Response to paper 4: Well Integrity

The Nova Scotia Fracking Resource and Action Coalition (NOFRAC) believes that the Hydraulic Fracturing Review Well Bore Integrity discussion paper (“discussion paper”) provides a thorough outline of problems and impacts from gas seepage behind the well casing system, including the scale and implications of the problems with aging and abandoned wells. This discussion paper echoes findings made by the Canadian Council of Academies (CCA) that much more needs to be known about the various risks of shale gas extraction.

That said, on very central questions the discussion paper makes numerous sweeping statements for which very little or no supporting evidence is offered. These statements often are at odds with the evidence-based conclusions in the CCA Report on the Environmental Impacts of Shale Gas Extraction in Canada.

  • Unlike the CCA Report, the discussion paper juxtaposes recognition of leaking well issues with a description of improvements in well construction and offering the opinion that the “incidence of leaking wells can easily be reduced.” (p.17) There is no reference to performance data.  Contrast this to the CCA Report:

The oil and gas industry has substantially improved on the practices used for cement sealing wells over the past decade, and there is no doubt that the cements used today are much more effective. However, the degree of improvements claimed has not been independently tested or verified.”  (p.58)



Natural gas leakage from improperly formed, damaged, or deteriorated cement seals is a long-recognized yet unresolved problem that continues to challenge engineers. Leaky wells due to improperly placed cement seals, damage from repeated fracturing treatments, or cement deterioration over time, have the potential to create pathways for contamination of groundwater resources and to increase GHG emissions. The issue of well integrity applies to all well types, including water and conventional gas or oil wells. Several factors make the long-term impact related to leakage greater for shale gas development than for conventional oil and gas development. These are the larger number of wells needed for shale gas extraction; the diverse chemicals used in hydraulic fracturing operations; the potential development of shale gas resources in rural and suburban areas that rely on groundwater resources; and possibly the repetitive fracturing process itself.” (p. xiii Executive Summary)

The CCA Report also says :

Information concerning the impacts of leakage of natural gas from poor cement seals on fresh groundwater resources is insufficient. The nature and rate of cement deterioration are poorly understood and there is only minimal or misleading information available in the public domain. (p. xvii Executive Summary)

  • More than once the discussion paper minimizes the human health consequences of methane gas leakages as at (p.1): “the consequences of such leaks, although negative from a climate change perspective, are not a great threat to health because natural gas is not a toxic substance.” The CCA Report goes to some length in the chapter on Water to explain that the effects of methane gas leakage into groundwater are a major question needing study.

The issue to be addressed here concerns the potential impacts of this type of natural gas leakage on groundwater quality. An important associated issue concerns other water quality aspects, that is, the biogeochemical processes that may attenuate the gas during transport by groundwater in freshwater aquifers away from the leaky wells.” (p. 84)


The biogeochemical processes that consume methane can increase hardness (calcium and magnesium concentrations) and produce hydrogen sulfide which, depending on the pH and other factors, may cause a rotten egg smell. According to Vidic et al. (2013), ‘methane can be oxidized by bacteria, resulting in oxygen depletion. Low oxygen concentrations can result in increased solubility of elements such as arsenic and iron. In addition, anaerobic bacteria that proliferate under such conditions may reduce sulfate to sulfide, creating water and air quality issues.’ However, all of these impacts have not yet been confirmed in field investigations in areas of shale gas development. 

The methods needed to assess the effects of methane contamination have been developed in studies of other types of groundwater contamination but have not yet been applied to assess the impacts of methane leakage from leaky oil and gas wells. Therefore, the degree to which the assimilation capacity of the groundwater zone for methane leakage will prevent long-term deterioration of groundwater quality remains unknown.” (p. 85)

The CCA Report concludes that:

the much larger number of wells needed for shale gas extraction, and the occurrence of shale gas development in areas of substantial rural and near-urban populations relying on wells for drinking water, suggest that the consequences of leakage will be correspondingly greater than for conventional oil and gas development.” (p.217)

  • The discussion paper makes repeated references to the “relatively straightforward task to establish good regulatory practices” without any reference to questions of effectiveness and performance of regulatory regimes. The CCA Report states:

