Revisiting a Questionable Study on Shale Gas and Methane Leaks

For those of us who pay attention to the ongoing question over “methane leakage” from shale development, it was hard to ignore the headlines earlier this month:

  • Los Angeles Times: “EPA drastically underestimates methane released at drilling sites”
  • E&E News: “Significant methane leaks found from wells still in drilling process – study”
  • “Study raises new concerns about emissions from shale gas wells”
  • Huffington Post: “Methane Emissions From Gas Wells Up To 1,000 Times Higher Than Federal Estimate: Study”

These headlines, among others, were describing research published in the Proceedings of the National Academy of Sciences, which looked at emissions data collected during a series of flyovers in southwest Pennsylvania (EID’s response to the study can be found here). Based on that data, the research team suggested shale gas wells were leaking significant quantities of methane, as much as 1,000 times higher than U.S. EPA estimates. The presence of methane with a particular fingerprint (a low ratio of propane to methane) led the researchers to conclude that the gas was coming from coal bed reservoirs, and was thus “leaking” during the drilling phase, not the completion phase (i.e. hydraulic fracturing).

What was largely overlooked, however, is that area monitored – southwest Pennsylvania, chiefly Greene County – is also the largest coal producing region in the entire state. A variety of laws dictate that coal mines must have methane ventilation systems to prevent explosion and to protect workers. The researchers did make note of the coal mines, but the discussion was largely stuffed away in the supplemental information.

Last week, Andy Revkin at the New York Times investigated the situation a bit further: if the researchers had identified coal bed methane as the culprit, then why was so little attention paid to the coal mines? It was a question that apparently few if any reporters bothered to ask once the press release hit their inboxes. The release, it should be noted, omits any mention coal mines.

First of all, Revkin actually identified the affiliations of the authors; most of the coverage limited those descriptions to little more than just “scientists.” For example, Anthony Ingraffea and Robert Howarth are referenced as “prominent foes of fracking,” and Renee Santoro is with Physicians Scientists & Engineers for Healthy Energy, of which Ingraffea is a member as well. PSEHE is described as “a nonprofit group that has been critical of fracking” (the executive director of PSEHE took issue with Revkin’s initial characterization of PSEHE as an “anti-fracking group”). To be clear, these affiliations are not in and of themselves enough to suggest the research is bogus. But it’s more than reasonable to demand that researchers who oppose or are critical of a process they are studying be identified as such to otherwise unsuspecting readers.

Revkin also had a more measured response to what the study actually concluded in the context of our understanding of methane leaks:

Much of the news coverage and commentary was greatly oversimplified, implying that airplane measurements taken on two days in 2012 and showing high methane levels over a handful of wells (and nothing unusual over almost all the other wells in the region) pointed to an extraordinary new pollution and climate change risk. A case in point was this Climate Central post: “Huge Methane Leaks Add Doubt on Gas as ‘Bridge’ Fuel.”

In fact, the study is consistent with other recent work covered here that shows there are specific and tractable issues that can be addressed… (emphasis added)

Revkin’s comments about the study being fully consistent with our current understanding (i.e. “issues that can be addressed”) were not an anomaly, either. Fred Krupp, president of the Environmental Defense Fund, and former New York City Mayor Michael Bloomberg – both of whom have made reducing greenhouse gas emissions a top priority – wrote in the New York Times today that the concerns associated with shale gas development and methane leaks are, in fact, manageable. As Krupp and Bloomberg put it:

“This is essentially a data acquisition and management problem — the kind that we know we can solve.”

Manageable risk doesn’t mean no risk, of course, and Krupp and Bloomberg did a decent job outlining the steps that individual state regulatory agencies – often working with industry and environmental groups alike – have taken to address concerns, ranging from water testing requirements to well integrity and air emissions.

The most important part of Revkin’s piece, however, was his outreach to another expert: Dr. Louis Derry, a geologist at Cornell University. Derry’s takeaway is quite nuanced, and includes a call for additional monitoring of local air chemistry before and after drilling to get a better handle on air emissions. But he made some other noteworthy observations, including:

“The local area they identify as anomalous has a number of coal mining operations, also a potentially large source of methane… Underground coal mines (active and abandoned) are routinely vented to prevent mine explosions.  There are other routes for coal gas to escape, including fractures or undocumented structures from legacy mines and abandoned wells.”

