Fuel fight: a look at the pros and cons controversial new drilling technique.
Like all extraction techniques, hydraulic fracturing, or fracking, has its pros and cons. So what is fracking, and why is it such a hot topic?
THE ENERGY DEBATE
Although researchers are working on ways to generate more energy from renewable sources like the sun, wind, and water, most of America's energy still comes from fossil fuels--oil, natural gas, and coal. New technologies like fracking are allowing oil and gas companies to access fossil fuel sources that used to be out of reach.
The U.S. imports nearly half of all the oil it uses. Canada, Mexico, and Venezuela supply most of this foreign oil. The rest comes from around the world, including politically unstable countries like Iraq.
In a time of rising gas prices and instability in the Middle East, there is general agreement that the U.S. should become more energy-independent. How we do that is a matter of debate.
The U.S. has vast oil and natural-gas reserves trapped in hard-to-reach places, but tapping into them could harm the environment.
FUEL FROM STONE
Deep underground, source-reservoir rocks hold oil and natural gas inside their pores the way sponges hold water. Traditionally, oil and gas drillers have tapped into rocks with high permeability, so oil and gas flow easily into wells and to the surface. "As soon as you tap it, it's like sticking a straw into a juice box that's being squeezed," says Ronald Bishop, a biochemist at the State University of New York at Oneonta.
Fracking, however, taps into reservoirs in which oil and gas are locked in shale--a rock with low permeability. "That oil and gas don't flow fast and it doesn't flow far," says Jennifer Miskimins, a petroleum engineer at the Colorado School of Mines.
To get at that oil and gas, workers bore a deep vertical shaft, and then drill horizontally through the shale. Then they crack the shale by injecting millions of gallons of water, chemicals, and sand under high pressure into the well (see diagram, right). Oil and gas flow through the cracks and up the well. The U.S. has many shale formations, with the largest, called Marcellus Shale, stretching beneath much of the Northeast.
Hydraulic fracturing has created a natural-gas boom. Because of its potential to generate jobs, it's a hot topic in this year's presidential race. But it's also raised concern that leaks from well pipes could contaminate drinking water. Another problem is disposing of used fracturing fluid. "We now are generating much larger volumes over much shorter time frames than anybody seemed to be prepared for," says Bishop. Many water-treatment plants aren't equipped to handle fracturing fluids. Some companies reuse the fluid, but eventually it becomes too dirty. A common disposal method--injecting the wastewater back underground--is thought to have triggered a string of earthquakes in Ohio last year. Scientists suspect that the injected water lubricated an existing fault, allowing the rocks to slide.
Engineers are researching better solutions, and the Environmental Protection Agency is investigating fracking's effects on drinking water. Fracking is on hold in New York State until more is understood about its environmental impacts. Other states are also considering regulations.
When it comes to energy, there's no simple solution. Alternative sources have downsides--but so does foreign oil. As Miskimins says, "The unconventionals have opened up a whole new world of self-sufficiency."
HOW HYDRAULIC FRACTURING WORKS
Hydraulic fracturing, also called fracking, is a way to extract natural gas from rock. The idea is simple but controversial: A well is drilled deep underground to reach natural gas trapped in shale deposits. A series of small explosions are used to crack the rock, then chemicals and water are pumped down to widen the fissures so the gas can escape and be captured aboveground.
(1) A drill bit on the end of a drill pipe bores a hole into the ground.
(2) A wide pipe is inserted into the hole.
(3) Cement is pumped around the pipe to prevent gas leaks from contaminating underground water sources.
(4) PERFORATING AND FRACTURING
The horizontal portion of the well is drilled. A smaller-diameter pipe, called a production casing, is inserted.
A perforating gun containing explosive charges is inserted into the casing. It blasts small holes in the shale.
Water, sand, and lubricants are pumped into the well under high pressure, forcing the shale to fracture, or break up.
(5) Gas flows up the well to the surface.
* Diagram is schematic, not to scale.
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|Title Annotation:||EARTH: NATURAL RESOURCES; hydraulic fracturing|
|Date:||Apr 13, 2012|
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