低渗透气田砂岩储层应力敏感试井模型研究

长庆苏里格气田具有低渗、低产及应力敏感等特点,应用不考虑应力敏感渗流模型分析不稳定压力动态会产生很大偏差。为了分析应力敏感性对井底压力不稳态特征的影响,应用渗透率模量的概念,建立了存在应力敏感的气藏不稳定试井模型,该模型具有很强的非线性,通过线性化变换对该非线性方程组进行了求解。分析结果表明：开始时,拟压力及其导数特征为一直线,随着无因次渗透率模量的增加,拟压力及其导数曲线往上翘,无因次渗透率模量越大,上翘越明显,而且上翘特征是有效储层不连续的反映,也可能是气井应力敏感的反映。所建立的不稳定渗流试井模型可以应用于低渗透应力敏感气藏试井资料分析中,这对我国低渗透砂岩应力敏感气藏不稳定试井分析具有一定的指导意义。

Study of Well Test of Stress-Sensitive Sandstone in Low Permeability Gas Reservoir

Changqing gas reservoir has the characteristics of with low permeability,low production and stress-sensitive.Considerable error might be generated when analyzing pressure transient using filtration flow model which did not consider stress.For the purpose of analyzing the impact of stress on wellbore pressure transient,a pressure transient welltest model for stress-sensitive formation gas reservoir was proposed using permeability modulus.This nonlinear equation was solved through linearization.Analysis indicates that the type curve of pseudo-pressure and its derivate are linear at beginning,with the increase of permeability modulus;pseudo-pressure and its derivate go up,the higher the permeability modulus the higher the go-up.The go-up characteristics represents discontinuity of the formation,and also might be the sigh of the stress-sensitive.The transient well test model can be used to analyze the well testing data in stress-sensitive gas reservoirs and provide some guidance for the well test analysis.