Article 5

Source: http://news.nationalgeographic.com/energy/2015/07/150723-fracking-questions-answered/

Fracking, Quakes, and Drinking Water: Your Questions Answered

We answer reader questions about the controversial method of extracting oil and gas known as hydraulic fracturing.

Hydraulic fracturing, combined with horizontal drilling, has opened up new reserves of natural gas and oil, particularly in states such as North Dakota, site of the pictured rig.

By Christina Nunez, National Geographic

PUBLISHED July 23, 2015

Does it really cause earthquakes? What about the impact on drinking water? These and other questions, including one about dinosaurs, surfaced when we asked what you want to know about fracking.

Some recognize the word as an expletive from the series Battlestar Galactica, but most know it as the more common version of frac —the industry term for hydraulic fracturing, the process used to extract oil and gas from the ground.

The controversial practice has revolutionized the oil and gas industry, leading to a U.S. energy boom. It’s also raised a lot of questions. Here are some of yours.

Quakes

User @ Quimby

Reply to @NatGeoEnergy: What do you want to know about fracking? Is fracking believed to cause or trigger Earthquakes? Or is this just a theory? 3:04 AM - 9 Jul 2015

Unknowns still exist, but there's little doubt that fracking activity does cause earthquakes, an issue raised by several readers including Quimby, above, and Michuel Nite. While quakes can be caused by hydraulic fracturing—the high-pressure injection of fluid and sand into rock, opening cracks that release oil and gas—more often, it's the underground injection of wastewater after fracking that is the culprit.

Last April, officials in Oklahoma—which saw a fivefold increase in quakes between 2013 and 2014—acknowledged the spike was likely caused by oil and gas industry's underground injections of wastewater. While Oklahoma has seen the most dramatic impact, as reader @Dawgnme notes, other states are seeing quakes from energy activity as well. The federal government has released a comprehensive analysis of the phenomenon, punctuating the risks for energy-producing states including Texas, Ohio, and Arkansas.

So if the link is established, "Why no action?" asked Afiba Johnson on Twitter. It depends on how you define action. Oklahoma's oil and gas regulator has ordered the operators of more than 500 oil and gas wastewater disposal wells to prove that they are not injecting wastewater below a certain threshold believed to boost the risk of quakes. In Colorado last year, officials temporarily halted wastewater disposal at a well in the northeastern part of the state because of temblors. Oklahoma and other states are grappling with the desire to keep oil and gas revenues flowing while preventing major damage or injuries from man-made quakes, most of which have been relatively minor.