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裂缝性页岩储层压裂时,如何通过调节压裂泵排量,使水力裂缝沟通更多天然裂缝,是缝网压裂的关键。选取龙马溪组页岩露头开展真三轴水力压裂试验,压裂过程中以逐步阶梯式方式提高排量,实时分析变排量压裂时水力裂缝扩展行为以及与天然裂缝的沟通情况。试验结果表明:采用变排量压裂,初始阶段,随着压力逐渐升高,会在井筒周围的弱面附近产生多个待破裂点,随排量突然提高会使水力裂缝沿着多个破裂点动态分叉扩展。随着排量阶梯式升高,泵压明显升高,排量越大,泵压波动越大,水力裂缝与天然裂缝沟通形态越复杂,天然裂缝产状和缝内净压力等影响到水力裂缝进一步沟通程度。试验结果证实,变排量压裂可以激活更多天然裂缝,有助于形成复杂裂缝网络。
When fracturing a shale reservoir, how to make the hydraulic fracture communicate with more natural fractures by adjusting the displacement of the fracturing pump is the key to fracture network. The true triaxial hydraulic fracturing test is carried out in the outcrop of Longmaxi Formation shale. The displacement is increased step by step in the fracturing process. The hydraulic fracture propagation behavior and the communication with natural fractures during variable displacement fracturing are analyzed in real time. The experimental results show that with variable displacement fracturing, in the initial stage, as the pressure increases gradually, a number of points to be fractured near the weak face around the wellbore are generated. With the sudden increase of displacement, the hydraulic fractures will fracture along several fractures Point dynamic divergence. As the displacement increases stepwise, the pump pressure increases obviously. The larger the displacement is, the bigger the pump pressure fluctuation is. The more complicated the hydraulic fractures communicate with the natural fractures, the natural fractures and the net pressure in the fractures affect the hydraulic fractures Further communication. The experimental results confirm that variable displacement fracturing can activate more natural fractures and help to form complex fracture networks.