Fluid mixing between fracturing fluids and regional brine is expected to significantly influence the chemistry of water produced from hydraulically fractured shales. However, limited knowledge exists regarding physical changes in the shale reservoir during hydraulic fracturing and early stages of flowback that could affect measured constituents in produced waters. For example, hydraulic fracturing could liberate colloids (&lt; 0.45 µm) such as clay particles from shale minerals, which would affect the chemical analysis of produced water and interpretations of subsurface processes controlling the long-term evolution of the fractured shale. In this study, we investigate the contribution of colloids to the chemistry of shale gas produced water by measuring major and trace elements, radiogenic strontium, and lithium isotopes in produced water samples filtered through different size fraction (0.45 µm, 0.22 µm, and 3kDa) membranes. Lithium (δ7Li) and strontium (87Sr/86Sr) isotopes are separated from sample matrix prior to isotopic measurements by the multi-collector ICP-MS (Neptune Plus). Mass balance calculations will quantify the contribution of colloids to the overall produced water chemical composition, providing insights of physical interactions that may occur during hydraulic fracturing. Results from this study also will be compared geographically with produced waters analyzed across the Appalachian Basin.

Contribution of colloids to major and trace element contents and isotopic compositions (Li and Sr) of water co-produced with natural gas from Marcellus Shale

252nd National Meeting (2016)

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