Understanding the composition, or formulations, of well stimulation fluid (WSF) is an important step in defining the upper limits of potential environmental impacts from hydraulic fracturing and other well stimulation technologies. The amount of chemicals added to WSF define the upper limits of the for the mass and concentrations of these chemicals that can be released into the environment. The chemicals added to WSF can also influence the release of metals, salts, and other materials found naturally in oil and gas bearing geological formations. Due to the economic value of individual WSF formulations, industry has been generally reticent about releasing detailed information concerning the types and amounts of chemicals used in specific formulations. Often when information is released, the information is incomplete or partially obscured. This lack of transparency has heightened concerns about the chemicals used in WSF. As part of the SB4 scientific study, we investigated the composition of WSF that are used in California with the objectives of developing a comprehensive list of chemicals used for unconventional oil and gas production, determining the concentrations at which the chemicals are used, and estimating the amount (mass) of each chemical that is used per well stimulation. This information was combined with information on hazard, toxicology, and other physical, chemical, and biological properties with the objective of establishing the hazard and ultimately the risks associated with chemicals used for unconventional oil and gas production. Voluntary disclosures included 21,705 entries for individual chemicals and chemicals mixtures reported to be used for 721 well stimulation operations at 716 wells conducted in California between May 17, 2011 and May 19, 2014. Two-hundred and thirty-eight (238) individual chemicals or chemicals mixtures were identified. Chemicals were sorted and ranked based on frequency of use, mass used per application, concentration of use, toxicological profile and other variables, such as biodegradability, that are important to understanding hazard and risk. The results of these studies will be presented with an emphasis toward understanding the hazards associated with commonly used WSF additives.

Composition and associated hazards of well stimulation fluids used in California (USA)

249th National Meeting (2015)

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