Safety analysis of completion tubing considering water hammer effect

Water hammer effect always cause excessive pressure and stress which will endanger the whole string system, for example fatigue damage, wear and tear damage and cracking damage. During well startup or shutdown, instantaneous changes of tubing's internal pressure will bring water hammer effect, so cause acute tubing vibration. So far there have few literatures to make quantitative analysis for the vibration caused by water hammer. This paper introduces improved four equation model analysis which can analyze water hammer effect accurately. According to the field experiment data, comparing the difference of vibration degree between the moment of water hammer effect and non water hammer effect. By finite element software this paper achieves vibration model diagram, natural frequency, and the stress distribution at dangerous moment after vibration acceleration is forced to the model. Finally taking stress as evaluation index to evaluate the safety of completion tubing under water hammer effect. The results show that, with water hammer effect completion tubing vibration is more intense, and occur destructive resonance easily, even cause plastic deformation of tubing.