New Duke University Study: Methane and ethane found in drinking water near natural gas wells: study, Increased stray gas abundance in drinking water wells near Marcellus shale gas extraction

New US study inflames SA’s fracking debate, A US study that links fracking to high concentrations of methane in drinking wells has sparked debate about the technique for extracting natural gas by Sarah Wild, June 28, 2013, Mail & Guardian, Africa’s Best Read

New Study: Fracking Contaminates US Water Wells by Stephen Leaphy, June 26, 2013, desmogcanada
Drinking water is being contaminated by fracking for natural gas a new US study revealed Monday. … The study’s take home message: The further your drinking water source is from fracking operations the safer it is likely to be said Robert Jackson of Duke University, the lead author of the Proceedings of the National Academies of Science study. “Distance matters when it comes to reducing the risk of water contamination,” Jackson told DeSmog. … Although the gas industry has long denied that fracking contaminates water wells and aquifers, hundreds of claims have been made over the industry’s 20 plus years of operation. Even though the use of fracking dramatically increased in the last eight years very little independent research has been done on the environmental impacts. Researchers at Duke University were the first to independently study water contamination. In 2011 they looked at 68 fracking sites in the Marcellus shale region in the northeast US. They found groundwater with methane concentrations 17 times higher than in wells located where fracking was not taking place. Some of the recorded amounts were higher than “immediate action” hazard levels.

This year Duke researchers wanted to trace back the source and cause of the water contamination. They analyzed the concentrations and special ‘chemical fingerprints’ of methane, ethane, and propane in 141 private water wells in six counties in northeastern Pennsylvania and southeastern New York. The fingerprint work is key to knowing if these gases came from natural sources or were the result of fracking.  Of the 141 water wells measured within one kilometre of drilling operations, 82% contained high levels of methane. Twelve of these wells showed “immediate action” hazard levels. About one third also had high levels of propane and ethane. Both are hazardous and flammable gases. The cause of this widespread contamination is likely poor well construction, said Jackson. Unlike conventional gas production, fracking uses very high pressures. It is likely faulty steel casings and poor cement sealing were behind the leakage into nearby waterwells he said. The study also found the older the well the more likely it is to leak.

New Alberta Report Documents Widespread Water Contamination
“The Duke study is an incredible affirmation of my work,” said Jessica Ernst, an Alberta-based environmental consultant. “The industry and the regulators know there is lots of water contamination happening but continue to lie about it to the public,” Ernst told DeSmog. “They still parrot the same lie that there never has been a case of water contamination.” An oil and gas consultant for 30 years, Ernst released a 93-page report last week documenting many cases of groundwater contamination from fracking operations. “It’s happening every where…there is plenty of proof if you know where to look,” she said. Ernst said her water was contaminated when industry giant EnCana used fracking between 2001 and 2004 near her home in Rosebud just west of Calgary. “My taps were whistling from all the gas. I could not believe I no longer had access to safe water.” She filed a $33 million dollar lawsuit against EnCana in 2007. The case is still before the courts.

Government regulators and the gas industry are “terrified” of potential liability from contaminating water that would cost them billions of dollars said Ernst. Fracking uses huge amounts of energy and water and no one has ever done a cumulative impact study of the more than 100,000 wells fracked in Alberta. Every year up to 15,000 new oil and gas wells are drilled. Albertans are fearful of speaking out against the oil and gas industry she said. “I lost my career and my former colleagues fear the same.”

“People here also believe contamination is the price of prosperity.” [Emphasis added]

Study links fracking with methane-contaminated drinking water by RT, June 26, 2013
Household drinking water that comes from wells near known fracking sites contains levels of methane six times greater than what’s common elsewhere, a new study has found. Researchers at Duke University sampled drinking water from 141 wells across northeastern Pennsylvania and southern New York and determined that the concentration of methane, the main component of natural gas, is much higher when those wells are within one kilometer of a hydraulic fracturing, or “fracking” sites. …  In addition to finding methane concentrations at around six times the usual level, Jackson also found ethane concentrations 23 times higher in drinking water at homes near fracking sites. In ten of the sites located within one kilometer of a drilling, propane was detected in 10 separate water samples.

