Source and Site Level Reconciliation of Methane Emissions at the Midstream Sector

Efficient methane reduction efforts require reliable, measurement-based and transparent inventories. Site-level technologies serve as essential tools for gathering data on emissions at operational sites. However, significant knowledge gaps persist regarding the performance of these technologies in real-world conditions and their effective utilization to enhance the accuracy of reported data by operators. This study evaluates the snapshot reconciliation - an instantaneous comparison- of site and source level quantification methods to provide midstream operators with general recommendations when the relevant quantification methods and reconciliation practices are applied at their sites.

Prior to this campaign, which took place at a compressor station in Zelzate, data from a previous phase of the project conducted in Spain -where controlled releases were carried out in real-world conditions- were analysed to understand the uncertainties associated with site-level technologies. This analysis was used for the selection of technologies with the best performance, i.e. closeness of the technology providers’ emission quantifications to the controlled and blind release rates. In Zelzate, a two-day campaign was designed, consisting of two distinct phases based on the operational status of one of the site’s compressors. During the campaign, site-level quantification methods were deployed in parallel with source-level quantification techniques.

The reconciliation process was assessed to understand how it can be implemented for verifying bottom-up data. Following the results of this test, detailed recommendations for implementing snapshot reconciliation were provided in alignment with OGMP 2.0 (Oil and Gas Methane Partnership 2.0) guideline. These recommendations prioritize identifying and addressing areas of improvement in emission quantification (e.g. bottom-up sampling and measurement strategy) to achieve consolidated Level 5 inventories. Furthermore, reconciliation process should not primarily focus on the potential overlap between site-level and source-level measurements, owing to limited understanding of the uncertainty ranges required for such analyses.

The outcomes of this study offer deep and valuable insights into several key aspects:

• Performance of Site-Level Methods: Understanding the capabilities and limitations of site-level quantification technologies in real-world field conditions.
• Reconciliation Recommendations: Providing practical guidance for implementing effective reconciliation procedures, with a focus on achieving robust and transparent methane inventories.