In the field of hydraulic fracturing for shale gas production, the pump rate has a significant effect on fracture network propagation. The random natural fractures in shale reservoir lead to confusion of parametric sensitivity analysis in hydraulic fracturing. Firstly, based on the fracture characteristic in shale reservoir, concrete specimens with three sets of orthogonal pre-existed fractures are prepared. Then, with true triaxial fracturing simulation experimental system, the fluid with constant pump rate is injected into the specimens under true triaxial loading. Finally, the area of fractures per unit volume (P32) is employed to analyse the effect of pump rate on fracture network propagation. The results show as follows. (1) In the specimens with small dimension of block element (high pre-existed fractures density), the phenomenon of stimulation reservoir volume is more significant. (2) The fluid with low pump rate can stimulate only pre-fractures in specimens. The fluid with medium and high pump rate can not only stimulate the pre-fractures, but also divert the direction of stimulated pre-fractures and open new hydraulic fractures in concrete, which increases the complexity of fracture network. (3) With the increase of injection rate, the P32 value of specimen after fracturing increases. However, when the injection rate increases to a certain value, the P32 value doesn't increase, or even decreases.%在页岩气水力压裂开发领域中,压裂液注入排量对裂缝网络的扩展形态具有显著影响.而页岩储层中的随机天然裂缝,会给水力压裂的参数敏感性分析带来不同程度的干扰.首先,根据页岩储层裂缝发育特征,制备了包含3组正交预制裂缝的混凝土试样;然后,采用真三轴压裂系统,对试样进行三向应力加载模拟地应力环境,并以恒定排量向其内部注入流体;最后,将单位体积裂缝面积P32作为体积压裂指标,来定量描述排量对压裂缝网扩展形态的影响.试验结果表明:(1)在块体单元边长较小(即预制裂缝密度较大)的试样中,体积压裂的效果更加显著;(2)小排量压裂液所产生的裂缝一般是激活的预制裂缝,而中排量和高排量压裂液可以使已激活的预制裂缝发生偏转,在混凝土基质中重新开启水力裂缝,从而增加裂缝网络的复杂性;(3)随着排量的增加,试样压裂后的P32值会升高;但排量增加到一定程度后,P32值不再增长,甚至略微下降.
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