Dynamic Analysis Of Semi-articulated Flexible Drill Pipe In Ultra-short Radius Horizontal Well

Ultra-short radius radial horizontal well is a new technology to tap potential remaining oil.Its curvature radius is generally less than 4m,and conventional drilling tools cannot meet its drilling requirements.Therefore,the drilling operation of ultra-short radius horizontal well needs special drilling tools.In recent years,semi-articulated flexible drilling tools have been widely used in drilling ultra-short radius horizontal Wells.In the drilling process of ultra-short radius horizontal well,the failure of flexible drill pipe often occurs.Because the flexible drill pipe is semi-hinged,it is easy to produce violent vibration in the drilling process,and it is also prone to frequent collision with the guide screen pipe.These factors make the dynamic characteristics of flexible drill tool very complicated.Research on dynamic characteristics of semi-articulated flexible drilling tool is the key to ensure the success of ultra-short radius horizontal well drilling.In this paper,according to the drilling technology and force state of semi-articulated flexible drilling tool,considering the additional mass of drilling fluid,buoyancy and pressure,the nonlinear dynamic model and numerical calculation method of three-dimensional contact between semi-articulated flexible drilling pipe and guide screen pipe are established.The rationality of the model is verified by an example.Taking the guide screen pipe and flexible drill pipe as the research objects,considering the additional mass,buoyancy and pressure of drilling fluid separately,the dynamic analysis of the flexible drill pipe in the inclined section is carried out,and the results show that the additional mass of drilling fluid has a restraining effect on the vibration of flexible drill pipe.The buoyancy of drilling fluid has little effect on vibration in all directions and has a stable effect on the movement of flexible drill pipe.The drilling fluid pressure makes the vibration of the flexible drill pipe more intense in all directions.Considering the fluid load of drilling fluid,the dynamic analysis of the flexible drill pipe is carried out.The results show that the lateral vibration and torsional vibration of the flexible drill pipe are large,while the longitudinal vibration is relatively small.The vibration in the three directions increases with the increase of well depth.The impact force between the flexible drill pipe and the guide screen pipe increases first and then decreases with the increase of well depth.Under the influence of drilling fluid load at the same time,carry out the speed and the influence of the flexibility half-and-half articulated flexible drill string dynamics research,it is concluded that: speed less influence on the transverse vibration of flexible pipe,with the increase of rotational speed,lateral vibration and torsional vibration increases gradually,flexible pipe and guide screen pipe collision force increases,the elliptical orbit of flexible pipe became flat.With the increase of the flexibility,the vibration and collision force of the flexible drill pipe increase sharply,and the trajectory of the flexible drill pipe becomes more disorderly and the motion range increases.The results of this paper provide a numerical method for dynamic analysis of semi-articulated flexible drill pipe,reveal the dynamic characteristics of semi-articulated flexible drill pipe,and provide a reference for dynamic optimization design of flexible drill pipe.