考虑启动压力梯度和高速非达西效应的低渗透气藏水平井产能

Horizontal well performance within low permeable reservoir taking into account of the start-up pressure and high rate non-Darcy effect

低渗透气藏存在启动压力梯度,对气藏产能存在很大影响。以具有顶、底不渗透边界的低渗透气藏为例,引入儒柯夫斯基变换,推导了考虑启动压力梯度及高速非达西效应的低渗透气藏水平气井产能计算公式,研究了高速非达西效应、启动压力梯度、水平段长度、渗透率各向异性比及偏心距等因素对气井产能的影响。结果表明,启动压力梯度和高速非达西效应的存在都使产能降低;在一定长度范围内,水平段长度越长,产能越大;渗透率各向异性的存在使产能降低;并做出了相应的流入动态关系曲线,为低渗透气藏中水平井合理配产提供了理论参考。

The problem of start-up pressure is existed in the low permeable reservoir and may affect he productivity greatly. Taking the low permeable reservoir constrained by the non-permeable top and bottom boundary as example, the Lefkovits conversion is introduced to derive the productivity calculation formula for the horizontal well in the low permeable reservoir after taking into account of the start-up pressure and high speed non-Darcy effect,and then the effects,such as non-Darcy effect,start-up pressure gradient,horizontal length,permeability heterogeneity,and eccentric distance,on the productivity of gas well is analyzed. It is revealed by the study that, the existence of start-up pressure and high-speed non-Darcy effects will hamper the productivity of the gas well, and under certain length,the longer the horizontal interval the higher the productivity,as well as the negative effect of permeability heterogeneity on the productivity. Moreover,the in-flow dynamic relationship curve is composed to provide the theoretical reference for the productivity evaluation and reasonable production allocation of horizontal well in the low permeable gas reservoir.