Fracking (Hydraulic fracturing)
Monday, 23 April 2012 at 2:25:PM
Not for the first time (see this BBC news item), there has recently been a great deal of publicity devoted to fracking, the process of using high-pressure water-based liquids to extract natural gas from underground. How can thermal desorption be of value in this field?
Hydraulic fracturing, or fracking as it has come to be known, has been around since the late 1940s as a means of increasing the yield from underground oil/gas reserves – indeed, the majority of new gas wells drilled today use fracking. However, technological developments such as horizontal drilling have meant that it is now economically feasible to apply fracking to ‘unconventional’ sources such as shale deposits. The widespread occurrence of these deposits, combined with continued demand for new gas sources, has led to a surge in fracking over the last few years, and resultant increased public concern about its effect on the environment and on public health.
The potential environmental impacts of fracking are varied, and extend beyond the obvious one of the contamination of groundwater from the chemicals used in fracking. To a large extent these impacts mirror those for extraction of petrochemicals, with the added potential for earthquakes (recently gaining coverage from the BBC and the press). These risks include:
- Blowouts, leaks and spills from stored chemicals, wells, pipelines and evaporation pits
- Emissions from flowback – the part of the fracking process when the fracturing fluids, water and gas return to the surface
- Emissions from the wells as part of normal operation
- Emissions from equipment and vehicles on-site.
Potential emissions associated with fracking are of more than just methane – other less volatile organic chemicals (VOCs) can also be released, either from the well itself or from associated activities above-ground. These include members of the groups known as ‘air toxics’ (also known as ‘hazardous air pollutants’) and ‘ozone precursors’, both of which have for many years been the subject of legislation.
To detect releases of such chemicals, gas chromatography (GC), whether used in conjunction with mass spectrometry (MS) or other detection techniques, is well-established. With thermal desorption (TD) as a pre-concentration tool, detection limits can easily be lowered to the point that enables early detection and reduction of negative impacts on the environment or human health. This makes TD–GC/MS an ideal technology to monitor concentrations of hazardous VOCs in air or liquids. However, methane itself is too volatile to be retained on the sorbents currently used with thermal desorption, so if this is to be quantified, then a dedicated methane-detecting system is needed.
With legislation and controls on fracking only now catching up with the reality on the ground, the one thing that we can be sure of is that fracking will remain in the spotlight for years to come. With this will come the need for environmental monitoring – where a range of technologies, including thermal desorption, will clearly have an important role to play.
David Barden received his Ph.D. in Organic Chemistry from Cambridge University in 2004, and during his time as an editor at the RSC wrote news pieces for Chemistry World on various scientific topics. He is now Technical Copywriter at Markes International, where he draws on the expertise of his colleagues to explain how new thermal desorption and mass spectrometry technologies can be applied to analyse volatile organic compounds in a wide variety of situations.
The following provides an overview examining the environmental risks associated with the technologies used to extract shale gas: M. Zoback, S. Kitasei and B. Copithorne, Addressing the environmental risks from shale gas development, Worldwatch Institute, July 2010.
An article primarily examining the issue of methane emissions from fracking can be found in: Methane: A new ‘fracking’ fiasco, Chemical and Engineering News, volume 90, issue 16 (16 April 2012), pp. 34–37.
On the same website there’s also a news article on regulations issued by the US Environmental Protection Agency (EPA) for the control of air pollution released during fracking. The US EPA regulations themselves and a summary fact-sheet issued by the EPA are also downloadable.
A short history of fracking and the current state of the technology from an industry perspective can be found in two back-to-back articles at:
C.T. Montgomery and M.B. Smith, Hydraulic fracturing – History of an enduring technology, Journal of Petroleum Technology, December 2010, pp. 26–32, and R. Beckwith, Hydraulic fracturing – The fuss, the facts, the future, Journal of Petroleum Technology, December 2010, pp. 34–41.