Unconventional Oil and Gas Development: Implications for Soil and Water Quality.

Hydraulic fracturing (HF) is a widely used technology that enhances oil and gas extraction from unconventional formations. The fluids used in HF contain about 90% water, 10% proppant and 0.5-1% HF fluid additives. Depending on formation geology, between 3-50 million liters of water, and therefore tens of thousands of liters of chemicals, are injected into each well. Produced water is the largest waste stream associated with oil and gas operations, with over 3 trillion liters produced annually in the U.S. Because of its origins in oil and gas reservoirs, produced water contains elevated levels of toxic petroleum hydrocarbons, total dissolved solids, heavy metals and naturally occurring radioactive materials. Additionally, this water may contain any remaining chemicals that are used during the drilling, hydraulic fracturing and well maintenance processes, as well as their transformation products.

This presentation will provide an overview of the key technological and societal challenges related with HF. Then a summary of findings from the following three projects will be discussed: 1) in order to better understand the potential environmental impacts of released hydraulic fracturing fluids, we have investigated the transformation of HF fluid additives under a variety of conditions covering the typical range encountered in unconventional shale formations, 2) since hydraulic fracturing frequently occurs in the vicinity of agricultural lands, improper storage and handling of hydraulic fracturing fluids or spills of flowback water may lead to soil and water contamination. Thus, we have elucidated the fate among commonly used HF fluid additives in agricultural soil, and 3) in Wyoming, produced water is typically treated through settling ponds where remaining oil is removed prior to discharge into surface waters. To determine the potential toxicological impact on downstream water quality we used chemical analysis and bioassays to quantify the toxicity and mutagenicity of the impacted water at multiple locations.