Faulting and fracking
Why has the University of Glasgow terminated my research database access?
Reputational smears in the UK gutter press - my response is here
See also my blog, Frackland
There is also a page commenting on a number of prominent and expert earth scientists who support hydraulic fracking in the UK
[ The geological and environmental risks of coal-bed methane, or CBM, extraction are discussed here. ]
Hydraulic fracturing, or 'fracking' is an oil industry process which is of public concern because of the damage it may do to the environment. Under the heading of fracking I include the whole process from drilling through to production, and not just the fracking process itself.
Fracking is the only known way of extracting oil or gas from compacted, or 'tight' shale rocks, which are carbon-rich. It has come to prominence since around 2003 in the USA, and many other countries are now actively investigating their previously locked-up gas reserves, for shale is a very common rock type. Here I am concerned with several European countries, but especially the UK, because this country is pursuing an aggressive policy of encouraging shale gas extraction by fracking.
A small company called Cuadrilla Resources Limited is in the vanguard of UK shale gas exploration, with licences in two regions; in Lancashire it has begun a fracking programme, and in the Weald Basin, Sussex, it has started exploration, joined by another company, Celtique Energie. The Weald Basin exploration is for unconventional oil, not gas.
A somewhat larger Swedish company, Lundin International, has a licence ostensibly for conventional oil/gas exploration in the Languedoc (France). This is discussed below.
I summarised the fracking problem in my submission to the House of Lords economic affairs select committee, November 2013. This document was limited to 3000 words and no diagrams, so references and end notes are in a separate file.
The fault problem
The oil exploration industry has a whole sub-industry of subcontractors offering their specialist services. One of these fields is determining whether or not geological faults in any particular area will seal off a potential oil or gas reservoir, or will act as a conduit. The default industry position on fault seal risk (which means the risk of the oil or gas being trapped - the desired outcome) is that faults do not normally act as seals.
I have found no authoritative study of the UK that mentions the fault seal problem in connection with horizontal fracking (sometimes also referred to as slickwater, high-volume fracking, or super fracking, to distinguish it from other methods of fracking which can safely be used). A leaky fault is a fast-track back to shallow groundwater and to the surface for methane and other gases, as well as (perhaps) for the contamination of water resources by fracking chemicals. Juxtaposed against this, the question of earthquake triggering is but a sideshow. In France fracking has been banned partly because of this risk, which was pointed out in 2011 by geologists from the University of Montpellier.
In NW Germany, a thorough study of fracking risks has been carried out by "neutral" academic experts (but funded by ExxonMobil), which includes the question of fracking through faulted zones. I have not yet digested the main report, which is in German; but one of the main conclusions of the English-language summary is that fracking in fault zones must be banned.
In England, by comparison nothing of substance has been published. Instead, we have Professor Richard Davies of Durham University, who uncritically quoted results from the USA (published incidentally, with sparse geological details, by petroleum engineers employed by Pinnacle, a Halliburton subsidiary) which imply that leakage via faults to the surface of fracking fuids and gases is not a problem. The Royal Society report of 2012 did not even discuss the question, even though it was raised in evidence submitted to the Society jointly by the Geological Society of London and the Petroleum Exploration Society of Great Britain. This evidence stated, under the heading Groundwater contamination from hydraulic fracturing:
"Another possible cause for both methane and fracking fluids leaking and migrating into groundwater supplies is the fracture stimulation process intersecting with open or unstable natural fractures and faults in the subsurface that extend upwards from the deeper prospective layers towards the surface where groundwater supplies might exist."
A 2012 British Geological Survey report, Potential groundwater impact from exploitation of shale gas in the UK, managed to avoid mentioning either faults or the permeability of the cap rock (the layers above the fracked zone) in its section on Routes to groundwater.
The USA work (even if it is to be believed) cannot be applied to Europe, because in the old continent the geology is extremely different. The English shale basins, for example, are 10-100 times smaller in area than the main US basins, but the shale deposits are 10 times thicker. Faulting is almost non-existent in the US basins, whereas it is a fundamental and important feature of the basins of the north of England, the Weald, the south of France, and NW Germany - all areas which are or have been considered for fracking. I have not yet looked at Poland.
An important new research paper (open access) was published on 4 May 2015 in the prestigious Proceedings of the National Academy of Sciences (of the USA). This paper proves, from a case history in Pennsylvania, that faults and/or fractures can and do act as a conduit from fracked shale to contaminate drinking water. A few faults have been identified in the locality, but in general such faulting is extremely rare in the US shale basins. The case history, written by environmental consultants acting for the affected homeowners, is also a sad illustration of the struggle that individuals will face if their water becomes contaminated. The gas company first drilled replacement water wells, without success, all the while denying liability. Finally, after litigation, the homeowners had to be bought out and compensated. The publication makes it clear that the contaminated water originated in the fracked Marcellus Shale, and could not have come from any other source.
Faults cannot necessarily be 'seen' in advance of drilling, for example using geophysical methods, and indeed it is common for exploration wells to drill through a fault zone without it even being spotted. Cuadrilla penetrated two (admittedly very minor) faults when drilling its Balcombe, Sussex horizontal appraisal well without recognising them. Its Preese Hall well near Blackpool triggered earthquakes on a previously unrecognised fault. A published study by Cuadrilla in December 2014 locates the earthquakes on a fault, but misleads in having the fault distant from the wellbore, when it is clear that the wellbore deformation was caused by the earthquakes deforming the well casing, which passed through the fault zone at an acute angle.
So before this new 'dash for gas' takes place in the UK, and certainly before any further fracking is undertaken, we need a thorough study in each area, to quantify the risk of faults being the potential source of leakage back to shallow levels. Why has this not been done? There are half a dozen academic groups in the UK which could undertake this kind of research.
NB some of the links above are to publishers' websites, where payment is required for access to copyrighted articles.
Other useful articles
The following articles and documents not hyperlinked above appear to be in the public domain, but are not readily accessible.
Letter from Cuadrilla Resources Ltd to Lancashire County Council, 16 November 2011 (about the Fylde 3D seismic survey).
de Pater, C.J. & Baisch, S. 2011. Geomechanical Study of Bowland Shale Seismicity, Synthesis Report for Cuadrilla Resources Ltd.
Green, C.A., Styles, P and Baptie, B.J. 2012. Preese Hall shale gas fracturing review & recommendations for induced seismic mitigation. Report to DECC.
Lundin International in southern France
This company obtained a permit to explore a huge area of two and a half thousand square kilometres of the Languedoc in southern France, along the coast of the Mediterranean between Montpellier and Narbonne. Allegedly the company is interested in conventional oil and gas, but the facts suggest that there is a hidden agenda - shale gas. Fortunately shale gas exploration using fracking is currently forbidden in France.
This pdf slide show (in French) summarises the state of play. It looks as if Lundin obtained the licence with a view to working up its value because of its shale gas potential.
In summer 2014 the company, having undertaken no field work, applied for an extension of its five-year licence, retaining just 50% of the original acreage.