MDN In-depth: New Duke Study on Brine Migration into Aquifers

Duke UniversityGrad students at Duke University have issued a new “peer-reviewed” paper/study/report, this time addressing the question of whether or not fluids from thousands of feet down in the Marcellus Shale layer can actually migrate upward through thousands of feet of solid rock and contaminate groundwater aquifer supplies. The new study is titled, “Geochemical evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania.” A full copy is embedded below for MDN subscribers.

You may recall more than a year ago the same Duke department issued a study looking at whether or not methane migrates from natural gas drilling to local groundwater supplies and concluded that where’s there’s drilling, there’s an increase in methane migration (see this MDN story).

So is this “the other shoe dropping” from Duke? The final nail in the coffin that proves anti-drillers have been right all along?

The first thing that MDN noticed when researching the current Duke study, which was published yesterday on the website of the Proceedings of the National Academy of Sciences (PNAS), is that the news media runs the spectrum in their reaction and analysis. It’s really quite amusing. Take a look at the search results when searching Google News for “Duke study Marcellus”:

Google Search - Duke study Marcellus

Depending on the source you read, this new study shows fracking wastewater does find it’s way to drinking water supplies, it doesn’t find it’s way there, it may find it’s way there, only natural (and not Marcellus drilling) brine finds it way there, or the findings of the report are “mixed.”

In reading various accounts of the report, and in reading the report itself, this is what MDN editor Jim Willis believes is what is said by the report:

  • There is such a thing as brine or salty water that exists thousands of feet below the surface of the earth. This brine “at depth” is naturally occurring.
  • In Duke’s research, they found some (but not widespread) instances where naturally occurring brine water has affected groundwater aquifers.
  • However, there was no correlation with natural gas drilling. That is, there is no statistically higher instance of brine contaminating aquifers near active Marcellus Shale drilling than away from active drilling. Ergo, the brine they did find was not coming from Marcellus drilling activity but was from natural sources.
  • But (and it’s a big “but” for the Duke researchers), the fact they found some naturally occurring brine in some locations leads them to theorize there are fractures that can reach from thousands of feet down up to or near the surface—they reach far enough to create a hydraulic pathway “from the depths” to surface aquifers.
  • Their further theory is that some geographies, like valleys, may be more susceptible to brine migration than other areas.
  • And the gajillion dollar question for Duke: how slowly, or how quickly, does brine (natural or manmade) migrate? They don’t know, but they want to try and figure it out.

Perhaps you can see how different people can lift different bits out of the report and proclaim the report says wastewater migration to the surface either does or could or does not happen because of drilling.

A chief criticism of the earlier Duke study leveled by MDN and others is that the sample size was very small. While they’ve increased the sample size for this study, it’s still small and only looks at data from six northeastern Pennsylvania counties. Much more research needs to be done across a wider geography before authoritative conclusions can be drawn.

The pernicious (and frankly, shallow) argument that will be made is: “We just can’t be sure, maybe someday, somehow this nasty drilling wastewater sitting down there will rise up to the surface and destroy our drinking water supplies—but maybe it’ll be five or ten years, maybe 50 years, who knows?” And the default response will be: “Let’s wait another generation to get the gas. Hey, it’s been there for millennia already, what’s another 50-100 years, you greedy landowners! We need more study, more delays.” That’s how this will be spun.

The father of the Marcellus, Penn State professor Terry Engelder, was one of the peer reviewers of this paper. His recommendation to the PNAS committee was to reject the paper and not publish it. His objections include:

“I think what the Duke study did in terms of interpretation is overstepped,” he said.

Mr. Engelder disagrees with the premise that fluids used in fracking eventually could use the naturally occurring pathways to contaminate shallow aquifers.

“When a well is fractured and starts to flow, that reduces the pressure inside the Marcellus, thus generating a pressure up the well bore,” he said. “The gradient is reversed. The well then acts as a safety valve, relieving the pressure.”

The act of drilling would pre-empt the salinated water from coming up.

“They don’t have an explanation for that,” Mr. Engelder said.

He does not disagree that the pathways are naturally occurring and that they have been there for hundreds of millions of years. But, he continued, are they effective for moving brine into the groundwater?*

A copy Dr. Engelder’s letter to PNAS strongly opposing publication of the new Duke study is also embedded below.

MDN’s thoughts: Read the study for yourself. And read the articles MDN lists below, as well as Dr. Engelder’s objections letter. By reading multiple sources you’ll get a better picture of what this study does, and does not, say. And what the study’s potential strengths and weaknesses are.

*Pittsburgh Post-Gazette (Jul 9, 2012) – Findings are mixed in fracking-water study

See also:

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