New unconventional fracking wells leak far more than older traditional gas wells, says a smattering of news media outlets reviewing a new study released by the Proceedings of National Academy of Sciences on June 30, 2014. Yet, these “findings” must be assessed in the context of the study’s own admitted limitations.
A team of four scientists analyzed 75,505 compliance reports for 41,381 conventional and unconventional oil and gas wells in Pennsylvania drilled from January 1, 2000, to December 31, 2012, to determine the failure rate in the well casing and cement. The data suggested “large differences” in structural integrity issues between well types, with unconventional (horizontal) wells showing an average six-fold higher incidence of cement and / or casing issues relative to conventional (vertical or “low-volume”) wells. In particular, the data suggested the highest failure rates occurred in the northeastern part of the state, where unconventional wells failed at an average rate of 9.5 percent as compared to conventional wells, which failed at an average rate of 3.75 percent over the 13-year study period. The study also made some suggestion of a comparison between wells drilled prior to 2009 and wells drilled after, noting that the data indicated “newer” wells leaked far more than “older” wells. The study does not go on to explain the differences noted.
Dozens of news media outlets have trumpeted these general findings without mention of the various caveats and qualifications admitted by the study’s authors. For example, the study cites notable discrepancies in inspection records for conventional and unconventional wells. Of the more than 41,000 wells drilled between 2000 and 2013, 24 percent of conventional and 4 percent of unconventional wells drilled have never received facility-level inspections or the relevant inspections are not included in the online database reviewed as the basis for the study, and therefore were not included in this analysis. As another example, the study cautions comparisons of “new” versus “old” wells may be “misleading” as temporal differences between well types may reflect more thorough inspections and greater emphasis on finding well leaks due to increased public awareness and activism, or other factors unrelated to real changes in rates of structural integrity loss.
Although this study provides the most recent fodder to incite both sides of the hotly contested fracking debate, all – including the study’s authors – agree further research is needed before conclusions are drawn about the association between the structural integrity loss in oil and gas wells and possible environmental effects.
The study’s lead author is Professor Anthony R. Ingraffea of Cornell University. The study "Assessment and risk analysis of casing and cement impairment in oil and gas wells in Pennsylvania, 2000–2012" can be found here.