Industry cautions that some methane hotspots caused by non-oil and gas activities, such as landfills and natural seeps
A new NASA study of methane emissions in the Four Corners region of the United States finds that just 10 per cent of the methane sources are contributing half of the emissions. Industry calls the study a “good start” but points out there is still more work to be done before scientists fully understand the problem.
In an extensive airborne survey, a NASA-led team has analyzed a “hot spot” of methane emissions in the Four Corners area, quantifying both its overall magnitude and the magnitudes of its sources, NASA said in a press release.
Scientists used two JPL airborne spectrometers to identify and measure more than 250 individual sources of methane. The sources emitted gas at rates ranging from a few pounds to 11,000 lbs. per hour.
NASA initiated its study after satellite images captured from 2003-2009 visually depicted the region with methane levels about 50 parts per billion (ppb), or 3 per cent, above common background levels of approximately 1,800 ppb. NASA’s study estimated methane levels from sites in New Mexico and Colorado from April 17-24, 2015.
Results are published this week in the Proceedings of the National Academy of Sciences in a paper titled “Airborne methane remote measurements reveal heavy-tail flux distribution in Four Corners region.” Christian Frankenberg of the Jet Propulsion Laboratory and Caltech is the lead author.
The experiment was a proof of concept for airborne detection of methane, according to Frankenberg.
“That we could observe this distribution in a widespread geographical area and collect enough plumes to perform a statistical analysis was a pleasant surprise,” he said.
The measurements represent a snapshot in time, focused only on oil and natural gas sites and not other known human and natural methane sources in the area, according to a statement released by a group of oil and gas industry associations (La Plata County Energy Council, New Mexico Oil & Gas Association, Western Energy Alliance, Colorado Oil & Gas Association, Colorado Petroleum Council).
The groups called the study a good first step but narrow in scope compared to other pending studies that are expected to provide more comprehensive analysis. Several other studies are underway that will include on-the-ground measurements of all sources of methane in the Four Corners area, including coal mines, landfills and natural seeps. Those studies are being conducted by the National Oceanic and Atmospheric Administration (NOAA), the University of Colorado and the University of Michigan in conjunction with NASA.
“The study represents a snapshot in time that can provide valuable information, but is not suitable for extrapolation to monthly, annual or other longer-term emissions estimates,” said Christi Zeller, executive director of the La Plata County Energy Council.
“Certain operational events, such as scheduled maintenance downtime, are temporary and can skew results. For example, one gas plant was measured five times, with one outlier measurement that occurred during a scheduled maintenance event.”
Steve Henke, president of the New Mexico Oil & Gas Association, says that natural methane seeps occur throughout the area from the Fruitland Formation outcrop.
“Also, the topography of the area traps air and causes methane to build up over time, whether from human or natural sources,” said Henke.
There is a built-in economic incentive for producers to minimize emissions and capture as much methane as possible, since it’s the very product they sell, says Kathleen Sgamma, vice president of government and public affairs for Western Energy Alliance.
“Natural gas producers have reduced emissions 15 per cent since 1990 even as production has increased 54 percent. Natural gas is the primary reason the United States has reduced greenhouse gas emissions more than any other country,” she said.
Oil and natural gas production has taken place in the Four Corners’ San Juan Basin since the 1940s. In the northwestern New Mexico portion, there are nearly 20,000 active natural gas wells and just under 2,000 oil wells. About 140 operators produced 646 Bcf of natural gas in 2015, according to the associations.
In the southwestern Colorado portion, there are approximately 3,400 active wells, about two-thirds of which are coalbed methane (CBM) and one-third conventional natural gas wells. About 34 operators produced 337 Bcf of natural gas in 2015.
