Title:

Air Quality Trends of Oil and Natural Gas Emissions in the Northern Colorado Front Range

Authors:

Detlev Helmig¹, Gabriel Greenberg¹, Dani Caputi¹, Michel Stahli¹, Gunnar W. Schade²

¹ Boulder AIR LLC, Boulder, Colorado, USA; ² Texas A&M University, College Station, Texas, USA

Presentation summary: 

The Colorado Denver-Julesburg Basin is the fifth-largest oil and natural gas (O&G) producing region in the United States. Most recent production growth has occurred in Weld County, north of Denver, where oil production doubled between 2014 and 2019. During this period, drilling and production activities increasingly expanded into populated areas of the Northern Colorado Front Range (NCFR), raising concerns among residents and local governments regarding air quality and public health. In response, Colorado has implemented a series of regulations intended to reduce emissions from O&G operations and mitigate their impacts. This study evaluates long-term atmospheric measurements to assess changes in primary O&G-related pollutants and resulting air quality trends.

We investigated atmospheric methane, nonmethane hydrocarbons (NMHCs), and nitrogen oxides (NOₓ) using multiple observational datasets, including continuous surface measurements from local monitoring programs, canister samples collected by the Colorado Department of Public Health and Environment, and tropospheric ethane column observations from the National Center for Atmospheric Research. Data were filtered by air-mass origin using wind direction and back-trajectory analyses to enhance sensitivity to O&G emissions. The filtered records were analyzed with a NOAA trend analysis tool to quantify seasonal, annual, and multi-year concentration trends. We also evaluated changes in NMHC/NOₓ relationships to assess potential shifts in the contribution of O&G emissions to regional photochemical ozone production.

Methane concentrations increased throughout the study period but at a slower rate than observed for the regional background atmosphere. In contrast, O&G-associated hydrocarbons, particularly ethane and propane, generally exhibited declining atmospheric concentrations across monitoring sites and measurement platforms, although the magnitude of the decline varied spatially. Several datasets also suggest that these decreases have slowed or plateaued during the most recent two to three years, indicating that further reductions in O&G emissions may have diminished.

Overall, the observations indicate that atmospheric concentrations of O&G-derived hydrocarbons have declined despite relatively stable production levels in recent years. These findings suggest that emissions intensity (i.e., emissions per unit of oil and gas produced) has improved over time, likely reflecting the cumulative effects of emission control measures and operational changes. However, the apparent recent stabilization of hydrocarbon concentrations may indicate that further progress in reducing emissions has slowed.

Presenter bio:

Dr. Helmig has 30 years of experience with atmospheric data collection and modeling. Most recently, his research has focused on Northern Colorado Front Range regional air quality monitoring and research, contracted by local governments including Boulder County, the City of Longmont, the Town of Erie, and the City and County of Broomfield. He also served as Co-P.I. on two Health Effects Institute-funded research projects investigating oil and gas emissions and their air quality impacts in the Permian Basin. Dr. Helmig has contributed to over 240 peer-reviewed publications, with over 20 of these specific to air quality in the Rocky Mountain West.