Environment Science & Technology (Online publication: Aug. 12, 2015; DOI: 10.1021/acs.est.5b00820) / by Robert M. Dilmore, et al.(free download with ACS registration)
Recent large-scale development of oil and gas from low-permeability unconventional formations (e.g., shales, tight sands, coal seams) has raised concern about potential environmental impacts. Legacy oil and gas wells co-located with that new development represent , if left improperly sealed, a potential pathways for unwanted migration of fluids (brine, drilling and stimulation fluids, oil and gas). Uncertainty in the number, location, and abandonment state of legacy wells hinders environmental assessment of exploration and production activity. The objective of this study is to apply publicly available information on Pennsylvania oil and gas wells to better understand their potential to serve as pathways for unwanted fluid migration. This study presents a synthesis of historical reports and digital well records to provide insights into spatial and temporal trends in oil and gas development. Areas with higher density of wells abandoned prior to mid twentieth century, when more modern well sealing requirements took effect in Pennsylvania, and areas where conventional oil and gas production penetrated to or through intervals that may be affected by new Marcellus shale development are identified. This information may help to address questions of environmental risk related to new extraction activities.