Analysis Of Drag Reduction In Axial Vibration Of Drilling In Large Displacement Wells And Tool Design

Large displacement wells are widely used due to the significant economic benefits of the large displacement well in the development of offshore oilfields.But the large displacement well is likely to cause "backing pressure",so that the drill tools will be damaged.Therefore,it is very important to study the friction of drilling in large displacement wells.For the characteristics of the large displacement well,the commercial software named Landmark simulates the friction change under various working conditions,which proves that the friction effect on the drilling is larger when drilling in the large displacement well,so that the drill string fatigue damage and other accidents will be happened.Through a single change in the angle,friction coefficient,pressure and other factors,it will be a greater impact on the friction between the drill pipes and borehole wall.For the method of axial vibration,the mathematical model of axial vibration drag reduction is established during drilling.The Newmark method is used to solve the drilling pipe's displacement,velocity and acceleration at the condition of axial vibration.It is proved that with the increase of the excitation force,the friction force ratio decreases rapidly,the drag reduction effect is obvious.With the inclination angle,the drill pressure,the size of the drill pipes increase,through increasing the "gravity effect",resulting in decreasing of drill pipes vibration speed,reducing the effect of vibration drag reduction significantly;with the vibration frequency and well angle increased,showing a significant change in the ratio of friction,then slowly change,which is due to a certain critical value,the damping effect on the drill string increases,resulting in decreasing of drill pipe vibration speed,thus affecting the vibration drag reduction effect.A new type of axial vibration drag reduction tool is designed,and based on the theoretical analysis results,the basic parameters of the tool are designed,and the design of the connecting part is innovated to achieve the purpose of replaceable parts,thus prolonging the service life of the axial vibration drag tool.At the same time,the finite element analysis of the core component cam of the new type Axial vibration drag reduction tool is carried out,and the result shows that the phenomenon of stress damage will not occur when the tool is in normal operation.