title: Strontium isotopes test long-term zonal isolation of injected and Marcellus formation water after hydraulic fracturing.
abstract: One concern regarding unconventional hydrocarbon production from organic-rich shale is that hydraulic fracture stimulation could create pathways that allow injected fluids and deep brines from the target formation or adjacent units to migrate upward into shallow drinking water aquifers. This study presents Sr isotope and geochemical data from a well-constrained site in Greene County, Pennsylvania, in which samples were collected before and after hydraulic fracturing of the Middle Devonian Marcellus Shale. Results spanning a 15-month period indicated no significant migration of Marcellus-derived fluids into Upper Devonian/Lower Mississippian units located 900-1200 m above the lateral Marcellus boreholes or into groundwater sampled at a spring near the site. Monitoring the Sr isotope ratio of water from legacy oil and gas wells or drinking water wells can provide a sensitive early warning of upward brine migration for many years after well stimulation.
authors.affiliation: Department of Geology & Planetary Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Courtney A Kolesar
authors.initials: CA
authors.lastname: Kohl
authors.forename: Rosemary C
authors.initials: RC
authors.lastname: Capo
authors.forename: Brian W
authors.initials: BW
authors.lastname: Stewart
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wall
authors.forename: Karl T
authors.initials: KT
authors.lastname: Schroeder
authors.forename: Richard W
authors.initials: RW
authors.lastname: Hammack
authors.forename: George D
authors.initials: GD
authors.lastname: Guthrie
mesh_terms: D002118:Calcium / Q000032:analysis; D005843:Geography; D019015:Geologic Sediments / Q000737:chemistry*; D060587:Groundwater; D008962:Models, Theoretical; D061329:Oil and Gas Fields / Q000737:chemistry; D010414:Pennsylvania; D012492:Salts / Q000737:chemistry; D013324:Strontium / Q000032:analysis*; D013325:Strontium Isotopes / Q000032:analysis; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D012492:Salts; D013325:Strontium Isotopes; D014874:Water Pollutants, Chemical; C017082:brine; D014867:Water; D002118:Calcium; D013324:Strontium