High Pressure And High Production Gas Well Tubing Gas-Liquid Two Phase Flow Characteristics Study

Natural gas as a clean energy has been attached importance to all the world increasingly,gas-liquid two-phase flow plays an important role in the oil and natural gas industry. In the high pressure and output gas wells testing and production process, the complicated dynamic load underground is easy to cause formation gas invasion to the annular space form slug flow,the formation of its flow characteristics have important influence on the work performance of oil tube. In reverse circulation washing well, the bottom there are solid, liquid, gas multiphase flow blocked tubing easily, and make dramatic changes within the tubing pressure, eventually led to the tubing collapsed failure.After reviewed the research status at home and abroad of the gas-liquid two phase flow,environmental research of yuanba block and for the case of tubing was macroscopic characteristics, physical and chemical properties analysis, microscopic metallographic analysis,in this paper, gas column pressure dropped sharply reasons are analyzed in the gas-liquid two phase flow in the tubing, and the tubing as the research object, using the method of combination of theory and numerical model, the formation of slug flow inside the tubing, the motion law of the air column in the tubing and the change characteristics of the pressure of the gas liquid two phase flow are simulated and calculated. Triaxial strength calculation method is used to calculate the collapse strength of the tubing..Finally, in order to avoid the tubing was collapsed and failure, this paper put forward the corresponding improvement measures.This paper concluded that: The tube sample in addition to the tensile strength is lower than the standard,yield strength and elongation accord with standard requirements, the mechanical condition of tubing collapse is relate to the downhole complex dynamic load(such as the pressure difference of the tubing inside and outside is bigger);tubing in gas liquid two phase flow in the gas column pressure fell sharply and tubing blocked after annulus water hammer effect caused tubing inside and outside differential pressure increases, eventually led to the collapse of tubing; Gas column pressure change within the tubing have related to the factors that the gas column length, the degree of tubing bottom plug, gas velocity and the tubing plugging depth and others;tubing is under external load has gone beyond the collapsing strength of the tubing.