Hydraulic fracturing of unconventional fossil fuel reserves poses complex environmental problems. Well permits for extracting natural gas from Marcellus shale in Pennsylvania, US have been steadily increasing since 2007. To extract the gas, up to 5 million gallons of fluid, composed of acid, in/organics, and salt, is pumped into the shale formation at high pressure. Approximately 10-30% of this fluid returns to the surface along with inorganic, organic, and radioactive contaminants from the geologic formation and components of the initial fluid additives. A mechanistic understanding of the relationship between injected fracture fluids and flowback contaminant origination within the shale formation will be a challenge to attain. However, such knowledge could help redesign fracturing fluids and promote methods for pollution prevention. In this study we designed two synthetic fracturing fluids (SFFs) based on chemicals used in drilling logs posted on fracfocus.org. Marcellus shale samples were pulverized, sieved, and then reacted with the SFFs for up to 72 h in a high pressure (10 bar), elevated temperature (60<sup>o</sup>C), stirred-tank reaction cell. The reacted fluids were analyzed for a suite of analytes including: total organic carbon, chemical oxygen demand, organic speciation by GC, gross alpha and beta radioactivity, pH, conductivity, total dissolved solids, trace metals, and anions and cations. The results will help identify contaminants that can be mobilized from shale and understand contaminant transformations under high pressure and temperature conditions.

Contaminant mobilization via reactions between Marcellus shale and synthetic fracturing fluids

249th National Meeting (2015)

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