Quantifying Atmospheric Methane Leakage Rates from Aging Offshore Oil and Gas Infrastructure in the North Sea Using Satellite Remote Sensing

Atmospheric methane (<i>CH₄</i>) is a potent short-lived climate pollutant, accounting for approximately 30% of global temperature increases since the pre-industrial era. While onshore fossil fuel infrastructure has been extensively scrutinized using satellite remote sensing, offshore oil and gas platforms remain critically under-monitored due to observational challenges over open water. This study presents a comprehensive quantification of atmospheric methane leakage rates from aging offshore infrastructure across the North Sea, covering the period from 2021 to 2023. By combining regional screening from Sentinel-5P TROPOMI with targeted high-resolution imagery from GHGSat satellites utilizing dedicated sunglint retrieval algorithms, we mapped and flux-quantified emission plumes across more than 400 active platforms. Our top-down empirical observations reveal an aggregate methane emission rate of 184 &#177; 32 kt CH₄ per year, a figure 2.4 times higher than official bottom-up inventories submitted under national reporting frameworks. Super-emitting events (&gt;1,000 kg/h), largely attributed to unlit or inefficient flaring, compressor seal degradation, and emergency venting routines, accounted for 43% of total detected emissions despite representing under 5% of observed facilities. Infrastructure exceeding 30 years of operational life exhibited a statistically significant three-fold increase in fugitive emission frequency compared to newer installations. These findings underscore systemic underreporting in standard bottom-up accounting methods and demonstrate the efficacy of satellite-based remote sensing for offshore environmental compliance. We outline key policy recommendations for integrating spaceborne surveillance into the European Union Methane Regulation and the OSPAR regional framework to drive verified mitigation in maturing offshore basins.