页岩储层水平井密切割压裂射孔参数优化方法

A Perforating Parameter Optimization Method for Horizontal Well Multi-Cluster Fracturing in Shale Reservoirs

页岩储层水平井密切割压裂过程中同一压裂段内各簇水力裂缝难以维持均衡扩展,这一问题严重制约了压裂改造效果。为此,建立了一套完全流固耦合的水平井密切割压裂多簇水力裂缝同步扩展数值模拟方法,采用水力裂缝体积标准差(δv)定量表征多簇水力裂缝均匀发育程度,提出了一套科学完善的页岩储层水平井密切割压裂射孔参数优化方法。研究结果表明:单段射孔簇数越多,缝间诱导应力干扰作用越强,各簇水力裂缝发育越不均匀;随着每簇射孔数减少,孔眼摩阻增大,δv降低,各簇水力裂缝发育越均匀,当δv≤0.01后,继续减少每簇射孔数,对水力裂缝均匀发育程度的改善效果有限,且过度减小射孔数量会导致施工压力过高;以δv≤0.01为优化目标,针对2口实例井分别开展了等密度与非等密度限流射孔参数优化设计,均取得了良好的增产效果。研究结果可为页岩储层水平井密切割压裂射孔参数优化设计提供理论依据和优化方法。

During horizontal well multi-cluster fracturing in shale reservoirs,hydraulic fractures in each perforation cluster in the same fracturing stage cannot propagate uniformly,which severely undermines the reservoir stimulation performance.A solid-fluid fully coupled numerical simulation method to mimic the synchronized hydraulic fracture propagation during horizontal well multi-cluster fracturing was established.The standard deviation of hydraulic fracture volume(δv)was used to quantitatively characterize the uniformity of hydraulic fracture propagation.Finally,a reasonable and comprehensive perforating parameter optimization method was developed for horizontal well multi-cluster fracturing in shale reservoirs.The results show that more perforation clusters in a single stage mean stronger induced stress interference between hydraulic fractures and thus more uneven propagation of hydraulic fractures of different clusters.With the decreasing perforation number in each cluster,the perforation friction grows and theδv declines,which results in more even propagation of hydraulic fractures.Whenδv≤0.01,further decline of the perforation number in each cluster only improves the propagation uniformity of hydraulic fractures to a limited extent,and an excessive reduction of perforation number may lead to very high operation pressure.Withδv≤0.01 as the target,this optimization method was applied to two example wells to optimize perforating parameters with uniform shot density and non-uniform shot density for limited-entry fracturing,both delivering good stimulation effects.The research findings provide the theoretical foundation and also an optimization reference for the design of perforating parameters for horizontal well multi-cluster fracturing in shale reservoirs.