低渗应力敏感地层凝析气井试井分析

WELL TEST ANALYSIS OF GAS CONDENSATE WELLS IN LOW-PERMEABLE AND STRESS-SENSITIVE FORMATION

低渗透和特低渗透凝析气藏生产过程中,井底储层的伤害及其对气井动态的影响一直是石油工作者关心和研究的课题,它关系到如何高效合理地开发这类气藏资源。实验已经证实一些低渗深层凝析气藏存在应力敏感性,共生水含量越高,对压力的敏感性越强。用常规的试井模型难以分析这种凝析气藏的试井测试资料。当气井共生水含量较大时,应对原来的试井解释模型与方法进行修正。为了给应力敏感凝析气藏试井测试资料分析提供理论基础,为此,根据低渗应力敏感凝析气藏当井底压力低于露点压力时的渗流特点,对原有凝析油气渗流微分方程进行修正,引入视渗透率模量的概念,建立了考虑共生水影响的应力敏感复合凝析气藏试井分析新模型。同时还考虑了井筒存储效应和表皮效应。利用拉普拉氏变换和摄动分析技术得出了模型的解,绘制了试井分析理论曲线并对曲线特征进行了分析,以及进行了实例分析验证。结果表明:较大量共生水的存在,将对试井解释结果产生较大影响,引起渗透率的较大降低和加深对气井储层的伤害。共生水的存在以及应力敏感性对低渗气田开发的影响应引起足够的重视。

Study on formation damage and its effect on gas well performance during recovery of low-permeability and extra low-permeability gas condensate reservoir is always paid great attention by petroleum workers.It has been proved by experiments that there's stress sensitivity in some low-permeability gas condensate reservoirs,and higher the connate water saturation,stronger the stress sensitivity.Well test data of such reservoirs are hard to analyze by conventional well test models,which should be properly modified when the connate water saturation is high.Therefore,to provide theoretical foundation for well test analysis of stress-sensitive condensate gas reservoir,modification was done to original differential flow equation according to flow characteristics at bottom-hole pressures below the due pressure,introducing the concept of apparent permeability modulus to build a new well test analysis model considering the effect of connate water,wellbore storage effect and skin effect.Thereafter,the model was solved by Laplace transformation and perturbation analysis technology,and theoretical curve was plotted and analyzed.It was shown by practical example that high connate water saturation had considerable effect on well test analysis results,greatly lowering the explained permeability and amplifying formation damage of gas wells.In a word,the effect of connate water and stress sensitivity on development of low-permeability gas reservoir should be paid enough attention.