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文章目的是研究计算凝析气实际流体临界点的理论算法，文中首先简要回顾了临界点研究的历史及确定临界点的方法。随后对临界点进行确定，临界点是气液一切性质差异均消失的状态，是区分流体类型最重要的参数，并得到了理论和工程应用的广泛验证，目前确定临界点大致有四种方法：①实验测定，通过观察临界乳光现象或记录流体的泡点和露点线；②经验关系式；③通过ＰＶＴ 软件计算流体的泡点和露点线；④利用热力学理论直接计算。由于实验测定临界点费时且费用昂贵，因此如何准确计算临界点一直是人们探讨的难题。当前在深部储层发现了更多的近临界凝析气藏，并且在凝析气藏的生产过程中可能存在复杂的临界相变，因此准确确定凝析气临界点是开发方式选择以及正确分析凝析气藏生产动态的重要基础，具有重要的理论和应用价值。文章结合热力学稳定性理论、五点微分数值算法和基于连续热力学的重组分特征化方法，提供了实际凝析气流体临界点的计算方法和步骤；实例计算表明预测值与实验结果吻合，这进一步证实本方法实用可靠。
The purpose of this paper is to study the theoretical algorithm for calculating the critical point of the actual fluid in the condensate gas. First, the history of the critical point research and the method of determining the critical point are briefly reviewed. Then the critical point is determined. The critical point is the disappearance of all the properties of gas and liquid. It is the most important parameter to distinguish the fluid type. It has been widely verified by theory and engineering application. Currently, there are four methods to determine the critical point: ① experimental determination, by observing the critical opalescence or recording fluid bubble point and dew point line; ② empirical relationship; ③ PVT software to calculate the bubble point and dew point of the fluid; ④ using thermodynamic theory directly. As the experimental determination of the critical point is time-consuming and expensive, how to accurately calculate the critical point has always been a challenge for people to explore. At present, more near-critical condensate gas reservoirs are found in deep reservoirs and complicated critical phase transitions may exist during the production of condensate gas reservoirs. Therefore, accurately determining the critical point of condensate gas is the choice of development mode and the correct analysis The important foundation of condensate gas production has an important theory and application value. Combined with the theory of thermodynamic stability, five-point differential numerical method and heavy component characterization method based on continuous thermodynamics, the article provides the calculation methods and steps of the critical point of the actual condensate gas fluid. The calculation results show that the predicted values agree well with the experimental results. Confirmed the method is practical and reliable.