Potential Impacts of Spilled Hydraulic Fracturing Fluid Chemicals on Water Resources: Types, Volumes, and Physical-chemical Properties of Chemicals

Abstract:

Hydraulic fracturing (HF) fluid chemicals spilled on-site may impact drinking water resources. While chemicals generally make up <2% of the total injected fluid composition by mass, spills may have undiluted concentrations. HF fluids typically consist of a mixture of base fluid, proppant, and additives. Additives, comprised of one or more chemicals, are serve a specific engineering purpose (e.g., friction reducer, scale inhibitor, biocide). As part of the USEPA’s Draft Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources, we investigated the different types, volumes injected, and physical-chemical properties of HF fluid chemicals. The USEPA identified 1,076 chemicals used in HF fluids, based on 10 sources covering chemical use from 2005 to 2013. These chemicals fall into different classes: acids, alcohols, aromatic hydrocarbons, bases, hydrocarbon mixtures, polysaccharides, and surfactants. The physical-chemical properties of these chemicals vary, which affects their movement through the environment if spilled. Properties range from fully miscible to insoluble, from highly hydrophobic to highly hydrophilic. Most of these chemicals are not volatile. HF fluid composition varies from site to site depending on a range of factors. No single chemical or set of chemicals are used at every site. A median of 14 chemicals are used per well, with a range of four to 28 (5^th and 95^th percentiles). Methanol was the chemical most commonly reported in FracFocus 1.0 (72% of disclosures), and hydrotreated light petroleum distillates and hydrochloric acid were both reported in over half the disclosures. Operators store chemicals on-site, often in multiple containers (typically in 760 to 1,500 L totes). We estimated that the total volume of all chemicals used per well ranges from approximately 10,000 to 110,000 L. The views expressed here are those of the authors and do not necessarily represent the views or policies of the USEPA.