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Fracking: How much gas and what about the water

Updated Thursday, 26th September 2013
Just how much gas is available by the process of fracking, and what volume of water is required?

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In the 1950s a man called Hubbert made a prediction of the life of gas (and other fossil fuels), assuming that the consumption would remain the same—which we now know of course is not the case.

Hubbert curve (a) Hubbert's original 1956 prediction for US oil production; (b) what actually happened

This predicted that there was a ‘lifetime’ for gas of 50-60 years. However, this also relied on known reserves and known drilling techniques.

These gas reserves are distributed as the diagram below shows. This results in the rest of the world exporting from and thus giving power to Russia, Qatar and Iran, as shown as trillion of cubic meters (tcm) of gas. To give you an idea of how much gas this is, the UK consumes 0.1% of this, of the order of 100 billion cubic metre (bcm) gas per year.

Natural gas reserves

Fracking blows this out of the water.

How much extra gas can we get with fracking?

The USA estimates 25 tcm, compared to the 12 tcm which was forecast using conventional gas drilling.

Not just America, but also parts of Europe, South America and Africa sit on as-yet-unknown quantities of gas. But the biggest shale-gas reserves may be in China. So all we can say for sure is that we don’t know when the end of gas reserves will be; maybe a few hundred years?

A security of supply will increase in these continents. As far as we know now, gas is the only fossil fuel to increase its share in meeting energy demand in the future. IEA estimates are for a 50% increase in global demand for gas between 2010 and 2035. This shale gas is easier to clean than coal so it can buy us time until renewables are more extensive globally.

Making more use of this gas can reap benefits. For example, USA has recorded a drop of 450 mtonnes in greenhouse gas emissions due to focused efforts on fracking closing coal-fired power stations. Also with a large drop in gas prices comes the possibility of an increase in economy and GDP; and of course there are the social benefits of increased employment.

Fracking well vs conventional well Left: conventional wells. Right: fracking wells. What does a fracking well look like anyway? The image on the right shows a bird's eye view.

Fracking wells are grouped into one small site, reducing surface land use by up to 90%.

Confining the production to one site also reduces the number of pipelines and access roads needed to support the wells.

What of the water?

Fracking uses water pressure to create fractures in rock to allow any oil and natural gas contained to escape.

The fracking wells are much deeper than tradition natural gas wells—anywhere between 300m and 3km depending on whether the drillhole is vertical or slanted. Furthermore the horizontal extent of the drilling can be many hundreds of metres. So it is not surprising that these wells require up to a hundred times more water (of the order of 20 million gallons) than conventional wells. To put it in context, in the UK a single person typically consumes 33 gallons a day.

This water has to be diverted from human use or natural water features (depleting the underground acquifers—bodies of rocks that hold and transmit water). What does this mean in terms of the water table? We are already in a state of water depletion so picking the location for drilling is critical to our sustainable future. The High plains in North America, Indus plain in North India and the North China plain aquifers may be the best choice.

Otherwise it may imply that areas across Europe that are subject to fracking wells could eventually become drought areas like North Africa and other desert areas.

The other aspect of concern is water contamination. This can be caused by the ‘flowback’ fluid and any damage to the fracking pipes which could cause contamination into the water aquifers supplying our drinking water. This could cause a problem for shale gas in populace regions like Europe.

The fracking fluid flushed down the well is approximately 95% water—the rest is made up of approximately 4% sand particulates and 0.5% toxic chemicals; these include polymer gels for sand suspension, descalers to break down the polymers, friction reducers to maintain smooth flow and a biocide disinfectant. The flowback fluid (which can be up to 70% of the initial flushing fluid) needs to be ‘cleaned’.

Fracking cycle

Up to 80% of the used water can be recycled after cleaning. Of course it goes without saying that water treatment carries a cost so if the nearby aquifers needs treating also there would inevitably be rising domestic and industrial water costs!

Experience in the USA so far shows that fracking is safe in this respect although there can always be accidents and malpractice – remember the Deepwater Horizon oil spill in the Gulf of Mexico.

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