非达西效应对低渗气藏气井产能影响研究

Study on the Influence of Non-Darcy Effects on the Gas Well Productivity in Low-permeability Gas Reservoirs

针对低渗气藏的渗流特征,以高速非达西渗流理论为依据,考虑应力敏感、启动压力梯度及滑脱效应等因素,推导出相应气井产能方程,以此为基础对低渗气藏气井的产能规律进行研究。研究结果表明:低渗气藏地层压力、渗透率分布曲线的形状均呈"漏斗"状;启动压力梯度和渗透率变形系数越大,地层压力下降越快,滑脱因子越大,地层压力升高越快;气藏渗透率主要受滑脱效应和应力敏感交互影响,滑脱效应使气井产能增大,且随着滑脱因子增大,气井产能不断增加,井底附近的压力敏感导致的"应力污染"现象最明显。

Gas well productivity equation is derived in view of the permeable flow feature in low permeability gas reservoirs,based on high speed non-Darcy flow theory and by considering the factors of stress sensitivity,start-up pressure gradient,slippage effect and so on.Gas well productivity law in low permeability gas reservoirs is studied based on the equation derived.The results of the study show that the curves of formation pressure and permeability distribution in low permeability gas reservoirs take on 'funnel' shape;the larger the start-up pressure gradient and the permeability deforming coefficient,the more rapidly the formation pressure declines;the larger the slippage factor and the more rapidly the formation pressure raises;gas reservoir permeability is mainly and interactively influenced by slippage effect and stress sensitivity,slippage effect increases gas well productivity,gas well productivity gradually increases with the increase in slippage factor and the stress damage caused by the pressure sensitivity adjacent to wellbore is mostly obvious.