Wind-induced Response Analysis Of Oil Rig Derrick Structure

During the exploration and development of the oilfield, the large rise rig derrick structure is the essential component that bears the loads. For the environment that it works is far more abominable than the general steel structure thing, especially with the development of marine petroleum industry, more attention has been paid on the derrick safe problem of vibration under the wind loads action. At present, study on the vibration of the derrick structure that was mostly carried out by the quiet strength method, can only satisfy basic demand in the derrick of design process, the derrick dynamic research is but few under dynamic loads. In order to decrease the derrick incidents that take place in oil field production many times and was caused by lose steady and blowing down under the wind loads effectively, carrying out the derrick vibration response analysis becomes the key to solve vibration and lose the steady problem. The study on the respond of dynamic wind loads, especially pulsating wind loads, have important directive significance on the derrick structure of wind resistant design and oil field safety evaluation. 　　In paper, the structure finite element method is used to study the derrick structure, through establishing the rational basic assumption, the finite element model has been set up. In addition, ANSYS software is adopted to calculate finite element model and conduct the mode analysis, in the calculation process, 10 steps of natural frequency and vibration type have been obtained; the vibration characteristic by oneself of the derrick further through the coefficient method of power has been investigated. Results show when the working rotational speed of the rotary table is in 2 shelves and 4 shelves, the resonance may occur. 　　The principle of the aerodynamics is used to study the land wind field characteristic of the Daqing oil field and the wind load spectrum theory of oil rig derrick has been established. By gathering the meteorological data of annual maximum wind speed for 44 years from 1960 to 2003 of Daqing oil field, the probability analysis mathematics model of extreme value I is founded, which provide the most wind resistant design wind speed value of the derrick. According to the production reality in oilfield, we set up 9 kinds of simulation derrick structural mechanics and analysis, then use structure vibration theory to calculate 4 sections of derrick structure of vibration coefficients at random and the equivalent pulsating wind loads. Finally, using the energy method, analyze various kinds of pulsating wind spectrum, and put forward with pulsating wind simulation method on the basis of triangular progression superpose synthetic method, besides, by Matlab6.5 software the numerical simulation result of the wind loads is given. In the dissertation, we also consider the safety evaluation method of causing wind vibration of the oil rig derrick. Through analysis on the wind load and interaction mechanism of the derrick structure and destroying the form, the safety evaluation methods of safety degree and tired checking computations are given. Through describing the leading wind direction in winter, summer and whole year in the area of Daqing with the wind rose picture, we set up the rig well location orientation diagram of Daqing oil field. It is found that the top of derrick structure in case of hurricane has already exceeded the control limit of the safety degree, it is likely to dumpage at first wind direction, but cann't been destroyed tiredly.