Characterization of chemical additives used for hydraulic fracturing in California

Hydraulic fracturing is an oil and gas well stimulation technique in which fluids are pumped into wells under high pressure to fracture geological formations, thereby increasing formation permeability and oil/gas yields. Hydraulic fracturing fluids are complex mixtures typically composed of water, proppant (e.g. fine sand), and chemical additives. Hydraulic fracturing is being practiced pervasively throughout the United States. The application of hydraulic fracturing in California is unique: treatments are typically applied for oil production using gelled fluids

Characterization of chemical additives used for hydraulic fracturing in California

Hydraulic fracturing is an oil and gas well stimulation technique in which fluids are pumped into wells under high pressure to fracture geological formations, thereby increasing formation permeability and oil/gas yields. Hydraulic fracturing fluids are complex mixtures typically composed of water, proppant (e.g. fine sand), and chemical additives. Hydraulic fracturing is being practiced pervasively throughout the United States. The application of hydraulic fracturing in California is unique: treatments are typically applied for oil production using gelled fluids

Identifying chemicals of concern in hydraulic fracturing fluids used for oil production.

Chemical additives used for hydraulic fracturing and matrix acidizing of oil reservoirs were reviewed and priority chemicals of concern needing further environmental risk assessment, treatment demonstration, or evaluation of occupational hazards were identified. We evaluated chemical additives used for well stimulation in California, the third largest oil producing state in the USA, by the mass and frequency of use, as well as toxicity. The most frequently used chemical additives in oil development were gelling agents, cross-linkers, breakers, clay control agents, iron and scale control agents, corrosion inhibitors, biocides, and various impurities and product stabilizers used as part of commercial mixtures. Hydrochloric and hydrofluoric acids, used for matrix acidizing and other purposes, were reported infrequently. A large number and mass of solvents and surface active agents were used, including quaternary ammonia compounds (QACs) and nonionic surfactants. Acute toxicity was evaluated and many chemicals with low hazard to mammals were identified as potentially hazardous to aquatic environments. Based on an analysis of quantities used, toxicity, and lack of adequate hazard evaluation, QACs, biocides, and corrosion inhibitors were identified as priority chemicals of concern that deserve further investigation