High spatial and temporal resolution simulations of methane column loadings due to routine emissions and emission events in oil and gas regions

Total column loadings of methane measured by satellites are increasingly used to estimate methane emission rates, using inversion calculations. Forward calculations of methane column loadings, based on detailed emission inventories at fine spatial resolution, coupled with fine spatial scale gridded chemical transport models, have the potential to inform approaches used in inversion calculations. As a case study of a forward calculation of methane column loadings, a site-level emission inventory for >104 oil and gas production and midstream sites was coupled with a gridded chemical transport model to estimate the variability in column loadings associated with routine emissions and large emission events from oil and gas facilities over a seven-month period. Data sets of gridded column concentrations at a one-hour temporal resolution and a 1.33 km horizontal spatial resolution have been created and archived. Ratios of the total column methane enhancements associated with emission events to the total column enhancements due to routine methane emissions were evaluated for various emission scenarios. The results indicate that in an oil and gas production region typical of the United States, a horizontal spatial resolution of ~1 km is needed for a 1000 kg/hr emission event to routinely produce a doubling of column methane loadings, compared to a baseline of enhancements in column loadings due to routine emissions. Enhancements ratios for column methane due to nearby emission events were generally insignificant. The enhancement ratio represents a relatively simple metric that could facilitate rapid and simple identification of emission events.