PVT状态方程的选择和分析

在油气田开采和油气输送过程中，要经常使用状态方程进行计算，但状态方程大都是半理论、半经验的关系式，都有一定的使用范围。常用的状态方程在计算纯气体和非极性分子热物性参数时，准确性普遍较好，但计算气体混合物，特别是计算含有CO2、H2S等酸性气体时，计算误差较大。常用的状态方程有SRK、RK、PR、PT、SHBWR和LHSS。根据现场事例，采用常用的6种状态方程来计算气液相的压缩因子Zg和Zt、气液相的逸度fg和fl以及汽化率e，通过计算结果得到PR、PT和LHSS状态方程在其适用范围内计算精度较好，采用SRK、RK、SHBWR状态方程则计算值偏小。

Choose and Analysis for Equations of State of PVT,

Equations of state (Eos) are usually used in oil and gas production and transportation. Eos are generally semi-empirical or semi-theoretical expressions; therefore, they have some application ranges. While Eos are adopted to calculate thermodynamic parameters of pure gas or non-polarity molecules,they have good agreement with field data,while Eos are used to calculate polarity molecules,they have bad agreement with field data. SRK,RK,PR,PT,SHMWR and LHSS Eos are often used to calculate the field data,such as compressibility factors of gas and liquid,fagacity of gas and liquid,and gas fraction which is using flash calculation. As result of calculation,PR,PT and LHSS Eos are better than others,and calculation values of SRK,RK,SHBWR Eos are much less than PR,PT and LHSS.