In part one of this series of blog posts, we provided evidence that hydraulic fracturing does not pose systemic threats to ground and surface water. Related to this issue is integrity of the wells, which allow oil and gas to come to the surface. If wells fail or crack, it’s possible that fracking fluids or oil and gas could migrate into the surrounding ground or water.

When pressure builds up inside a well that could potentially force fluids out of the well, it’s known as sustained casing pressure (SCP). SCP reflects the failure of one or more barriers but does not necessarily mean that environmental contamination took place. In their review of SCP estimates, the researchers found that:

“Results from surveys of wells offshore and onshore show distinct differences in rates of SCP, reflecting the importance of geology and well construction. In the Gulf of Mexico, 11–12% of wells in an 8,000-well survey showed SCP on outer casing strings, with results ranging from 2% to 29% across fields. In Alberta, companies reported that 3.9% of 316,000 wells showed evidence of SCP, with one region east of Edmonton having 15.3% SCP” (p.338).

To be clear, the presence of SCP does not mean fluid leaked into the environment.

Indeed, the risk of a blowout, which can lead to the uncontrolled release of oil or gas, is quite low. A review of environmental regulations and compliance published in the journal Environmental Geosciences found that of the 3,533 wells drilled in the Pennsylvania Marcellus Shale from January 2008 to August 2011, only four experienced a blowout. That amounts to 0.11 per cent of wells. Data on three of the four blow outs show that remediation had taken place and that in two of the cases the companies faced a fine of $51,478 and $353,419.

In a review of hydraulic fracturing in the United Kingdom, researchers concluded that “[t]he probability of well failure is low for a single well if it is designed, constructed, and abandoned according to best practice” (p.4). Conclusions on the risk of well integrity failures are similar to other areas of risk for hydraulic fracturing—while there are of course risks, they tend to be quite low.

One potential option to help further reduce the risk of well failure could be to establish for-profit or non-profit third party verification entities that would certify that a well was properly drilled and cased before production could commence.