致密气藏气井非稳态线性渗流特征分析新方法

压裂后的致密气藏气井在生产过程中的较长时间内均表现为非稳态线性渗流，因此对该类气井线性流特征分析是进行气藏开发方案设计及生产数据分析的理论基础。针对致密气藏非稳态渗流方程，首先定义考虑应力敏感效应的拟压力函数，将天然气非线性渗流偏微分方程初步线性化。再利用Boltzmann变换方法将偏微分方程转化为常微分方程，通过打靶法结合四阶龙格库塔方法求解方程。将计算所得结果与数值模拟器Eclipse对比，二者吻合度较高，验证了模型的正确性。定流压生产时，分析压敏指数对气井早期产量变化以及压力场分布的影响，结果表明：压敏指数越高，产量递减越迅速，压力场延滞效应越严重。将模型运用到实际气井生产数据分析当中，可得到较为准确的结果。研究成果为致密气藏气井非稳态线性渗流特征的分析提供了一种快捷而精确的半解析求解模型。

A novel method for analysis of transient linear flow behaviors for tight gas well

Transient linear flow will exhibit long periods of production in tight gas well after fracturing.Thus,analysis of linear flow behaviors is the theoretical basis for designing development facility and production data analysis.Pseudo-pressure function was defined considering pressure-sensitivity and the partial differential equation was linearized preliminarily.Then the PDE was converted into ODE by the utility of Boltzmann transformation and solutions would be got by fourth-order Runge-Kutta algorithm coupling with shooting method.Comparing the results by proposed model with numerical simulator Eclipse,it shows that they are in good agreement which validates the model.Under the condition of constant bottom-hole flowing pressure,the influence of pressure-sensitivity index on rate performance and pressure profile was conducted.It shows that rate decline is rapid and carryover effect of pressure profile is serious when pressure-sensitivity index is large.The accurate results can be obtained by applying the model to the analysis of actual gas well production data.A new method of solving gas flow equation was proposed and the research results provide an effective semi-analytical model for analysis of transient linear flow performance in tight gas well.