Research On The Load Characteristics Of Offshore Drilling Rig Lifting System

With the increasing depletion of onshore oil resources, developing marine equipment, intensifying efforts to exploit offshore oil and gas become a strategic initiative of the world’s major countries, and our country is no exception. As a high-tech marine equipment, the advancement of offshore drilling rig is mainly reflected in the lifting system control level, which key part is drawworks. Currently, in response to the complex and harsh working environment of offshore drilling rig, improving the reliability, the redundant system constituted with S7-300 PLC has a long switching time and unstable. In addition,the traditional PID control mode can not adapt the time-variability and non-linear characteristic any more. The system is artificial, tedious and not easy to maintain. The load of the lifting system is increased. The drill bit is wore and the equipment utilization is reduced.To solve the above problems, combining the latest research results, on the basis of the previous research, a drawworks redundant control scheme is presented and the drawworks load characteristics is analyzed. The purpose is optimizing the lifting system load, reducing the drilling costs and improving the ability to resist risks. The system has a redundant hardware architecture based on S7-400 PLC, achieving a CPU redundancy, I / O module redundancy and PROFIBUS-DP redundancy. Its switching time is in milliseconds and the reliability is greatly increased. In addition, by analyzing the factors that affect the cost of drilling, a kind of WOB optimization algorithm is also be introduced and then the optimum drilling database is established. About the control mode, a WOB loop and a speed loop control algorithm are gave. Among them, the WOB loop is designed with fuzzy PID controller, that is to say the fuzzy control and the conventional PID control are combined with each other and learn from each other. Not only increase the control accuracy and the robustness of the system, but also improve the ability of self-learning and self-adjusting.Finally, part of the PLC program has been written by STEP7 IDE. The system has now been successfully applied to the "New Victories One" jack up platform equipped with ZJ70 DB drilling rig. By analyzing the drilling data curve of Chengbei 6GA-15 well, with the support of the optimal drilling database, the system can optimize the lifting system loadand meet the actual production needs.