Strontium Isotopes as Tracers for Contamination from Potential Marcellus Shale Waters

Monday, 15 December 2014
Zhang Cai, Pennsylvania State University Main Campus, University Park, PA, United States, Li Li, Pennsylvania State University Main Campus, John and Willie Leone Family Department of Energy and Mineral Engineering, University Park, PA, United States and Alexandra Hakala, National Energy Technology Laboratory Pittsburgh, Pittsburgh, PA, United States
Mineralogical and geochemical conditions vary significantly in natural water systems, including groundwater aquifers and rivers. In addition, contamination events are often elusive. As a result, it is often challenging to pinpoint the contamination of natural waters by specific types of water sources. The strontium isotope ratio R87Sr, defined as 87Sr/86Sr, has shown promise in discerning contamination from different types of wastewaters related to Marcellus Shale development. The R87Sr of potential end members, including Marcellus shale produced water (0.710-0.712) and Upper Devonian/Lower Mississippian formation brine (0.720-0.721), have been shown to be distinct from those in natural waters. Here we use reactive transport modeling (CrunchFlow) to understand key process and factors that govern the evolution of R87Sr, and the conditions under which we can discern contamination sources in natural water systems. Simulation results show that ion exchange reaction plays an important role in the evolution of R87Sr while release rate has a relatively minor impact on R87Sr evolution. Even with large dilution factor where the volumetric flow rate of natural waters is orders of magnitude higher than the release rates of contamination source water, the R87Sr is still sensitive to different types of source contamination waters. Insights gained here suggest that strontium isotopes can potentially be used as a tracers for different type of water contamination. The modeling tool developed can offer a powerful tool for understanding, predicting, monitoring of natural water contamination.