Reconciliation of Source-Level Methane Emissions Measurement with Site-Level Measurement Using a Drone-Mounted Sensor: New Insights for Standardisation and Global Deployment

Abstract Accurate and transparent reporting of methane emissions is vital for targeted and defensible methane reductions in the energy sector. This is recognised in the United Nations’ new reporting framework (OGMP2.0) where measurement-based reporting of methane emissions that is accompanied with a statement of reconciliation constitutes the highest level of conformance (‘level 5’). A fully traceable top-down measurement system suitable for onshore and offshore deployment was developed to conform with OGMP2.0 level 5 expectations. Site-level methane emissions are measured by means of a drone-mounted methane sensor flown downwind of oil and gas production facilities. The sensor was deployed on quadcopter and fixed-wing drones with comparable results. Atmospheric methane concentrations were converted into an emission rate through mass balance calculations, considering meteorological parameters. Results from 11 offshore surveys acquired between 2021 and 2023 showed generally low emissions of less than 40 kg/h, with two outliers measured at 106 ± 31 kg/h and 347 ± 97 kg/h respectively. Emissions followed a ‘fat-tail’ distribution with 27% of sites accounting for 87% of the total methane emissions in the sample, highlighting the value of top-down measurement in identifying abatement opportunities. Two-thirds of sites measured in 2023 were successfully reconciled to OGMP2.0 level 5. The analysis emphasized the importance of high-quality source-level data for successful reconciliation and sites where such data is available should be prioritized when scheduling top-down measurements. A successful top-down strategy should follow a process of continuous improvement that considers emissions materiality, range of emission rates under normal operating conditions, demonstrable quality of bottom-up inventories, and the option to group sites into representative populations. Standardisation and industry collaboration is needed to ensure consistency in the methodology of both the top-down measurement and reconciliation, including application of uncertainty, which is key for transparent, traceable, and credible reporting of methane emissions from oil and gas facilities.