The quantification of methane emissions based on measurements directly at the emission sources (bottom up) and on the basis of comprehensive measurements at site level (top down such as using drones or satellites) can vary – sometimes by orders of magnitude over the annual operating cycle of an oil and gas plant. Therefore, an appropriate combination of measurement strategy and methods should be chosen to consider the evolution of the different emission types.

We report results based on the first case studies executed to deliver data reconciliation in the mid-stream sector. This data matching compares methane emission inventories built through source measurements (in accordance with OGMP 2.0 framework - Level 4) with emission data collected through a different measurement campaign and technology at the site level (in accordance with OGMP 2.0 framework - Level 5) to provide a comprehensive and more accurate evaluation.

This Level4/Level5 reconciliation will most likely become a mandatory part of the upcoming new EU methane regulation, which is expected to come into force in early 2024.

Site-level measurements complement source-level measurements, rather than replace them. Our projects experience showed that the process of reconciliation helps to improve accuracy, thoroughness, and confidence in the determined emissions. A risk-based approach according to OGMP2.0 framework is used to determine the frequency of site-level measurements. Those should be carried out no less frequently than once a year.

Site-level measurements were performed independently (using independent methods and technologies) from source-level measurements. In the case studies we documented complete emissions to ensure that the main emission sources have not been overlooked in the inventory at source level. Measurements at site level also considered the possibility of rare but significant emission events.

The respective uncertainties of both the source-level and site-level measurements were included in the assessments.