Fire water by J.P., June 25th 2013, The Economist
New research just published in the Proceedings of the National Academy of Sciences by Robert Jackson, from Duke University, and his colleagues will add fuel to the controversy. … Concentrations of the gas in such homes were also six times higher than for those farther away. Levels of ethane and propane, other ingredients of natural gas, were higher, too. All were well above the levels the Department of Interior considers safe. The relationship cannot be put down to gasmen’s penchant for plonking their drills in spots where natural gas is most abundant in the first place. In the absence of drilling the gas, being trapped in the shale beds 1,500-2,500 metres beneath the countryside, would stay put; concentrations nearer to the surface would remain unaffected. Nor, Dr Jackson insists, did his team cherry-pick homes whose occupants complained of high methane concentrations, as some critics of his research have suggested. Finally, the analysed drilling sites were dotted more or less randomly around the Marcellus so the contamination cannot be pinned on a clutch of rule-breaking wells. … The risks have always been evident; witness all the regulation already in place. Dr Jackson’s research shows that they have not gone away. [Emphasis added]

Study finds more gas in water near Marcellus Shale wells by Laura Legere, June 25, 2013, Times Shamrock
Natural gas has likely seeped into Northeast Pennsylvania water supplies from both deep gas drilling and natural processes, researchers at Duke University reported in a paper released Monday. The article published in the journal Proceedings of the National Academy of Sciences found that methane, ethane and propane concentrations were higher in drinking water wells located within a kilometer of a gas well than in more distant water supplies. The researchers detected methane in 82 percent of 141 water wells and ethane in 30 percent of 133 sampled wells, but methane levels were six times higher and ethane levels were 23 times higher on average in the water supplies close to gas wells. The study is an expansion of a paper the researchers published in 2011 using 60 water wells, which was criticized for lacking information on methane concentrations in wells before drilling started, among other issues. This time the scientists used multiple tools, including studying carbon, hydrogen and helium isotopes, propane and ethane concentrations and the ratios of gases, to help distinguish the source of gas in water wells in Bradford, Lackawanna, Sullivan, Susquehanna, Wayne and Wyoming counties. They found evidence that some water wells may have been contaminated by gas from the Marcellus Shale while others showed signs of gas from shallower rock layers or a mixture of gas types that might come from either gas drilling or natural pathways. “Our research strongly suggests contamination with stray gas for a subset of homeowners,” said co-author Robert Jackson, a professor of environmental sciences at Duke. “Not everyone has a problem,” he said. “The emphasis should be on how to keep the problems that we’ve seen from happening in other places.” …

Regulators have determined that poorly constructed natural gas wells caused high levels of methane to seep into drinking water wells in parts of Susquehanna and Bradford counties and the state revised its drilling laws and regulations to try to prevent future problems. In other cases, including a high-profile investigation in Franklin Twp., the Department of Environmental Protection determined that high methane levels in water wells could not be attributed to natural gas drilling activity.

Researchers have also detailed the widespread natural occurrence of methane in the region’s water wells in places where drilling had not yet begun. Last week, the U.S. Geological Survey released a study of 20 randomly selected water wells in an area of Sullivan County without shale drilling and found that seven contained some naturally occurring dissolved methane with one containing enough of the gas – 51.1 milligrams per liter – to create a potential explosion risk. The methane in two wells was thermogenic – gas that comes from deep underground, not from the breakdown of biological matter near the surface.

