Research On Dynamic Load Performance Of AC Conversion Electric Driven Drilling Rig Hoisting System

The development status and trend of oil rig and electrically-driven drawworks home and abroad were mastered through research. Structural analysis was carried out on electrically-driven drawworks at work, and their advantages and disadvantages were found out in order to go deep into the design of new electrically-driven drawworks for rig.In order to deeply study the dynamic characteristics of the hoisting system of the rig, combining the well drilling technology and working process of rig, the kinematics and dynamics are analysed in theory in this paper. A mechanics model of the hoisting system that has considered the elasticity of the wire rope and derrick is made. It is a vibration system with three quality and two degrees of freedom, and the movement differential equiations of the hoisting system has been made a deduction.In the first instance, these differential equations are solved in theory in the condition of without regard for the frictional resistance between the drill string and wall of a well, we get the vibration frequency, response of the hoisting system, along with the dynamic load coefficient of the hook, we also analysed the characteristics of the fluctuation for the displacement and acceleration of the hook. And then we get the numerical solution for the initial value problem of the differential equation, combining with the actual drilling tool combination and the working characteristics of the JC30DB-WZ AC conversion electric driven drawwork in the condition of taking the frictional resistance between the drill string and wall of a well into account. We also fully analyse the results and get the dynamic load coefficient in the condition of there is frictional resistance. We separately discuss the operating conditions with the initial velocity is zero and it is not zero, which provide a good basis for the improvement of the control accuracy for the drawworks. In order to furtherly study the influence to the hoisting system caused by the frictional resistance between drill string and wall of a well, the simulation software of ADAMS is adopted in this paper in the condition that the characteristic of electric motor and the frictional resistance is taken into account at the same time to carry out the caculation and analysis to the JC30DB-WZ AC conversion electric driven drawworks hoisting system. We can see from the results: Results show: dynamic force exits during lifting; the dynamic force coefficient changes when lifting conditions change; the stability becomes worse during lifting because of the friction between drill string and wall of a well; after considering the random load and the instability during the lifting is increased, such increasing the load of the hook and unbalancing the velocity of roller and hook.