Several prior posts have noted the greenhouse impact of methane (aka natural gas); it has many times the warming effect as carbon dioxide (CO2), which seems to be the focus of so much discussion about global warming. The posts have focused on the numerous "natural" sources of methane emissions (e.g., methane hydrates [Arctic seafloor and wetlands], plants, sheep, cattle and their feed). See, for example, http://www.epa.gov/methane/sources.html. Now, forthcoming studies suggest that natural gas wells may pose a risk due to "leakage" of methane into the atmosphere.
The researchers note that the problem is that planet-warming methane, the primary component of "natural gas", is escaping into the atmosphere in far larger quantities than previously thought. The researchers posit that as much as 7.9% of it is escaping from shale gas wells (e.g., intentionally vented or flared, or seeping from loose pipe fittings along gas distribution lines). This may very well offset natural gas's most important advantage as an energy source: it burns cleaner than other fossil fuels and releases lower carbon dioxide emissions. Needless to say, industry spokespersons dispute the size of the leakage issue.
This assertion comes on top of a report in January by the nonprofit journalism organization ProPublica which noted that the Environmental Protection Agency had recently doubled its estimates for the amount of methane that is vented or lost from natural gas distribution lines. See http://www.propublica.org/article/natural-gas-and-coal-pollution-gap-in-doubt. [Criticism of this report can be found at http://www.energyindepth.org/2011/01/propublica%E2%80%99s-fuzzy-math/.]
Of course natural gas provides other benefits, besides the GHG emission issues noted. Combustion of natural gas produces far fewer aerosols and particulates, which as noted in prior posts have significant adverse human health impacts.
Even so, if the benefits of methane (natural gas) are to be realized, this "leakage" problem needs to be addressed.
A pre-print version of the report (along with some correspondence) can be found at http://184.108.40.206/scholar?q=cache:jS8ORqlfuSgJ:scholar.google.com/+natural+gas+methane+leakage+wells+pipelines+greenhouse+gas+global+warming+%22robert+howarth%22&hl=en&as_sdt=0,5.