A recently updated study by Cabot Oil and Gas Corp. contractors and employees found detectable levels of methane in 78 percent of 1,700 water wells it sampled before drilling nearby in Susquehanna County, but only 3.4 percent of those samples exceeding the state’s action level of 7 milligrams per liter for dissolved methane. It also found that high methane concentrations in water wells generally correspond to how close they are to valleys, not their proximity to gas wells. The Duke study released Monday reaches a different conclusion: The researchers found that distance to gas wells was “highly significant” in influencing the amount of methane in water wells and was “the only statistically significant factor” influencing ethane, while distance from a valley bottom or a geological deformation called the Appalachian Structural Front were less or insignificant.

Thermogenic gas does occur naturally in areas without shale gas development, the researchers found. In fact, “most of the natural methane” in the sampled wells “is thermogenic,” Dr. Jackson said. But the combination of multiple tools helped the researchers distinguish between natural seeps and man-made problems. Dr. Jackson said cases of contamination by Marcellus Shale-like gas are likely caused by structural problems with the steel casings used to keep gas in a well from seeping into aquifers, while contamination by shallower thermogenic gas is likely tied to failures in the cement that is meant to keep gases from migrating between casings or up the outside of wells.

The research did not find evidence of contamination from the gas extraction process of hydraulic fracturing, or fracking. Fred Baldassare, the state’s former stray gas inspector who now consults for industry and other clients with his firm ECHELON Applied Geoscience Consulting, said the most notable aspect of the Duke paper is the identification of “post-mature” thermogenic gas – deeply buried gases similar to those produced from the Marcellus Shale – in some of the sampled water wells. Most cases of drilling-related methane contamination have traced the thermogenic gas in water wells to shallower rock layers, not the target shale. But he said that the Duke researchers picked water wells to sample in areas with known drilling-related gas contamination so it would be wrong to conclude from their data that water wells in close proximity to gas wells are likely to be tainted by gas. “That’s not taking into consideration the thousands of gas wells that have been drilled in that area,” he said. “The percentage that don’t have gas well migration incidents is far higher than those that do. If you read their paper you wouldn’t know that.” Industry groups criticized the study for an apparent lack of random sampling and pointed out that measurable concentrations of methane were found in more than 50 sampled water wells that were not close to gas wells. “Not exactly a smoking gun,” Energy in Depth spokesman Steve Everley wrote in a blog post on the industry group’s website. [Emphasis added]

Gas drilling taints groundwater, Chemical analysis links methane in drinking wells to shale-gas extraction by Jeff Tollefson, June 25, 2013, Nature 498, 415–416 (27 June 2013) doi:10.1038/498415a
“The problems we’ve seen are probably more common than people realize,” says Rob Jackson, director of Duke’s Center on Global Change and lead author of the paper. … The study is the latest salvo in an ongoing debate about the environmental impacts of shale-gas extraction, which has transformed the US energy landscape and is now moving abroad. Such operations are also causing concerns about air pollution and methane emission, which could offset some of the climatic benefits of replacing coal with natural gas. But fears about the potential impact on ground­water resources have taken centre stage in a number of high-profile disputes between scientists, regulators and industry. Last week, for example, the US Environmental Protection Agency (EPA) cancelled its probe of groundwater contamination in Pavillion, Wyoming, more than two years after issuing a controversial draft report pinpointing fracking as the cause. The decision leaves the investigation in the hands of state officials, who had criticized the EPA’s assessment. And in Dimock, Pennsylvania, which lies in the area covered by the Duke research, allegations of ground­water contamination led state regulators to halt some drilling operations temporarily in 2009 and to fine the primary operator, Cabot Oil and Gas Corporation of Houston, Texas, which settled a lawsuit out of court but did not admit fault. … The data “raise important issues”, says Mark Zoback, a geophysicist at Stanford University in California, who served on a high-level panel that in 2011 recommended improving industry practices to minimize environmental impacts. “There’s a real need in the future to have this kind of sampling before, during and after shale-gas development.” Officials from Cabot, which operates most of the wells in this area, declined to comment on the study. [Emphasis added]

