Study on Dynamic Response of Downhole Tools under Perforation Impact Load

A model of a multibody system is established to investigate the dynamic response of an oil tube-shock absorber-perforating gun system in downhole perforation-test joint operation. In the model, the oil tube and perforating gun are modeled as elastic rods and the shock absorber is modeled as single particle system with damping and a spring. Two force continuity conditions are used to simulate the interactions among the three components. The perforation impact load is determined by an experiment of underwater explosion of perforating bullets. Using the model, the effects of charge quantity of perforating bullet, the number of shock absorbers, and the length of oil tube on the dynamic response of oil tube and packer are investigated. On this basis, a basic principle of the combination design of shock absorber and oil tube is proposed to improve the mechanical state of downhole tools. The study results can provide theoretical support for the design of downhole perforation-test joint operation.