超高压气藏气体偏差因子的求取方法

利用气体分子运动论和流体状态方程理论证实,超高压下气体偏差因子与拟对比压力呈线性关系。将DAK拟合方程与其他高压拟合方程计算结果进行了对比,实际气体高压物性实验数据和高压图版验证结果表明,在超高压下,当气体拟对比压力大于15时,运用DAK方法外推求取高压范围的气体偏差因子和按Standing-Katz图版线性外推求取气体偏差因子的方法可行,且Standing-Katz图版外推方法适用于干气、湿气以及凝析气藏。

Determination of natural gas deviation factor of ultra-high pressured gas reservoir

Based on the theory of gas molecule movement and the equation state for fluid, it is proved theoretically that gas deviation factors under the ultra-high pressure are linearly dependent on pseudo-reduced pressure. The calculation result of Dranchuk-Abou-Kassem fitting equation was compared with that of the other fitting equations for high pressure and extra-pressured conditions. The performance of the DAK equation was also identified by experimental data of field gases under ultra-high pressure and by Standing-Katz correlation. The results show that it is possible and practical to generate the deviation factors of gas in ultra-pressure gas reservoirs by extending the application region of DAK equation and linearly extrapolated Standing-Katz correlation when the pseudo reduced pressure is over 15 in the same area. Furthermore, this linear extrapolation method of Standing-Katz correlation could be applicable to calculate the deviation factors for dry gas, wet gas and gas condensate reservoirs.