|The tracing method has been field-tested at a spill site in West Virginia and downstream from an oil and gas brine wastewater treatment plant in Pennsylvania. Source: Avner Vengosh|
The question that left them scratching their heads: “When we see contamination, how will we be able to differentiate it from kind of the history of contamination for example, because much of the drilling of hydraulic fracturing takes place in an area where there is a legacy of decades of conventional oil and gas drilling,” Vengosh says. “So when you see contamination, how could you tell whether this contamination is not a result of past activities — 20, 30 years ago — and is it really related to fracking today?”
That big unknown culminated into two years of research, co-led by Vengosh, and an answer — a geochemical tracing method — funded by the National Science Foundation and published in the Environmental Science and Technology journal in October 2014.
This tracing method can help drilling companies better understand the scope of the problem when flowback disposal and containment methods fail, and help shield companies from blame when fracking fluid isn’t actually the source of contamination in an area.
How It Works
“What we were looking at is … what would account for a difference to really tell apart what might have been historical oil and gas production compared to more recent hydraulic fracturing fluid,” says Nathaniel Warner, lead author of the study. “What we sort of zoned in on was, what’s the major difference? … With the fracking fluids you’re going after these tight formations … and you’re really targeting the source material there, so what we thought might be different was the availability of some of these ions, boron and lithium isotopes that might be stuck on that shale.”
Hydraulic fracturing fluids typically contain mixes of water, sand and proprietary chemicals. Drillers inject large amounts of the fluids down gas wells at high pressure to fracture shale formations deep underground, which allows natural gas trapped within the shale to flow up the well. Once the process is complete, the fracking fluids flow back up the well to the surface along with the gas.
The findings show that the hydraulic fracturing process causes naturally occurring boron and lithium elements from shale formations to break off and return up the well in flowback fluid. Being able to identify actual shale properties in fracking flowback samples scientifically links the fluid to fracking, distinguishing it from any other possible sources of contamination.
“What we are suggesting in our paper is that we have a tracer that is independent of the chemicals that they’re actually adding into hydraulic fracturing fluid,” Vengosh says.
This means determining where fracturing fluids have or haven’t been released into the environment is possible without having to know what chemicals initially made up the fracking fluids used in a particular area of contamination.
“It’s really just making very precise measurements of both the concentration of what’s in that water — the chemistry of what’s in that water — and the isotope ratios of what’s in that water,” Warner says. “It’s not a gadget you take out in the field and you survey. It’s not that at all.”
On Site Testing
The tracing methods were field-tested at a spill site in West Virginia and downstream from an oil and gas brine wastewater treatment plant in Pennsylvania. After obtaining various fluid waste samples from conventional oil and gas drilling along with hydraulic fracturing, the scientists brought them to their lab at Duke and analyzed them using a mass spectrometer. First, they systematically measured samples to show a statistically valid difference between hydraulic fracturing fluid and conventional oil and gas waste. Then, they took examples of contamination from the two sites to demonstrate that they could actually identify hydraulic fracturing fluid in the environment.
Vengosh says the new tracing method provides an important first step for any monitoring or remediation process that would need to take place. “When you see contamination, it’s not only important to say ‘Oh, we have a problem,’ but ‘How we can solve it?’ and identification of the source is the first step of resolving the problem.”
He says he’s very familiar with the widespread skepticism of residents, particularly water well owners, in areas of fracking and that by no means is the tracing method intended to nail down the fracking industry. Calling his research efforts objective, he highlights the good the new technology could do for hydraulic fracturing companies and well owners alike.
This scientific process could help companies within the hydraulic fracturing industry avoid hundreds of lawsuits in cases where fluids in the environment don’t trace back to them, Vengosh says. As for the opposite side of the debate, he says the method offers knowledge as to the source of contamination. “We can provide a scientific-based screening … If homeowners think their water’s been contaminated [by fracking fluid], we’ll use the chemistry and the isotopes to have some idea whether this fear is justified or not.”
Vengosh acknowledges a key weakness in the tracing method is that, in some cases, the fracking industry might put boron in its fluids, complicating the tracing process. His team has yet to run into such an occurrence in their samples, though.
Speaking of samples, they can never have too many. Warner says he isn’t satisfied with the handful of samples they have from the two basins. “Testing in other basins; that’d be great to really make sure it’s robust and it’s not just working in a few specific basins.”
The call for more is just the way science goes, he admits. “I think it’s really promising. I’m excited about how it’s moving forward, but there are always more questions than answers. You reach the end, or you get into the research and realize there’s so many more things you want to investigate and look at. So it’s never ending.”
Calling the revolutionary tracing method a part of a bigger picture in their investigation of hydraulic fracturing’s environmental impacts, Vengosh says he has big hopes for its future implications.
“I think one of the issues with fracking today is that all of the debate is based on public relations, campaigns, a lot of emotion in it, and we would like to increase the science part … I hope this tracer will make the discussion more civilized and more into the science.”
Valerie King is associate editor of National Driller.