5 things you need to know about fracking    • With AFP Story by
Veronique DUPONT: US-Energy-Gas-Environment A Consol Energy
Horizontal Gas Drilling Rig explores the Marcellus Shale outside
the town of Waynesburg, PA on April 13, 2012. It is estimated
that more than 500 trillion cubic feet of shale gas is contained
in this stretch of rock that runs through parts of Pennsylvania,
New York, Ohio and West Virginia. Shale gas is natural gas
stored deep underground in fine-grained sedimentary rocks. It
can be extracted using a process known as hydraulic fracturing ?
or "fracking" ? which involves drilling long horizontal wells in
shale rocks more than a kilometre below the surface. Massive
quantities of water, sand and chemicals are pumped into the
wells at high pressure. This opens up fissures in the shale,
which are held open by the sand, enabling the trapped gas to
escape to the surface for collection. AFP PHOTO/MLADEN ANTONOV
(Photo credit should read MLADEN ANTONOV/AFP/Getty Images)
MLADEN ANTONOV      What is