Study on Explosion Energy Conversion of a Perforating Shaped Charge during Perforation Detonation

The perforation-acidizing-testing combined technology has become the key technology for increasing the efficiency and speed of ultradeep well completion testing. However, the shock load and the wellbore pressure surge affect the stability and local strength of the lower packer string system during the perforation detonation. The energy generated by the perforation detonation is the fundamental source of the shock load and the wellbore pressure surge. The effect laws and distribution characteristics of the explosion energy of the perforating shaped charge is urgently needed. Therefore, a fluid-structure coupling method based on a structural-arbitrary Lagrangian-Euler algorithm (S-ALE) is used to construct a numerical model to forecast the explosion energy. The feasibility of the numerical model is verified by comparison with the field experimental results. The detailed studies on the output value and distribution characteristics of the explosion energy are carried out. The main control factors and influencing laws of the explosion energy are clarified. Then, an equation for the explosion energy prediction is fitted to lay the foundation for studying the wellbore pressure surge and the lower packer string system failure caused by the perforation detonation. The obtained results indicate that the explosion energy is mainly divided into three parts: the jet kinetic energy, the shell case energy, and the pressure surge energy. The pressure surge energy can reach 59.254 to 66.08%, the jet kinetic energy can reach 9.895 to 17.159%, and the shell case energy can reach 21.426 to 24.325%. The major sensitive parameters that affect the pressure surge energy are ranked as follows: the explosive mass, the explosive type, the shell thickness, the standoff distance, the cone angle of the liner, and the shot density. This work provides a reliable prediction method for the accurate description of the explosion energy conversion, which is critical for improving the success rate of the perforation-acidizing-testing combined technology.