研究了该系统的相平衡和热力学性质。高达 600 bar (60 MPa) 且 NaCl 浓度高达 6 mol/kgH2O。模型参数是通过对被认为可靠的子系统（即 CH-H2O、CH-CO 和 CH-H2O-NaCl）的可用实验数据进行拟合而获得的，并结合了子系统的可用参数（即纯成分，CO-H2O 和 CO-H2O-NaCl）。使用本研究中开发的 SAFT EOS，我们预测了 (CH + CO) 气体混合物在纯 H2O 中的溶解度，并将其与可用的实验数据和四个流行数值模拟器的预测值进行了比较。结果表明，我们的模型可以为 CH-CO-H2O 三元体系提供可靠的预测。随后，我们进一步预测了 NaCl 在 0 至 6 mol/kgH2O 范围内变化的 CH-CO-H2O-NaCl 体系的相平衡和密度。我们还利用 SAFT EOS 来预测 CO 提高采收率的水-气交替过程中 CO 和 CH 的溶解度，这与通过 Peng-Robinson EOS 预测 CO 和 CH 溶解度所获得的模拟结果非常吻合。这些预测的 CH-CO-H2O-NaCl 系统中的热力学性质和相行为为枯竭油气藏中二氧化碳储存的影响提供了定量见解。