考虑动态滤失系数的压裂井裂缝闭合及返排优化

依据渗流力学理论,借助岩心滤失试验,引入动态滤失系数,建立致密气井压裂后强制裂缝闭合理论模型和动态滤失系数模型,对加砂压裂及压后关井过程中的压裂液滤失量、滤液侵入机制、近缝地层压力剖面进行动态分析。结果表明:动态滤失系数模型可更好地描述压裂液滤失的动态过程,前期滤失速率大,后期滤失速率变小并趋于定值;压裂液滤失由缝口至缝端逐渐降低,侵入伤害带主要集中在缝口处,侵入深度与储层的物性参数、压裂液流体参数及施工规模有关;气井中压降主要集中在原状地层区,返排的主要能量来源于压裂及关井过程中地层气体压缩产生的附加能量。

Fracture closure and flowback optimization for fractured wells considering dynamic fluid loss coefficient

According to the core filtration experiment and introducing the dynamic filtration coefficient,a theoretical model of forcing fracture closure and a dynamic filtration coefficient model were developed for post-fracturing tight gas well based on percolation mechanics theory,by which the fracturing fluid loss,the filtrate invasion mechanism and the formation pressure profile near the fracture were dynamically analyzed during the sand fracturing and the shut in period after fracturing.The results indicate that the dynamic filtration coefficient model could better describe the dynamic process of the fracturing fluid loss.The filter loss rate is high in the early stage,and becomes low with time and is almost a fixed value in the late stage.The fracturing fluid loss decreases from fracture-start to fracture-end,and the invasion damage zone mainly concentrates on the fracture-start.The invasion depth is related to the reservoir petrophysical parameters,the fracturing fluid parameters and the construction scale.For gas well,the pressure drop mainly occurs in the undisturbed formation,and the energy for flowback mainly comes from the additive energy resulting from formation gas compression during the fracturing and the shut in period.