低渗透气藏气井产能试井资料分析方法研究

低渗透气藏渗流机理不同于常规气藏，尤其是束缚水饱和度（S_wr＞30%）较高的低渗透气藏存在启动压力梯度，从而使测得的气井修正等时试井资料二项式产能分析曲线斜率为负值，无法分析应用。为此，文章基于低渗透气藏非达西低速不稳定渗流微分方程，推导出具有启动压力梯度的低渗透气藏气井稳定产能方程和不稳定产能方程，并提出低渗透气藏等时试井资料优化分析新方法，应用该方法不仅可以快速确定气井产能方程,评价气井产能，同时还能求出气藏的启动压力梯度、渗透率、表皮系数等物性参数。实例应用表明，所提出的产能试井分析新方法具有实用价值。

DATA ANALYSIS METHOD OF GAS WELL PRODUCTIVITY TEST FOR LOW PERMEABLE GAS RESERVOIRS 1)

The percolation mechanism of low permeable gas reservoirs is different from that of conventional gas reservoirs, especially for the low permeable gas reservoirs with high irreducible water saturation (Swr >30%), which have the threshold pressure gradient. Therefore, the slope of binomial production curves in the measured isochronal test data for gas well modification is negative, which can’t be used for data analysis. Based on the unsteady percolation differential equation of non Darcy flow for low permeable gas reservoirs, the steady productivity equation and the unsteady productivity equation are derived for the gas wells of low permeable gas reservoirs with threshold pressure gradient. And the new method of optimization analysis is proposed for isochronal test data of low permeable gas reservoirs. Using the method can not only determine the productivity equation of the gas well and evaluate the productivity of the gas well rapidly, but also calculate the physical parameters such as the threshold pressure gradient, permeability, skin factor etc. Real cases application shows the proposed new method of production test analysis is practicable.