“…one well pad appears to be the source of a methane plume, since only background methane was observed upwind but anomalous levels were found just downwind. A nearby circuit showed higher methane upwind of a pad than downwind, indicating a source outside the target area, possibly from nearby mine vents. On another of their flights, a very strong gas anomaly showed up near a well pad that was also near a coal mine. The mine signal is so strong that it’s not possible to resolve any contribution from the well pad. These results give an indication of the complexity of gas sources in the area.”

“The drilling phase is transient, and even if there are high leak rates as the drill penetrates coal-bearing strata they are likely to persist for a matter of days, or at most until the well is cased, usually a couple of weeks.  One way to assess their magnitude is to use the instantaneous flux, which implies a large effect from the newly identified sources. But if these sources are only active for a week or two, their integrated impact drops substantially. The headlines to the effect that “gas leaking at 1,000 times E.P.A. estimates” might be true in a very narrow sense but do not reflect the transient nature the process.  And it may turn out that at least some of this flux is not the result of shale gas drilling at all.” (emphasis added)

Revkin took Derry’s criticisms to Prof. Paul Shepson at Purdue University, the lead author of the PNAS paper released last week, which is available on YouTube. Shepson disputed Derry’s suggestion that the methane could have been coming from sources other than the well pads, although his defense of that point was more dismissive than substantive. Nonetheless, Shepson said during the interview that methane leakage “is a solvable problem,” and that increased use of natural gas “has a very big human health benefit” by reducing certain localized air emissions such as sulfur dioxide. In watching the video, Shepson comes across as a fairly honest broker on the issue, and certainly a far cry from some of the activists who co-authored the paper.

One issue that did not come up in that conversation was the total volume of leaked gas that would correspond to the “plumes” identified in the study. Derry said that the leakage rates identified would be equivalent to “about a million cubic feet a day,” which not only is a large amount of gas, but should also raise some serious red flags. A well leaking that much gas would not escape the notice of workers on the drilling rig, and would in fact sound comparable to a freight train running through the well pad. If that much gas were coming out of the well during the drilling phase, it would likely have to be flared.

In other words, the assumption that wells were losing that much gas through “leaks” is at best highly questionable – and yet, it forms the core of what was reported to the public.

After the release of the study, we also discovered one potential reason why the headlines were so eye-popping: some of the authors wanted them to be.

Physicians Scientists & Engineers for Healthy Energy, an anti-fracking group a group critical of fracking with offices in Ithaca, N.Y., and Oakland, Calif., sent out an email from its executive director to its members on Friday, April 18, that bragged in the subject line: “1 week, 3 new studies.” The email detailed the methane study, as well as two other papers on health risks related to shale development. The opening paragraph was remarkable in its honesty:

“This has been a very big week for PSE Healthy Energy and I wanted to tell you all about it! Three peer-reviewed articles written or co-authored by PSE staff and leadership have been released over the past 4 days and are changing energy headlines across the U.S. and the world. Your generous support today can help us to reach even more media sources and to generate and translate more critical studies.” (emphasis added)

PSEHE had just gotten a study published in one of the most respected scientific journals in the United States, and its executive director was bragging first and foremost about the “headlines” they generated. Even worse, he proceeded to plead for money – not primarily to fund more research, but to “reach even more media sources.”

It’s difficult to say from this email whether last week’s study on methane “leaks” was premised on securing headlines and capturing media attention (especially since the lead author is not a member of PSEHE), or whether engaging in the difficult scientific discussion over shale development played second fiddle to PSEHE’s primary interest. But you have to give credit to PSEHE for a job well done. Unfortunately, that “good job” is also likely the reason why the shortcomings in the study — and, by extension, key facts about what the study does and does not tell us — were given such short shrift.


  1. Stecher, DG says:

    A million cubic feet per day well leak? That rig and crew would never work again anywhere in our basins. Think of the revenue waste alone and the explosive conditions.


  1. [...] there are numerous reasons to be wary of the findings of this study, it does a service to the industry highlighting how beneficial actions are that trap methane in the [...]

  2. [...] it worse than coal, but that hyperbole has been countered by numerous authorities. See here, here and [...]

Speak Your Mind