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通常人们采用气井某一时刻的稳定产能方程结合废弃井底流压来计算废弃地层压力。事实上，随着地层压力的下降，与产能方程系数密切相关的气层渗透率等物性参数尽管变化很小，可认为是常数，而天然气偏差系数和粘度的变化不容忽视。气田开发初、中期与后期相比，稳定产能方程差异较大，原方法所计算的气井废弃地层压力误差较大。该文考虑气井开采过程中与产能方程系数密切相关的参数变化，推导出计算气井任意时刻的二项式系数计算公式，由此可得到气井废弃时的稳定二项式方程。以经济评价结合地面工程论证，确定气井废弃产量和废弃井口流压，进而根据垂直管流法计算气井废弃井底流压，最终求得较可靠的废弃地层压力。
It is common practice to calculate the pressure of abandoned formations by using the stable capacity equation at a given moment in the gas well in combination with the pressure at the bottom of the well. In fact, with the decrease of formation pressure, physical parameters such as permeability, which are closely related to the coefficient of productivity equation, can be regarded as constant though the change is small. However, the variation of natural gas deviation coefficient and viscosity can not be neglected. Compared with the early stage, middle stage and later stage of the gas field, the stable productivity equation is quite different, and the pressure error of the abandoned well in the gas well calculated by the original method is larger. In this paper, we consider the parameters which are closely related to the coefficient of productivity equation in the process of gas well production and deduce the formula of binomial coefficient for calculating the gas well at any time. Thus, the stable binomial equation can be obtained when the gas well is abandoned. Based on the economic evaluation combined with the ground engineering demonstration, the gas well abandonment output and abandoned wellhead flow pressure are determined, and then the vertical well flow method is used to calculate the pressure of bottom hole flow in the well and finally the more reliable pressure of the abandoned formation is obtained.