基于对射孔压裂各阶段裂缝发育特点及常规射孔方式的分析,提出了交错定面射孔的思路,采用两种型号射孔弹进行了大型射孔打靶实验,模拟页岩中交错定面射孔过程,分析交错定面射孔条件下近井筒裂缝形态、形成机理以及扩展规律,并讨论近井筒裂缝的人工控制方法。研究表明：①交错定面射孔加强了同一定面内以及相邻定面间射孔的联系,易形成连通裂缝并有序扩展;②射孔时伴随着孔道生成,孔周发育3种微裂缝,分别为Ⅰ型径向微裂缝、Ⅱ型斜交微裂缝和Ⅲ型射孔尖端发散微裂缝,3种裂缝相互连通形成复杂的近井筒裂缝;③不同型号射孔弹采用不同定面夹角和交错角组合时,近井筒裂缝形态和扩展规律不同;④采用交错定面射孔方式,对各定面按照螺旋单向或连续“之”字形等方法进行排布,可促进形成所需的近井筒裂缝,有利于非常规油气储集层及复杂常规油气储集层压裂时对主缝的人工控制。图13参18
An innovative perforation method of interlaced fixed perforation was put forward based on the analysis of the characteristics of fractures in various periods of perforation and conventional perforation modes. By conducting a large-scale perforation shooting experiments, we investigated the morphology, propagation mechanism and propagation law of the near-wellbore fractures generated during perforating processes under different fixed angle and interlaced angle combinations, and discussed the control method of near-wellbore fractures in different types of unconventional oil and gas reservoirs. The experimental results show that: (1) The interlaced fixed perforation strengthens the connectivity between the perforation tunnels not only in the same fixed plane but also in adjacent fixed planes, making it likely to form near-wellbore connected fractures which propagate in order. (2) Three kinds of micro-fractures will come up around the perforation tunnel during perforation, namely type I radial micro-fracture, type II oblique micro-fracture and type III divergent micro-fracture at the perforation tip, which are interconnected into complex near-wellbore fracture system. (3) Different types of perforation bullets under different combinations of fixed angles and interlaced angles result in different shapes of near-wellbore fractures propagating in different patterns. (4) By using the interlaced perforation on fixed planes, arranging fixed planes according to the spiral mode or the continuous “zigzag” shape, the desired near-wellbore fractures can be obtained, which is conducive to the manual control of main fractures in the fracturing of unconventional or complex conventional reservoirs.
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