Quantifying methane super-emitters from oil and gas production in Romania with the AVIRIS-NG imaging spectrometer

Reported methane (CH₄) emissions from Romania's onshore oil and gas (O&G) production contribute 16% to onshore O&G emissions in Europe (55 out of 346 kt, IEA estimate). In October 2019, CH₄ emissions from the O&G infrastructure were measured during the ROMEO campaign with a wide range of in situ measurement techniques in southern Romania. The measurements confirmed a log-normal distribution of emissions with a small number "super-emitters" contributing strongly to the overall emissions.

However, overall emissions remain uncertain because some CH₄ super-emitters are difficult to identify with ground-based campaigns due to the large number of potential sources and sometimes elevated emission plumes. In contrast, airborne imaging spectrometers are well suited for identifying super-emitters due to their good spatial coverage and sensitivity to vertical columns. To identify super-emitters, the airborne AVIRIS-NG imaging spectrometer was flown in July 2021 in southern Romania covering an area of about 3000 km² that contains about 80% of known O&G infrastructure in the region.

CH₄ enhancements in the AVIRIS-NG lines were retrieved using a quantitative matched-filter method. In total, 38 emission plumes were identified that were assigned to 26 individual sources. Emissions were estimated using the integrated mass enhancement approach and ranged from 13 to 515 kg/h, which suggests annual emissions of about 30 kt assuming continuous emission rates. The sites were visited by ground crews, who confirmed that at least 17 of the sources were also active in December 2022.

The observed 30 kt/a from only 26 sources already represent more than half of the reported emissions from the onshore O&G emissions in entire Romania. The campaign demonstrates the importance of airborne imaging spectrometers to identify and quantify CH₄ super-emitters for monitoring CH₄ emissions from O&G infrastructure.