Dynamic Characteristics Analysis For Derrick Raising Process Of Ultra-deep Drilling Rig

Ultra-deep drilling rig is a new kind of drilling rig, which is developed for drilling oil and gas in deep stratum. It is becoming increasingly important in the oil production industry. Derrick is the main supporting parts of ultra-deep drilling rig. It bears much static and dynamic load under different conditions. So there are high requirements for design and performance of derrick. The raising process is one of the most dangerous conditions for derrick. In order to ensure safety of installation, the dynamic characteristics of derrick raising mechanism must be analyzed, and raising method must be also evaluated. This work is great significant for developing ultra-deep drilling rigAfter analyzing the components and working principle of raising mechanism, a mathematical relationship between pulling of fast line and raising angle is deduced based on the geometric relation and balance principle of moment. This relationship is established when ignoring the effect of dynamic load. According to the two-dimensional curve of that relation, the change trend of raising force that firstly increase and then descend with the increasing of raising angle is shown.A geometrical model and dynamic ones of derrick raising mechanism are established using Pro/E and ADAMS respectively. Three-dimensional entity model of derrick raising mechanism without cable is built by Pro/E, and then the geometrical model is created using ADAMS. Considering the main characteristics of cable and feasibility of solving model, a improved simplification method is proposed and a dynamic model of the cable-pulley system is established by this method. Then, a virtual prototype of derrick raising mechanism is created.After simulating the raising process based on the virtual prototype, the dynamic characteristics of raising process could be obtained from the results. Firstly, the impact of different hoisting rotate speed on raising process is shown by comparison of derrick's raising velocity and acceleration under different hoisting inputs. Severe vibration happens when hoisting stop abruptly. Secondly, position of maximum stress on derrick is got by analyzing forces on fast line, hoisting cable, hook, and critical position on derrick. Finally, normal mode analysis of raising mechanism is accomplished under different raising state, so the natural frequencies and vibration modes of global preceding 4 steps are obtained. Then, a conclusion that derrick is apt to resonate by external excitation is also discussed. A suggestion that raising procedure should be smooth, slow and continuous is proposed subsequently.