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Bakken wells drove a sudden reversal of global decline in ethane emissions

REUTERS/Andrew Cullen
The emissions measured over the Bakken are 10 to 100 times larger than producers have been reporting to regulators, according to research published Friday in the journal Geophysical Research Letters.

Oil and gas production in North Dakota’s Bakken formation is the key culprit in a worldwide rise  in atmospheric levels of a potent greenhouse gas that also contributes to ozone formation near the Earth’s surface.

Moreover, the emissions measured over the Bakken are 10 to 100 times larger than producers have been reporting to regulators,  according to research published Friday in the journal Geophysical Research Letters.

The gas at issue is ethane, a hydrocarbon that ranks No. 3 behind carbon dioxide and methane as a driver of the greenhouse effect and global warming. Also of concern is its contribution to poor air quality when it reacts with sunlight and other atmopheric chemicals to create eye- and lung-irritating ozone, which can be harmful to certain crops and has heat-trapping properties of its own.

According to an announcement from the University of Michigan, where the paper’s chief author, Eric Kort, teaches in the department of climate and space sciences and engineering:

Globally, the atmosphere’s ethane levels were on the downswing from 1984 to 2009. The gas gets into the air primarily through leaks in fossil fuel extraction, processing and distribution. Scientists attributed its declining levels to less venting and flaring of gas from oil fields and less leakage from production and distribution systems.

But in 2010, a mountaintop sensor in Europe registered an ethane uptick. Researchers looked into it. They hypothesized that the boom in U.S. oil and gas brought about by hydraulic fracturing could be the culprit — even a continent away.

Ethane concentrations have been increasing ever since.

Huge surges in production

Zeroing in on the Bakken, where oil and gas production have surged in the last dozen years – oil production went 3,500-fold from 2005 to 2015, while gas went up by a factor of 180, with the sharpest increases coming after 2009 — the researchers flew over its oil fields in a light aircraft equipped with air-sampling gear.

Their measurements, made over a 12-day period in May 2014, determined that the Bakken’s ethane output to the atmosphere amounted to about a quarter-million U.S. tons per year. From the paper (with citations and some technical notes omitted, and emphasis added):

This estimate indicates that the growth rate in emissions from the Bakken alone reached a sustained level in 2012 … sufficient to cancel half the average long-term decline rate in global ethane emissions.

This is consistent with the hypothesis that the large increase in U.S. oil and gas production has led to a reversal in the declining atmospheric ethane burden, and highlights the disproportionate role played by the Bakken region, which represented only 2% of shale gas production in the U.S. in May 2014 and yet emitted 1-3% of total global ethane emissions.

The very heavy composition of raw gas in the Bakken shale helps explain the relatively high emissions. Other shale plays in the U.S. have notably lower ratios [of ethane to methane].   

One of many compounds that make up natural gas — second only to methane in volume at the wellhead — ethane is also a significant byproduct of oil refining. It escapes from leaky drilling, storage and transport equipment, and large amounts are who deliberately vented in the course of extraction, even though it has value in making a variety of industrial chemicals required for manufacturing plastics (think polyethylene).

In the Bakken, the researchers say, their sampling found an ethane/methane mix indicating that most of the emissions arrived in the atmosphere as raw gas, not byproducts of processing operations.

A byproduct of fuels production

Worldwide, energy production accounts for about two-thirds of atmospheric ethane; natural seeps and miscellaneous sources, like big forest fires, add the rest.

The Kort team’s finding as to the ethane/methane ratio over the Bakken,  according to a good piece in the Washington Post, “could have big implications for future methane assessments.”

In many oil and gas fields, methane is often the primary natural gas present — sometimes accounting for up to 90 percent or more of the gas that is released during extraction. Ethane often tends to be present in smaller proportions. In the Bakken, however, the researchers found that ethane accounted for nearly 50 percent of all the natural gas composition, while methane was closer to 20 percent.

This is important because researchers sometimes use trends in global ethane emissions to make assumptions about the amount of methane that’s being released by fossil fuel-related activities. While it’s possible to measure the total methane concentration in the atmosphere, it’s difficult to say exactly where that methane came from, because there are so many possibilities: thawing permafrost in the Arctic, emissions from landfills and agriculture are just a few examples.

