Editor & Publisher, Marcellus Drilling News (MDN)
Methane migration, when man-caused, is not the fault of either horizontal drilling or hydraulic fracturing, says a new study, but correctable casing issues.
Another new “study” and already the headlines have been blaring. A research team led by Ohio State University and composed of researchers at Duke, Stanford, Dartmouth, and the University of Rochester have just published their findings that methane migrates from some shale wells into local water wells.
It certainly doesn’t sound like earth-shattering news, but the headlines across the country range from “Bad fracking wells taint water, scientists find” (Sacramento Bee) to “Weak wells not fracking caused US gas leaks into water” (BBC). The media has picked up on this latest study and, depending on the view of the reporter, has spun it to either say fracking is the culprit, or fracking isn’t the culprit – and just about everything else imaginable in between. Here’s how we see it at MDN.
New Methodology Used to Analyze Methane Migration
The “big deal” and “new news” to come from this study is the methodology used by the researchers. They attempted to answer two questions: (i) Are elevated levels of hydrocarbon gases in drinking-water aquifers near gas wells natural or anthropogenic? (ii) If fugitive gas contamination exists, what mechanisms cause it?
And, how did the researchers answer those questions? By measuring the presence of noble gases and their isotopes: helium, neon and argon. It is the innovation of using the presence of noble gases that has, according to the researchers, given them ironclad assurance as to whether the methane in someone’s well is naturally occurring, or from shale drilling.
Perhaps the best starting point for understanding the research and its results is the press release issued by Ohio State University – the lead researchers who published the study (emphasis added):
A study has pinpointed the likely source of most natural gas contamination in drinking-water wells associated with hydraulic fracturing, and it’s not the source many people may have feared.
What’s more, the problem may be fixable: improved construction standards for cement well linings and casings at hydraulic fracturing sites.
A team led by a researcher at The Ohio State University and composed of researchers at Duke, Stanford, Dartmouth, and the University of Rochester devised a new method of geochemical forensics to trace how methane migrates under the earth. The study identified eight clusters of contaminated drinking-water wells in Pennsylvania and Texas.
Most important among their findings, published this week in the Proceedings of the National Academy of Sciences, is that neither horizontal drilling nor hydraulic fracturing of shale deposits seems to have caused any of the natural gas contamination.
“There is no question that in many instances elevated levels of natural gas are naturally occurring, but in a subset of cases, there is also clear evidence that there were human causes for the contamination,” said study leader Thomas Darrah, assistant professor of earth sciences at Ohio State. “However our data suggests that where contamination occurs, it was caused by poor casing and cementing in the wells,” Darrah said.
In hydraulic fracturing, water is pumped underground to break up shale at a depth far below the water table, he explained. The long vertical pipes that carry the resulting gas upward are encircled in cement to keep the natural gas from leaking out along the well. The study suggests that natural gas that has leaked into aquifers is the result of failures in the cement used in the well.
“Many of the leaks probably occur when natural gas travels up the outside of the borehole, potentially even thousands of feet, and is released directly into drinking-water aquifers” said Robert Poreda, professor of geochemistry at the University of Rochester.
“These results appear to rule out the migration of methane up into drinking water aquifers from depth because of horizontal drilling or hydraulic fracturing, as some people feared,” said Avner Vengosh, professor of geochemistry and water quality at Duke.
“This is relatively good news because it means that most of the issues we have identified can potentially be avoided by future improvements in well integrity,” Darrah said.
“In some cases homeowner’s water has been harmed by drilling,” said Robert B. Jackson, professor of environmental and earth sciences at Stanford and Duke. “In Texas, we even saw two homes go from clean to contaminated after our sampling began.”
The method that the researchers used to track the source of methane contamination relies on the basic physics of the noble gases (which happen to leak out along with the methane). Noble gases such as helium and neon are so called because they don’t react much with other chemicals, although they mix with natural gas and can be transported with it.
That means that when they are released underground, they can flow long distances without getting waylaid by microbial activity or chemical reactions along the way. The only important variable is the atomic mass, which determines how the ratios of noble gases change as they tag along with migrating natural gas. These properties allow the researchers to determine the source of fugitive methane and the mechanism by which it was transported into drinking water aquifers.
The researchers were able to distinguish between the signatures of naturally occurring methane and stray gas contamination from shale gas drill sites overlying the Marcellus shale in Pennsylvania and the Barnett shale in Texas.
The researchers sampled water from the sites in 2012 and 2013. Sampling sites included wells where contamination had been debated previously; wells known to have naturally high level of methane and salts, which tend to co-occur in areas overlying shale gas deposits; and wells located both within and beyond a one-kilometer distance from drill sites.
As hydraulic fracturing starts to develop around the globe, including countries South Africa, Argentina, China, Poland, Scotland, and Ireland, Darrah and his colleagues are continuing their work in the United States and internationally. And, since the method that the researchers employed relies on the basic physics of the noble gases, it can be employed anywhere. Their hope is that their findings can help highlight the necessity to improve well integrity.
This research was funded by the National Science Foundation, Duke University, and a gift from Duke alumni Fred and Alice Stanback to the Nicholas School of the Environment.*
MDN’s Takeaways from this Study on Methane Migration
1. This appears to be serious research that tackles an important issue. The researchers are not (from all appearances) agenda-driven. They let the science do the talking.
2. The researchers used a new innovation to help identify the “fingerprint” of methane: noble gases (helium, neon and argon). This is the crux of what’s new and different about this research versus other studies done in the past.
3. The media is sensationalizing this research by blaming fracking. However, the researchers clearly state fracking itself does not cause methane to migrate! What causes the migration, when it happens, is faulty construction of the vertical well. It has zero to do with fracking itself. The media either ignorantly or intentionally confuses “fracking” with the larger topic of “shale drilling”.
4. The media misuses the term “contamination” of water supplies. While you can argue that methane traveling into a water well is “contamination”–it’s not like chemical contamination. As the authors of the research point out–methane migration (or “fugitive” methane) is a fixable problem. Eminently fixable. Even after a well casing has failed methane leaks can be fixed and the methane will stop. You don’t die from drinking water with methane in it (i.e. “contaminated” water). You can die if the methane collects in an enclosed space and explodes when a spark or fire source occurs nearby. To say methane “contaminates” water, knowing that most people think of that word in the chemical sense, is misleading at best.
5. The study looked at two specific areas where they either knew–or suspected–methane had leaked or migrated from shale wells into local water supplies. Hey, it happens. It gets fixed. The shortcoming of this study, if we can be sold bold as to point it out, is in characterizing how often it happens. It’s easy to look for the precise area where a problem occurs and measure it–but what if there are only a very few places where it actually happens? What if, in the vast majority of cases, methane migration from faulty wells doesn’t happen? The study doesn’t answer how often well casings fail and leak methane–it only focuses on a few cases where it did happen.
6. We welcome this kind of intelligent, thoughtful, in-the-field research and applaud this group for the work they have done and continue to do. We (those of us who support shale drilling) will learn and grow and fix problems because of this kind of research. No one on “our side” of the drilling debate has ever pretended there are no problems. This industry is so fantastic precisely because year after year it gets better. We learn, we fix things, we improve the way we do things. And this type of study will further that effort. As will this one demonstrating much the same thing.
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