Abstract

Blending hydrogen into methane is expected to facilitate efforts towards energy decarbonization. One critical challenge remains the possibility of hydrogen separation from methane during underground pipeline leak events, owing to their differences in molecular properties. Therefore, in depth knowledge about the potential for hydrogen stratification during releases from an orifice is imperative. The current study explores this issue through a combined experimental and numerical modelling approach. To mimic leak scenarios, an NPS24 pipe was buried in a soil tank and equipped with a 1 mm (diameter) leakage orifice located at the 12 o’clock position. Release pressures were on the order of 3.4 MPa. A soil containment tank: 2.4 m (width) by 7.2 m (long) by 2.4 m (deep) filled with bedding sand represented the controlled soil environment where the pipe was buried.

Results obtained from real-time monitoring indicate diffusion dependence on leakage flow rate and blend percentage. The initial leakage momentum due to pressure, led to an instant upwards migration of gas blends. However, preferential hydrogen build-up was observed across the soil in some cases. This was followed by a rapid break through with reduced concentration detected around near surface regions as hydrogen diffused into the atmosphere at a faster rate. As hydrogen blend ratio increased from 10, 20, to 30 % respectively, a noticeable change in diffusion efficiency manifested in the form of slight increase in concentration distribution over an expanded range. Similar occurrence was also witnessed as increase in leakage flow rate led to pronounced hydrogen concentration around diffusion-affected zones. Furthermore, the numerical model results showed good agreement with experimental results, thus validating the findings from this study.

Overall, this research offers valuable insight towards understanding the underground migration behaviour of hydrogen blended methane. It provides the basis for a quantitative model that can effectively support large-scale risk assessment and other leak detection efforts.

Authors:

Drake, Corey

Publisher:

ASME The American Society of Mechanical Engineers
2026 International Pipeline Conference

Year Published:

2026

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