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Carbon Briefing: what does extracting shale gas mean for the local environment?

  • 15 May 2013, 16:50
  • Robin Webster

As the energy minister Michael Fallon encourages companies to explore for shale gas, concerns remain that the extraction process is safe. We asked at what so-called fracking will do to the local environment, and what regulation is needed.

Several official reports - from Parliament's Energy and Climate Change (ECC) Committee, the International Energy Agency (IEA) and the Department for Energy and Climate Change (DECC) appear to agree that the local impacts of shale gas extraction are manageable.

And the government's now on the same page. In front of a Parliamentary Committee today, new energy minister Michael Fallon said the government is "creating the right framework to accelerate shale gas development in a responsible way", adding that it is now up to oil and gas companies to come forward with plans to explore the country's shale gas potential.

Despite the reassurances, many communities are worried. Here's a quick and dirty run down of the main issues, with a few of the caveats.

How to frack

Shale is a sedimentary rock formed from deposits of mud, silt, clay and organic matter. It's very common. According to the British Geological Survey, it makes up 35 per cent of the world's surface rocks - but until recently it wasn't that easy to extract gas from it. That's because shale gas is very fine-grained, so the gas sticks to the rock.

Hydraulic fracturing involves pumping a fluid made of water mixed with chemicals at high pressure into a well that has been drilled. The fluid creates fractures in the rock, making it possible to get the gas out. According to oil and gas company Cuadrilla, the fracking process may take a couple of hours, and be repeated several times over a period of weeks in order to create one well.

Earthquakes

In this country, initial fears focused on the possibility that fracking could cause earthquakes. In 2011, exploratory fracking by Cuadrilla caused two earth tremors, measuring 2.3 and 1.5 on the Richter scale.

But a subsequent study commissioned by DECC from the Royal Academy of Engineering pointed out that the quakes are unlikely to pose a threat. In comparison, coal mining has been causing earthquakes for years - up to about 4 on the Richter scale. It concluded:

"the magnitude of seismicity induced by hydraulic fracturing would be not greater than 3ML [on the Richter scale]...felt by few people and resulting in negligible, of any, surface impacts".

A more recent study from the Durham Energy Institute published in April agrees, concluding that fracking causes earthquakes - but not significant ones.

Pollution of drinking water

In its 2011 report ' Are we entering a golden age of gas?', the IEA illustrated some of the key environmental concerns connected to shale gas drilling:

Screen Shot 2013-05-15 At 17.24.18

In any circumstances, drilling for gas is a risky process - opening the possibility of accidental spills and water contamination. Particular concerns have been raised about fracking, because:

  • the chemical additives used in the process could leak into groundwater underground; or alternatively by accidentally spilling on the surface;
  • the gas itself could leak into drinking water. The campaign film, 'Gasland', highlighted this possibility.

The reports are pretty dismissive of the possibility that groundwater leakage could occur, because the gas is usually situated far below the water table. The IEA says:

"For example the deepest potential underground sources of drinking water in the Barnett shale [in Texas] are at a depth of 350 metres, whereas the shale layer is at 2000 to 2300 meters".  

There appears to be  some evidence that leakage of gas into drinking water has taken place in the USA - although this is  contested - and research led by Durham's Energy Institute indicates that the risk is extremely low. DECC told the  ECC committee that this was "incompetent" operators' fault, and would not happen in the UK.

Professor Richard Davies from Durham recently told BBC News that worries about the fracking process are a distraction and that cracks in the well or accidental surface spills are far more significant risks. This means that well design - keeping it intact and safe over a possible thirty year lifespan - is an  important part of regulation.

Water use and storage of wastewater

The process of opening up the rock by fracking uses a lot of water. According to the IEA, each well might require anything from a few thousand to 20 million litres of water. The Tyndall Centre for climate change research has calculated the figure at nine to 29 million litres per well.

It may be possible to recycle the water, reducing the amount needed. The ECC committee concludes, "there is only a small risk that the large volumes of water required for hydraulic fracturing will place undue stress on the water supply" - but that the risk could be more significant during times of drought.

After it's been used for fracking, the wastewater - now contaminated by chemicals, hydrocarbons and naturally occurring radioactive material - must either be cleaned up or stored safely. The IEA says the technology exists to treat the water appropriately, or to store it, depending on location.

Disruption - noise and number of wells

The disruption and industrialisation of rural areas associated with shale gas extraction may in the end prompt more objections to fracking than any other factor.

In a blog post, Michael Liebreich from Bloomberg New Energy Finance calculates that, in the hypothetical situation where the decline in North Sea gas is replaced entirely with UK-produced shale gas up to 2030, the country would need to construct 2,500 new wells.

Drilling the well in the first place is the most intensive - and disruptive - part of the process. According to the IEA it could involve "between 100 and 200 truck movements to deliver all the equipment" - and once it starts, will operate for 24 hours  a day.

But the extracting the gas is by far the longest part of the process and may go on for up to thirty years. During this time, the well is less visually intrusive - it uses what the IEA calls a "Christmas tree" of valves, typically about one metre high, sitting on top of the well.

Regulation, regulation, regulation

Two years ago the ECC Committee concluded that there is "nothing inherently dangerous" about fracking, provided there is a robust regulatory regime. Reports by the IEA and Institute of Mechanical Engineers agree that it can be done - so long as laws are put in place to make it happen safely.

Since then, the government has lifted a temporary moratorium on fracking. Despite concern from government advisers the Committee on Climate Change that expanding a domestic gas industry will undermine the UK's carbon targets, the chancellor George Osborne appears strongly supportive of the technology and has introduced tax breaks to encourage its development.

As UK fracking moves from theoretical debate in the media and between politicians to drilling on the ground, it will become clearer whether the government's regulatory regime can keep shale gas drilling safe. 

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