Stray gases found in water wells near shale gas sites

Jun 24, 2013

Homeowners living within one kilometer of shale gas wells appear to be at higher risk of having their drinking water contaminated by stray gases, according to a new Duke University-led study.

Duke scientists analyzed 141 drinking water samples from private water wells across northeastern Pennsylvania's gas-rich basin. Their study documented not only higher methane concentrations in drinking water within a kilometer of drilling—which past studies have shown—but higher ethane and propane concentrations as well.

Methane concentrations were six times higher and ethane concentrations were 23 times higher at homes within a kilometer of a shale gas well. Propane was detected in 10 samples, all of them from homes within a kilometer of drilling.

"The methane, ethane and propane data, and new evidence from hydrocarbon and helium isotopes, all suggest that drilling has affected some homeowners' water," said Robert B. Jackson, a professor of environmental sciences at Duke's Nicholas School of the Environment. "In a minority of cases, the gas even looks Marcellus-like, probably caused by faulty well construction."

The ethane and propane contamination data are "new and hard to refute," Jackson stressed. "There is no biological source of and propane in the region and Marcellus gas is high in both, and higher in concentration than the Upper Devonian gas found in-between."

The team examined which factors might explain their results, including topography, distance to gas wells and distance to . "Distance to gas wells was, by far, the most significant factor influencing gases in the drinking water we sampled," said Jackson.

The peer-reviewed findings will appear this week in the online Early Edition of the Proceedings of the National Academy of Sciences.

, also called hydrofracking or fracking, involves pumping water, sand and chemicals deep underground into horizontal at high pressure to crack open hydrocarbon-rich shale and extract natural gas. Accelerated shale gas drilling and hydrofracking in recent years has fueled concerns about contamination in nearby drinking water supplies.

Two previous peer-reviewed studies by Duke scientists found direct evidence of methane contamination in water wells near shale- sites in northeastern Pennsylvania, as well as possible connectivity between deep brines and shallow aquifers. A third study conducted with U.S. Geological Survey scientists found no evidence of contamination from shale gas production in Arkansas. None of the studies have found evidence of contamination by fracking fluids.

"Our studies demonstrate that distances from drilling sites, as well as variations in local and regional geology, play major roles in determining the possible risk of groundwater impacts from shale gas development," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School. "As such, they must be taken into consideration before drilling begins."

"The helium data in this study are the first from a new tool kit we've devised for identifying contamination using noble gas isotopes," said Duke research scientist Thomas H. Darrah. "These tools allow us to identify and trace contaminants with a high degree of certainty."

Explore further: Groundwater unaffected by shale gas production in Arkansas

More information: "Increased Stray Gas Abundance in a Subset of Drinking Water Wells Near Marcellus Shale Gas Extraction," Robert Jackson, Avner Vengosh, Thomas Darrah, Nathaniel Warner, Adrian Down, Robert Poreda, Stephen Osborn, Kaiguang Zhao, Jonathan Karr. Proceedings of the National Academy of Sciences, Online week of June 24, 2013. www.pnas.org/cgi/doi/10.1073/pnas.1221635110

Related Stories

Fracking risks to ground water assessed

May 17, 2013

(Phys.org) —Extraction of "unconventional" gas from sedimentary rocks such as shale could provide a clean energy source and help some regions to become energy independent, but concerns have been raised ...

Analysis of fracking wastewater yields some surprises

Jan 22, 2013

Hydraulically fractured natural gas wells are producing less wastewater per unit of gas recovered than conventional wells would. But the scale of fracking operations in the Marcellus shale region is so vast that the wastewater ...

Recommended for you

New research on Earth's carbon budget

6 hours ago

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 8

Adjust slider to filter visible comments by rank

Display comments: newest first

VENDItardE
2.2 / 5 (14) Jun 24, 2013
if they didn't test the wells prior to fracking then this study is useless.
antialias_physorg
3.8 / 5 (13) Jun 24, 2013
if they didn't test the wells prior to fracking then this study is useless.

Not necessarily. If they can also show that wells sited within reach of shale gas deposits where no drilling is going on have lower concentrations on average then that is good enough.

A longitudinal study would have been better, but a cross-sectional study can still give you solid statistical results.
NikFromNYC
2.3 / 5 (9) Jun 24, 2013
Methane is the new radon? Well, sure, but it's not toxic or radioactive, so it's quite green isn't it?
PPihkala
2.3 / 5 (3) Jun 25, 2013
Methane is the new radon? Well, sure, but it's not toxic or radioactive, so it's quite green isn't it?

Methane is worse greenhouse gas than CO2. So it is very non-green. Would you like to have methane or ethane in your drinking water? I don't think so.
GSwift7
2.3 / 5 (4) Jun 25, 2013
if they didn't test the wells prior to fracking then this study is useless.
Not necessarily. If they can also show that wells sited within reach of shale gas deposits where no drilling is going on have lower concentrations on average then that is good enough


You could both be right. These situations vary greatly from one place to the next. You need to know specifics of the geology where the water was pumped from in order to determine if either of you are correct. You really need to evaluate each site in its own context, as they are all different. Petro gases can seep up through the ground for thousands of years in small amounts and get into deep ground water. Pumping ground water out can trigger that deep ground water to seep up into the higher water table. This is fairly common, and it's no coincidence that petro wells are drilled in areas where gas is contaminating water. In some cases, fracking can also 'cure' a contamiation problem by removing gas pressure.
antialias_physorg
3.7 / 5 (3) Jun 25, 2013
These situations vary greatly from one place to the next. You need to know specifics of the geology...You really need to evaluate each site in its own context

The wider spread your study the less susceptible to local bias. At some point it's just a matter of statistical power and the right test. Since they're not doing a multivariate analysis and have already over 100 samples the statistical power could well be acceptable if a similar number of wells were tested in other regions with similar deposits nearby.

Statistics is a frightfully complex subject:
There are tests (you may have heard of these in school: like "student T-test" or "F-test", or...).
There are test for the tests (to see if you used the right test according to your test subject's distribution).
There are tests for THESE tests for the tests.
There are even tests for the tests for the tests for the tests (at which point it gets really crazy - but which is still important in e.g. financial mathematics).
TheGhostofOtto1923
1 / 5 (3) Jun 25, 2013
The wider spread your study the less susceptible to local bias. At some point it's just a matter of statistical power and the right test
Sorry but g is correct. Engineering studies take into consideration a wide variety of parameters which resist generalization. That is why they cost lots of money and take a long time to perform.

No examples of fracking contamination from depth has yet been presented however. Contamination is most likely from leaky well casings and surface spills.

"An EPA report released on Monday reaffirms that fracking is not contaminating drinking water supplies. The Washington Times reported,

After a 16-month investigation, state regulators Monday said that natural gasfracking, contrary to highly publicized claims, isn't to blame for high methane levels in three families' drinking water in a northern Pennsylvania town."
GSwift7
1 / 5 (1) Jun 25, 2013
Statistical date of this type can tell you if further study is needed, and it looks like it is here. Since the data shows a trend, they need to see what the specifics are. If there are certain conditions where fracking causes contamination, then they can test for those conditions before allowing a permit.

What has me baffled is that I grew up in that area, and there aren't very many people on well water up there. That's a fairly densely populated area and municipal water is the norm. The house I lived in couldn't have a well or a septic tank because the front yard had bedrock a few feet under it, and that's common in shale country up there.

More news stories

Magnitude-7.2 earthquake shakes Mexican capital

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.