考虑应力敏感的致密气藏水平井产能计算方法

PRODUCTIVITY CALCULATING METHOD OF THE HORIZONTAL WELLS IN TIGHT GAS RESERVOIRS CONSIDERING THE STRESS SENSITIVITY

除启动压力梯度外致密气藏还存在应力敏感,在实验确定应力敏感参数的基础上,引入虚拟裂缝概念,利用保角变换方法,考虑应力敏感和启动压力梯度建立了气藏水平井产能方程,同时分析了应力敏感、启动压力梯度、水平井长度等对产能的影响。结果表明:产能方程与试采产能的误差小于7%,验证了产能方程的可靠性;应力敏感和启动压力梯度均使产能降低,其中应力敏感占主要作用;应力敏感在低井底流压时对产能影响严重,启动压力梯度在高井底流压时对产能影响较大;水平井长度是影响产能的主控因素。该研究丰富了致密气藏水平井产能计算方法,并为水平井长度和生产压差的优化提供了理论指导。

In addition to threshold pressure gradient,tight gas reservoirs have the stress sensitivity. Based on the stress sensitive parameters determined by the experiments,the concept of the virtual fracture was introduced,and the horizontal well productivity equation considering the stress sensitivity and threshold pressure gradient was derived from the conformal transformation. At the same time,the influences of the stress sensitivity,threshold pressure gradient and horizontal well length on the productivity were analyzed. The results show that the error between the productivity and test productivity equations is less than 7% and the reliability of the equation is verified; the stress sensitivity and threshold pressure gradient can reduce the productivity,and the former is the main influencing factor; when the bottomhole flowing pressure is rather lower,the stress sensitivity influences the productivity significantly,so does the threshold pressure gradient at higher bottomhole flowing pressure; the horizontal well length isthe main controlling factor of the productivity. This study enriches the productivity calculating methods of horizontal wells in tight gas reservoirs,and provides the theoretical guidance for the optimizations of the horizontal well length and producing pressure differential.