Dynamic Simulation For Perforating And String Safety Evaluation

Perforation completion is the most widely used well completion method in oil industry now.After explosion of charges, detonation wave releases within the wellbore, part of which is for perforation tunnel by breaking down the formation. And the other part generates shock wave in the wellbore, which causes strongly axial vibration on string. When it comes to some special field conditions, such as long perforation interval and a large quantity of loading charges, the dynamic load after explosion will cause perforating string buckling, even string broken.In order to solve the above two problems, based on explosive detonation, forming and penetration of shaped perforating jet, ALE algorithm was used to describe the interaction between fluid and solid phases. By using the finite element software—LS-DYNA, the perforation process, which includes explosion, jet forming and penetration of case-cement-reservoir, was simulated in this paper. The detonation wave distribution and corresponding string response were also studied. Analytical works are as follows:1. Mechanics theories of shaped charges detonation, perforating jet forming/movement/penetration were analyzed. And the finite element method for solving dynamic equations was described in chapter two.2. Based on the ALE algorithm, the multiphase coupled model for perforation process, including metal cover deformation, perforating jet movement and penetration of case-cement-reservoir, was simulated. A single perforating charge was analyzed in chapter three.3. After detonation, perforating jet travels and lengthens, which causes liner deformation and corruption. In chapter three, the pressure wave at different test points of well was obtained and all material responses were pictured, which is helpful for perforation differential pressure and shot gun design.4. Based on the pressure wave at different test points, the string response was interpreted in chapter four. By analyzing the axial force and displacement of string, this paper verified the strength of packer, absorber and tubing.5. Chapter five shows the “Perforation Pressure Wave and String Response Analyzing Software”, which was realized by using LS-DYNA and VB6.0 computer language. This system includes eight modules—basic data, numerical model, numerical simulation, distribution of pressure wave, string dynamic response, safety evaluation of string, results output and help file.6. By using the designed software, two production wells were verified in chapter six. The errors are 7.34% and 9.74% respectively, which clarifies the reliability of this software.