22nd September

‘Probable low and manageable risk’ from fracking

A report released by the Environmental Protection Agency (EPA) that reviews the geological and engineering aspects of fracking; potential environmental impacts and the existing regulatory framework in different countries, concludes that the procedure presents a low and probably manageable risk to ground water, whereas potential impact on the atmosphere from associated methane emissions and the risks of increased seismicity are less well known.

Hydraulic Fracturing or ‘Fracking’: A Short Summary of Current Knowledge and Potential Environmental Impacts , was prepared for the EPA by Dr Dave Healy, a senior lecturer in Geomechanics at the Department of Geology and Petroleum Geology at the University of Aberdeen. It can be downloaded from the EPA web site.

 

Noting that much of the media coverage on fracking to date ‘is often misinformed’ the study warns that critical evaluations of shale gas fracking and the potential impacts on the environment ‘must be based on peer-reviewed, scientific analyses of quantitative data’.

It finds too that agencies like the EPA – responsible for regulating or monitoring environmental impacts – need to be at the forefront of this effort. It added that the design of any national regulatory framework to protect the environment from hydraulic fracturing operations ‘should start with the supranational European Union directives and recommendations from working groups in progress”.

As for these potential environmental impacts, the study singles them out while cautioning that reference material is currently dominated by material originating from the USA.

Summary findings

Ground Water Contamination:
Ground water contamination is by far the most serious local environmental concern, and probably the most contentious. The potential risk to ground water comes from two sources: the injected fluid (water + chemical additives) and the released natural gas. Current opinion is that all scientifically documented cases of ground water contamination associated with fracking are related to poor well casings and their cements, or from leakages of fluid at the surface rather than from the fracking process itself.

Chemical additives
Defining the toxicity level of additives used in the fracking phase should be a relatively simple and quantifiable scientific task, however in some countries fracking companies are under no legal obligation to declare the exact composition of this mixture. Note that the Irish regulatory regime (and that of the European Union) requires full disclosure of all additives to the Environmental Protection Agency (Ireland).

Blow outs
Surface and subsurface blow outs have been documented in the USA. If the fluid injected into the well head does not fracture the rock volume around the bottom of the well as intended the elevated fluid pressure will drive the fluid into other open and permeable pathways. These pathways can include the injecting well bore, but also any other boreholes in the vicinity that are not capped for these high pressures. Explosive eruptions of drilling fluid and/or oil and gas from neighbouring wells are a direct consequence of pre-existing permeable connectivity at depth. Seepage of any surface spillage from a blow out into the ground could then lead to ground water contamination (see below).

Water sources
Sourcing the vast volumes of water required for an extended fracking programme can be challenging, especially in arid or depleted areas. Estimates of water volume required vary widely, with between 90,000 and 13,500,000 litres per well. Local extraction of water from small catchments could have an impact on the ecology and hydrology of rivers in these areas. Finding sustainable sources for these volumes of water is clearly a challenge, but related environmental impacts may also develop from transporting water in to the drilling site from further afield.

Fate of the fracking fluid
How to dispose of fracking fluid after use during the fracking process presents further challenges. Some operators in North America have chosen to pond this flow back fluid in man-made pools and then allow it to either evaporate, or be transported away at a later date. Scope exists to develop new fracking fluids free from chemical additives, although the sand proppant will probably still be required.

 

Emissions to the atmosphere from fracking
The emission of gas and/or vapour to the atmosphere from the fluid, either of original additive chemicals, entrained contaminants from the shale formation or the methane released by the fracking process. There is an ongoing debate about the relative leakage rate of methane into the atmosphere from the exploitation of shale gas in comparison to the emission rate from conventional gas. This is potentially important because a high leakage rate might mean that  methane  released  by  fracking  operations  into  the  atmosphere  from  shale  gas extraction could have a higher net greenhouse gas footprint than, say, coal. Fracking operators should therefore seek to minimize all emissions to the atmosphere, and monitoring processes need to be actively enforced.

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