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Anatomy of a Gas Well

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Several layers of steel casing typically enclose a well bore. The empty spaces between can be sealed with cement.

un-naturalgas.org

May 4, 2009, 9:44 p.m.

Thanks for the diagram.

Viewers should be cognizant of the fact that by necessity such illustrations are not to scale.  What looks sturdy in any diagram such as this one is actually thin and fragile in relation to its length.

Also, such diagrams illustrate how the process is designed to work when all goes as intended, so generally don’t show the many fissures and fractures in the surrounding rock, into which concrete can be lost when the casing is being cemented. These gaps and fractures can make it extremely difficult and in some cases impossible to properly cement the casing, leading to the groundwater contamination and gas migration incidents that we’re hearing more and more about.

This article is part of an ongoing investigation:
Fracking

Fracking: Gas Drilling's Environmental Threat

The promise of abundant natural gas is colliding with fears about water contamination.

The Story So Far

The country’s push to find clean domestic energy has zeroed in on natural gas, but cases of water contamination have raised serious questions about the primary drilling method being used. Vast deposits of natural gas, large enough to supply the country for decades, have brought a drilling boom stretching across 31 states. The drilling technique being used, called hydraulic fracturing, shoots water, sand and toxic chemicals into the ground to break up rock and release the gas.

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