New Duke study bolsters finding of water contamination from drilling by Mike Soraghan, June 24, 2013, E&E News
Natural gas is commonly found in drinking water wells in northeastern Pennsylvania, but a new Duke University study says there’s a lot more of it near Marcellus Shale gas wells. The study expands on a 2011 Duke study that shook the world of shale drilling by offering the first peer-reviewed findings correlating drilling and contaminated drinking water (Greenwire May 9, 2011). It is also a response to an industry study that discounted the Duke findings by deeming methane in the area’s drinking water “ubiquitous” (EnergyWire, May 31).  The team, which also includes researchers from the University of Rochester and California State Polytechnic University, sampled 81 new drinking water wells in six counties in northeastern Pennsylvania. It combined the data with results from 60 previously sampled wells in Pennsylvania and included a few wells in New York’s Otsego County. The researchers detected methane, the principal component of natural gas, in the drinking water of 82 percent of the 141 homes. Concentrations were six times higher in homes within a kilometer (about 3,300 feet) of natural gas wells, the study found. Of 12 houses where the concentration of methane were greater than the federal threshold for immediate remediation, 11 homes were within the 3,300-foot radius. The only exception was a house 1.4 kilometers (4,600 feet) from a well. The study also found that ethane and propane were more common closer to wells. They are both components of natural gas but are found in the deep shale gas that drillers want. They are not found in the shallow, “biogenic” gas that is commonly found in well water supplies. “Our observed values within 1 kilometer of drilling seem to rule out a biogenic methane source,” states the peer-reviewed study, authored by Duke biology professor Rob Jackson and released today by the journal Proceedings of the National Academy of Sciences. The original Duke study was criticized by the oil and gas industry and state regulators. Industry figures said that without knowing methane concentrations in the water wells before drilling occurred, the study couldn’t draw a solid link between drilling and methane contamination.

Methane found in drinking water near natural gas wells: study by Deborah Zebarenko, June 24, 2013, The Globe and Mail
Elevated levels of methane, ethane and propane gases were found in drinking water wells in Pennsylvania, close to operations that shake natural gas loose from underground shale formations in a process known as fracking, scientists reported on Monday. Detection of contaminated drinking water suggests the gas wells are leaking, according to Robert Jackson of Duke University, lead author of a study published in the Proceedings of the National Academy of Sciences. An industry group disputed these findings, saying that methane occurs naturally in water in this area. … Based on analysis of 141 drinking water wells in northern Pennsylvania that sit atop a natural gas-rich underground formation called the Marcellus shale, Mr. Johnson and his colleagues found 82 per cent of drinking water samples contained methane, with concentrations six times higher for homes within 1 kilometre of natural gas wells than for homes farther away. Ethane concentrations were 23 times higher for homes close to natural gas wells; propane was detected in 10 drinking water wells, also within 1 km of a natural gas well. “We found much higher concentrations of methane, ethane and propane in people’s drinking water within one kilometre of the shale gas wells,” Mr. Jackson said by telephone. “What that means to me is that those gases are leaking out of the wells and into the shallow aquifers.” He noted that no fracking chemicals or radioactivity were detected in drinking water wells.

“The researchers found methane in virtually every water well they sampled, irrespective of its proximity to gas drilling. They suggest a link to Marcellus gas wells, but pre-drill testing in the same part of the state directly contradicts them,” Steve Everley of Energy in Depth said in an e-mail response to questions about the study. Energy in Depth is a program of the Independent Petroleum Association of America that focuses on shale and fracking. Fracking operations in the Marcellus shale – which takes in Pennsylvania, New York, Ohio and West Virginia – are often more than a 1.5 km deep, while aquifers are only a few hundred feet underground, Mr. Everley said. This indicates, he said, that there is no direct leak from where the gas is being extracted up through the rock. Instead, it is more likely that in some cases, the wells are leaking closer to the shallower drinking water sources. Mr. Jackson said little is known about long-term health effects from methane and other gases in drinking water, and the Environmental Protection Agency does not regulate methane in drinking water. [Emphasis added]

