Source Attribution and Fine Scale Impact Assessment of Oil and Gas Site Emissions

Oil and gas exploration and production activities may have significant near-source ozone and other air quality impacts (e.g., toxic formaldehyde exposure), particularly when large combustion activities take place. For example, multiple large compressor engines at pipeline compressor stations, or very large flares at natural gas processing facilities can add over 3 ppb of 1-hour average ozone within 10 km downwind of an oil and gas site, as shown in a previous high resolution modeling study. The HARC neighborhood air quality model is a superfine resolution 3D Eulerian model that can simulate rapid near-source chemistry due to large industrial emissions of nitrogen oxides, highly reactive VOCs, and radical precursors. While the HARC model can be run in the traditional forward mode, it can also be run in adjoint mode, so that inverse estimation of emissions and other model parameters may be performed using the 4D variational (4Dvar) data assimilation technique. The HARC air quality model has been combined with the QUIC urban wind model to improve the accuracy of source attribution and fine scale impact assessment at industrial sites. A real-world application of the HARC model will be presented based on the analysis of field study data collected in the Dallas-Fort Worth metropolitan area located over the Barnett Shale formation. The potential for enhancing routine monitoring of oil and gas site emissions and the improvement of oil and gas emission inventories will then be discussed.