9/15/14, "Well Leaks, Not Fracking, Are Linked to Fouled Water," NY Times, Henry Fountain
"A
study of tainted drinking water in areas where natural gas is produced
from shale shows that the contamination is most likely caused by leaky
wells rather than the process of hydraulic fracturing used to release
the gas from the rock.
The
study looked at seven cases in Pennsylvania and one in Texas where
water wells had been contaminated by methane and other hydrocarbon
gases. Both states have extensive deposits of gas-bearing shale that
have been exploited in recent years as part of a surge in domestic
energy production. Some environmental groups have suggested that
hydraulic fracturing, or fracking, could cause the gas to migrate into
drinking water aquifers.
Shale-gas
producers commonly drill a deep vertical well that is then extended
horizontally in several directions into the rock, like spokes from a
hub. In fracking, water and chemicals are injected at high pressures
into these spokes, creating fissures and releasing the natural gas
trapped within.
But in their analysis,
published Monday in The Proceedings of the National Academy of
Sciences, the researchers found no evidence that fractured shale led to
water contamination. Instead, they said cement used to seal the outside
of the vertical wells, or steel tubing used to line them, was at fault,
leading to gas leaking up the wells and into aquifers.
“In all cases, it basically showed well integrity was the problem,” said Thomas H. Darrah,
a researcher at Ohio State University and the study’s lead author. The
gas that leaked, he added, most likely came from shallower gas-rich
pockets that the vertical wells were drilled through on their way to the
shale formations, rather than from the shale itself.
“The
good news is, improvements in well integrity can probably eliminate
most of the environmental problems with gas leaks,” Dr. Darrah said.
Richard J. Davies,
a professor at the Newcastle University in Britain and a petroleum
geologist not involved in the study, said it confirmed what he and
others had shown in earlier research, that the fissures created by
fracking were generally not long enough to affect aquifers."...
===================
8/12/14, "Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett
Shales," PNAS.org
"Abstract:" "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." (last sentence)
==========================
9/15/14, "Weak wells not fracking caused US gas leaks into water," BBC, Matt McGrath
"Researchers in the US analysed the gas content in 130 water wells in Pennsylvania and Texas....In none of the investigated wells was there a direct link to fracking.
"These results appear to rule out the possibility that methane has
migrated up into drinking water aquifers because of horizontal drilling
or hydraulic fracturing, as some people feared," said Prof Avner
Vengosh, from Duke University."...
.
No comments:
Post a Comment