Design And Dynamic Characteristics Of A New Type Of Composite Impactor

With the increase of global energy consumption,the development of oil and gas fields has shifted from shallow wells to deep wells and ultra-deep wells.The deepening of the drilling depth will lead to a significant increase in the strength,hardness and abrasiveness of the formation rock,resulting in lower rock breaking efficiency.As the length of the drill string increases the system is prone to stuck,stick-slip.For the sake of improving the breaking efficiency of the drill bit and reducing the stick-slip of the drill string,a new form of composite hammer is proposed in this paper,and its structural design and dynamic characteristics are further explored.The main contents are as follows:Firstly,the working principle and structural design of the new composite hammer are completed by investigating the related downhole tools that have improved the rock breaking efficiency and reduce the stick-slip of the drill string.The new composite hammer can simultaneously provide axial and circumferential torsional impact for the shaft,which consists of three parts:powertrain,transmission assembly and impact assembly.The powertrain provides power for the rotation of the hammerhead,the transmission assembly transmits torque and speed,and the impact assembly supplies the instant impact force and frequency for the tool.The hammer head of the impact assembly rotates with the screw rotor,and the hammer head periodically collides with the hammer seat to generate an impact force.The contact surface between the hammer and the seat is a sloped surface,and impact force can be equivalently decomposed into the axial direction and rotary direction and be transmitted to the drill bit through the hammer seat,thereby improving the rock breaking ability and the vibration of the stick-slip for the drill bit.Secondly,the speed and collision frequency during operation are calculated for the motion analysis of the hammer head collision,and the kinematics model of the hammer head and the hammer seat is established.According to the collision theory,the motion law of the hammer head is investigated for the impact vibration model of the slope to get an operating frequency,impact force of the collision,axial impact force and circumferential impact torque of the new system.Then,with the help of finite element software the strength of important parts of the new composite hammer is to verify that the string bearings meet the conditions of downhole use.Meanwhile,ADAMS simulation is used to complete the multi-body dynamics simulation of the impact assembly.The effects of rotor speed,spring stiffness,spring pre-pressure,collision surface spiral angle and hammer quality on the performance of the new composite hammer are analyzed.Finally,the condition assumption for the model of the vertical well drill string is completed,and the multi-degree-of-freedom bi-directional drill string system dynamics model is established without using the new composite hammer.The new composite hammer is used in the position of near the drill string system to generate axial and rotary excitation,according to the dynamic equation of the drill string under the excitation and the drilling parameters a numerical analysis of the model is completed.The calculation results show that when the input torque and rotation speed are increased,the stick-slip vibration can be reduced.At the same time,the influences of the axial impact force generated by the new composite hammer are studied further.Through the research of the dynamics of the drill string based on the new composite hammer,it shows that the new tool can reduce the stick-slip vibration of the drill string,assist the drill to break rock without losing pressure causing from the drill vibration.According to the characteristics of the structure and work condition for the new composite hammer,the collision and motion models of the tool are established and calculated for the impact effects,and the multi-degree of freedom bidirectional dynamics of the drill string is constructed when the new composite hammer is used or not.The effects of tool on the torsion-slip and axial vibration in the drill string system are compared,and the rationality of the theoretical calculation is verified by the relevant software simulation results,which provides a theoretical basis for improving the breaking efficiency of the rock,preventing stuck drilling and reducing the stick-slip vibration.