Drinking water contaminated by gas near fracking sites in US, Households within a kilometre of shale gas fracking wells could be at higher risk of having their drinking water contaminated by flammable gases, a study suggests by Nick Collins, June 24, 2013, The Telegraph
A study of 141 drinking water samples from bore holes in Pennsylvania found higher levels of methane, ethane and propane in those within a kilometre of shale gas fracking sites. … The study will also raise concerns about the risk of explosions if pockets of methane are able to form in pipes. … The new study, by researchers from Duke University in North Carolina, found that levels of methane were six times higher at homes within a kilometre of a shale gas well. Ethane levels, although much lower than those of methane, were 23 times higher in homes within a kilometre of drilling sites than those further away. … The gas most likely made its way into drinking water wells after escaping through cracks in the casing of underground gas chambers, or through faults in the cement which seals the gaps between the casing and rock, they said. Robert B Jackson, a professor of environmental sciences who led the study, said the new findings “All suggest that drilling has affected some home owners’ water”. … Stuart Haszeldine, professor of sedimentary geology at Edinburgh University, said the amounts of gas found to be escaping are “undesirable, but not fatal”, and future fracking attempts in Britain should be carefully analysed. “This is a really strong piece of evidence that some methane, ethane and propane have moved from the deep gas formation into the drinking water formation,” he said. [Emphasis added]

Fracking linked to well water methane by Dan Vergano, June 24, 2013, USA Today
Drinking water wells near natural gas “fracking” sites were six times more likely to be contaminated than others, finds a new study of New York and Pennsylvania homes. … In a new study released Monday by the Proceedings of the National Academy of Sciences, a research team led by Robert Jackson of Duke University sampled 141 drinking water wells across northeastern Pennsylvania and southern New York. All of the fracking wells were in northeastern Pennsylvania. The results add to a 2011 study that first linked closeness to fracking wells to drinking water contamination with methane. “it is looking like we are seeing a problem with well construction in some places and not others,” Jackson says. Along with finding methane more likely to be contaminating drinking water wells within about 1,000 feet of fracking sites, the study found propane in 10 nearby wells. Ethane gas was 23 times more likely to be seen in homes similarly close to fracking sites. The ethane and propane are signatures of fracking, Jackson says. The gases probably escaped from leaks in the steel or concrete casing lining the uppermost part of the natural gas wells, called the wellbore. … There was no evidence of wide-scale leaks of methane far from the fracking sites beyond naturally occurring amounts seen in recent U.S. Geological Survey reports from the region. [Emphasis added]

Fracking a risk to drinking water – study by AFP,  June 25, 2013
The ethane and propane contamination data are “new and hard to refute,” Professor Jackson said. “There is no biological source of ethane and propane in the region and Marcellus gas is high in both, and higher in concentration than the Upper Devonian gas found in-between,” he said in a statement.

Fracking raises risk of contaminated drinking water by Agence France-Presse, June 24, 2013, Global Post
Hydraulic fracturing…has been banned in other countries such as France due to environmental concerns.

Contaminated Home Wells Found Near Pa. Fracking Site: Study by Dennis Thompson, June 24, 2013, HealthDayNews
Homes that are close to fracking sites are at higher risk of having their drinking water contaminated by combustible gases, according to a new study. … They detected methane in 82 percent of the drinking water samples, with the average concentrations six times higher for homes less than one kilometer — about six-tenths of a mile — from a natural gas well…. In the study, which was strongly disputed by the oil and gas industry, the scientists also found higher concentrations of ethane and propane in drinking water wells less than six-tenths of a mile from shale gas drilling. … “We were surprised to find such high concentrations, but we were also surprised to see such a strong effect of proximity to gas wells,” said Robert Jackson, a professor of environmental sciences at Duke’s Nicholas School of the Environment. Jackson added that there is no biological source of ethane and propane in the region, which makes the Marcellus wells the chief suspect for the contamination. The risk of fire and explosion is the main public health risk from the presence of these gases in drinking water, said Dr. Georges Benjamin, executive director of the American Public Health Association in Washington, D.C. “These are volatile gases and in particular concentrations, they burn,” Benjamin said. “If they leak into your home and build up, particularly in enclosed spaces, there’s an explosive risk.” … Jackson believes the contamination is the result of faulty well construction, with gases escaping from flaws in either the steel tubing or the concrete seal that surrounds the tubing. “We don’t think the gases are migrating up through thousands of feet of rock to contaminate ground water,” he said. “If the well isn’t sealed properly with cement, you can have gas from thousands of feet down move up the outside of the well and into people’s drinking water without ever seeing natural gas leak out from the Marcellus.”

