Underwater release of hydrogen-natural gas blends

The transport of hydrogen and hydrogen-natural gas blends through subsea pipelines introduces significant safety risks in the event of pipeline damage or rupture. Such incidents can lead to the release of gas, forming a bubble plume that ascends to the ocean surface. Elevated surface concentrations of hydrogen and hydrogen-natural gas may pose serious hazards to life and infrastructure. Risk assessments typically involve a sequence of analyses, with gas migration and dissolution in the water column representing a source of uncertainty. This study presents a transient, three-dimensional computational fluid dynamics model developed to quantify the surfacing gas volume, its composition, and spatio-temporal distribution for a multicomponent gas. The model aims to improve the accuracy of quantitative risk assessment related to subsea hydrogen transport. The model is applied to underwater release scenarios with varying hydrogen content and model results demonstrate that the risk increases with increasing hydrogen content. • A numerical model assessing underwater release of multicomponent gas is documented. • Relevant material properties for hydrogen, methane, oxygen and nitrogen are documented. • The model is consistent with experimental observations. • The model is applied to releases with various gas mixing blends. • Simulations demonstrate that risk potential increases with hydrogen content.