Development And Experimental Analysis Of A Dynamics Testing Apparatus Of Horizontal Rotating Beam In Pipe

Drill pipe which defined as the integral part of horizontal wells drilling presents extremely complex dynamical state, such as longitudinal vibration、transverse vibration、torsional vibration、whirling motion and the coupling of each other, cause fatigue damage for drill pipe、borehole and induce bad influence on drilling efficiency. In the underground environment, drill pipe’s motion state easily affected by many aspects, such as bit weight、rotational speed、torque、drilling fluid、damping、borehole、downhole and so on. There are a number of problems with drill pipe itself, and the current study of drill string dynamics states mainly concentrated on the conventional vertical Wells, so the horizontal well drilling string is simplified into the horizontal rotating beam in pipe to carry out the development of testing apparatus and experimental analysis.This article construct the expression of displacement、velocity and acceleration, analyses the force and torque of the model of bit-downhole and beam-borehole. The nonlinear dynamics equation and linear equation of horizontal well drill string are derived based on timoshenko beam theory and Hamilton principle. The dynamical model is dispersed by finite element method(FEM), and the horizontal well drilling string state of nonlinear dynamics is obtained from the simulation analysis of the discrete model.For effective observation of horizontal well drill string motion state and validation of the theoretical model, this article developed a set of testing apparatus of horizontal rotating beam in pipe based on similarity theory and rotor-bearing system theory. The testing apparatus consist of drilling pressure system、rotation system、fluid circulation system、pipe line system and downhole simulation system, which can simulate different factors of influencing the drill string state and reproduce the real dynamic state of horizontal well drilling string. The signal can be collected through sensors. This article analysis the mechanism of the horizontal well drill string by way of experiment. Combining test analysis results with theoretical model analysis, it is concluded that the influence law of bit weight and rotation speed on drill string dynamics state, and providing certain scientific basis for improving the serve life of drill pipe and setting reasonable operating parameters.