 “The Canadian regulatory framework governing shale gas development is evolving and remains untested. … Advanced technologies and practices that now exist could be effective to minimize many impacts, but it is not clear that there are technological solutions to address all of the relevant risks, and it is difficult to judge the efficacy of current regulations because of the lack of scientific monitoring. The research needed to provide the framework for improved science-based decisions concerning cumulative environmental impacts has barely begun.” (p. xx Executive Summary)

  • The discussion paper concludes: “Moderate tectonic stresses and strong rock mean that wellbore instability during drilling will be largely absent; high quality wellbores lead to higher quality primary cementing operations, and therefore fewer cases of leaking wells.” (p.18) Again, no supporting evidence or analysis is offered. This appears to be at odds with the CCA statement noted above, that “the nature and rate of cement deterioration are poorly understood” and to the CCA suggestion that industry claims be subjected to more rigorous scrutiny. The question also remains, even if the quality is higher, what will the percentage of leakage be and over what time period, with what effects on water quality and GHG emissions, and is this an acceptable level of risk?
  • The discussion paper suggests that intermediate strings of casing may not be necessary in Nova Scotia. This appears specifically at odds with the CCA on this question (p.44). Nor does this discussion paper reflect the central importance that the CCA Report attaches to knowing much more about the geology and hydrogeology of the Intermediate Zone of geological strata.
  • The discussion paper states the common argument that “there is apparently no known case of fracturing liquids or gas migration from the target horizon [the shale bed being fractured] directly up through the rock mass to the surface or into shallow aquifers.“ (p.12) And compelling supporting evidence is offered that propagation of fractures all the way up to the groundwater zone or the surface are both unknown and extremely unlikely.  But the CCA Report queries at length the considerably more likely potential for transmission of fluids and gas indirectly, via natural faults, especially through the little studied or understood Intermediate Zone  [pp. 7, 69, 72-76, 78-79].

Nova Scotia would do well to heed the CCA concluding remarks to their chapter on Water:

“Although there are published claims that no proven or verified impacts of shale gas development on groundwater exist, more recent publications and reports dispute these. The burden of proof should not be on the public to show impacts, but on industry to verify that their claims of performance are accurate and reliable over the relevant scales in space and time. There is reason to believe that shale gas development poses a risk to water resources, but the extent of that risk, and whether substantial damage has already occurred, cannot be assessed because of a lack of scientific data and understanding.

The main potential cause of groundwater contamination is expected to be from upward gas migration along well casings or in combination with natural fractures causing entry of gas over extended time into freshwater aquifers or into the atmosphere. In aquifers, the gas may be assimilated by natural geochemical processes, but these same processes may release natural contaminants such as metals and hydrogen sulfide that could degrade water quality.” (p. 96)

Concluding Comments:

While the discussion paper touches on many of the potential problems, it also appears unrealistically optimistic that problems will not occur to any significant extent in Nova Scotia, and if they do, that they can be “easily” identified and fixed. This is where we believe the paper should be amended to integrate and reflect analysis of actual performance. Phrase such as “easily repaired,” “easily monitored”, “issues will be minimized,” “can reasonably be left to effective monitoring” do not reflect available evidence.

Analysis of post 2009 shale gas wells in Pennsylvania by Dr. Tony Ingraffea concludes, “Thorough analysis of well integrity data in “modern” wells with “tough” regulations indicates significant failure rate continues.”  Ingraffea found higher well failure rates in modern unconventional wells than in conventional wells. [1] Information from Saskachewan’s Auditor General indicates that the government is unable to keep up with reclamation of leaking wells, and the wells represent significant potential cost to taxpayers.[2]

The natural “can do” approach of industry and of engineers that issues of monitoring can be resolved in some nebulous manner is not a reasonable formula for preventing harm. A realistic assessment indicates that Nova Scotia already has problems monitoring and cleaning up even a few industrial sites, let alone the prospect of the widely distributed intensive industrial infrastructure characteristic of shale gas development.

We urge the panel to amend this paper to realistically reflect the steep challenges; to base their recommendations on reasonable standards of risk, and thorough sober assessments of monitoring capabilities.


Steering Committee, Nova Scotia Fracking Resource and Action Coalition

June 19, 2014

[1], slide 19,  Well bore integrity: Failure Mechanisms, Historical Record, and Rate Analysis, Slide 11



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