Simulation analysis on the stress intensity coupling of perforating gun and casing under the action of detonation and shaped charge jet

In order to explore the mechanical performance of the casing under the detonation impact load of jet perforating, the 3D model of perforating charge-perforating gun-casing was established using the software LS-DYNA. Then, detonation, fluid-solid transformation of shaped charger liner, large deformation of penetrated casing and perforating charge and fluid-solid coupling were simulated based on the application of ALE operator splitting algorithm. Finally, the effects of the detonation wave superposition on energy, density, efflux velocity, casing and perforating gun intensity were analyzed. It is shown that the perforation diameter of the perforating gun is 18.7 mm, that of the casing is 7.7 mm, indicating that a great amount of energy is consumed in the process of penetrating the blind hole of the perforating gun. In the broad band of 125 mm connecting the holes of perforating gun, the minimum stress is 774 MPa, which is close to the yield strength of the material. It is meant that under the action of high detonation pressure, " bulging gun” happens. Compared with one perforating charge, the casing penetrating time of three perforating charges is 8 μs shorter, its maximum stress is 260 MPa higher, and the excess of the casing stress beyond the yield strength of the material is 2.5 mm ring larger. The casing stress in the center of the detonation superposition area is 739 MPa higher than that of one perforating charge, demonstrating that superposition of detonation wave increases the damage to the casing. The research results provide technical guidance and new ideas for the safety optimization design of perforating gun and the mechanical performance analysis of casing running under detonation impact.