Methane Migration from Abandoned Fracking Sites Significant

The EPA has recently proposed controversial new regulations that place limitations on the amount of methane released during hydrofracking operations. Now a study conducted by researchers from the University of Vermont has revealed that methane from fracking sites can migrate through disused wells and escape to the atmosphere undetected. As these sites are no longer monitored, these greenhouse gas emissions are not being measured. The study, which appears in the current edition of Water Resources Research (20 October 2015), shows that fractures produced in the surrounding rock during the fracking process provide a conduit for methane to migrate to preexisting abandoned gas wells nearby, allowing the gas to leak to the surface.

Methane Migration Cause of High Methane Emissions at Abandoned Wells

In another paper that recently appeared in the Proceedings of the National Academy of Sciences researchers revealed that methane emissions at abandoned gas wells situated near current fracking operations can be significantly high, although the source of the methane was not investigated in this study. "The debate over the new EPA rules needs to take into account the system that fracking operations are frequently part of, which includes a network of abandoned wells that can effectively pipeline methane to the surface," said James Montague, a PhD student in the Environmental Engineering department at the University of Vermont and lead author of the new study. The study concentrated on gas wells in the Marcellus Shale formation in the state of New York, which has been extensively fracked until the recent ban on fracking in the state halted fracking operations in the area. The Marcellus Shale formation, which consists of layer of hydrocarbons and shale, lies beneath an area that has exploited by oil and gas companies using conventional drilling methods for well over a century. The Department of Environmental Conservation has records for around 40,000 existing gas wells for the oil fields in the state of New York, of which 30,000 are sited within the Marcellus Shale formation. However, they estimate that a total of 70,000 wells have been drilled.

Modeling the Probability of Methane Migration

Since many of the wells are undocumented and their location is unknown — surprisingly common in many areas where fracking occurs — the researchers used mathematical modeling techniques to determine the likelihood that fractures produced during fracking operations at a randomly sited new gas well could connect up with an existing well-bore. The model showed that the probability of new fracking induced fractures linking up with an existing well-bore to be between 0.3-3%. However, information that has emerged since the study was published greatly increases these probabilities. While conditions at fracking sites differ, they all tend to have a similar hydrocarbon profile which attracted oil and gas companies using conventional drilling methods in the past. Consequently most of these sites, like the ones sited in the Marcellus Shale formation, have many abandoned wells, a large percentage of which are undocumented and thus their locations unknown. However, not all abandoned wells serve as a conduit for the release of methane. Only when the well’s concrete wall that prevents migration of gases to the surrounding soil becomes damaged, can gases escape and migrate through soils and fractures in rock to surrounding wells. However, according to co-author, George Pinder, a professor of environmental engineering at the University of Vermont, considering how many abandoned wells are out there, even a relatively small percentage of damaged well-bores, pose a potentially high environmental risk.

Featured Image by Simon Fraser University, via Flickr