Hydraulic fracturing has revolutionized the U.S.’s energy portfolio by making shale reservoirs productive and commercially viable. However, the public is concerned that the chemical constituents in hydraulic fracturing fluid, produced water, or natural gas itself could potentially impact groundwater or adjacent streams. When considering the potential for unconventional oil and gas development to impact groundwater resources, there are several contamination pathways one can consider. One of the more probable groundwater contamination pathways is a surface spill of produced fluids and/or hydraulic fracturing fluid. The purpose of this project is to evaluate the risks associated with these frequent and potentially high volume surface spills of hydraulic fracturing fluid and flowback/produced water on groundwater resources in the Front Range of Colorado. We conduct fate and transport simulations to assess the mobility and persistence of contaminants such as biocides, friction reducers, surfactants, hydrocarbons, and salt based on sorption to soil, degradation potential, and spill statistics. We seek to understand the hydrologic (e.g. depth to groundwater table, intensity and duration of rain events) and site (e.g. soil type, fraction of organic carbon) conditions under which a surface spill would pose risk to groundwater quality in the event of a release. This coupled analytical-numerical modeling approach could be duplicated by environmental consultants. We focus on the South Platte Alluvial Aquifer, which is located in the greater Denver metro area and overlaps a zone of high-density oil and gas development. This analysis does not consider potential soil contamination. Results suggest that risk of groundwater pollution, based on predicted concentration at the groundwater table, is low in most areas of the South Platte system for the contaminants investigated under common spill conditions. However, substantial risk may exist in certain areas where the groundwater table is shallow. In addition, transport of certain contaminants is influenced by interactions with other constituents in produced or stimulation fluids. By helping to identify locations in the Front Range of Colorado that are at low or high risk for groundwater contamination due to a surface spill, it is our hope that this work will aid in improving prevention, mitigation, and remediation practices so that decision-makers can be better prepared to address accidental releases in Colorado.

Evaluating the risks of surface spills at unconventional oil and gas production sites: A contaminant transport modeling study in the South Platte alluvial aquifer

251st National Meeting (2016)

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