H105-06
Investigating the sources and extent of groundwater contamination in areas of extensive oil, gas, and coal extraction using data mining

Thursday, 10 December 2020: 20:50
Virtual
Samuel Shaheen1, Tao Wen2, Alison Herman3 and Susan L Brantley1,3, (1)Pennsylvania State University Main Campus, Department of Geosciences, University Park, PA, United States, (2)Syracuse University, Department of Earth and Environmental Sciences, Syracuse, NY, United States, (3)Pennsylvania State University Main Campus, Earth and Environmental Systems Institute, University Park, PA, United States
Recorded Presentation
Abstract:
Using large groundwater data sets and data mining techniques, the potential water quality impacts of shale gas extraction can be assessed on a regional scale. However, such methods have not previously been implemented in shale plays where shale gas extraction overlaps with extensive urbanization, legacy oil and gas drilling, and/or coal mining. Such overlap may complicate the attribution of contaminant sources or interact with shale gas drilling to exacerbate groundwater contamination.

In this study, anthropogenic and geologic influences on groundwater chemistry in an area of widespread contemporary and legacy oil, gas, and coal extraction were analyzed using a large dataset of groundwater samples from southwestern Pennsylvania. Concentrations of methane, sulfate, and chloride were particularly emphasized given their association with potential sources of groundwater contamination in the region. We used a geospatial data mining technique to identify regions in which increases in methane, sulfate, or chloride concentrations may be attributable to oil and gas drilling, coal mining, road salting or regional (hydro)geology. In addition, we used a machine learning model (non-negative matrix factorization) to assess the relative contributions of various sources of methane, sulfate, and chloride in the study area.

Preliminary results identify 1.) a small number of localities where methane concentrations in groundwater increase in proximity to oil and gas wells, 2.) larger areas where methane and sulfate concentrations increase nearby coal mining, and 3.) methane in groundwater predominantly derives from natural sources. Additionally, multiple lines of evidence suggest that shale gas wells in the study area may be less prone to methane migration than wells in northeastern Pennsylvania. While these results suggest groundwater has been relatively well-protected during hydrocarbon extraction, the infiltration of road salt nearby highways was widespread and road salt is an appreciable source of chloride in groundwater on a regional scale.

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