Downward Trend in Methane Detected in a Northern Colorado Oil and Gas Production Region Using AIRS Satellite Data

Abstract

The oil and gas (O&G) sector is estimated to be the largest contributor to anthropogenic methane (CH4) emissions in Colorado. Since 2004, the State of Colorado has implemented multiple regulations to significantly reduce emissions from the O&G sector.The Denver-Julesburg Basin (DJ Basin) is a significant O&G producing region in northern Colorado, and O&G production here has steadily increased over the last decade. To assess CH4 trends in Northern Colorado, we selected CH4 retrievals from the NASA Atmospheric Infrared Sounder (AIRS) instrument for 2003-2020. The study grid cell includes Denver, Boulder, and much of the dense O&G production in the DJ Basin. We computed mean June-August ascending node AIRS 700 hPa CH4 for each year and subtracted mean June-August CH4 sampled at NOAA's Niwot Ridge (NWR) station, a high-altitude background site. Differences represent estimated enhancement over background. Linear regression shows an annual change of -2.84 ppb +/-0.8 ppb from 2012-2020 (R-squared 0.90) and an estimated reduction of 56% for 2012-2020, despite substantial increases in O&G production. Local CH4 enhancement is strongly correlated with surface measurements of ethane at Platteville which is in the center of the O&G fields (correlation coefficient 0.96), and this is evidence that reductions in O&G emissions are driving reductions in CH4. We conclude that AIRS CH4 can be used to measure the efficacy of emissions control programs in this region and that regulatory requirements are having an effect.

Synthesis of Satellite and Surface Measurements, Model Results, and FRAPPÉ Study Findings to Assess the Impacts of Oil and Gas Emissions Reductions on Maximum Ozone in the Denver Metro and Northern Front Range Region in Colorado

“…NASA AIRS satellite-derived annual DDJB methane enhancement data for June-August 2011-2020 and median annual Platteville ethane for 2012-2020 were acquired from a data repository (Reddy & Taylor, 2022b) created in support of the paper by Reddy and Taylor (2022a). In the current study these are compared with annual fourth maximum O 3 and O&G VOC emissions estimates to determine if decreases in O&G VOC emissions are reflected in O 3 trends.…”

“…The datasets used in this study include calculated DDJB methane enhancement data for June-August and median annual Platteville ethane for 2012-2020 from a data repository (Reddy & Taylor, 2022b), AIRS Methane and OMI Tropospheric NO 2 data from the NASA Giovanni website (https://giovanni.gsfc.nasa.gov/giovanni/), ethane, O 3 , and NO 2 monitoring data from the CDPHE Air Pollution Control Division (https://www.colorado. gov/airquality/tech_doc_repository.aspx), O 3 and NO 2 data from the EPA (https://aqs.epa.gov/aqsweb/airdata/ download_files.html), monthly methane data for Niwot Ridge from the NOAA Global Monitoring Laboratory (https://gml.noaa.gov/), and NCEP Reanalysis data from the NOAA Physical Sciences Laboratory (https://psl.…”