Unconventional oil and gas (OG) development uses the subsurface injection of large amounts of a variety of industrial chemicals. Although well stimulation typically occurs below the useable aquifer, there are concerns that produced water (PW) from stimulated wells may contain mixtures of added OG chemicals and reaction products that present unique and poorly understood risks during the management, treatment, reuse, and disposal of wastewater at the surface. PW, including any flowback of injected fluids, must be managed so as to protect human health and the environment, and understanding the chemistry of PW from stimulated wells is necessary to ensure the overall safe management of PW. New regulations in California require that operators select and monitor representative OG chemicals in PW from unconventional wells. Hydraulic fracturing (HyF) using high concentrations of guar gum is the most commonly applied unconventional OG technique and most operators have selected guar as the indicator chemical. Other than guar, a variety of surfactants, solvents, and biocides have been selected for use as indicator chemicals. There is a need to independently review the selection of indicator chemicals in the context of providing adequate environmental protection. Additionally, methods for measuring indicator chemicals in PW need to be developed and validated. PW have complicated and unique biogeochemistry and analytical methods developed for less complex surface and ground waters need to be proven for measuring contaminants in PW. The objective of this research is to determine what OG chemicals are appropriate candidates as indicator chemicals and to establish verified or validated methods for the measurement of indicator chemicals in PW. A systematic approach is being taken to review and validate analytical methods that are currently used to measure indicator compounds (e.g. guar-carbohydrate, surfactants, biocides), identify interfering substances in PW, and to establish novel methods as needed.

Monitoring hydraulic fracturing indicator chemicals in produced water

2019 Spring National Meeting

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