复合储层气井稳定产能方程的应用与分析

Application and analysis on steady productivity equation of gas well in compound formation

气井稳定产能二项式方程是根据均质地层中稳定渗流理论推导而来,在非均质地层中不能简单地进行套用,有必要对稳定产能方程在非均质地层中适用性进行分析。根据试井渗流理论中的叠加原理对复合地层中气井的稳定产能方程进行推导,得到了两个不同渗透区域的稳定产能方程和无阻流量计算公式。理论和实例分析证实:无论复合地层中内外区渗透性如何改变,生产范围为内区得到的无阻流量始终比外区的大。外环渗透性变得越好,后期与初期得到的无阻流量越接近;外环渗透性越差,后期较初期得到的无阻流量减少得越多,则气井产量降得也快。通过分析证明,稳定产能方法适用于外区渗透性高于内区渗透率的复合地层中气井产能评价,而对于外区渗透性变差的气井,用稳定产能方法很难指导现场气井生产。

Being derived from steady filtration theory of homogenous porous media, steady productivity binomial equation of gas well cannot be applied directly in heterogeneous porous media. Thus it is necessary to analyze applicability steady productivity binomial equation of gas well in heterogeneous porous media. Based on superposition principle, steady productivity binomial equation of gas well in compound formation is developed. Two steady productivity binomial equations and open flow rate calculations are obtained. Analysis on equations and cases show that open flow rate of inner-annular zone is always higher than that of outer zone, even though permeability in outer zone becomes higher than that in inner zone. If permeability in outer zone is much higher than inner zone, the outer open flow rate can be close to inner one. On the other hand, if permeability in outer gets lower, the outer open flow rate decrease with the producing period increasing. Therefore, steady productivity binomial equation can be applied in gas well productivity evaluation in compound formation, in which permeability in outer zone is much higher than inner one.