Research On The Universal Joint Shaft Structure Of A New Type Of Screw Drilling Tool

With the development of petroleum exploration and development technology,in order to enhance oil recovery and increase oil and gas field production,the proportion of horizontal wells,lateral wells and extended reach wells is increasing.The performance and reliability of oil drilling and production equipment have been greatly improved due to the significant change of power source of oil drilling and production equipment from ground power to underground power.At present,the commonly used oil drilling and production equipment mainly includes screw drilling tools and turbine drilling tools.Due to the structural characteristics of turbine drive,some problems inevitably arise,such as unstable working time,inability to monitor the operation status of drilling tools,poor selectivity of drilling tools and confusion in drilling tool management.These problems limit the application of turbodrill.In comparison,the screw drill drive shaft assembly has many advantages,such as simple structure,easy operation,large displacement,low speed,large torque,low energy loss,reliable operation of equipment and so on.The screw drilling tool is mainly composed of bypass valve,motor,universal shaft and transmission shaft.Universal shaft connecting motor rotor and transmission shaft is the core component of screw drilling tool.Its function is to transform the planetary motion of motor rotor into fixed axis rotation of transmission shaft,and transmit torque to transmission shaft and drill bit at the same time.Bad working conditions in underground will lead to failure of cardan shaft.The friction between upper and lower petals will lead to the peeling off of upper and lower petals,the broken root of petals,and the open structure of petals will lead to the direct contact between internal structure and drilling fluid,which accelerates the wear of pressure steel ball and petal contact surface.The contact area between ball-articulated cardan shaft and small rigid ball will be crushed.Sealing failure,etc.In order to solve the above problems,we use finite element analysis software and fatigue analysis software to simulate and analyze the universal shaft of screw drill.The main tasks completed in this article are as follows:Firstly,the basic structure and working principle of petal cardan shaft,spherical articulated cardan shaft and spline cardan shaft of screw drilling tools are analyzed.The force analysis of three kinds of torque transfer structures is carried out.The failure forms of three kinds of cardan shaft of screw drilling tools are analyzed,It is concluded that the main failure modes are three kinds of fracture,wear and seal failure.Secondly,the finite element models of the petal cardan shaft,spherical hinge cardan shaft and spline cardan shaft of the screw drilling tool are established.Torque transfer parts of the three kinds of cardan shaft of the screw drilling tool are analyzed by using the finite element software.Mises stress values of the three kinds of cardan shaft of the screw drilling tool are compared and analyzed,among which the stress of the spline cardan shaft is the smallest,3157 MPa.The structure of spline universal shaft was improved,and the structure before and after improvement was compared and analyzed.The improved structure was optimized by morphology.The stress value of the improved structure was reduced by 87.2 MPa and 19.5 MPa,respectively,compared with that of spline universal shaft and before optimization.A new type of universal shaft structure of screw drilling tool is designed.The finite element analysis model of the universal shaft is established.The finite element analysis of the new type universal shaft is carried out by ABAQUS.The stress of the new type universal shaft under extreme conditions is analyzed.The maximum Mises stress of the structure is 510.1 MPa.Finally,the fatigue life of the universal shaft structure of screw drilling tools is analyzed,and the fatigue life of the four universal shafts is compared and analyzed.It is concluded that the longest life of the four universal shafts is 262421 times of the new universal shafts.