Shale pits environmental versus economic interests

Sep 24, 2013 by Marc Preel
An anti-fracking protester holds a "Fracking kills" poster outside a test drill site in Balcombe, southern England, on August 20, 2013.

Shale oil and gas may be massive untapped energy sources, but the risks of extracting them has drawn calls for tighter regulation or an all-out ban.

To release oil or natural gas locked inside sedimentary shale rock, energy companies inject at a mixture of water, sand and chemicals deep underground to crack the layer (sometimes called source rock) where the hydrocarbons lurk.

The technology, known as or "fracking," is typically used at depths of 2,000 to 4,000 metres (6,500 to 13,000 feet) below the earth's surface.

The fracking mixture is then partially pumped back up.

Environmentalists have warned gas, mostly methane, or some of the remaining injected mix can eventually rise toward the surface on its own, polluting fresh-water supplies.

But geologists interviewed by AFP downplayed that risk, saying the cracks formed by fracking are generally more than 1,000 metres below the , with thick layers of rock in between keeping aquifers safe.

Only one controversial draft study in 2011 by the US Environmental Protection Agency found evidence of ground-water contamination linked to fracking in the town of Pavillion, Wyoming. But EPA officials dropped their probe in June and handed it over to without drawing final conclusions.

Geologists say the main risk is actually closer to the surface, where the well drilled to inject the fracking mixture underground intersects with the water table.

The well is made of metal tubes encased in cement. If these crack of spring leaks due to the higher pressure then ground-water supplies could be contaminated.

"The risk either comes from the fluids injected into the tube or the fluids coming up out of the tube or even the fluids of the aquifer crossed by the drilling, but it cannot come from something that is by definition very deep like the source rock," said geologist Bruno Goffe at France's National Centre for Scientific Research (CNRS).

Drilling itself is the riskiest aspect, but fracking also brings "additional risk," said Goffe.

Explanation of the controversial technique of shale gas extractoin by hydraulic fracturing.

"They're using very high pressure in the tubes to crack the rock deep below, and with very very high pressure near the surface, there can obviously be cracks or accidents," he said.

US geologist Susan Brantley recently estimated that between one and three percent of fracking wells have experienced this type of problem. Other studies have found that more than six percent of wells have been affected.

As fracking spreads, so does the risk.

In the United States, more than 10,000 shale wells are drilled each year. And more than a dozen other countries are exploring for shale hydrocarbons or taking steps to do so.

Fracking also takes a big toll on local water supplies.

Every shale-gas well needs between 10 million and 20 million litres (2.64 million and 5.28 million gallons) of water, plus 500 tonnes of sand and 50 tonnes of chemicals, according to Thierry Froment, director general of the oil and gas division at French utilities group Veolia.

About 60 to 80 percent of that mixture eventually comes back to the surface, he said. The rest stays underground.

In the United States, the chemical-laden fracking water is either dumped into separate "waste wells" or treated for re-use in fracking.

The water could be treated for agricultural or other use, but that would cost at least four times as much, according to Veolia.

Opponents condemn use of dangerous chemicals in fracking such as acids, polymers biocides in fracking. Some of these, but not all, can be replaced with biodegradable alternatives.

Some of these chemicals, but not all, can be replaced with biodegradable alternatives.

They also warn fracking can trigger earthquakes.

Geologists say the water injected into "waste wells" can in fact provoke increased seismic activity, but can only trigger significant tremors when an active fault is hit.

Another key concern is leaks of methane, a greenhouse gas 25 times more polluting than carbon dioxide.

Even if just three or four percent of the methane trapped beneath a given well is released, the carbon footprint of shale gas expands to the size of coal's, the most polluting fossil fuel.

A new study from the University of Texas, however, suggests that US fracking operations have sharply reduced methane leaks under tighter regulations.

"There's always a little (that escapes), but it's like plumbing—if you have a good plumber, you have less leaks," said CNRS geologist Goffe.

Explore further: Fracking risks to ground water assessed

add to favorites email to friend print save as pdf

Related Stories

Fracking risks to ground water assessed

May 17, 2013

(Phys.org) —Extraction of "unconventional" gas from sedimentary rocks such as shale could provide a clean energy source and help some regions to become energy independent, but concerns have been raised ...

Poland starts shale gas extraction

Aug 28, 2013

Shale gas extraction has begun at a test well in northern Poland, a first for the EU member, a minister said in a newspaper interview on Wednesday.

Study finds fracking chemicals didn't spread

Jul 19, 2013

(AP)—A landmark federal study on hydraulic fracturing, or fracking, shows no evidence that chemicals from the natural gas drilling process moved up to contaminate drinking water at a western Pennsylvania drilling site, ...

Brussels says no plans for EU-wide shale gas ban

Jul 16, 2013

The European Union has no plans to impose a blanket ban on hydraulic fracturing, a controversial shale gas extraction method, but it will lay out rules to address environmental concerns, a top EU official ...

Recommended for you

US delays decision on Keystone pipeline project

Apr 18, 2014

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

Apr 18, 2014

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...