Does Proximity of Hydraulic Fracturing and Wastewater Disposal to Geologic Basement Rocks Increase the Likelihood of Seismicity in the Central and Eastern US?
Over the past decade, the increased use of enhanced oil and gas recovery operations is thought to be largely responsible for a dramatic rise in earthquakes in the in the Central and Eastern US. However, some areas that have experienced such an increase, such as in Pennsylvania and North Dakota, appear to have little if any earthquakes related to these operations. This study seeks to better understand these geographic differences by examining whether the subsurface proximity of oil and gas operations to geologic basement rocks promotes earthquakes. Located a few miles below the surface, the basement is comprised of igneous and metamorphic rocks that can contain numerous ancient faults. Both hydraulic fracturing and wastewater disposal operations result in deep fluid injection occurring close to the basement may have the potential to reactivate these basement faults, producing earthquakes. This study seeks to test this idea by improving earthquake detection, refining knowledge of how deep the basement is, and comparing these to the geographic location, depth, and timing of oil and gas operations. In particular, the researchers will apply new processing of seismic data to better detect small earthquakes, compile detailed records of well operations from state databases, and produce regional basement-depth maps across the Central and Eastern US. To accomplish these goals, this project will leverage new approaches to developing large-scale undergraduate research involvement. This project will also increase knowledge transfer with geologic surveys, state regulators, and the oil and gas industry. The researchers will continue to build on a track record of public outreach including proactive dissemination and discussion with the news media considering the national debate over hydraulic fracturing.
To improve the detection of induced seismicity, this research will first employ a template matching approach that has successfully discerned induced from natural earthquakes. This research will also utilize an emerging technology for detecting the repetitive microseismic swarms commonly associated with induced events, without requiring a previously cataloged earthquake as a template. These approaches will be employed on seismic stations throughout the Central and Eastern US and will provide a more uniform detection of induced seismicity. To improve basement depth characterization, this research will integrate recently constructed basement maps, particularly those by state geological surveys and regional compilations. Deep wells will also help characterize geology between injection/hydraulic fracturing target intervals and basement to determine if the mechanical properties of these subsurface rocks may influence the occurrence of induced earthquakes. This project will actively engage state geologic surveys in the Central and Eastern US to accomplish the project goals. In some cases our research will benefit from existing basement, geologic, or seismicity characterizations performed by state geological surveys and other agencies. In other cases we expect to generate and contribute this information to these institutions. Geologic surveys are also key communicators to the general public, so this research will capitalize on the opportunities to integrate new results from this project with existing educational resources that these state surveys already provide. This project will also utilize new undergraduate curricular structures to introduce foundational research concepts early in a student?s college career to engage a larger number of students in research project such as this one. Mentoring will be formalized to establish thematic research teams focused on the project goals. The results will be disseminate with and beyond the academic community, continuing to engage industry and regulators as well as the general public.
