Development of a Comprehensive Risk Quantification Methodology for Gas Pipeline Networks in Populated Areas of Southwest Nigeria

Quantifying major hazard risk from gas pipeline networks passing through densely populated areas requires rigorous probabilistic methodologies that account for the complex interplay of pipeline failure probability, consequence escalation physics, and population vulnerability. This study develops a comprehensive quantitative risk assessment (QRA) methodology specifically designed for gas pipeline networks in the populated areas of southwest Nigeria, addressing limitations in existing international QRA approaches when applied to the distinctive Nigerian urban, demographic, and infrastructure context. The research methodology involves: development of Nigeria-specific pipeline failure frequency distributions from the NUPRC incident database (2005 to 2023), derivation of thermal radiation and explosion overpressure consequence models validated for Nigerian pipeline gas compositions, construction of population density and spatial distribution datasets from National Population Commission census data for Lagos, Ogun, and Osun corridors, and development of vulnerability functions appropriate for Nigerian building stock typologies. These components are integrated into an original QRA computation framework implemented in Python, capable of producing individual risk contours, societal risk FN curves, and risk-informed pipeline management recommendations. The study's original contributions include: the first published Nigerian pipeline failure frequency dataset derived from national incident records, a building stock vulnerability model for Nigerian low-income residential construction under jet fire and blast loading, and a risk-informed land use planning framework for gas pipeline corridors in Nigerian urban settings. Findings reveal that individual risk contours from several existing Lagos pipelines significantly exceed the broadly acceptable risk threshold of 1 in 1,000,000 per year at the nearest occupied premises. Recommendations include urgent pipeline burial programme for above-grade sections in high-population areas and mandatory QRA for all new urban gas pipeline consents. Keywords: quantitative risk assessment, gas pipeline, urban Nigeria, Southwest, pipeline risk.