Hydraulic Fracturing and Water Quality
First Person: Avner Vengosh
Avner Vengosh is a geochemist studying water quality at Duke University. His most recent research has looked at water quality issues posed by hydraulic fracturing (better known as fracking), as natural gas has overtaken coal as the foremost source of energy for electricity in the United States, following the shale gas boom in the mid-2000s. Vengosh’s 2014 paper reviewing the risks of shale gas extraction and 2013 paper on fracking wastewater disposal in Pennsylvania were honored as editors’ picks for best articles in the journal Environmental Science and Technology. He was also elected as a fellow of the Geological Society of America this year. He spoke with associate editor Katie L. Burke about new developments in his field.
Why do you think the public debate around fracking has been so heated?
Unlike conventional oil and gas, where you have one well in a large area, hydraulic fracturing is more intense and requires many wells. There is also a large decline in the production of both gas and petroleum from shale gas or from tight sand. After the first year, the amount of gas goes down about four to five times relative to the original level. You need to drill more to keep the system going and to keep the investor happy. Unconventional shale gas and tight sand are very intensive. If you live where this happens, it will change your life.
Many people were caught up with finding out the chemicals used for hydraulic fracturing. Now, we all know what’s there, more or less, but it was a trade secret for many years. This kind of secrecy made people suspicious that there were very toxic elements. There are some, but there are many other industries that involve other toxic elements.
Here at Duke, we are trying to find the balance between the public’s concern and the industry’s lack of concern. We have collected data for thousands of wells and surface water from Pennsylvania to New York and covering West Virginia, Arkansas, Texas, North Dakota, and Colorado. We try to provide an objective picture of what the issues are and how we can cope with them.
How does shale gas extraction work?
The major advance of unconventional energy exploration was that two technologies that have been around for some time were merged together. One is the combination of horizontal and vertical drilling into a low-permeability shale or tight-sand formation. Conventional drilling would not be able to extract hydrocarbon efficiently from such formations. The second was high-volume hydraulic fracturing, in which a high volume of water mixed with manmade chemicals is injected to crack the shale formation or open fractures within the sand.
Those combined technologies started the natural gas boom in 2005 and enabled industry to triple the amount of gas extraction in the United States.
Fracking has inspired fierce opposition from some environmental groups. What is your assessment of its risks?
There are several environmental risks identified. First of all, there are water issues, such as contamination and water use. There are issues involving air pollution and methane admission to the atmosphere. Methane has about 20 times the effect on global warming relative to carbon dioxide. There is some debate about what the magnitude of the escape of methane is during hydraulic fracturing. Several recent studies show that it is much higher than previously thought.
In addition, there are domestic issues. For people living in areas of shale gas exploration, their community becomes an industrial zone. There are many other issues in addition to the direct effect on water or air associated with hydraulic fracturing.
Some of these issues from my perspective already existed with conventional oil and gas, but given the magnitude of unconventional oil and gas and the number of wells, all issues have increased.
What are the environmental risks specific to water use and contamination?
My colleagues and I identified at least three major issues with respect to water. One is the water footprint. If too much water is pumped from an aquifer, long-term degradation of the water quality results. The second issue is groundwater contamination. We have strong evidence for stray gas contamination from parts of the shale gas well. The third is surface water contamination derived from spills, leaks, or disposal of wastewater coming from oil and gas operations without adequate treatment.
How does water consumption for hydraulic fracturing compare to that of other energy sources like coal?
We’re writing a paper right now evaluating the water footprint of hydraulic fracturing. Each well takes between 15 million liters of water, the amount for hydraulic fracturing in a shale formation like the Marcellus, and 8 million liters for tight-sand formations like the Bakken in North Dakota. If you multiply this amount by the number of wells, you get a large total amount of water.
From a national perspective, the amount of water used for hydraulic fracturing is negligible compared to other water uses. It’s a fraction of a percent of the total water used in the United States. Water use for cooling coal plants takes about 40 percent of the total water used in the nation.
At the same time, if you’re in a community in western Texas where the water use is maximized for agricultural and domestic purposes, adding another source of water for hydraulic fracturing could be problematic. I think it’s important when you talk about the water footprint to do this distinction between the nationwide perspective relative to specific areas in the western United States, where less water is available.
Stray gas contamination, where methane from fracking enters local drinking water wells, has caused alarm. How does this contamination happen, and how do you know when it’s from fracking?
We have seen evidence for this contamination in wells in Pennsylvania and in Texas in shallow aquifers overlying the Barnett shale. In such cases, the amount of gas in the water in a private well suddenly will be higher. This is problematic because methane is an inflammatory hazard. There was some debate about this issue, because in many areas of shale gas exploration, there’s also naturally occurring methane flux into the aquifer. One of the difficult issues was how to differentiate between natural flow of gas into shallow aquifers relative to actual contamination from the shale gas well. We developed a method published last year in the Proceedings of the National Academy of Sciences that showed how to make this distinction.
Following injection of water deep into rock during fracking, wastewater is produced that contains industrial chemicals as well as leached compounds. Much debate has arisen about what to do with this wastewater. What are the water quality issues it poses?
