Numerical Prediction Of H₂S Diffusion And Influence Area Of Natural Gas Leakage

H2S diffusion during natural gas leakage accidents will cause potential hazards such as the large economic loss and serious casualties. Until now there's no proper model for H2S diffusion research especially the proper one for the complex terrain and weather conditions. As a result, in order to realize the safe and sustainable development of the rich-in-H2S natural gas exploration, it is of vital importance to research the technology for the numerical prediction of H2S diffusion and influence area of natural gas leakage under complex terrain and weather conditions.The essential of the subject was pointed out with the research of the differences between H2S diffusion in the open air and the general mass transfer. Parameters that influence the diffusion are listed and analyzed, and the difficulties and key problems to work out the subject are suggested.Based on the analysis of the component and development of the numerical diffusion technology and the theory of air pollution controlling, we successfully developed PUGdiff software with FORTRAN, which can simulate the H2S diffusion influence area based on its predicted meteorological data considering the complex terrain conditions of the place where the natural gas leakage accident happened. With the comparisons of the simulating samples, the feasibility of PUGdiff model was discussed, and the result shows that this model can be used for H2S diffusion prediction under complex terrain conditions.The academic research of the natural gas pipeline leakage was given. Based on the theories of thermodynamics and fluid mechanics, together with the use of ideal gas equation of state, adiabatic equation and energy conservation equation, the natural gas leakage process was studied and divided into two leakage phases, the critical phase and the sub-critical phase. Equations were obtained for calculating the leakage flow rate of the whole leakage process, and examples were given to analyze the influences of various parameters on leakage flow rate and the relationship between the leakage hole diameters and leakage flow rate.The relationship between H2S diffusion and its main factors including leakage rate, weather condition and terrain condition was researched with PUGdiff model. With the analysis of the simulations, the result shows that big range of leakage flow rate, weak wind and complex terrain like basin terrain are the most disadvantageous factors for the H2S diffusion, which means under these conditions, H2S is not easy to diffuse and will cause serious potential hazards.Finally a practical simulation for H2S diffusion during natural gas leakage accidents in a natural gas field in Sichuan was given, including the comparison between the simulated value and real measured value of the meteorological data, the definition of the basic parameters of the natural gas field, the analysis of the simulation result on typical date with weak wind and the infection of the leakage hole diameters and so on. With a great amount of the data analysis, it proves the feasibility of the PUGdiff model and indicates that the model can supply reliable data for the contingency plan establishing.