| Various vibration usually occured in drill engineer.During the drilling process,longitudinal vibration was caused when the cone drilles into the rock intermittently and the rock crushed as accordingly owing to the uneven well bottom,which is the most serious destructional vibration form,not only damage the drilling tool,but also slow down reduce the drilling speed and increase the cost.While it stick,the jarring releasing is able to solve the sticking accident through the jarring action caused by longitudinal vibration.So,it has significant meaning to get the best jarring releasing effect when has the minimum damage during the longitudinal vibration of drill stem in the straight hole.Firstly,drill stem working load and enviromental load are analyzed and the longitudinal vibration model of drill string based on single shock absorber and double shock absorber are establsied according to the configuration scheme.Secondly,establise the mathematical model for longitudinal free vibration of drill string based on elastic rod theory and deduce the longitudinal vibration natural frequency and vibrate formula under different shock absorbers configuration through motion partial differential equation and boundary condition.Then analyze the natural frequency change rules of drill stem by comparing the longitudinal vibration in different models.Thirdly,analyze the drilling fluid and shock absorber’s influence on drill steam longitudinal vibration influence from the point of drill bit by using modal superposition method based on obtaining the natural frenquency of drill string longitudinal vibration and steady state response under the four order Runge Kutta method.Finally,the velocity response and displacement response of drill string under initial deformation are established and then the stick pint jarring load were deduced by establishing the shaker mechanical model,longitudinal vibration mechanical model,longitudinal vibration mechanical model and mathematical model. |
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