Right up the well bore itself - on the outside of the steel casing and on the outside of the cement sheath. Because the well bore is nothing but a enormous hole in the ground - that opens a pathway through every gas bearing formation that it encounters on the way to the target. And horizontal shale gas wells are ten times more likely to leak than vertical gas wells -because the well bore is that much wider and longer. What a surprise ! Who would have guessed ?
Some of the usual hair-splitting about whether the gas came from the target shale formation - or another gas bearing strata. Who the frack cares which geological epoch it came from ? The well bores leak. Over time, all of them will leak - because they are constructed of ferrous metal casings - which rusts out - and cement which cracks and shrinks allowing gas to vent up the water column in the well bore. Class dismissed.
Texas Drinking Water Tainted by Natural Gas Wells, Scientists Find
The shale-gas boom of recent years has contaminated drinking-water wells in North Texas’ Barnett Shale and the Marcellus Shale in Pennsylvania, a study published Monday concludes.
The study, by researchers from five universities, concludes that neither drilling itself nor the hydraulic fracturing that follows it is directly to blame. (A rhetorical leap of faith - since the well bore is the leak source)
Instead, gas found in water wells appeared to have leaked from defective casing and cementing in gas wells, meant to protect groundwater; or from gas formations not linked to zones where fracking took place.
The study, published in Proceedings of the National Academy of Sciences, adds to a growing body of science that examines the environmental impacts of natural gas production, which has seen a rush of drilling and processing in numerous states over the past decade.
The study’s other authors are scientists from Duke University, Stanford University, Dartmouth College and the University of Rochester.
Barnett Shale
The U.S. gas boom began a decade ago in the Barnett Shale region, which starts in West Dallas and covers about 5,000 square miles across parts of 18 counties. Texas regulators have issued 20,493 Barnett Shale drilling permits since 2005, many in residential neighborhoods.
No drilling has taken place in Dallas, although other Dallas County cities have wells.
To extract gas from shale thousands of feet below the ground, producers fracture the rock by pumping in millions of gallons of water, sand and chemicals under high pressure.
Critics say the practice poses risks of gas and chemicals leaking into water supplies. Denton residents will vote Nov. 4 on a proposal to ban fracking in that city.
The gas industry and many regulators, including the Texas Railroad Commission, defend the practice, saying fracking has revolutionized the U.S. energy mix without endangering health or the environment.
The commission had not reviewed the new study last week. “Our staff has no comment on a study they have not seen,” spokeswoman Ramona Nye said.
The researchers sought to find the origins of gas found in water wells and to determine how it got there.
They took samples from wells in which gas levels had risen over time, clustered in seven locations in western Pennsylvania’s Marcellus Shale and one in the Barnett region.
Sufficiently high concentrations of natural gas in drinking water can put harmful fumes in homes, creating the risk of a fire or explosion.
The Barnett Shale samples were taken in southern Parker County, not far from a home whose owner, Steve Lipsky, is being sued for defamation by a gas company, Range Resources. The U.S. Environmental Protection Agency has blamed the company for causing gas to infiltrate Lipsky’s water.
Isotopes studied
The university scientists analyzed water samples for amounts and isotopes of hydrocarbons and noble gases, a group of inert elements that includes helium, neon and argon. Isotopes are versions of the same element whose nuclei have the same number of protons but different numbers of neutrons.
The analysis yielded “signatures” indicating where the gas came from and how it reached the aquifers. The researchers said they believed it was the first time noble gas isotopes had been used to produce such an analysis.
In some cases, the gas came from shallower formations unrelated to fracking, said Darrah, the Ohio State researcher. In others, he said, shale gas traveled up a gas well and then leaked into the aquifer through faults in the well. (The well bore provides the pathway for the gas to leak)
But the gas “is definitely not released by hydraulic fracturing breaking out of the shale and migrating into groundwater,” he said.
If the study had found that fracking were directly releasing gas into aquifers, he said, that “could have other, later, and potentially more serious environmental implications.”
