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 it?

    Fracking is short for "hydraulic fracturing," and the catch-all term used to describe the process of extracting oil and natural gas from shale rock formations deep underground. The process goes roughly like this: A company drills down more than a mile deep into the shale rock formations. Then comes what is known as "horizontal drilling" - effectively, the drilling turns 90 degrees, so that the well is exposed to more rock than it would be otherwise.

    After the well is reinforced with concrete, tubes with perforating guns are sent down to set off explosions that create perforations in the rock surrounding the well. Then millions of gallons of "fracking fluid" - a mixture of water, sand and chemicals - is pumped down into the well at high pressure. The pressure builds up in the well, and the rock fractures. That frees the oil and gas that had been trapped within the rock, which flows back up through the pipe to be captured above ground. The process is repeated multiple times, with much - though not all - of the fracking fluid brought back up through the well.

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