Energize Weekly, June 27, 2018
The leak rate of methane emissions from oil and gas operations is about 60 percent higher than federal estimates, according to a study published June 22 in Science magazine.
The findings are based on measurements taken at more than 400 well pads in six basins and midstream facilities, as well as aerial surveys over oil and gas operations and infrastructure.
The study found that the leak rate of methane, a potent greenhouse gas, was 2.3 percent, putting 13 million metric tons of the gas into the air each year. The federal Environmental Protection Agency (EPA) has calculated the leak rate at 1.4 percent.
The work was done by 24 researchers from universities and government research labs under the auspices of the Environmental Defense Fund (EDF).
“Scientists have uncovered a huge problem, but also an enormous opportunity,” Steven Hamburg, EDF’s chief scientist, said in a statement. “Reducing methane emissions from the oil and gas sector is the fastest, most cost-effective way we have to slow the rate of warming today, even as the larger transition to lower-carbon energy continues.”
There are two ways of calculating emissions, the study said. The “bottom up” approach measuring leaks and emission on the ground from equipment and then extrapolating the result across the basin. The other approach, the “top down,” measures total emission using airplanes or other aerial devices. This study used both methods.
The largest source of emissions was from production sites, followed by gathering infrastructure. The researchers also measured emissions from processing, transmission and storage, local distribution, refining, and transportation.
The EDF study calculated emissions were higher than those of the EPA for production, gathering, processing and transmission, and storage.
The researchers said the likely reason for the discrepancy is that “the existing inventory methods miss emissions released during abnormal operating conditions.”
For example, an analysis of site-scale emission measurements in the Barnett Shale “concluded that equipment behaving as designed could not explain the number of high-emitting production sites in the region.”
An extensive aerial infrared camera survey of more than 8,000 production sites in seven oil and gas basins found that about 4 percent of surveyed sites had one or more observable high emission rate plumes.
“Emissions released from liquid storage tank hatches and vents represented 90 percent of these sightings,” the paper said. “It appears that abnormal operating conditions must be largely responsible, because the observation frequency was too high to be attributed to routine operations.”
“This paper is consistent with the fact that methane emissions were low,” Erik Milito, the American Petroleum Institute’s upstream group director, said in a statement. “The industry has achieved continued emissions reductions thanks in large part to technology advancements and this innovation has been fundamentally important to our shared goal to reduce emissions.”
Milito said that methane emissions are down 14 percent since 1990, while at the same time natural gas production has increased more than 50 percent.
Some producers are moving ahead with programs to reduce fugitive emissions. For example, in April, BP set its first quantitative methane target, and in May, ExxonMobil committed to cut methane emissions.
