The Research Of Vibration Mechanism And Analysis Of Dynamic Response For Tubing String

On the basis of surveying the damage of the tubing and researching the fact data of production and pressure during producing gas in the east. part of Sichuan, this paper puts forward the main reason that causes the tubing string to vibrate, and the vibration of the tubing can lead to the early damage of the tubing. In the past, the tubing string vibration was lack of researching, however the tubing string statics was regarded as the main research. First, applying hydromechanics and fluid vibration, we will study the mechanism about the gas leading to the tubing vibration when it flows inside the tubing string; and then, we set up the analytical model of tubing vibration and dynamic response by applying the modern vibration theory, and systematically analyze the traits of the tubing string vibrating in the well bore based on the fact data of the east part of Sichuan; finally, we put forward the method to relieve the tubing vibration by analyzing and calculating.When the variable frequency of the gas actuation force by flowing in the tubing approaches to any rank innate frequency of the tubing string, the tubing string will make resonance, which will promotes the tubing's damage. On the basis of the primary theory of the hydromechanics, this paper analyzed the flowing form of gas in the tubing and set up the transmission formula and the motion differential equation about the gas flowing in the tubing. It has been also analyzed the area of the swirl when the gas flowing in the tubing, and it was provided the method of analyzing swirl. Making use of the method of the liquid oscillation mechanics, it has been set up the amplitude equation of the tubing when the gas flows in the tubing. It has been solved the gas oscillation flowing field by using the method of parameter polynomial expression. On the basis of established theoretical model, it was quantitatively researched variation of the inner diameter of tubing, the bend of the tubing, the variation of the flow velocity in the switch of the choke value, the variation of gas production and pressure that may urge the vibration of tubing when the gas flow in the tubing string. Calculating indicates that when the gas flows through the tubing, the variation of the inner diameter of tubing, the bend of the tubing and the choke value will cause the change of the gas velocity and the pressure that the gas effects on the tubing which can promote the vibration of the tubing string. At the same time, the variation of the flow velocity also can erode the tubing. As far as the high pressure and high production gas wells are concerned, vibration and erosion are the main reason to damage the tubing.It has been established the vibration analytical model of tubing string by utilizing the modal theory about the whole tubing string. And the working conditions of vibration analytical model includes having damp, without damp and fluid-solid coupling vibration, etc. It is solved conveniently the vibration analytical model of tubing string by the discretization of the tubing structure. The trait of tubing inherent vibration can be expressed according to the inherent vibration frequency, vibration form (modality), modal damp and other parameters. On the basis of analyzing the tubing vibration equations, it has been put forward the methods of working out the tubing vibrating peculiarity by inverse power method and Larczos method. With the higher vibration steps and the increasing of the tubing vibration frequency, the actual example calculation indicate that the tubing vibration frequency with the packer is more than the frequency without the packer. With the rising of the vibration steps, the waveform period of the vibratory type projective curve will get shorter, but for the tubing with packer the projective curve waveform can occur jump in the middle of the tubing string on the axial flat of the through tubing string. Along with the increasing of the tubing diameter, its inherent vibration frequency will increase and the amplitude will reduce. With the growing of the well depth, its inherent vibration frequency will get lower and amplitude will increase. With the growing of gas production, the tubing string inherent frequency will reduce, and the tubing string is easier to take place resonance and the amplitude will get higher.The thesis has put forward the way to solve the tubing dynamic response by using non-linear dynamic response analysis method after comparing the linear dynamic response with the non-linear one, and gives a convergence criterion. The variation laws of stress, speed, accelerometer with time can be obtained at any point on the tubing string by using the method. The living example calculation shows that the maximal value of the response compounding stress, speed and accelerometer will reduce. With the growing of the well depth, the maximal value of the response compounding stress will get lower, and the maximal value of the response speed and accelerometer will get faster.Through the calculation, comparison and analysis the thesis has posed the concept of the tubing damp vibration, and design the working principles and installation place of the vibration dampener. Moreover, it has given a train of thought to reduce the tubing vibration.By analyzing the tubing vibration, the thesis has got the tubing dynamic load that provides the reliable basis for the gas well tubing design, and it is also important to prevent the oil tube from pre-damage.