We are generating a huge volume of wastewater from hydraulic fracturing. In most of the cases in Texas, Oklahoma, and California, over 90 percent of this wastewater is injected back into the geological system. In some cases, it induces seismicity and earthquakes. In Texas, Oklahoma, and Ohio, the injection of this large volume of wastewater has triggered earthquakes in areas that had never experienced them before.
This phenomenon has been known for decades. Once you inject water into the subsurface, you induce earthquakes if you are unlucky and the injection well is located near a fault line. In most of the cases, it’s not the hydraulic fracturing itself causing the earthquake but the wastewater injected into the well.
On the global scale, I think that produced water is going to be a huge issue. Outside the United States, it’s often illegal to inject water into the subsurface, like in the European Union or in China. Managing the wastewater is one of the major challenges of dealing with hydraulic fracturing fluid both in the United States and beyond. The topic needs a lot of attention to decide how to manage it. You can treat it to reduce the level of salt and contaminants, but who’s going to cover the cost?
We showed that in Pennsylvania, where they treat the wastewater coming from fracking and also from conventional oil and gas, the treatment is not sufficient. They’re not removing all the contaminants. We found some contaminants in wastewater discharged into streams, rivers, and waterways. We identified elevated levels of chloride, bromide, iodide, and ammonium, which are highly toxic to aquatic life, as well as an elevated level of radioactivity. This radioactivity naturally occurs in the brines in the wastewater from hydraulic fracturing. What we found was that once there was a spill or disposal of the wastewater, the water may be diluted with local streams. Some of the radium isotopes—a constituent chemical that results in radioactivity—is adsorbed into the sediments of the streams or the soil. Because of this adsorption, the radioactivity remains at the site. In some cases, for example at the Josephine Brine Treatment Facility in Pennsylvania, we found that the level of radioactivity even exceeded the threshold value that defines a radioactive waste disposal site according to U.S. law.
In a study we are conducting right now in North Dakota, we are showing that brine has a large impact on aquatic life and can cause dead zones [in waterways] where a spill took place. There are hundreds of spills like that.
To me, the wastewater creates more water footprint issues than the water use itself, because it causes, in many cases, water with high levels of contaminants that could have devastating effects. I see the wastewater as one of the key issues for sustainable use of hydraulic fracturing.
What are the main sources of water contamination—from industrial chemicals used in fracking or from natural sources within the rock formations?
Many people are focusing on the unique manmade chemicals that are added for hydraulic fracturing. Some of those chemicals are indeed toxic and some of them, like biocides, could be affecting human and aquatic life. What we are finding is that it’s common to find naturally occurring contaminants, like salts. In fact, what we found in another study that we published last year is that even a tiny amount of brine, naturally occurring bromide that’s coming from a spill, could have a devastating effect on communities living downstream from the discharged water, because when communities use surface water, they usually disinfect the water to get rid of bacterial contamination. This disinfection process generates by-products if the water contains two components: One is organic matter, which is common in many of the streams and rivers; the other component is halogen, which means bromide and iodide. We did some experiments with colleagues from Stanford University and showed that a tiny amount of hydraulic fracturing fluid mixed with surface water could trigger the formation of disinfection byproducts. Some components, such as iodinated trihalomethanes, which are extremely toxic, are not being regulated by the Environmental Protection Agency (EPA) and could be generated from the introduction of the wastewater into drinking water utilities. Even a tiny spill with a small amount of the bromide and iodide could trigger the formation of those highly toxic disinfection by-products in drinking water.
Naturally occurring contaminants, including the radioactivity, may have more effects and be more widespread than the manmade chemicals that everybody is making their focus.
What is your perspective as a scientist observing the contentious public debate about fracking?
We are in the middle of everybody who is upset about it. I always say that if you give me only a fraction of the money industry puts into blogs and communications, it would be nice to conduct real research. But, for example, when we published a paper that did not show any evidence for stray gas contamination in Arkansas, we got slammed by the environmental groups, who accused us of working with the industry. We’ve been slammed by both sides.
I was fortunate to be at Duke, which served as a good platform to work without any restrictions on our research. I know that those in other institutions were not so lucky, and there were some institutional forces implying that certain research directions could harm the nation—this coming, for example, from a potential donor. Duke was above that, which was fortunate for us.
What message do you think the public needs about this topic?
There is research that I think the EPA is reluctant to conduct, or cannot do even if it wants to, especially with regard to large-scale studies. What we are left with are initiatives coming from private or state universities with fewer resources to do a large-scale evaluation compared to the EPA or industry. Everyone agrees that this is one of the most important issues. We need to empower someone, such as the National Science Foundation (NSF), to allocate funding to address this question.
The problem is if you give it to one of the interest groups, either environmental nongovernmental organizations or industry, that could bias research, or the research won’t be trusted by the public. The way to enable such trust is to provide independent funding, either through NSF or other entities.
Our work shows we don’t have any ideology involved. We are trying to understand the issues with fracking, and how it affects the environment and could affect human health. At the end of the day we are in the same boat with the industry, who need to know how to do it correctly in order to make it sustainable.