Nomograph derivation for underwater sour gas releases in shallow waters based on computational fluid dynamics simulations

Abstract

Ruptured underwater pipelines releasing sour gas (i.e., natural gas with high concentrations of H2S) pose significant threats to environmental safety due to their toxic and contaminative properties. This study suggests a transient Eulerian-Eulerian multiphase computational fluid dynamics (CFD) model for assessing the environmental impact of sour gas releases in shallow, ecologically sensitive waters. Employing the Realizable k-ε turbulence model and additional bubble plume mechanisms, the model was rigorously validated against well-documented experimental data, showing high levels of agreement across multiple metrics. Key environmental safety parameters—such as rise time and H2S surface gas concentration, indicative of toxic exposure risk to aquatic life and human health—were extracted for multiple release scenarios. To present generalized and easily accessible data, these parameters were nondimensionalized and incorporated into a nomograph, enabling environmental risk assessments to be conducted four orders of magnitude faster than with high-fidelity simulations. The study emphasizes the nomograph's utility in rapid, environmentally relevant risk assessment and emergency planning for mitigating the impact of sour gas spills. An error and sensitivity analysis revealed uncertainties of ±7 % for rise time and ±58 % for surface gas concentration, pinpointing avenues for future research.