Range Resources’ defamation suit against Lipsky stemmed from his release of a home video that showed flaming water coming out of his garden hose.
A complaint from Lipsky in 2010 led to an EPA emergency order that held Range responsible for gas in Lipsky’s water well. Range, based in Fort Worth, denied that its wells were the source.
The Railroad Commission exonerated Range after a hearing in which the gas company and commission staff presented evidence, but neither Lipsky nor the EPA took part.
The EPA later withdrew its order in an agreement that was viewed as heavily favorable to the company. The EPA’s inspector general later determined that the original order had been properly issued.
Despite industry claims and misinterpretation of new study in Proceedings of the National Academy of Sciences, Americans Against Fracking released the following statement:
“There seems to be some confusion about whether the new study today in Proceedings of the National Academy of Sciences showing water contamination from shale gas extraction is good news or bad news for fracking. It’s bad news,” said John Armstrong, spokesperson for Frack Action, a member organization of Americans Against Fracking. “Some media reports indicate that this study - which linked water contamination in Pennsylvania and Texas to well integrity and cement failures - clears some fracking operations of blame. This is not accurate.
“The public rightly uses the term ‘fracking’ to refer to the whole process related to unconventional oil and gas extraction, including clearing of the land, drilling, blasting apart the bedrock, dealing with the wastewater, and more. You can’t frack without drilling, which requires wells, pipes and casings. The industry has gone to great lengths to mince words about the fracking process, but let’s be honest with the public: this study shows that the oil and gas industry contaminated people’s water.
“You can’t separate any part of the process from the inevitable leakages that happen and poison people’s water immediately or 5, 20 or 50 years down the line. As the gas industry noted in some media reports, they’ve known about these well integrity and cement failings for decades, and still haven’t figured out a way to fix it. These are inherent failures that inevitably lead to water contamination.
“The bottom line is that unconventional oil and gas extraction - the whole process, commonly known as fracking - contaminates people’s water, in addition to polluting the air, making people sick and exacerbating climate change through significant methane leaks.
“As Duke University’s Rob Jackson, co-author, said, ‘I don’t think homeowners care what step in the process the water contamination comes. They just care that their lives have changed because drilling has moved next door.’”
Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales
Thomas H. Darraha,b,1, Avner Vengosha, Robert B. Jacksona,c, Nathaniel R. Warnera,d, and Robert J. Poredae
Abstract
Horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts. Identifying the sources and mechanisms of contamination can help improve the environmental and economic sustainability of shale-gas extraction. We analyzed 113 and 20 samples from drinking-water wells overlying the Marcellus and Barnett Shales, respectively, examining hydrocarbon abundance and isotopic compositions (e.g., C2H6/CH4, δ13C-CH4) and providing, to our knowledge, the first comprehensive analyses of noble gases and their isotopes (e.g., 4He, 20Ne, 36Ar) in groundwater near shale-gas wells. We addressed 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? Against a backdrop of naturally occurring salt- and gas-rich groundwater, we identified eight discrete clusters of fugitive gas contamination, seven in Pennsylvania and one in Texas that showed increased contamination through time. Where fugitive gas contamination occurred, the relative proportions of thermogenic hydrocarbon gas (e.g., CH4, 4He) were significantly higher (P < 0.01) and the proportions of atmospheric gases (air-saturated water; e.g., N2, 36Ar) were significantly lower (P < 0.01) relative to background groundwater. Noble gas isotope and hydrocarbon data link four contamination clusters to gas leakage from intermediate-depth strata through failures of annulus cement, three to target production gases that seem to implicate faulty production casings, and one to an underground gas well failure. Noble gas data appear to rule out gas contamination by upward migration from depth through overlying geological strata triggered by horizontal drilling or hydraulic fracturing.
Whole article: http://www.pnas.org/content/early/2014/09/12/1322107111.full.pdf+html?with-ds=yes
{ 0 comments… add one now }