WASHINGTON (AP) — In Pennsylvania’s gas drilling boom,
newer and unconventional wells leak far more often than older and
traditional ones, according to a study of state inspection reports for
41,000 wells.
The results suggest that leaks of methane could be a
problem for drilling across the nation, said study lead author Cornell
University engineering professor Anthony Ingraffea, who heads an
environmental activist group that helped pay for the study.
The
research was criticized by the energy industry. Marcellus Shale
Coalition spokesman Travis Windle said it reflects Ingraffea’s "clear
pattern of playing fast and loose with the facts."
The Marcellus
shale formation of plentiful but previously hard-to-extract trapped
natural gas stretches over Pennsylvania, West Virginia and New York.
The study was published Monday by the Proceedings of the National Academy of Sciences.
A team of four scientists analyzed more than 75,000 state inspections of gas wells done in Pennsylvania
since 2000.
Overall,
older wells — those drilled before 2009 — had a leak rate of about 1
percent. Most were traditional wells, drilling straight down.
Unconventional wells — those drilled horizontally and commonly referred
to as fracking — didn’t come on the scene until 2006 and quickly took
over.
Newer traditional wells drilled after 2009 had a leak rate
of about 2 percent; the rate for unconventional wells was about 6
percent, the study found.
The leak rate reached as high as nearly
10 percent horizontally drilled wells for before and after 2009 in the
northeastern part of the state, where drilling is hot and heavy.
The
researchers don’t know where the leaky methane goes — into the water or
the air, where it could be a problem worsening man-made global warming.
The
scientists don’t know the size of the leaks or even their causes and
industry officials deny that they are actual leaks. The study calls it
"casing and cement impairment," but the study’s lead author says that is
when methane is flowing outside the pipe.
"Something is coming
out of it that shouldn’t, in a place that it shouldn’t," said Ingraffea,
who has been part of a team of Cornell researchers finding problems
with fracking. Also, Ingraffea heads a group of scientists and engineers
that has criticized fracking and two of his co-authors are part of the
group.
The study didn’t discuss why the leak rate spiked.
Ingraffea said it could be because corners are being cut as drilling
booms, better inspections or the way the gas is trapped in the rock
formation.
Pennsylvania regulatory officials said their records
show that gas leaks peaked in 2010 and are on the way down again,
reflecting their efforts to stress proper cementing practices. Further
in 2011, the state focused more on unconventional wells to make leak
protection efforts "more stringent," wrote Morgan Wagner, a spokesman
for the state environmental agency.
Energy industry officials attacked the study and Ingraffea.
Chris
Tucker, spokesman for industry-supported group Energy In Depth, said
what they measured may not be leaks but state inspectors detecting
pressure buildup.
"The trick these researchers are pulling here is
conflating pressure with leakage, trying to convince folks that the
mere existence of the former is evidence of the latter," Tucker wrote in
an email.
But outside scientists, even pro-drilling ones, praised the study.
Terry
Engelder of Pennsylvania State University, a pioneering supporter of
the Marcellus fracking boom, said it shows there is plenty of room for
improving drilling safety.
"It clearly indicates that there is a
problem with the production" of the wells, said University of California
Santa Barbara engineering professor and methane expert Ira Leifer, who
wasn’t part of the study.