Industry spokesman Jim Smith criticized what he called key flaws in the Duke study. For example, he noted that the water samples were not taken randomly, but from wells chosen by the researchers in cooperation with homeowners’ associations and other local contacts. Smith, a spokesman for the Independent Oil and Gas Association of New York, added that the researchers found no fracking fluid in the contaminated wells. “If the methane that was found in the water was a result of fracking, then certainly frack water would be found in those wells as well, and they found no evidence of that,” he said. Smith also doubted that poor well construction would be involved in the contamination, citing the stringent regulations adopted by the state of Pennsylvania to regulate gas drilling. Jackson argues that flaws in the concrete seal would allow gas to migrate while still preventing leakage of fracking fluid. [Emphasis added]

Fracking can increase methane in drinking water, study finds by Neela Banerjee, June 24, 2013, LA Times
Scientists have found that methane and other gases pose a significant risk of contaminating drinking-water wells near natural gas drilling, raising new questions about possible health and safety risks from the production technique known as fracking. … The gas occurs naturally in the area’s aquifers, but the study showed the chemical composition of methane in wells near the drilling sites is the same as the natural gas extracted in the area. Methane that accumulates in confined spaces such as basements and sheds poses a risk of explosion, but there is little research into the effects on human health of prolonged exposure to methane, said the study’s lead author, Robert B. Jackson, professor of environmental sciences at Duke University. … The fact that methane, ethane and propane were found in so many homes near gas wells points to “problems with multiple independent gas wells,” Jackson said. … Of the 59 homes, a dozen had water wells with methane concentrations greater than 28 milligrams per liter of water, which the Interior Department has identified as the threshold for immediate remediation of a well. “When the methane concentrations are that high, the water can bubble like champagne,” Jackson said. [Emphasis added]

Study reveals fracking can cause water pollution by Sarah Wild, June 24, 2013, Mail and Guardian Africa’s Best Read
“Little research has been conducted on the health effects of drinking methane contaminated water.” [Emphasis added]

Natural gas found in drinking water near fracked wells by John Roach, June 24, 2013, NBC News
“That is the point of the ethane and propane analyses in the paper,” Jackson said. “Those are gases that are not generated by microbes” that can live in the ground and affect well water. … The biggest known risk of high methane concentrations in drinking water is an explosion or fire due to the buildup of the gas in a confined space such as a basement or a shed, Jackson noted. “The flip side of that is the Environmental Protection Agency doesn’t regulate methane in drinking water, so we really don’t know much about the health risks.”

Naturally occurring methane is “ubiquitous” in water wells throughout the study region, Steve Everley, with the natural gas industry group Energy-in-Depth, writes in a blog post that characterizes the new study as full of flaws. Chief among them, Everley argues that methane is ubiquitous in the region, and that the Duke University research team found methane in water wells “nowhere near natural gas wells.” The group also notes that the new research does not find evidence of fluids used during fracking in the groundwater. “On that point, at least, we’re happy to agree with them,” Everley writes. Radisav Vidic is a civil and environmental engineer at the University of Pittsburgh who recently conducted a review study of the scientific literature about environmental issues related to hydraulic fracturing. The new research, he told NBC News, will “help us to better understand the whole picture of potential risks,” related to the fast-evolving industry. But, he added, there is a lack of background data on these drinking water wells from before the onset of drilling for comparison. So, the findings of higher methane contamination near natural gas drilling is “not a direct proof” of a link, he said. “We don’t have the data from before the industry came to town.” Jackson and his team are trying to build this baseline data, which requires greater disclosure from the natural gas industry through the release of well records, for example, so researchers can compare the chemical signature of the methane, ethane and propane they find in drinking water with the natural gas wells. [Emphasis added]

Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction by Robert B. Jackson, Avner Vengosha, Thomas H. Darraha, Nathaniel R. Warnera, Adrian Down, Robert J. Poreda, Stephen G. Osborn, Kaiguang Zhao and Jonathan D. Karr, approved June 3, 2013 (received for review December 17, 2012), in Proceedings of the National Academy of Sciences of the United States of America. PNAS 2013 : 1221635110v1-201221635.
Overall, our data suggest that some homeowners living <1 km from gas wells have drinking water contaminated with stray gases. … We present comprehensive analyses for distance to gas wells and ethane and propane concentrations, two hydrocarbons that are not derived from biogenic activity and are associated only with thermogenic sources.

Dissolved methane was detected in the drinking water of 82% of the houses sampled (115 of 141). Methane concentrations in drinking water wells of homes <1 km from natural gas wells (59 of 141) were six times higher on average than concentrations for homes farther away…. Of 12 houses where CH4 concentrations were greater than 28 mg/L (the threshold for immediate remediation set by the US Department of the Interior), 11 houses were within 1-km distance of an active shale gas well…. The only exception was a home with a value of 32 mg CH4/L at 1.4-km distance. Similar to the results for methane, concentrations of ethane…and propane…were also higher in drinking water of homes near natural gas wells (Fig. 1). Ethane was detected in 40 of 133 homes (30%; 8 fewer homes were sampled for ethane and propane than for methane). …

Casing leaks can arise from poor thread connections, corrosion, thermal stress cracking, and other causes (43). If the protective casing breaks or leaks, then stray gases could be the first sign of contamination, with less mobile salts and metals from formation waters or chemicals from fracturing fluids potentially coming later. In contrast, faulty cement can allow methane and other gases from intermediate layers to flow into, up, and out of the annulus into shallow drinking water layers. In such a scenario, the geochemical and isotopic compositions of stray gas contamination would not necessarily match the target shale gas, and no fracturing chemicals or deep formation waters would be expected, because a direct connection to the deepest layers does not exist; also, such waters are unlikely to migrate upward. [Emphasis added]

[Refer also to:

US EPA suddenly delays fracking study on risks to groundwater two years until 2016

Fracking company Encana suspected of contaminating ground water at Pavillion Wyoming, takes control of investigation, EPA refuses to finalize study blaming fracking for water pollution

Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing ….we document systematic evidence for methane contamination of drinking water associated with shale-gas extraction. In active gas-extraction areas (one or more gas wells within 1 km), average and maximum methane concentrations in drinking-water wells increased with proximity to the nearest gas well and were 19.2 and 64 mg CH4 L-1 (n = 26), a potential explosion hazard; in contrast, dissolved methane samples in neighboring nonextraction sites (no gas wells within 1 km) within similar geologic formations and hydrogeologic regimes averaged only 1.1 mg L-1 (P < 0.05; n = 34). … Based on our groundwater results and the litigious nature of shale-gas extraction, we believe that long-term, coordinated sampling and monitoring of industry and private homeowners is needed. Compared to other forms of fossil-fuel extraction, hydraulic fracturing is relatively poorly regulated at the federal level. … More research is also needed on the mechanism of methane contamination, the potential health consequences of methane, and establishment of baseline methane data in other locations. We believe that systematic and independent data on groundwater quality, including dissolved-gas concentrations and isotopic compositions, should be collected before drilling operations begin in a region, as is already done in some states. Ideally, these data should be made available for public analysis, recognizing the privacy concerns that accompany this issue. Such baseline data would improve environmental safety, scientific knowledge, and public confidence. ]

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