The Scienttific Alliance Newsletter - Changing and informed scientific debate

Pros and cons of fracking

There has been much debate recently about the advisability or otherwise of drilling for oil or gas deposits in shale using the technique popularly known as fracking (more properly called hydraulic fracturing). Supporters point to the transformation of the US energy market by the development of a domestic supply of gas (including a sharp drop in wholesale prices) while opponents point out numerous economic and environmental problems.

While it would be unwise to project exactly the same transformation of the energy market on this side of the Atlantic if shale gas was to be fully exploited, it is equally unwise to block this on the basis of ill-informed criticism. Fracking is neither new nor inherently more dangerous than other forms of mineral extraction. And, on a parochial note, on-shore drilling for oil and gas is not new to the UK: more than 2,000 wells have been drilled, with the first in 1902.

Conventionally, oil and gas are extracted by drilling straight down into deep reservoirs. Being under pressure, they come to the surface naturally, although recovery rates can be increased by injection of water or carbon dioxide. As the vast reserves in the US and Middle East have been depleted and oil prices have risen, so it has become economic to drill in more difficult sites (eg, the North Sea and other deep water fields) and exploit what are still referred to as ‘unconventional’ sources.

These include the so-called tar sands in Canada, which require considerable heat energy to separate heavy oil (and are still the subject of controversy as EU legislators would like to penalise their use) and oil- and gas-bearing shale. In this case, the minerals are not found in highly porous rocks from which they flow easily, but in the much smaller pores of shale, a sedimentary rock. Although drilling into this does not result in a ready flow of oil or gas, such rocks are easily fractured, since they are laid down in thin strata which are readily fractured.

This property is exploited by hydraulic fracturing, whereby water is forced into the rock at high pressure. The other requirement is to keep the fractured structure open to recover gas or oil, so sand is injected with the water to prop the larger fissures open. One criticism often levelled at fracking is that a toxic mix of chemicals is pumped underground, which can lead to pollution. The fact that the exact composition of the mixtures used is commercially confidential means, it is suggested, that drillers have a dirty secret to hide.

In practice, fracking is little different from conventional drilling which uses synthetic ‘mud’ to lubricate the bit and bring rock fragments to the surface. In the case of fracking, the basic mixture of water and sand has a number of minor additives: a biocide (to prevent microbial growth) at about 0.01% and about 0.1% each of a surfactant, a polymeric lubricant and a stabiliser. A significant proportion of the water used is recovered and reused for subsequent fracking operations.

The other difference between recovering oil or gas from conventional reservoirs and shale beds is that, whereas a handful of wells is normally sufficient to tap most of the conventional resource, each well drilled into a shale bed collects from a relatively small volume around the length of the frack. This means that individual wells produce for a relatively short time, but the solution is to bore multiple wells from a single point. Because shale is laid down in horizontal beds, these wells are also drilled horizontally once the shale has been reached. Much more detail about all the technology can be found in a Heartland Institute paper: Hydraulic fracturing – a game-changer for energy and economics.

This paper is very clearly pro-fracking, and it is undeniable that the American energy situation has been very positively transformed. Manufacturing industry, for example, has been made considerably more competitive by lower energy costs, gas has displaced coal as the preferred choice for electricity generation and LNG import terminals are being turned into ports for export. But there is also plenty of opposition to shale gas, which in the UK last year focussed on the activities on Caudrilla near the Dorset village of Balcombe (which, interestingly did not include fracking, but facts are not always allowed to get in the way of a good protest).

Other negative claims are made, most controversially in the film Gasland. One of the key claims made in this piece of activist film-making is of contamination of groundwater, with one scene showing flammable gas coming from a water tap. But the US energy industry strongly refuted the claims made in the film, which certainly seems to take worst case examples as typical and tries hard to damn the entire industry. Readers who want to look further into both sides of this debate may like to go to this NYT article: Groundtruthing Academy Award Nominee ‘Gasland’.

Critics rightly say that extracting shale gas in much of Europe could have more impact on local communities, as population density is higher than across the Atlantic. However, it is not often recognised that the largest on-shore oilfield in Western Europe is in Dorset, near Poole Harbour, which borders three nature reserves. Even in Balcombe itself, a well was drilled very close to the last year’s in 1986, with no opposition.

Onshore oil and gas production need not cause problems, as the established well head is far less intrusive (as well as more productive) than a wind turbine. Establishment of the well is different, of course. It is estimated that there would be about 1,000 HGV movements during the drilling and fracturing process, which should take no more than two months. However, a single wind turbine requires twice as many lorry movements during its construction.

Another accusation is that fracking causes earthquakes. It is true that very small earth tremors were detected when Caudrilla was drilling test wells near Blackpool a few years ago and the process was temporarily stopped while these were investigated. However, talk of ‘earthquakes’ is a gross exaggeration (Fracking does cause earthquakes – but you won’t feel them) and conventional mining has a significantly greater potential to cause problems.

The main reason behind objections to fracking is almost certainly the argument that exploiting more fossil fuel reserves simply prolongs the effort to reduce emissions. However, the evidence in America is that gas has displaced coal and given real benefits in terms of air pollution as well as reducing carbon dioxide output. The conflict is really between a fundamentalist view that a complete change to renewable energy is needed as soon as possible and a more realistic position that a secure, affordable energy supply is vital for modern societies.

Gas is surely going to be an important part of the mix for many years to come, and a domestic source cannot be ignored. The effect on energy costs may be modest, but security of supply and tax benefits are not to be sniffed at. There is really no reason why properly regulated fracking should not proceed. 

Copyright © 2014 The Scientific Alliance, All rights reserved.