Research On The Design And Working Mechanism Of Flexible Hydraulic Telescopic Well Tractor

Production via horizontal wells has become an important way to improve oil recovery in oil and gas fields.Up to now,more than 20,000 horizontal wells have been drilled in more than 20 countries in the world,and the number is still increasing rapidly with the development of drilling technology for horizontal well.Meanwhile,the displacement of horizontal section of horizontal well is getting larger and larger,and the downhole working condition is becoming more and more complex,which puts forward higher requirements for traction force and reliability of downhole tractor.In conclusion,based on the investigation and analysis of the development status of downhole tractors at home and abroad,a flexible hydraulic telescopic downhole tractor with large traction force,flexible adherence to the shaft wall and electro-hydraulic drive is designed in this paper.The overall mechanical structure design of tractor,the design of hydraulic control system,the calculation and selection of hydraulic component parameters,the layout method and the feasibility analysis of entering the well are completed by CAD.The lockout performance simulation analysis,kinematics characteristic research and hydraulic system control cycle design of tractor support mechanism are completed by CAE.Based on the indoor lock experiment of tractor support mechanism,the rationality and feasibility of the design of working section of tractor are verified.In view of the above contents,the following research work has been carries out:(1)Integral Structure Design of Flexible Hydraulic Telescopic Downhole Tractor,On the basis of investigating,analyzing and summarizing the advantages and disadvantages of existing tractors at home and abroad,the overall structural design scheme of the flexible hydraulic telescopic downhole tractor is put forward,and its working mechanism is studied.Detailed design of working section,control section and hydraulic control system of tractor is carried out by CAD.Abaqus is used to optimize the design of grasping arm(spring blade)to find the structure of spring blade with the best elastic resilience.Based on the mechanical analysis of the supporting mechanism,the relationship between the pushing force of the supporting cylinder and the diameter of the casing pipe is found out.Based on this,the parameters of the hydraulic components are calculated and the hardware selection is selected.Design and check of the thread and sealing and virtual assembly of the tractor are carried out based on the mechanical design and hardware selection of the tractor.At last,the layout of the tractor and the feasibility of entering the well are analyzed.(2)Performance analysis of grabbing and unlocking of Flexible Hydraulic Telescopic Downhole Tractor.The motion state of the tractor support mechanism in the supporting process and the traction process is simulated,and the supporting and locking state of the tractor is observed.Whether the theoretically calculated thrust meets the requirement of the tractor's thrust during the support and traction processes is verified.The motion state of the tractor support mechanism after unloading is simulated to observe whether it can overcome the friction force produced by the sealing ring to make the push rod return,and the change rule between spring restoring force and casing diameter is found out.Finally,the material selected of the tractor support mechanism is verified by simulation whether it meets the mechanical performance requirements in the process of support and traction.(3)Study of supporting mechanism kinematics characteristics of Flexible Hydraulic Telescopic Downhole Tractor.Kinematics simulation of flexible hydraulic telescopic downhole tractor supporting mechanism is carried out by Adams,and its locking performance and kinematics characteristics under different casing sizes are analyzed.Whether the tractor can meet the locking performance requirements within the designed pipe diameter range is verified,and its maximum load under the corresponding pipe diameter is obtained.(4)Design of Control Period for Hydraulic System of Flexible Hydraulic Telescopic Downhole Tractor.The hydraulic system of tractor is modeled,simulated and analyzed by Amesim,and the motion cycle of each cylinder and the control cycle of the whole tractor are obtained.(5)Laboratory experimental study of supporting mechanism of Flexible Hydraulic Telescopic Downhole Tractor.According to the mode of enduring force and characteristics of tractor supporting mechanism,the experimental scheme of locking of tractor supporting mechanism is designed.Based on the designed experimental scheme,the experimental device of supporting mechanism of flexible hydraulic telescopic downhole tractor is designed and manufactured.The locking experiments of tractor are carried out to verify the rationality and feasibility of the design of the working short section of flexible hydraulic telescopic downhole tractor.