Analysis On The Dynamics Of Flexible Drill Pipe When Rubbing The Sidewall

With the deepening of the exploration and development of geological resources,the research on the dynamics of drilling is becoming more and more important.The key technologies that are urgently needed is to achieve precise control of the trajectory of the downhole drill pipe system,through effective use of the characteristics and motion laws of the drill pipe dynamics.Studying the nonlinear dynamic characteristics of the slender flexible drill pipe not only helps the drilling engineer to recognize the downhole working condition and reduce the drilling accident,but also is an important special case for nonlinear mechanics research.Therefore,it is a hot research topic to establish a reasonable drill pipe-wellbore-bit dynamics model system and study the system motion law and mechanical properties.This paper mainly analyzes and studies the dynamics of drilling,especially the vortex and the buckling state of the drill pipe,from the theoretical model of drill pipe dynamics,rigid-flexible coupling dynamics simulation of drill pipe,and the indoor model test.In terms of theoretical models,analyzing the trajectory of the drill pipe and the centrifugal force of rubbing resistance and centrifugal force firstly.Then the theoretical model of drill pipe dynamics is established by combining finite element and elastic mechanics,the general equations for the dynamics of the drill pipe are derived.After that the eddy trajectory of the drill pipe is fitted by MATLAB calculation software.Finally,the numerical calculation method of transient steady state motion of nonlinear dynamics is analyzed.In terms of dynamic simulation models,the actual drill pipe-wellbore-bit model is simplified,and the modal neutral file of the finite element drill pipe is established by ANSYS firstly.Then introduce ADAMS and add constraints and driving to do co-simulation of flexible drill pipe and rigid well wall and drill bit.Finally,the fast Fourier transform algorithm(FFT)is used to analyze the displacement,velocity,acceleration and collision force data of the drill pipe.In the indoor model test,designing and building a model test device based on similar criteria firstly.In the test,multiple sets of camera shooting modes are used to record the movement state of the drill pipe.Finally,the influence of drill pipe trajectory and speed anddrilling pressure on drill pipe motion is discussed and analyzed through Video Studio X9 combined with sensor data.This paper combines theory,simulation and experiment to reduce the trajectory of the drill pipe axial point in the direction of the respective horizontal plane and the whole wellbore;It also shows that there are transverse,longitudinal vibration,torsion,forward and reverse vortex and vibration coupling in several directions in the movement of the drill pipe;The variation law of the relationship between the buckling deformation of the drill pipe,the swing frequency and amplitude,the rotation frequency and the swing frequency is analyzed in detail with the increase of the rotational speed and the drilling pressure.This topic provides a reference for the research and development of drill pipe dynamics and well trajectory control.