Design And Simulation Of Constant Torque Drilling Tool

Deep and ultra-deep Wells require longer drill strings to pass the axial force and torque required for rock breaking,but slender drill strings are prone to stick and slip,which have a serious impact on drilling efficiency,equipment life and safety.A tool called“Constant torque drilling tool”was designed in this paper,which was of great practical significance to effectively reduce or avoid stick-slip phenomenon.Firstly,the overall structural design scheme of the tool was determined.The tool mainly relied on the cooperation of spring system and screw drive mechanism to achieve three functions of weight transmission,torque transmission and axial expansion.Secondly,the theoretical model about drilling torque,the helix Angle of screw transmission mechanism,the elastic coefficient and the deformation of spring system was built.Force of the spring system under the condition of different helix Angle was compared while the drilling torque range was 4×10~3～1.2×10~4 N·m.The results showed that the better value for helix angle was about 45°,the force range of the spring system was 5.7×10~4～1.71×10~5 N,and the total elastic coefficient of the spring system was at least5.7×10~5 N/m.Thirdly,the structure of the spring system was designed.The spring system consisted of disc spring with a certain elastic coefficient and size and the numbers of synclastic superposition layers and reversed superposition layers were respectively 2 and84.The mechanical characteristics,static stiffness characteristics,stress characteristic and fatigue characteristics of the spring system were analyzed,and the results showed that the total elastic coefficient range was 1.07×10~6～1.17×10~6 N/m during the deformation of the spring system and fatigue life met working requirements.Fourthly,screw drive mechanism was designed.Screw drive mechanism was composed of 16-head outer helix mandrel and inner helix body.It adopted sliding spiral drive,45°helix angle and trapezoidal thread.The material selection,non-self-locking inspection and strength calculation were carried out.And ANSYS Workbench software was used to check outer helix mandrel strength.The results showed that the screw drive mechanism was non-self-locking and all the strengths were within the allowable range.The above work has laid the foundation for the design and manufacture of Constant torque drilling tool.Finally,the anti-stick-slip effect of the tool was simulated.A three-dimensional model of the screw drive mechanism was established by using Solid Works software.Adams software was used to simulate and axial motion state and torque variation trend of outer helical mandrel were analyzed.The simulation results showed that Constant torque drilling tool could adjust the torque of the bit and have a good anti-stick-slip effect.