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在油藏组分模拟中，通常假设每一时间步长内，存在所有物相间的局部热力学平衡，而且遍及整个油藏。对每一地块，相态的计算是用一状态方程（EOS）进行的。这计算通常要占用中央处理器（CPU）很大一部分的总时间。本论文对用于压力和给料组成二者均变的过程的一种简化热力学模型〔王及斯汀拜（WangandStenby），计算机与化学工程，16，5449，5456，1992〕的扩展，进行阐述。对此改进模型，用凝析油实验数据及从EOS计算得的数据进行了检验。所得结果指出，新模型能很好地表示给料组成及压力变化对K值的影响。该新模型被充实到一油藏组分模拟软件，UTCOMP中（张Y．B.，博士论文，德克萨斯大学，奥斯汀，1990）。为三个给定的（烃）混合液的自然衰减及北海一凝析油的干气循环（回注）过程进行模拟。用这种方法模拟的结果，可与用平及拉宾逊状态方程（PREOS）计算的结果对比。但用这种方法的CPU时间比用PREOS需要的时间约减少50％。此外本论文指出，用新提出的求解相分离的拉福特－拉亥斯（Rachford－Rice）方程的程序［拉博未斯及尼窝乞（LeiboviciandNeoschil），流体相平衡，74，303－308，1992］，CPU时间还可减少。
In reservoir component simulation, it is generally assumed that there is a local thermodynamic equilibrium between all phases within each time step, and throughout the reservoir. For each plot, the phase behavior is calculated using a state equation (EOS). This calculation usually takes up a significant portion of the total time of the central processing unit (CPU). In this paper, a simplified thermodynamic model for the process of equalizing both the pressure and the feedstock composition (Wang and Stenby, Computer and Chemical Engineering 16,5449,5456,1992) is elaborated . The improved model was tested using condensate data and data calculated from EOS. The results show that the new model can well represent the influence of feed composition and pressure on K value. The new model is enriched in a reservoir component simulation software, UTCOMP (Zhang Y.B., PhD thesis, University of Texas, Austin, 1990). The natural decay of three given (hydrocarbon) mixtures and the dry-gas recycle of the North Sea-condensate oil were simulated. The results simulated in this way can be compared with the results calculated using the flat and the Raineson equation of state (PREOS). However, the CPU time using this method is approximately 50% less than using PREOS. In addition, the paper points out that with the newly proposed Rachford-Rice equation procedure [Leiboviciand Neoschil, the fluid phase equilibrium, 74,303-308, 1992], CPU time can be reduced.