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定面射孔技术是为了提高体积压裂改造效果而提出的一种新的射孔方案。根据岩石力学及流-固耦合理论,建立了定面射孔地层的三维弹塑性流固-耦合地应力模型,采用数值方法进行求解,结合最大拉应力准则,研究了定面射孔水力裂缝的起裂规律。经过大量计算发现:定面射孔条件下,裂缝首先在射孔面内的射孔眼起裂,然后射孔眼相互贯通而形成扇形裂缝面,增大了水力裂缝的波及体积及井筒的连通性;同一平面内两侧孔眼在中间孔眼上产生的附加应力降低了Y方向主应力而增大了X方向和Z方向主应力,导致正断层采用定面射孔时,起裂压力较大,起裂压力随射孔方位角的增大而降低,只有当射孔方位角大于60°时,定面射孔起裂压力低于螺旋射孔起裂压力;对于逆断层,射孔方位角越小,起裂压力越低,且均低于螺旋射孔起裂压力;减小射孔间夹角、增大射孔直径及深度均可降低起裂压力。
Faced perforation technology is a new perforation scheme proposed to improve the effect of volumetric fracturing. According to the theory of rock mechanics and fluid-solid coupling, a three-dimensional elasto-plastic fluid-solid coupling stress model is established and solved by numerical method. Combined with the maximum tensile stress criterion, Law of initiation. After a large number of calculations, it is found that under the condition of perforating the surface, the fissure first fissures in the perforating surface of the perforating surface, and then the perforation eye interpenetrates to form a fan-shaped fracture surface, which increases the volume of the hydraulic fracture and the connectivity of the wellbore; The additional stress in the middle hole on both sides of the same plane reduces the principal stress in the Y direction and increases the principal stress in the X direction and the Z direction. As a result, when the normal fault adopts the fixed perforation, the cracking initiation pressure The pressure decreases with the increase of the azimuth of perforation. The initiation pressure of the perforation is lower than that of the helical perforation only when the azimuth of the perforation is greater than 60 °. The smaller the azimuth of the perforation is, The lower the cracking pressure is, the lower the initiation pressure of helical perforation. The smaller the angle between perforations and the larger the diameter and depth of perforation can reduce the initiation pressure.