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通过物理实验和数值模拟相结合的方式,研究了水平缝螺旋射孔条件下的裂缝起裂、扩展规律。根据水平缝地层的地应力大小和实验条件的相似准则确定物理实验方案,利用大尺寸真三轴实验装置对水平缝的起裂、延伸进行物理模拟;依据损伤力学原理,利用有限元法对部分实验的裂缝起裂、扩展进行数值模拟。结果表明:60°相位角、高密度射孔可以小范围降低水平缝的破裂压力;压裂过程中,井筒附近可能产生多点起裂,但是随着压裂过程的进行,只有最上面射孔位置或者最下面射孔位置的1条裂缝能继续向前延伸形成主裂缝,其他裂缝止裂。数值模拟结果与实验结果相一致,证明实验结果合理。
Through the combination of physical experiment and numerical simulation, the initiation and propagation of cracks under horizontal helical perforation were studied. According to the principle of similarity between the horizontal stress and the experimental conditions, the physical experiment scheme is determined, and the large-size true triaxial experimental device is used to simulate the initiation and propagation of the horizontal seam. According to the damage mechanics theory, Experimental crack initiation and propagation for numerical simulation. The results show that the 60 ° phase angle and high-density perforation can reduce the fracturing pressure of the horizontal seam in a small scale. In the fracturing process, multi-point fracturing may occur near the wellbore. However, with the fracturing process, only the top perforation One crack in the position or the bottom of the perforation can continue to extend forward to form the main crack, and the other cracks can stop cracking. The numerical simulation results are consistent with the experimental results, which proves that the experimental results are reasonable.