Real-Time Measurements of Ethane for Source Attribution of Methane Plumes from Oil and Gas Facilities

The Aerodyne Mobile Lab has conducted several recent studies of the methane emissions from Oil and Gas facilities at varying stages of production: well-heads; processing facilities; and compressor stations. Accurate quantification of methane emission rates are can be complicated by other local sources, notably livestock and microbial production. Methane emissions from oil and gas facilities are always accompanied by small amounts of ethane, while biogenic plumes contain no ethane. A prototype ethane spectrometer based on the Aerodyne-Mini chassis, has been deployed to oil and gas facilities in the Veracruz region of Mexico, as part of the 2013 Short-Lived Climate-Forcing project, and during ground-based measurements in the Barnett Shale in Texas as part of the Barnett Oil and Gas Observation Study. These results suggest a source-dependence in the ethane-to-methane ratio in oil and gas emissions. The results will be contrasted with 13CH4 methane isotope ratios determined using Aerodyne's Methane-Dual instrument. The limits and advantages of ethane-methane ratios and methane isotopes will be discussed. In the current instrumentation, the precision of determined ethane-to-methane ratios in a single plume encounter exceeds the analogous carbon isotope quantification.