High potential for CH4 emission mitigation from oil infrastructure in one of EU's major production regions

Ambitious methane (CH₄) emissions mitigation represents one of the most effective opportunities to slow the rate of global warming.  The oil and gas (O&G) sector, a significant source of CH₄ emissions, offers technically feasible and cost-effective emission mitigation options. Romania, a key O&G producer within the EU, with the second highest reported CH₄ emissions from the energy sector in 2020 can play an important role towards the EU’s emission reduction targets. Based on UNFCCC data, during the period 1990-2019, one of the largest reductions in fugitive CH₄ emissions from O&G were observed in Romania. However, the concentrated reduction in mostly a single year raises questions about the true extent of emission reductions. The Romanian Methane Emissions from Oil and Gas (ROMEO) project aimed to characterize CH₄ emissions related to onshore O&G production in Romania at a component, facility, and basin scale using a variety of both ground- and airborne-based measurement techniques. In the first phase in 2019 in the southern main oil production region, measured emissions were characterised by heavily skewed distributions, with 10% of the sites accounting for more than 70% of total emissions. Integrating the results from all site-level quantifications, we derive a central estimate of 5.4 kg h^–1 site^-1 of CH₄ (3.6 – 8.4, 95% confidence interval) for oil production sites. Aircraft quantifications from mass balance flights and raster flights, combined with atmospheric modelling, confirm these high emission rates. Based on the site-level results, we estimate a total of 120 ktons CH₄ yr^–1 (range: 79 - 180 ktons yr^–1) from oil production sites in our studied areas. This is approximately 2.5 times higher than the reported emissions from the entire Romanian oil production sector for 2020. During the second phase in 2021, targeting the Transylvanian gas production basin, more emitting sites are observed, but the emission rates per gas production site are lower than those from the oil production sites in the oil production region. Based on the source level characterization, up to three quarters of the detected emissions from oil production sites are related to operational venting. In 2021, following reported repairs by operators to address open vents, additional aircraft flights using a remote sensing method targeting the southern oil production region detected fewer emitting oil production sites. However, there is large uncertainty surrounding the exact magnitude of emissions below the method’s high detection threshold. Additionally, high emissions were observed from large vent stacks that had not been detected with the ground-based measurements in 2019. Our results suggest massive mitigation potential in Romania's O&G production infrastructure by capturing gas and minimizing operational venting and leaks. By synthesizing the findings and data collected across different spatial and temporal scales during the ROMEO campaigns, we can gain better understanding and valuable insights into the true magnitude and distribution of CH₄ emissions from Romania's O&G sector. The results of this data integration can allow us to fill critical gaps of missing information and address discrepancies between existing emission inventories and empirical estimates.