A regional assessment of methane emissions from natural gas production in the Transylvanian Basin, Romania

Jarosław M. Necki, Paweł Jagoda, Foteini Stavropoulou , Jakub Bartyzel, Piotr Korbeń, Sara Defratyka, Martina Schmidt, Hossein Maazallahi, Marius Corbu, Sebastian Iancu, Andreea Calcan, Magdalena Ardelean, Sorin Ghemulet, Cristian Pop, Andrei Radovici, Alexandru Mereuta, Horatiu Stefanie, Calin Baciu, Thomas Röckmann

Romania hosts one of the largest and oldest natural gas production sectors in Europe, yet direct measurements of methane emissions from its principal gas-producing region, the Transylvanian Basin, remain limited. Here, we present the first basin-scale, measurement-based assessment of methane emissions from natural gas production facilities in the Transylvanian Basin based on 160 methane emission quantifications performed at 127 facilities and complementary screening surveys covering 520 facilities. Methane emissions were quantified using multiple independent approaches, including the Tracer Release Method (TRM), Other Test Method 33A (OTM-33A), Gaussian Plume Method (GPM), High-Flow Sampling (HFS), and a novel Large-Scale Flow Chamber (LSFC). Site-level methane emissions exhibited strongly skewed, approximately log-normal distributions and pronounced temporal variability, with repeated measurements frequently differing by up to an order of magnitude. Combining all representative facility-scale measurements yielded a methane emission factor of 1.7 kg CH₄ h⁻¹ site⁻¹ (95% confidence interval: 1.1–2.6 kg CH₄ h⁻¹ site⁻¹). While emissions from natural gas production facilities were primarily associated with leaking infrastructure components, two previously undocumented water-degassing tanks were identified as methane super-emitters, with combined emissions exceeding those measured from all quantified production facilities. Upscaling the derived emission factor yielded methane emissions of approximately 42 kt CH₄ yr⁻¹ (95% confidence interval: 27–64 kt CH₄ yr⁻¹) from natural gas production well sites in the Transylvanian Basin. This estimate is comparable to currently available national-scale estimates for Romania’s natural gas sector, highlighting the importance of measurement-based approaches for improving greenhouse-gas inventories and identifying methane mitigation opportunities.