Chemical additives make up only a fraction of the fluids used in hydraulic fracturing (fracking) operations on oil and natural gas wells, but fluid is used in such great volumes that the amount of chemicals still adds up to impressive totals, according to the Environmental Protection Agency (EPA).
"Among the entire data set, the sum of the maximum hydraulic fracturing fluid concentration for all additive ingredients reported in a disclosure was less than 1% by mass in approximately 80% of disclosures, and the median maximum hydraulic fracturing fluid concentration was 0.43% by mass," the agency said in an analysis of fracking fluid data from the FracFocus registry.
The median total water volume per disclosure was about 1.5 million gallons, so even those small percentages of chemical additives "may mean hundreds or thousands of gallons of chemicals could be transported to, and present on, the well pad prior to mixing the fracking fluid," said EPA science adviser Tom Burke. "Remember, 1% of one million gallons is a large number -- 10,000 gallons."
The most commonly reported additive ingredients were methanol, hydrochloric acid and hydrotreated light petroleum distillates, but 692 unique ingredients were reported to FracFocus. Among proppants, quartz was the most common material reported, and water made up an average of 88% of frack fluids, EPA said.
EPA analyzed data from more than 39,000 FracFocus disclosures provided to the agency by the Ground Water Protection Council two years ago. "Each disclosure contained data for an individual oil and gas production well," EPA said, and frack dates were between Jan. 1, 2011 and Feb. 28, 2013. Wells were located in 406 counties in 20 states and the data was reported by a total of 428 well operators.
EPA also released state-by-state summaries of FracFocus data. By far the most disclosures came from operations in Texas (18,075 disclosures), where the majority of onshore drilling occurs.
The analysis is part of a larger study, "Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources," being conducted by EPA and due out later this year.
"When the assessment is complete, EPA's scientific work will result in a robust, rigorously peer-reviewed study that connects as many dots as currently possible given the state of the science," Burke said. "And states, tribes, industry and communities will have a fuller picture of what the science currently tells us when making important decisions about how to best protect water resources and safeguard public health."
A long-awaited rule for fracking on public and tribal lands, released earlier this month by the Department of Interior, requires operators to temporarily store produced water in aboveground tanks and disclose most of the chemicals they use to the FracFocus registry (see Shale Daily, March 20). The rule ran into immediate opposition (see Shale Daily,March 26).