Background for this classification summary
- Visit the Classification Index to see other groups.
- The summary on this page follows the classification scheme of Elsner and Hoelzer, 2016. Quantitative Survey and Structural Classification of Hydraulic Fracturing Chemicals Reported in Unconventional Gas Production. Environmental Science and Technology. 3290-3314. DOI: 10.1021/acs.est.5b02818.
- Elsner and Hoelzer’s thorough and influential article provides a wealth of chemical context about fracking materials including health and environmental implications and suggestions for deeper analysis. However, the work was based partially on a early set of FracFocus (through 2013). Subsequent years have added new materials and millions more records. To extend their analysis to the rest of the FracFocus materials, we used Google’s Gemini to assist us in assigning classifications in line with EH’s methodology.
- Analysis from a FracFocus download, Jan 2025.
- Masses are not available for all records, so reported masses below are sums of only the available masses. See documentation.
- To provide useful technical information about these chemical groups, we use generative AI tools to assist with summaries (Google’s Gemini). These tools are prompted with details of the classification scheme (by Elsner and Hoelzer, 2016) and information about reported chemicals in the group. To limit inaccuracies, we feed the resulting output to competing models (OpenAI’s ChatGPT) to check for accuracy and ambiguity. In addition, we consulted Fink, Johannes, “Petroleum Engineer’s Guide to Oil Field Chemicals and Fluids” Third Edition. (2021) Gulf Professional Publishing. 1028pp.
- Functions reported here are summarized from the FracFocus field “Purpose.” There are limitations to this data: not all chemical records have a reported purpose (the “systems approach” explicitly excludes “Purpose” values from chemical records). Furthermore, “Purpose” typically describes the product, not individual chemicals within the product. The individual ingredient may serve a chemical role in the product that is different from the reported “purpose” (for example, synthetic polymers might be labeled “proppant”, but they are not primary proppants, but rather coatings for sand grains to enhance their performance.) In general, consider these “functions” as the larger purpose played by the product that contains the ingredient.
Organic oxidizing agents, as reported to FracFocus, are organic compounds capable of causing other substances to lose electrons in a chemical reaction. These compounds typically contain oxygen-oxygen single bonds (peroxides) or other highly oxidized functional groups, making them strong oxidizing agents.1
Reported examples include:
- Tert-Butyl hydroperoxide (75-91-2), an organic peroxide
- Peracetic acid (79-21-0), a peroxycarboxylic acid, and its sodium salt, Ethaneperoxoic acid, sodium salt (1:1) (64057-57-4)
Between 2014 and 2024, 6,430 records of organic oxidizing agents were published on FracFocus, representing a total reported mass of 12,100,000 pounds. Products containing these agents are reported to be used in various capacities in hydraulic fracturing, including:
- Breakers (to degrade polymers)
- Biocides (to kill microorganisms)
- Crosslinkers (to form chemical bonds between polymer chains)
- Water conditioning
- Bleaching agents
- Oxidizers
- Acidizers
- Oxygen scavengers
The oxidizing power of these agents is central to their role in many hydraulic fracturing functions.
| Material | Name | Records and mass |
|---|---|---|
75-91-2 | tert-Butyl hydroperoxide | 3,520 records — 4,340,000 pounds |
79-21-0 | Peracetic acid | 2,190 records — 3,820,000 pounds |
64057-57-4 | Ethaneperoxoic acid, sodium salt (1:1) | 711 records — 3,960,000 pounds |
- All molecular structure images courtesy of the US EPA, except where noted. ↩︎