What Is Fracking?

Опубликовано: 29 Январь 2015
на канале: BrainStuff - HowStuffWorks

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You’ve heard of fracking, and you’re pretty sure lots of people don’t like it, but do you know how it actually works?

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Fracking. You’ve heard of it. You know it’s controversial. But you might not know what it actually involves. Never fear: We’re here to put some fracking knowledge in your brain.

Fracking is the delightfully cheeky-sounding nickname for Hydraulic Fracturing... which sounds a little bit less delightful and more like something you do to your enemies in Starcraft. But no! It is something we do to rocks.

In the simplest terms, hydraulic fracturing is a way of getting more of the valuable fluids, like oil and natural gas, out of geologic formations under the ground.

Deep under earth’s surface, there are deposits of rock that have huge reserves of oil and natural gas within them. But these fossil fuels aren’t like big lakes where you can just stick a straw in and suck. No, these reserves of oil and natural gas are found locked up in pores distributed throughout vast layers of rock, like shale. So how do you get them out at a reasonable pace?

Let’s look at a typical fracking setup for something like shale gas: You start with a deep, vertical well, drilling a hole down to the level of the shale you want to mine.

The depth will vary, but just for example, one company claims its average fracking well depth is 7,700 feet. That’s deep: almost one and a half miles, or about 2.3 kilometers.

When you’re at the right depth, you take a 90-degree turn and continue to drill horizontally, parallel to the target rock layer. This horizontal section of the well can also travel thousands of feet. Now here’s where the “fracturing” comes in.

First, you open up holes in the horizontal section of the pipe. Then, you vigorously push a liquid cocktail known as fracking fluid down into the borehole under high pressure.

This fracking fluid is usually a mixture of water, some chemical additives -- like acids to help dissolve the rock, and gels to thicken the fluid -- and finally, solid particles called proppants – we’ll get to those in a second.

When the mixture reaches the horizontal section of the pipe, it bleeds out through the holes into the surrounding rock, and the extremely high pressure causes the rock to form tons of little fractures, or cracks. Through these cracks, the reserves of fossil fuels contained in the rock can escape into the well to be pumped back up to the surface.

What once was entombed in ancient rock is now on the way to powering your car or heating the water for your next shower. And those proppants I mentioned, which are often just grains of sand, help “prop” the cracks in the rock open, so the Earth’s precious bodily fluids continue to escape into the well without the miners applying continuous pressure.

So that’s how it works, but then there’s the entirely separate question of whether fracking is a good idea. It’s controversial in many parts of the world.

Some people claim it consumes too much fresh water, and worry about what will be done with the fracking fluid after it’s been used. And some opponents wonder if it will create earthquakes, or cause chemical contaminants to leak into our groundwater.

SOURCES:

http://science.howstuffworks.com/envi...

http://education.nationalgeographic.c...

http://www.bbc.com/news/uk-14432401

http://www.britannica.com/EBchecked/t...

http://geology.utah.gov/surveynotes/g...

http://www.bfenvironmental.com/pdfs/C...