Source attribution of seasonal variations in light alkane emissions from oil and gas operations in the Permian Basin

Multi-year seasonal variations of methane emissions from oil and gas operations in the Permian Basin of west Texas have been reported, based on satellite observations, and tower and aircraft measurements. The estimated seasonality of emissions varies in magnitude depending on the observation platform but is as large as a factor of two between summer minima and winter maxima. This work uses ground measurements and spatially and temporally resolved emission inventories, coupled with gridded chemical transport modeling and dispersion modeling of light alkane concentrations, to identify potential oil and gas emission sources that could cause observed seasonal variations in emissions. Light alkane ratios (e.g., propane to ethane ratios), indicate that variability in emissions over weekly to month-long periods occurs but is not spatially uniform throughout the Basin and is not consistent over multi-year periods at individual locations. The magnitude of the temporal variation in emissions necessary to explain the observations was examined for specific locations and times using emission modeling at hourly resolution for the ~150,000 oil and gas sites in the Permian Basin. The analysis suggests that for the Midland County region in 2022, the most probable cause of higher winter emissions is widespread sources with emission compositions characteristic of produced gas, however this assessment changes over time and by location.