Cng Filling Stations Gas Wells Channeling Failure Analysis

With the development of national economy and the progress of our society, the number of vehicles grows rapidly, which results in the contradiction between the supply and demand of automobile fuel. At the same time, the emission pollutant to the ecological environment keeps increasing. Utilizing natural gas as automobile fuel is a positive choice. In recent years, the gas storage well bolted out frequently everywhere, those accidents usually result in the failure of the pipe's junctions on the shaft collar. Sometimes even the whole tub broke out from the ground. As a result, the natural gas leaks, gas storage well is abandoned, even causes big fire, explosion, and human casualties. Therefore, it is needed to analyze tub with Elasticity method, the tub bolt out failure mechanism was studied in this paper, then preventative measurements were proposed in order to ensure the safe operation of CNG station, and guarantee the property and safety of human beings.Considered casing, cement mantle and layer as elastic material, elasticity theory and thick-cylinder theory were adopted, Casing-Cement-Mantle layer model was built in the paper. Statics was used to solve the model mentioned above. Meanwhile, the stress distribution of the coupled mode was also made clear, at the same time, analog computation was used to prove the validity of the model proposed.Furthermore, basic dynamic parameters of layer, geometric and physical parameters of cement mantle, and geometric parameters of casing were analyzed. Their influencing regulations on tub were obtained. And the reasons of failure of gas storage well were revealed. The problem of abhesion was studied, with the help of the crackle under the action of cyclic loading spread theory, the relation between cyclic loading and velocity of interface abhesion was also obtained. Driving factors of tub accidents were indicated.Based on the analysis above, considering two cases such as uniform terrestrial stress and non-uniform terrestrial stress, bearing regulation of tub was studied. In conclusion, the thicker the wall of gas storage well casing, the smaller the bearing force of outer and inner wall of cement mantle is. The bigger the elastic modulus of cement mantle, the smaller the Poisson Ratio is, and the stronger the resistance ability of cement mantle. The smaller the elastic modulus of cement mantle, the bigger the Poisson Ratio is, and the bigger the resistance to tension of cement mantle. The thicker the cement mantle, the smaller the bearing force of outer and inner wall of cement mantle is. The bigger the elastic modulus of cement mantle, the smaller the Poisson Ratio is, and the stronger the resistance ability of layer.Based on the regulations above, some measurements to control gas well accidents were suggested: in order to prevent accidents, casing with a thicker wall, cement with smaller elastic modulus and bigger Poisson Ratio, and a thicker cement mantle should be chosen. Gas storage well should be built on hard layer. In addition, cohesive strength between casing and cement mantle should be strengthened.