Former CSU student Bradley Wells (M.S. ’14) collects canister samples downwind of a well pad and measures the distance between his location and the tracer release system.
Garfield County air quality study results presented to public
Updated July 1, 2016
Data from an extensive multi-year Colorado State University study of air emissions from natural gas operations in Garfield County, Colorado have been presented publicly by a CSU research team.
Study leader Jeffrey Collett, professor and head of CSU’s Department of Atmospheric Science, presented the study results during a session of the Garfield County Board of Commissioners June 14. The presentation was streamed live and is archived on the Garfield County government website. Read the county’s news release.
The study, Characterizing Air Emissions from Natural Gas Drilling and Well Completion Operations in Garfield County, Colorado, was commissioned in 2012 by Garfield County. It was aimed at characterizing the extent of air emissions from natural gas extraction activities.
The western Colorado county contains the Piceance Basin and has some of the highest oil and gas activity in the state. Collett and other researchers, including co-principal investigator Jay Ham, CSU professor in the Department of Soil and Crop Sciences, obtained air samples for scientific data surrounding well pad activities. Air Resource Specialists, a company that offers air quality monitoring and modeling, also contributed to the project.
Garfield County contributed $1 million toward the study, which was organized through an intergovernmental agreement between CSU and the county. Approximately $700,000 in additional support came from industry gifts to CSU from Encana Corp., WPX Energy, Ursa Resources Group, Bill Barrett Corp., Caerus Oil and Gas and Laramie Energy. A technical advisory committee comprised of air quality and emission experts from government, industry, and the National Center for Atmospheric Research periodically consulted with the research team during the study, and reviewed the findings.
The CSU researchers collected and characterized emissions from three activities during new well development: drilling, hydraulic fracturing (“fracking”) and flowback – all processes typical of unconventional natural gas extraction. They quantified air emission rates and dispersion of air toxics, ozone precursors and greenhouse gases during each of these processes.
“What we have done is document the types of chemicals, and the amounts of those chemicals, that are emitted when new wells are prepared,” Collett said. “The focus was on volatile organic compounds (VOCs) that are of concern as air toxics and as precursors to ozone formation, and on methane, a potent greenhouse gas. We wanted to look at drilling, fracking and flowback, because emissions from these activities have received little prior study, especially for VOCs. The study focused on directly quantifying emissions, so that findings could be used to generate maps of concentrations for times and places of interest, under a variety of weather conditions, to examine issues like potential health or air quality impacts.”
Notably, the team observed higher rates of emission of many volatile organic compounds and methane during flowback operations than during drilling or hydraulic fracturing. Flowback is last in the chain of well completion events, and refers to water and fracking fluids flowing up from the ground after injection of water and chemicals into the well, the process known as hydraulic fracturing.
Methane, a potent greenhouse gas that has been targeted for emission reductions by the state of Colorado and the federal government, was the most abundant compound in measured emissions, with median emissions of 2.0, 2.8, and 40 grams per second (g/s) for drilling, hydraulic fracturing, and flowback activities, respectively. Other emitted VOCs of interest and their overall median emission rates included ethane (median emission rate of 0.31 g/s), propane (0.15 g/s) and other short-chain hydrocarbons that are important constituents of natural gas. They also looked at air toxics such as benzene (0.04 g/s) and toluene (0.27 g/s). Wide ranges of emissions were observed both across activity types and within a given activity.
Collett’s team was charged with quantifying emissions, but not related health risks, which were not within the scope of the project. The Colorado Department of Public Health and Environment (CDPHE) plans to use the data to conduct a human health risk assessment.
“This evaluation will improve our understanding of the potential for health risks directly attributable to air emissions from oil and gas,” said Mike Van Dyke, CDPHE branch chief of Environmental Epidemiology, Occupational Health and Toxicology.
Methods of collection
The CSU field team, led by research scientist Arsineh Hecobian, and assisted by CSU graduate students, postdoctoral researchers and scientific staff, conducted a total of 21 separate experiments from 2013-15 at various natural gas operations sites in Garfield County. Access to drilling and other operation sites, thanks to industry cooperation, was critical to gathering accurate information and was key to the study’s success, Collett said. Emission measurements were conducted at well drilling and completion sites operated by Encana Corporation, WPX Energy, and Ursa Resources Group.
The team was somewhat limited by a slowdown in new well drilling over the course of the study, but they were able to complete 21 of 24 planned experiments.
They used what’s called a tracer ratio method to identify and calculate rates of emissions of compounds of interest including methane, ethane, propane, benzene and toluene. Most experiments included measurement of emissions of a suite of 48 VOCs, plus methane.
Using acetylene as the tracer gas, the researchers designed experiments with a mobile plume tracker for real-time measurements of methane, and canisters that collected air samples for three-minute periods. They released the tracer, then located it downwind of the well pad in order to capture snapshots of typical emissions. Several sets of canisters were set up at each experiment station and later analyzed in a CSU laboratory using gas chromatography. The researchers also performed real-time sampling of methane emissions at each site, using a cavity ring-down analyzer. Continuous measurements of meteorological conditions were made during each experiment to support efforts to model dispersion of emitted pollutants downwind of the well pads.
Collett and his team are conducting a similar study of air pollutant emissions from oil and gas activity along the northern Front Range, commissioned by the state of Colorado. That study focuses on methane and VOC emissions from hydraulic fracturing, flowback, and production of oil and gas.
Anne Ju Manning