Hydraulic fracturing is a measure used to increase oil production. To accurately predict the pressure of fracturing, which is the key of the successful implementation of the hydraulic fracturing. Through deriving the burst pressure of homogeneous formation a-gain based on the fractal theory, the breakdown pressure calculation model is established. Based on Fractal theory, this paper analy-zes the relationship between fracture toughness of rock along the fractal crack and straight crack with the help of matlab. The theoret-ical analysis shows that the fracture extending toughness of rock along the fractal crack is greater than that of the straight line model. that’ s why the current theory calculation value of hydraulic fracturing construction pressure is always less than one of the actual con-struction of pressure. Furthermore, it’ s also proved that the computational model is closer to the actual situation in this paper.%水力压裂是油井增产通常采用的一种措施，准确地预测压裂井的破裂压力是水力压裂成功实施的关键所在。利用分形理论对匀质地层的破裂压力进行了重新推导，建立了分形理论下的破裂压力计算模型，并借助Matlab，结合分形相关理论推导并分析了沿分形裂纹与直线裂纹断裂的岩石断裂韧性之间的关系。理论分析表明，考虑裂纹分形扩展后岩石的断裂韧性大于沿直线模型扩展的断裂韧性，从理论上证实了目前水力压裂作业中理论计算值常低于施工压力的结论，说明计算模型更接近实际情况。
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