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.
Gases, as reported to FracFocus in the context of hydraulic fracturing, are substances in their gaseous state under standard conditions, utilized across various stages of the process.1 The two reported gases are:
- Nitrogen (7727-37-9): Typically used in its compressed or liquefied form as an “energized fluid.” It plays a significant role in improving proppant transport by aiding in foam creation, reducing water requirements, and supporting the flowback of fluids post-fracturing.
- Carbon dioxide (124-38-9): Similar to nitrogen, carbon dioxide is utilized as an energized fluid. Its primary functions include enhancing foam formation for proppant delivery, minimizing water use, and facilitating the recovery of fracturing fluids during the flowback process.
Between 2014 and 2024, 3,330 records of Gases were published on FracFocus, with a total reported mass of 1,390,000,000 pounds.
The primary roles of these gases in hydraulic fracturing include:
- Facilitating foam generation to enhance proppant transport
- Reducing water consumption
- Aiding in the flowback of fracturing fluids after the process
| Material | Name | Records and mass |
|---|---|---|
7727-37-9 | Nitrogen | 3,050 records — 1,270,000,000 pounds |
124-38-9 | Carbon dioxide | 285 records — 124,000,000 pounds |
- All molecular structure images courtesy of the US EPA, except where noted. ↩︎