During perforating，the high velocity jet penetrates the casing-cement-formation assembly. This not only causes damage to the cement sheath but also leads to bonding damage at the casing-cement interface. Such degradation tends to cause cross-flow of wellbore fluids along channels in the casing-cement interface，ultimately severely shortening the lifespan of oil and gas wells. Given this，a numerical model of high velocity jet penetration into the casing-cement-formation after perforating charge explosion is established using the fluid solid coupling method. The dynamic damage evolution law of the casing-cement bonding interface in the process of penetration is analyzed，and the effects of the cement sheath material parameter （shear modulus），cohesive unit parameter （fracture energy） and casing types on the damage area and maximum damage radius of the bonding interface are investigated. The results show that with the penetrating of jet，damage appears at the casing-cement sheath bonding interface，and the damage zone continuously expands. When the jet penetrates into the formation，the damage area reaches the maximum. With the increasing of shear modulus or fracture energy of cement sheath，the damage degree of the bonding interface decreases. Increasing borehole cleaning or using fiber containing cement slurry can reduce the damage of jet penetration to the bonding interface. When aluminum alloy，titanium alloy，nickel base alloy and other highly resistant casings are used，the damage area and maximum damage radius of the casing-cement bonding interface increase significantly during perforation penetration. The findings of this research provide theoretical support for wellbore integrity protection and engineering parameters optimization during perforating.

As oil and gas wells are gradually extended to deep and ultra-deep layers，the safety of completion strings during perforation has attracted more attention. Based on the principles of computational fluid dynamics，a perforated interval-packer detonation wave propagation model was established，revealing the detonation wave propagation and reflection rules in the wellbore completion fluid and clarifying the characteristics of the influence of completion fluid on detonation wave propagation. Research shows that the detonation wave propagation process demonstrates extremely strong non-periodicity and irregularity. When the detonation wave propagates to the packer position，the amplitude of the detonation wave pressure is reduced by up to 75.65%. The detonation reflected waves show better periodicity，and the amplitude of the detonation pressure waves is reduced by 23.4% when it propagates to the perforated interval. The density of the completion fluid not only has a great influence on the amplitude of the detonation waves during propagation，but also has a great interference on the waveform characteristics of the detonation waves. The viscosity of the completion fluid has almost no impact on the waveform characteristics of the detonation waves during propagation，and has a small impact on the amplitude of the detonation waves. With the impact of detonation waves on the completion string considered only，priority should be given to selecting a completion fluid system with low density and high viscosity to reduce the impact of detonation waves on the downhole completion string. The research results of this article provide a reference for the design of on-site completion fluid parameters for oil and gas wells.

Based on actual engineering applications of conventional drilling and percussion drilling，and considering the material parameters and intrinsic model of rock dynamic mechanics，a numerical model of rock breaking of the cutters of Polycrystalline Diamond Composite（PDC） bit was established. The penetration depth，damage area，size of rock debris particles and rock breaking volume of PDC cutters under different percussive drilling models were compared and analyzed. The results show that the rock cutting pattern is very similar between the numerical simulation results and the laboratory physical experimental model of single-cutter. The penetration depth of single tooth of rotary，torsional，and combined percussive drilling increased by 19.8%，6.6% and 26.9% respectively compared with that of conventional drilling，and the combined percussive drilling saw the most significant increase in rate of penetration. When there is axial impact load during percussive drilling（such as combined percussive drilling or rotary percussive drilling），it will cause visible damage to the rocks below the cutting surface，which facilitates the “second cutting” after the drilling cutters turn 360 °，but large rock debris particles can be produced，so it is necessary to optimize the drilling fluid parameters to keep the wellbore clean. The fluctuation range of penetration depth of the cutter in torsional percussive drilling is small，which indicates that this method helps reduce the risk of bit stick-slip，and the rock debris particles produced are small which makes it easy to keep the wellbore clean. The research results are of great significance for the selection of different types of percussion drilling tools and tool parameters optimization.