Performance Analyses And Researches On Drawworks Of Electrically-Driven Drilling Rig

The development status and trend of oil drilling 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 design new electrically-driven drawworks for drilling rig. Compared with traditional mechanical drilling rig and direct current driven drilling rig, AC variable-frequency electrically-driven drilling rig and drawworks have extremely obvious advantages and high technical performance. As a result, oil drilling rig and drawworks are increasingly developing heading AC variable-frequency electro-drive nowadays.Aimed at the shortcomings of our traditional drawworks such as complexity in transmission, low precision in control, trouble in maintenance, low efficiency in transmission, asymmetry in bit feed, instability in bit weight, a new type of drawworks structural model was designed: model JC30DB-WZ single shaft drawworks of AC variable-frequency motor direct-drive , which can fulfill the multi-working condition requirement such as constant torque and permanent power. The design reliability was assured through ANSYS finite element analysis of the Stiffness and Strength of roller and roller shaft. In this drawworks, the roller is directly driven through shaft couplings by two special AC variable-frequency electric motors which are of high-power, low speed and great torque, without the supplemental parts of large gear reducer casing and large clutch, etc. Auxiliary brakes such as eddy current brake and hydraulic brake no longer exist, forming a single shaft roller drawworks model with motor out-laid and roller integrative. This model has advantages of structural novelty, wide timing range, high precision, and strong adaptability. Its technical performance and parameters can meet the standard of SY/T5532-2002"the drawworks used on oil drilling rig". It can satisfy the drilling operation request of model ZJ30/1700DB drilling rig, and can be widely used in matching of 3000 meters AC variable-frequency drilling rig home and abroad.Combining Drilling technology and working process of drilling rig, the kinematics and dynamics processes analysis were carried out on drilling rig hoisting. Influential Factors on control performances of AC variable-frequency electrically-driven drawworks were found out, which can create the theory foundation for making our own AC variable-frequency drawworks control system.The simulation software ADAMS was used to calculate and analyze model JC30DB-WZ AC variable-frequency electrically-driven drawworks hoisting system. Results show: dynamic force exits during hoisting; the dynamic force coefficient changes when hoisting conditions change; the stability becomes worse during hoisting because of the friction between drillstring and wellpore; instability coefficient is about 1% without the consideration of the friction; after considering the random load the instability during the hoisting is increased, such increasing the load of the hook and unbalancing the velocity of roller and hook. Besides, different combination of drilling tools will affect the friction of drillstring. In order to reduce the dynamic force coefficient, we can use the method of control the characteristics of the motor. In fact, decreasing the starting current can efficiently reduce the dynamic force during hoisting.The development status and trend of automatic bit feed system home and abroad were analyzed, as well as the latest research result and the problems during design and use processes. Automatic bit feed system and control methods based on motor auxiliary and drawworks mainframe integrative were offered. Using fuzzy control theory, problems in control the complex, nonlinear, uncertain system were solved. All these problems are rather difficult to solve during automatic bit feed in oil drilling rig. The technical performance and reliability of drawworks on drilling rig were greatly improved by intellectualized control using computer.Through the related parameter acquired in the field while drilling, from project experiment angle, the actual performance of the rig hoisting system, the dynamic load of the derrick, the natural frequency, and the torque and rotate speed of the drawworks have been analysed. By contrast with the results of testing and theory research , the result shows that the test research result and theoretical research result still coincide fairly, which further perfects and enrich the theoretical result.