Article courtesy of Caroline Winter | November 6, 2014 | Bloomberg Business Week | Shared as educational material
Despite the concerns about wastewater from hydraulic fracturing, it can be difficult to keep track of where the drilling fluids end up. Now a team of researchers claims to have figured out how to trace leaks and spills of fracking fluids—and even detect their presence in treated water.
The method, detailed in a study published in the journal Environmental Science & Technology, relies on identifying a specific combination of geochemical characteristics unique to fracking wastewater. “There’s a particular chemical signature we look for,” explains Nathaniel Warner, postdoctoral fellow at Dartmouth College and lead author of the study. That signature is independent of ingredients that make up fracking fluids, which vary and are often proprietary. Instead, it relies on elements that merge with the fracking fluids underground.
Fracking, as the name suggests, fractures rock formations deep below the surface of the earth to stimulate the flow of oil and gas, making it possible to recover greater volumes. Large quantities of fluids made from a mixture of fresh water and chemicals are injected into the ground at high pressure, eventually flowing back to the surface from the pressure below.
These so-called flowback fluids, which typically contain the injected chemicals as well as materials picked up underground, are notoriously difficult to trace. “In some cases, it’s also difficult to determine whether salinity or contamination of shallow fresh water might have been from the most recent hydraulic fracturing or whether it’s associated with this historical development,” says Warner.
To solve the problem, Warner and his team began thinking about what might be different about hydraulic fracturing flowback fluid and found that it contains much higher concentrations of boron and lithium. “When you’re injecting these fluids into the rock formations, you’re breaking apart the shales, and attached to a lot of these shales are boron and lithium,” he says. “We believe [the fluids] pick off that boron and lithium.”
To test for fracking fluids, Warner’s team tests for specific isotope ratios of boron and lithium, as well as elemental ratios of lithium to chloride and and boron to chloride. The team tested their method on 39 samples in Pennsylvania and Arkansas and at a spill site in West Virginia. The method worked even for detecting flowback water that had been treated at a municipal treatment plant. The next step will be to test samples at other basins.
Warner hopes the method will eventually be adopted by regulators and anyone looking to identify the origins of pollution. “Regulators could say, for example, ‘Hey, we have this data, and the spill appears to be associated with hydraulic fracturing fluids, not historic oil and gas production.’ ”
Risks of contamination, of course, will remain a problem.