High Temperature And Pressure Yielding Corrosive Gas Well Completion String And Wellhead Equipment Damage Mechanism

The gas well with high temperure,high pressure,high production is a great challege in gas exploration. For the gas well head assembly & completion strings in the high temperure,high pressure,high production and corrosion environment, the abominable working conditions and complexed loading situation is the key damage reason, it decline the string strength and working security and it will cause completion string & well head assembly problems and other complexed situations, even then makes the gas well abandoned, brings great economic loss. To prevent the completion well strings & well head assembly breakage in the "Three High", and corrosion environment, it is very important to discovery the breakage mechanics mechanism the effect factors and the mutual action relationships.In the course of research, the article persists in the integral research ways and technology thoughts of practice-theory-re-practice-re-theory. In order to solve the well completion pipe string intensity fault and prevention in West Sichuan, the article takes Well xin851 as example, adopts fault case random inspection and study and literature investigate and theory research in the same time. The prime reason of pipe string fault is found out by studying fault mechanism, analyzing the high-temperature-and-high-pressure gas well completion pipe string history and adopting the indoor fitting experiment analyse technology. The article studies the carbon dioxide and sulfureted hydrogen's erosion mechanism of high-temperature-and-high-pressure well completion pipe string environmental factors under the acid condition in a large of energy and time.In the acid gas reservoir, the pipe string erodes badly and has serious sap-erosions and even perforation. The erosions make the gas well pipe string intensity decline greatly and give rise to the serious hidden security trouble in the gas well production. It is very important to research and appraise the eroded pipe string intensity to prevent the security problems arisen from the erosion. But there are some big difficulties in the mechanics analyse owing to the erosions positions' complex, badly anomalistic shapes. The article establishes the finite element mechanics model of the easily-eroded pipe string intensity by applying the elastic-plastic finite element analysis theories and ways, and considering the material's non-linear characteristics and intensity-destroyed rules. Then it carries through the finite element mechanics behavior simulation analyse, studies the intensity and stress distribution state of the eroded pipe string, appraises the eroded pipe string residual intensity, finds out the rules in which the erosion affects pipe string intensity and provides some scientific basis to the pipe string's use in the corrosive environment.The geometry model was established which described the well head assembly insidegeomertry character and construction features. The finite differential methord based on controlling the inside volume of the well head assembly was used to calculate the wall stress,eroding amount and corrosion volume. Through the mutiphase fliud eroding mechanism research was taken, and the key eroding corrosion position was found.The numinical model was established according to the gas well head assembly inside size and fliud mechanics character,the gas well pressure,production, gas velocity and the gas well fact working conditions,and the checking situation of the eroding corrosion. The flowing situation was modeled, the results provide theory basis to find out the air dynamics damage reason of tubing rupture and well head assembly eroding corrosion breakage.Considering about fliud dynamic pressure which affects on the tubing, the tubing longitudinal librotion model was set uo based on the solid-liquid coincidence libration theory, and the frequency equation was present in the paper. A added dynamic load will come out in the high pressure and high production situation. The study results using the data of XIN851 gas well shows that the important reason is the pressure stir in high pressure,high production working conditions. The dynamic load is the key breakage reason , it must be considered in the tubing design.The thread intensity is one of the key factors in the high-temperature gas well. The temperature stress that the temperature field produces affects obviously the casing pipe thread's intensity. So, to research the influence which temperature exerts on the casing pipe thread's intensity and leakproomess is an important problem in solving the pipe string intensity and reliability in high temperature condition. The article establishes the mechanics analyse mode, which embodies the temperature's influence on the casing pipe intensity, by applying the related thermodynamic theories and analyse ways and variation principle, and mostly analyzes the leakproomess of API long-round thread and flat-trapezoid thread in the different compounding load. Some rules are found on the basis of researching the high-temperature-and-high-pressure casing pipe threads' leakproomess and structure integrality. They have definite direction action in actual on-the-spot operation, and then enhancethe security reliability and the serviceable life of the high-temperature-and-high-pressure gas well pipe string.According to the workings above and the related theories' research, the article puts forward a suit of theories and ways that are fit for the high-pressure gas well completion pipe string design, and forms a suit of the high-pressure gas well pipe string intensity fault mechanism analyse methods, the technology versions and measures to avoid Breakage.