Abstract: 6 petroleum shock absorber breaking accidents happened from 2004 to the beginning of the 2005 in Tarim oil field, in which, there were 4 times of flower bond box thread root breaking, 1 cylinder box thread root breaking and 1 mandrel breaking. In view of the above accidents, the authors of the paper establishe the analytical mathematical model of integral drill string longitudinal vibration in which the installation position of the shock absorber is not limited and the length of the drill rod and the drill collar is flexible, figure out the calculation method of the model, draw up the drill string assembly and the well depth used in the calculation, obtain the calculation value by computer simulation at different rotational speeds and different installation positions of the shock absorber. So the authors deduce the conclusion: the different installation positions of the shock absorber on the bit can get different damping effects and variable rock breaking dynamic loads. When the shock absorber is at the optimum installation position which is determined by the damping effect and the rock breaking dynamic load, the shock absorber effect can be enhanced from several to more than 10 times and the ability of rock breaking can be enhanced on the condition that it doesn't add drill pressure. The new drill string assembly with the optimum installation position of shock absorber is successful in the Da Bei 3 well belonging to Tarim oil field, which indicates that the research has wide application prospect.

Key words: petroleum shock absorber, Installation position, drill string assembly, longitudinal vibration, mathematical model