Posted July 8, 2015
Before getting into the latest in a series of research studies on energy-related methane emissions, it’s important to stay focused on the big picture – this one:
The chart above, based on data from EPA’s Greenhouse Gas Inventory Report published this spring, shows that net methane emissions from natural gas production fell 38 percent from 2005 to 2013 – even as natural gas production rose dramatically. Also: Methane emissions from hydraulically fractured natural gas wells declined 79 percent from 2005 to 2013, EPA found.
That’s the appropriate context for 11 new studies just published in the scientific journal Environmental Science & Technology, reporting research in the Barnett Shale play in North Texas. The studies follow others coordinated by the Environmental Defense Fund (EDF). One released in 2013 found that methane emissions from natural gas drilling were a fraction of previous estimates. Another released earlier this year found that that vast majority of natural gas facilities – from the production phase to distribution via inter- and intra-state pipeline networks – recorded methane loss rates of below 1 percent.
The Barnett Shale studies released this week also show low leakage rates, largely due to industry efforts to capture emissions of a marketable commodity:
Barnett Shale O&G wells produced 5.6 Bcf day – natural gas and 54.5 Mbl oil and condensate day − in October 2013. Assuming a constant production rate and weighted average gas composition of 88.5% methane by volume, our O&G emission estimate is equivalent to 1.2% (1.0−1.4%) of gas production. If oil production site emissions (4% of O&G total) are excluded, then the natural gas leak rate decreases to 1.1% (1.0% − 1.3%).
The 1.2 percent leakage rate is significant because EDF has estimated that an emissions rate of 3.2 percent is the point where the environmental advantage of natural gas in power generation is negated. The 1.2 percent leakage rate also is below the 1.6 percent rate cited by EDF as the point where compressed natural gas-fueled vehicles are a viable component of a climate strategy. API Upstream Group Director Erik Milito:
“Even as oil and natural gas production has risen dramatically, methane emissions have fallen thanks to industry leadership and investment in new technologies. Emissions will continue to fall as operators innovate and find new ways to capture and deliver more methane to consumers, and existing EPA regulations are working.”
Now, let’s briefly discuss researchers’ claim that the studies showed methane emissions 50 percent higher than EPA’s estimates. Katie Brown at Energy In Depth explains that comparing the studies’ “top-down” measurements collected from flying aircraft over the Barnett Shale to “bottom-up” measurements collected by EPA might not be valid:
The problem with that approach is that the researchers are taking EPA’s methane data for the entire country and prorating them in terms of how many compressor stations, processing facilities, wells, and other equipment are in the Barnett Shale. To put it another way, they’re using national data to estimate what the data would be for the Barnett Shale, then comparing their “top-down” measurements against their own assumptions. EDF has long contended that it’s not appropriate to argue that methane emissions in different shale producing areas are uniform, due to the presence of “super-emitters.” Indeed, that’s what many of today’s studies also suggest. Yet by prorating national data, and assuming emissions rates for the entire nation are indicative of the Barnett Shale specifically, that’s exactly what the researchers themselves are doing. It’s possible that Barnett emissions rates are higher or lower than what the researchers assumed, which could have a significant impact on whether they can claim their data show leakage rates “50 percent higher” than EPA.
So, again, focus on the larger picture noted above – falling methane emissions amid climbing natural gas production. The larger story is that emissions reductions are occurring, mainly because industry wants to reduce them. Earlier this year Howard Feldman, API senior director of regulatory and scientific affairs, said industry has “every incentive” to reduce emissions and provide more natural gas to consumers:
“We’re making remarkable progress reducing emissions, and this progress will continue as operators detect and seal leaks – including leaks from the few high emitting sites … Burdensome new regulations would only interfere with our progress reducing emissions and jeopardize production of the clean-burning natural gas that has helped drive U.S. carbon emissions to near 20-year lows.”
ABOUT THE AUTHOR
Mark Green joined API after a career in newspaper journalism, including 16 years as national editorial writer for The Oklahoman in the paper’s Washington bureau. Mark also was a reporter, copy editor and sports editor. He earned his journalism degree from the University of Oklahoma and master’s in journalism and public affairs from American University. He and his wife Pamela live in Occoquan, Va., where they enjoy their four grandchildren.