Two recently published studies indicate groundwater supplies in Pennsylvania have been affected very little by the natural-gas drilling boom the state has seen in the last 10 years.
Pennsylvania is now second only to Texas in the nation for gas production as more than 11,000 wells have been drilled since 2008. And a pair of studies says groundwater has not had much impact in recent years from hydraulic fracturing, the practice that extracts oil and gas from shale underground.
One study, published recently in Proceedings of the National Academy of Sciences, was the work of a team of researchers from Yale University. They drilled eight water wells and regularly drew samples for two years while seven natural gas wells were drilled nearby. Their results showed methane spiking in some water wells, but due to natural variability, not oil and gas drilling.
A second study was published in Environmental Science & Technology. In it, a team from Penn State University looked at 11,000 groundwater samples from the Pennsylvania Department of Environmental Protection with what they described as a “novel data-mining technique” and concluded water quality was unchanged for the most part. The report states the researchers found methane only seven of 1,385 shale wells in the study area.
Both studies, while contributing to the technical literature on methane and groundwater, have also generated some questions as well. For example, the second study focused on just one county in Pennsylvania.
NGWA’s flagship technical journal, Groundwater®, also had a special section on subsurface methane and its migration in its March-April 2018 issue. Five papers and a guest editorial make up the section exploring various aspects of methane occurrence and migration in groundwater.
Topics covered include the effects of CO2 injection on methane migration, gas leakage from faulty petroleum wells, and methane migration in shallow aquifers in the Karoo basin in South Africa.
The research papers highlight both natural and anthropogenic sources of methane related to unconventional drilling, as well as the techniques to distinguish between these and to model the migration of methane.
Since 1963, Groundwater has published a dynamic mix of papers on topics focused on groundwater such as flow and well hydraulics, hydrogeochemistry and contaminant hydrogeology, application of geophysics, management and policy, and the history of hydrology.
NGWA has also developed the information brief, Water Wells in Proximity to Natural Gas or Oil Development.