In the first of a two-part debate, the Shell Professor of Earth Sciences at Oxford throws down the gauntlet in defence of a practice that has provoked intense opposition.
Hydraulic fracturing, or ‘fracking’, is a mining technology in which hydraulically pressurised liquid is used to crack rock, thereby allowing the recovery of hydrocarbons such as gas and oil. Almost no issue of our times has aroused as much heated debate as fracking, to the point where the real issues are almost overwhelmed by Hollywood films, lobbying groups and geo-political arguments. Here we present the first half of a two-part debate.
FOR: Joe Cartwright
Dr Joe Cartwright (pictured right; DPhil in rift systems, 1988) was appointed the Shell Professor of Earth Sciences at Oxford in 2012. He worked for Shell International as an exploration geophysicist, was at Imperial College as a Senior Lecturer until 1999, and was appointed Honorary Professor of the Institut Français du Petrole in 1998.
Fracking has already been used in more than two million boreholes so is hardly a new and unproven methodology. For instance, fracking is routinely used to enhance recovery of oil and gas from many conventional reservoirs of sandstone and shale, such as, for example, in Europe’s largest onshore oil field in Dorset, Wytch Farm, nestled in the beautiful New Forest. The legitimate concerns relating to fracking are no greater than would apply to any industrial operation, and are addressed by the right regulatory framework. But there is huge public fear and even unrest in many countries and indeed, in the US itself, at the prospect of fracking coming to ‘our community’.
Hydraulic fracturing of a shale gas reservoir involves drilling into the reservoir and pumping fluid into it at sufficiently high pressure to overcome the natural tensile strength, plus the confining stress. There is nothing intrinsically dangerous about pumping fluid into the deep subsurface at high pressure, provided the well is monitored carefully throughout. The resulting minor ‘earthquakes’ are tiny, relative to destructive earthquakes, and smaller than even those caused by mining operations. Fracking requires large volumes of water, but on a scale comparable to many other industrial activities.
In countries such as the UK and the USA, the regulatory framework for onshore drilling operations is sufficiently tight to allay fears. As we have seen over the years with conventional oil and gas drilling operations, accidents can and do happen. But such accidents are very rare compared to the scale of the activity.
There is another concern: that the chemicals being incorporated with water and sand into the fracking fluid will eventually penetrate groundwater aquifers. This is a fear that rests on a failure to grasp the scale of fracking. A typical fracture is less than a centimetre across and no more than 200 to 300 metres tall. Because shale gas reservoirs are only exploited at depths of 2 to 3km below the surface, and groundwater aquifers are typically a few hundred metres beneath the surface, the likelihood of fractures propagating anywhere near the water supply is extremely small. The greatest risk to groundwater comes instead from poor drilling methods, and particularly from poor quality cement lining of the borehole, which is a recognised problem for all drilling operations and for which regulations are already specifically designed. The chemicals used in fracking fluid also amount to about one per cent of the total pumped volume, and are strictly controlled in the US and UK.
Methane leakage to the atmosphere is not well quantified at present, partly because of the paucity of data on natural leakage of methane from the deep subsurface into shallow aquifers and to the surface, but this does need careful monitoring in the future.
Without a doubt, the greatest risk to communities where fracking operations would be undertaken comes not from pollution from drilling, or from induced seismicity, but from the vastly increased road traffic that would be required to supply the drill site. Only local communities can judge whether this disruption is justified by the privileges of living in a highly developed society, fuelled at least for the time being in large measure by oil and gas.
Read the case against fracking, by green energy expert Jeremy Leggett
This article first appeared in the Michaelmas 2014 issue of Oxford Today. Read the full issue online here, or download in pdf, iPhone/iPad or Android format. Image of oilfield © Christopher Halloran / Shutterstock.com