Study of natural gas emission from a hole on underground pipelines using optimal design-based CFD simulations: Developing comprehensive soil classified leakage models

Abstract

Gas leaks from natural gas pipelines can lead to catastrophic incidents, especially in the case of sour natural gas owing to the combination of its toxicity and flammability. As a safety consideration, these pipelines are underground to protect humans and installations. However, no comprehensive model has yet been proposed that can predict the leakage rate from the damaged buried pipelines in a wide range of influential factors. In this work, to compensate for this shortcoming, a set of soil classified models are presented considering the emission of sour natural gas in silty, sandy, and gravelly soils using the results of optimal design-based CFD simulations. In this way, a wide range is selected for effective factors of pipe pressure (2–100 bara), leakage hole diameter (2–40 mm), pipe diameter (4–56 in), soil porosity (0.3–0.45), and soil particle diameter (0.002–40 mm). These ranges cover the specifications of both urban distribution pipeline systems and transmission ones. A two-step solution strategy is implemented to consider the effect of pressure drop on the leakage rate. The CFD simulations are in good agreement with experimental data reported in literature. The leakage models are capable to predict the results of random simulations with a mean absolute percentage error of 13%, 9%, and 7.7% for silty, sandy, and gravelly soils, respectively, over a wide range of pressure and leakage hole diameter. Furthermore, the effects of soil mass properties and pipe wall thickness on the leakage process are investigated. To clarify the effect of soil mass on leakage rate, the CFD analysis of an aboveground leaking pipe is also performed comparatively.