WORKING WITH CITIZEN SCIENTISTS AND HOMEOWNERS IN PENNSYLVANIA TO UNDERSTAND HYDROCARBON-RELATED CONTAMINATION OF WATER RESOURCES
Open Access
- Author:
- Woda, Joshua
- Graduate Program:
- Geosciences
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 25, 2019
- Committee Members:
- Susan Louise Brantley, Thesis Advisor/Co-Advisor
Katherine Haines Freeman, Committee Member
Demian Saffer, Committee Member - Keywords:
- Shale gas
water quality
methane
hydraulic fracturing
oil and gas
contamination
citizen science - Abstract:
- Extensive shale gas development around the world has generated concerns about environmental impacts such as migration of natural gas into surface and groundwater resources. However, in Pennsylvania, these concerns are only the most recent in the state’s long history of hydrocarbon development which spans back to the mid 1700’s. Both recent and legacy forms of hydrocarbon extraction have the potential to leak hydrocarbons and other contaminants into the subsurface and the atmosphere. Legacy hydrocarbon development includes old and abandoned oil, gas and coal extraction. Yet, a lack of understanding exists regarding how hydrocarbons behave in the subsurface during leakage and how they may change aquifer quality during prolonged leaks. There is also a knowledge gap regarding how legacy extraction techniques cause contamination years after their abandonment. This thesis evaluates hydrocarbon leakage and its associated consequences from unconventional oil and gas activity in a specific case study, and broader regional leakage trends from various forms of hydrocarbon extraction statewide. In Chapter 2, I studied high gas concentrations in surface and groundwater at a site near problematic Marcellus Shale gas wells to determine the geological explanations and geochemical implications. I found that prolonged methane migration had changed redox conditions in the aquifer, mobilizing metals and transforming sulfate to sulfide. I also explored geochemical tracers in the waters that may be useful diagnostic tools to find other areas with recent methane migration (i.e., possible leakage related to human activity) rather than methane that has been present for a long time (i.e. methane from natural sources). In addition, I identified geologically “risky” areas where drillers should consider taking extra precautions. In Chapter 3, the objective was to collect stream methane samples in a broad area of the Appalachian Basin focused on Pennsylvania to learn which hydrocarbon sources are leaking methane. The goal was to investigate background concentrations and leakage while helping local groups and organizations learn about and understand hydrocarbon leakage in their areas. Throughout this study I helped organize sampling campaigns in streams across Pennsylvania and into West Virginia using the help of citizen scientists. The nonscientists helped with sampling and finding problematic areas at the same time that we emphasized communication between scientists and the community. Many citizen scientists brought with them local concerns (usually not previously known to scientists) about contaminant source locations within their respective regions. This helped immensely with scientists’ decisions about where to focus resources during sampling. Sampling campaigns targeted areas with different techniques of hydrocarbon extraction, ranging from old to modern. Elevated stream methane was mostly observed around conventional oil and gas and coal mining activity. Specifically, the data showed that more leakage may be occurring near the oldest subset of conventional oil and gas wells. The methane concentrations in streams near wells emplaced before 1955 were often highest. In streams near abandoned coal mines, it was commonly observed that methane dissolved in water is escaping from the mines. Such methane ultimately emits into the atmosphere across Pennsylvania from flooded coal mines at a rate of at least 150,000 kg/y. This value is much lower than the rate of emission from abandoned oil and gas wells, newly emplaced unconventional wells, or non-flooded coal mines. Finally, in many areas of suspected hydrocarbon leakage, I discovered orange-colored springs reminiscent of abandoned mine drainage (AMD) but which were not associated with known coal mining activity. Geochemical analysis of these springs suggests that this phenomenon is a previously-unreported byproduct of some cases of hydrocarbon migration. This new type of discharge is referred to here as Gas Leak Drainage (GLD). GLD differs from AMD in that it is characterized by low sulfate concentrations, relatively low specific conductivity, and high hydrocarbon concentrations. The findings presented in this thesis highlight the importance of monitoring and research associated with the environmental impacts of both current and legacy hydrocarbon extraction. The extent of these types of methane leakage and associated migration in the subsurface remains poorly characterized. Additionally, legacy environmental impacts can continue to grow and evolve as infrastructure ages, justifying the need for continued research. The impacts of legacy hydrocarbon development should also be taken into account when considering future development.