Mechanical Response and Integrity Failure of Wellbore During Perforation

During the process of perforation,the failure of wellbore sealing integrity mainly includes the damage of cement sheath and the formation of micro-annulus at cementing interface.Based on LS-DYNA finite element calculation platform,the downhole perforation process was simulated by means of numerical calculations,the stress response and failure characteristics of casing and cement sheath during perforation were analyzed,and the penetration test on cylindrical target was performed.The results show that the calculation method of shaped charge jet penetration into wellbore could be used to quantitatively analyze the stress response of wellbore during perforation.When a wellbore is perforated,the tensile and shear failure of cement sheath is mainly concentrated within the cone angle of 60°; high-load perforating charge,low modulus cement sheath and high confining pressure increase the stress peak of cement sheath and increase the risk of cement sheath damage.The conclusions provide theoretical support for the optimization of perforations and the prediction of wellbore integrity before fracturing in oil and gas wells.