 But because ethane is primarily emitted as a byproduct of fossil fuel development — and because methane and ethane tend to be emitted together in those cases — researchers sometimes use trends in global ethane emissions to make assumptions about how much of the Earth’s methane output can be attributed to oil and gas development.

According to the Associated Press, the Kort study has the attention of the U.S. Environmental Protection Agency, which has had its own difficulties arriving accurate estimates of methane emissions; a spokesman said the findings were under review and added that a tightening of federal limits on methane emissions ought to help with the ethane problem as well.

Detection “a game changer’

And North Dakota’s top environmental health official said the state has bought a new camera that detects otherwise invisible gases at the source leak, adding that he thought companies weren’t necessarily venting the stuff deliberately.

“It’s a game changer,” Dave Glatt told the AP. “A lot of the companies thought they were in good shape, and they looked through the camera and saw they weren’t.” 

The Kort paper notes that production in the Bakken has slowed somewhat since their surveys, which presumably would also bring a reduction in ethane emissions.

And while ozone formation downwind from drilling zones was happening at fairly slow rates during the study, because of cold springtime temperatures, they suggest that ethane plumes could push communities out of compliance with federal air quality standards in warmer months.

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The paper, “Fugitive emissions from the Bakken shale illustrate role of shale production in global ethane shift,” can be read here without charge.

Comments (5)

  1. Submitted by Neal Rovick on 05/03/2016 - 02:30 pm.

    As the price of oil and gas fall the economics of capturing releases becomes worse.

    If natural gas is worth a 1/3 of what it was 10 years ago and costs of capturing are twice what it was–how much effort do you think that will be put into capturing escaping gases ? And if you don’t have a pipeline to a wellhead, what are you going to do? I would tend to think that there is not a whole lot of effort or expenses going into capturing stray gases, no matter what the volume.

    And given the current strategy of pumping more in the face of falling prices worldwide, I would think we are making the release of CO2 and it’s equivalents much worse.

    The current CO2 level is around 404 ppm, and CO2-equivalents (like ethane) is around 480 ppm.

    It’s getting really hard to see how 2 degrees C is a meetable goal.

  2. Submitted by Connie Sullivan on 05/03/2016 - 04:35 pm.

    When is somebody going to penalize the oil and gas companies for letting these gases “leak”? They will continue to hem and haw until the government hits them in the pocketbook with fees and fines that HURT. They have not bothered with fixing or capping “leaks,” which are gigantic (enough to push the global levels of ethane and methane and ozone up again!!!), and yet all the companies that “leak” these gases dangerous to earth get federal subsidies of all kinds to . . . help their businesses.

    Of course, this is just another scientific study that indicates business abuses of the earth, and all good Republicans will block their eyes, ears, and minds to it. And block any government action.One despairs.

  3. Submitted by Neal Rovick on 05/03/2016 - 09:07 pm.

    Certainly no connection with drought in India and 21,000 wildfires in the Himalaya mountains this spring….

    Or 90 degree temps and massive wildfire in Ft. Mc Murray Alberta (home of tar sands!) forcing the evacuation of 60,000 people…

    Or China’s shipping line to use the Northwest Passage through the Arctic Ocean thereby saving transit time…

    Or this year’s hailstorm damage from 2 March storms is already more than a year’s average loss, and does not count damage from a larger April storm…

    on and on.

    You don’t need a weatherman
    To know which way the wind blows

  4. Submitted by Mike martin on 05/03/2016 - 10:30 pm.

    Increase demand for natural gas by switching trucks and buses to burning natural gas or methane instead of diesel from oil.

    Cars could burn natural gas too. But converting the US fleet of cars to natural gas could take decades.

    Increase demand for natural gas by allowing oil companies to export it. Current US laws severely limit the export of oil or natural gas. Less consumers have to pay $4/gal for gas.

    One major cause of low natural gas prices is opposition to building new pipelines.

    • Submitted by Neal Rovick on 05/04/2016 - 09:36 am.

      Natural gas is also a hydrocarbon and its use produces carbon dioxide. It is estimated that going to natural gas for a fuel will lower emitted CO2 by about 10%.

      That 10% reduction is offset by leakages that occur in the system, to the extent that leaks exceed the cow as the largest producer of greenhouse gas.

      There is far more natural gas available around the world than can be used, so this has the real depressing effect on the price of gas.

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