Characterization of chemical additives used for hydraulic fracturing in California
Poster Number
29
Introduction/Abstract
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.
Purpose
In this study, chemical additive use for hydraulic fracturing in California was characterized to evaluate the potential hazards related to human health and the environment. Assessment of chemical use was also intended to guide selection of appropriate treatment technologies and disposal strategies. The study objectives were to determine the: 1) most commonly used chemical additives, 2) chemical additives used in the largest quantities, 3) availability of toxicity data, 4) availability of physical and chemical properties, and 5) data gaps in current knowledge.
Method
Chemical additive use for hydraulic fracturing in California was characterized using data from the FracFocus Chemical Disclosure Registry. Physical, chemical, and biological data was compiled from publicly available online chemical information databases and reference books. Toxicity data for chemical additives was categorized according to the United Nations’ Globally Harmonized System of Classification and Labelling of Chemicals (GHS) acute toxicity categories.
Results
The data set consisted of 45,058 records for 1,623 hydraulic fracturing treatments conducted in California from January 30, 2011 to May 19, 2014. Based on chemical descriptions and/or Chemical Abstract Services (CAS) numbers, 345 unique hydraulic fracturing components were identified. Of these components, 111 lacked CAS numbers and could not be definitively identified for physical, chemical, and toxicological properties. The chemical additives were used as gelling/foaming agents, friction reducers, crosslinkers, breakers, pH adjusters, biocides, corrosion and scale inhibitors, iron controllers, clay stabilizers, and surfactants. Chemical additives were characterized based on broad chemical categories and functionality in hydraulic fracturing. The analysis revealed unique patterns of chemical additive use. For example, solvents and surfactants are used extensively and multiple solvents and surfactants are used in individual treatments. Toxicological data was located for most of the most commonly used chemical additives although data could not be located for chemical additives missing CAS numbers.
Significance
The number of chemicals used in hydraulic fracturing in California is large. CAS numbers are not being reported for many chemicals, with operators claiming that the information is proprietary and represents a trade secret. Physical, chemical, and toxicological data are missing for some of the most commonly used chemicals. Future regulatory efforts could focus on reducing the number of chemical additives used and pre-approval for chemical additives based on the availability of the appropriate data sets (including environmental data). Better disclosure of chemical use and characterization is needed to better understand the hazards associated with hydraulic fracturing in California.
Location
DeRosa University Center, Stockton campus, University of the Pacific
Format
Poster Presentation
Characterization of chemical additives used for hydraulic fracturing in California
DeRosa University Center, Stockton campus, University of the Pacific
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.
