How Hydraulic Fracturing Works

The type of natural gas drilling proposed to access Utica Shale formations is unique for its depth, vertical as well as horizontal nature, and the use of hydraulic fracturing techniques.  Click on the graphic below to enlarge details of hydraulic fracturing.

© Copyright 2012 Thomson Reuters (http://blog.thomsonreuters.com/index.php/hydraulic-fracturing-fracking-graphic-of-the-day/)

First, a vertical well is drilled to a depth of about 6000-8000 feet.  Parallel horizontal drills originate from this vertical depth and are situated to optimize the geology of the natural fracture patterns.  Each horizontal drilling length is typically about 4500 feet (but can reach 12000 feet).  A mixture of water (3-7 million gallons per well), sand, and chemical additives is then injected under high pressure to fracture the shale, freeing the natural gas for extraction.  The sand helps to hold the fractures open, while the chemical additives prevent bacterial build-up and mineral deposits, scale and rust.

Watch a short video detailing the hydraulic fracturing process in Chesapeake Energy natural gas operations.

Hydraulic fracturing requires vast amounts of water.  After fracturing, the majority of the water and additives remains underground, but a small percentage returns to the surface as flowback through the vertical well bore.  This water not only contains the chemical additives (or frac fluid), but also may contain dissolved salts and naturally occurring radioactive elements and heavy metals dislodged from the shale deposits during fracturing.  Flowback must be disposed of through deep well injection on site or elsewhere or transported to a treatment facility.  Read more about the details of hydraulic fracturing at http://www.earthworksaction.org/issues/detail/hydraulic_fracturing_101#.ULesdeRlW8A and http://fracfocus.org/hydraulic-fracturing-how-it-works/hydraulic-fracturing-process.

After fracturing the well, flaring or a controlled burning of the produced natural gas is sometimes utilized to determine well pressure and until flow and pressure is stabilized.  Read more about flaring at the Ohio Environmental Protection’s website http://www.epa.state.oh.us/portals/0/General%20pdfs/gas%20flaring.pdf.