油藏物理学英文油藏物理学 (3).ppt
Equation-of-state describes the exact relationship between the variables P,V,and T of natural gas.状态方程就是描述气体体积、压力和温度的关系式状态方程就是描述气体体积、压力和温度的关系式2.4 Equation of state(EOS)2.4 Equation of state(EOS)天然气的状态方程式天然气的状态方程式1、Behavior of ideal gases ideal gas：（1）The molecule particles are no volume and no mass（2）these molecules have no attractive or repulsive forces between them,and that all collisions of molecules are perfectly elastic.modifier formula（experimental method）In order to express a more exact relationship between the variables P,V,and T,a correction factor called the gas compressibility factor,gas deviation factor,or simply the z-factor。2、Behavior of real gases The gas compressibility factor z is defined as the ratio of the actual volume of n-moles of gas to the ideal volume of the same number of moles at the same T and PconceptionAs Z，attractive and repulsive forces are equal As Z，attractive forces is less than repulsive ones，real gas is more difficult to be compressed than ideal gas.As Z，attractive forces is more than repulsive ones，real gas is easier to be compressed than ideal gas.3、compressibility factor calculations 的的计算算（1 1）single component gas 单组分气体单组分气体 （chart by laboratory measurement）methane甲烷甲烷ethane乙烷乙烷N2氮气氮气(2)poly-component gas (correlation in pseudo-reduced parameters)多组分气体（对比状态原理）多组分气体（对比状态原理）Under the same conditions of reduced pressure(对比压力)and reduced temperature(对比温度),pure-hydrocarbon gases have the same compressibility factors ZPseudo-reduced pressure 对比压力对比压力Pr:Pr:Pseudo-reduced temperature对比温度对比温度Tr:Tr:Where:Where:气体气体分子式分子式分子量分子量临界压力(MPa)临界温度(K)甲烷甲烷CH416.04.64190.67乙烷乙烷C2H630.14.88 303.50丙烷丙烷C3H844.14.26 370.00正丁烷正丁烷nC4H1058.13.79 425.39CO2CO2CO244.017.38 304.17H H2 2S SH2S34.09.00373.56N N2 2N228.03.39126.11Pc and Tc for some hydrocarbon gasesPseudo-critical parameters calculations:Pseudo-critical parameters calculations:临界参数的计算方法临界参数的计算方法:1 1 equation method equation method 公式法公式法:2 2 graphical method graphical method 查图法法:4、solving steps of z-factor 天然气天然气压缩因子的求解步因子的求解步骤1.Calculate Pc、Tc2.Calculate Pr、Tr,given by the P、T3.Based on the Tr、Pr,presented a generalized gas compressibility factor chart as shown in Figure 5、Adjust the z-factor 天然气天然气压缩因子的校正因子的校正（1 1）NN2 2的影响的影响(20%(20%时误差时误差3%)3%)
