Study On Hydrate Prediction And Prevention Of Natural Gas Ground Pipeline

The requirements of hydrate were easily reached while at the process of natural gas were gathering and transporting, and in this process the natural gas temperature continues to drop that caused by decreasing pressure, the hydrate in the pipeline may be generated when the pressure and temperature of the natural gas meet certain conditions, and then the gas pipeline will be blocked and the normal production of gasfield will be affected. So it is necessary to carry out the techniques research about hydrate formation prediction methods and ground gas pipeline hydrate control of the hydrate formation conditions.At the basic of the three kinds of prediction methods of hydrate formation conditions, I have carried out the basic research of preventing the hydrate technology applied methods about alcohol injected and electric heating.Based on this, the main tasks of the theoretical research papers completed as follow ings:(1) Gas and formation water physical parameters of calculation methods were given: including natural gas relative density、deviation factor、volume coefficient、viscosity、 density and specific heat at constant pressure、formation water viscosity、density and gas-liquid interfacial tension. The reasonable and correctness of the calculation method was verified by sensitivity analysis, and it has paved the way for the calculation latterly.(2) The key technology of the hydrate prediction and prevention was predicted accurately of the hydrate formation conditions, for this paper, it has analyzed the behavior of hydrate formation and thermodynamics, achieved graphical method, empirical formula and calculate statistical thermodynamics, and completed the programming calculation.(3) It has established the ground gas pipeline gas pressure and temperature prediction model, has analyzed the gas production, liquids production, wellhead temperature, gas pipeline diameter and absolute roughness on the ground pipeline pressure drop along the way,as well as gas production wellhead, pipeline buried deep in the ground temperature, gas pipelines outside diameter and overall heat transfer coefficient on the ground temperature drop along the pipeline effect.(4) Application the prediction methods of pressure and temperature prediction models and hydrate formation conditions, the pressure from wellhead to the gas pipeline gas gathering station, temperature and hydrate formation temperature distribution were given, and prevention maximum hydrate formation temperature drop was calculated, combining the empirical formula Hammerschmidt of rich concentration and fitted mathematical formula of gas saturated water content, and considering the consumption separately in the gas and liquid phase, and a reasonable inhibitor injection amount calculation model was given to calculated the parameter of injection alcohol.(5) According to the multi-layer fluid flowing through the cylindrical wall tube heat transfer theory, considering the earth temperature change, natural gas physical parameters and other factors, it has given the electric heating gas pipeline buried numerical methods and calculation formulas of thermodynamic, and that was applied in scene. Pipe wrapped with electric heating outlet temperature was significantly higher when wellhead temperature under certain conditions.