Page 186 - Environment: The Science Behind the Stories

70 drilling), or was it biogenic meth- In light of these findings, Osborn’s
ane produced at shallow depths team recommended more research into
Active
extraction by microorganisms (p. 543)? To methane’s underground movements,
60 areas determine this, they analyzed ratios as well as “long-term coordinated sam-
Nonactive of isotopes (p. 42) of carbon and pling and monitoring” near drilling sites.
extraction hydrogen in the methane as well as They also urged that more data should
Methane concentration (mg CH 4 /L) 40 Action level for methane from well water near drill- PNAS, critiquing the paper. Some
areas
50
be required—and made public—before
ratios of methane to other hydrocar-
drilling proceeds.
bon gases.
Several researchers wrote to
Their analyses showed that the
thought the results did not rule out
ing sites was thermogenic gas that
natural seepage or the effects of
had originated deep underground. In
30
past drilling. Some felt the fact that
contrast, methane present in small
they did not find fracking fluids in the
amounts in wells far from drilling sites
hazard mitigation
was mostly of shallow biogenic origin.
20
(US Department
not have come from hydrofracking.
Moreover, the chemistry of the natu-
of Interior)
Others complained that the sampling
ral gas in wells near drilling sites was aquifers meant the methane could
10 consistent with the chemistry of the of homeowners was nonrandom. All
Marcellus Shale formation underly- pointed out that to truly determine
ing the region. This suggested that whether fracking was responsible for
0 the methane near drilling sites likely methane in groundwater, one would
1000 2000 3000 4000 5000 6000 resulted from drilling. need to make careful comparisons
0
Distance to nearest gas well (m) Still, the Marcellus Shale lies of wells before and after drilling
1–2 km below the surface, whereas occurred.
Figure 2 Methane concentrations were the drinking water wells extend While countering most of these
far higher at water wells near gas drilling only 36–190 m underground. How complaints, Osborn’s team agreed that
sites (left end of graph) than at wells far could methane from so far down the sampling of homeowners was non-
from them (right end of graph). Data from have reached these shallow wells? random, but said this is unavoidable
Osborn, S.G. et al., 2011. Methane contamination when researchers need to seek their
of drinking water accompanying gas-well drilling Osborn’s team proposed three pos- permission for sampling.
and hydraulic fracturing. PNAS 108: 8172–8176. sible ways:
Osborn’s team agreed with its
Let’s say you are going to 1. Gas-rich solutions from deep under- critics that before-and-after com-
sample two new water wells for ground were displaced by fracking parisons of water quality in areas
methane, one just 250 m from a gas and traveled upward through existing where drilling occurred would offer
drilling site, and one 5000 m from a fractures to the shallow aquifer. (This the best way to determine whether
drilling site. Based on the data shown CHAPTER 7 • Envi R onm E n TA l Poli C y : mA king D EC i si ons A n D s olving P R obl E m s
here, predict, for each of these wells, the explanation seemed unlikely to the hydrofracking has impacts on water
likelihood that methane concentrations researchers, given that fracking fluids quality. They pointed out that such
will be above the “Action level for hazard and salty fluids from deep under- a comparison could easily be done,
mitigation.” ground had not gotten into the wells.) because the gas industry possesses
2. Fracking unintentionally created or archived data from many hundreds
enlarged fractures in shallow areas of water wells in Pennsylvania before
the range of the federal government’s far above the shale formations, drilling began. Osborn’s team pro-
defined action level for hazard mitiga- allowing gas to travel to the surface. posed that they would gladly col-
tion. Nine samples were above the (The researchers judged this expla- laborate with industry, landowners,
action level. nation unlikely but possible.) independent analysis labs, and
The team then sought to deter- 3. Some gas well casings were leaking, the Pennsylvania Department of
mine where this methane had come allowing gas pulled up from deep Environmental Protection to conduct
from: Was it thermogenic methane below to escape from the well casing a joint study using such data. To date,
produced deep underground along near the surface and infiltrate shallow the researchers have yet to receive an
with fossil fuel formation (which aquifers. (The team judged this to be agreement from the gas industry to
would suggest contamination from the most likely explanation.) conduct such studies.

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