SINOPSIS

In cases involving fires and explosions caused by fugitive natural gas, adequate modeling and quantification of the gas migration process is extremely important, as a properly performed analysis permits the identification and verification of the gas leak path from the leak source to the point of ignition, the quantity of gas that migrated, and the time it took to reach the ignition source. Additionally, a properly made gas flow analysis will provide the calculations and data to rule out other potential gas leak source/sources. This work describes a modern approach for modeling gas migration in soils using the finite element method and combines the solution of the coupled diffusion and seepage equations to describe gas flow in porous media. The methodology employs the open source finite element application Tochnog, which allows multidimensional analysis and both transient and steady state solutions to be found. The method of analysis is validated by comparing the predictions of the model to published data for low-pressure leaks. The solution technique is also applied to a higher-pressure 275,790 Pa (40 psig) gas leak. The methodology proposed also allows calculation of leak flow rate from a known pressure source if the soil composition and distribution are known.