A study led by the National Aeronautics and Space Administration (NASA) into methane (CH4) emissions from the Four Corners region is a good first step, but narrow in scope versus other pending studies expected to provide more comprehensive analysis, several oil and gas industry trade groups said Monday.
NASA released Aug. 15 the results of its study of methane emissions from the Four Corners, where the states of Colorado, Utah, Arizona and New Mexico meet in the United States. The study, conducted during April 2015, was initiated in response to observations by satellites that found the Four Corners region to be a hot spot of methane emissions, according to an Aug. 15 NASA press release.
The analysis, conducted using near-infrared and thermal infrared imaging spectrometers from aircrafts, identified and measured over 250 individual sources of methane, which emitted methane at rates ranging from a few pounds to 11,000 pounds per hour. The result of the study were published this week in the Proceedings of the National Academy of Sciences, Airborne methane remote measurements reveal heavy-tail flux distribution in Four Corners region.
The study found that just 10 percent of the individual methane sources are contributing half the emissions. The total point source emissions NASA found were approximately .3 Teragram/year (Tg/y), Christian Frankenberg, lead author of the study, told Rigzone.
“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, in an Aug. 15 press statement.
The Energy Council and groups such as the Western Energy Alliance, the Colorado Oil & Gas Association and the New Mexico Oil & Gas Association, noted that 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.
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. These 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.
“We look forward to the results from NOAA and the universities to provide a more complete picture of methane in the area,” Zeller commented.
For their study, researchers targeted what they saw as the largest methane enhancement from space, Frankenberg told Rigzone. Researchers did not intentionally limit their study to oil and gas sites, Frankenberg said, but just found most of the plumes over industrial facilities.
Researchers “actually also found a few natural seeps, but the majority of the big plumes came from gas extraction sites, which is why the paper focused on what we found, not what we targeted,” Frankenberg explained.
The analysis was a proof of concept experiment for the airborne detection of methane, said Frankenberg in an Aug. 15 press statement.
“That we could observe this distribution in a widespread geographical area and collect enough plumes to perform a statistical analysis was a pleasant surprise,” Frankenberg stated.
The U.S. Environmental Protection Agency (EPA) uses a process-based approach to estimate methane emissions from oil and gas facilities. This approach assumes a normal distribution of emissions for each process used in production, processing and distribution.
“In reality, the flux distribution can be heavily skewed, resulting in a heavy-tailed distribution,” researchers noted in the paper. “This suggests that a relatively small percent of the sources in a given field may dominate the overall budget.”
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