Today I had a chance to see a talk by Duke University’s Professor Avner Vengosh, whose research spans a variety of water quality and contamination issues. One of his major study areas is shale gas and hydraulic fracturing (fracking), and I wanted to present some of his most recent findings that he shared with us. Personally, I have a long ways to go before I can pass judgment on fracking one way or the other. The science is still young, and many questions do not yet have a clear answer.
For starters: what is fracking, and why is it so controversial? Simply put, the earth beneath our feet is made up of layers of rock. These layers vary in composition, thickness, and orientation, but all of them make geologists very excited. No matter the rock type, it is easiest in this context to imagine a sponge. The rock itself is made up of grains, separated by empty spaces or pores. The total volume of of pores is called the porosity. The porosity of a sandstone, for example, might range from 5 to 30%, while a shale might fall between 0 and 10%. Another important concept is permeability, which refers to the interconnectedness of the pores. In high permeability rocks, the pores connect to form channels through which fluids can easily flow, while in low permeability rocks, pores are almost completely isolated from one another.
Pores don’t just stay empty. They fill with fluid – often air, water, oil, or natural gas. Conventional oil and gas reservoirs generally have high porosities and permeabilities, meaning that once a well is drilled, oil can easily be drained from the rock. As more and more conventional reservoirs are used up, industry has turned to unconventional sources. One such source is shale gas or ‘tight gas’. In these rocks, the porosities and permeabilities are much lower, and the gas is effectively trapped. Fracking involves the injection of water under very high pressure to form cracks in the rock through which gas can flow. A variety of chemical additives help to dissolve the rock and mobilize gas, while solid particles such as sand prevent the cracks from closing.
So what’s the problem? To phrase it very generally, fracking is going through growing pains. In the past decade, it has risen from little more than background noise to a widespread practice, used in 35,000 new wells per year in the US alone. As is inevitably the case with such a rapid boom, the science and policy lag behind the technology, which forms the root of our problem. Without passing judgment on fracking itself, I think it’s safe to say that the science has not yet answered questions crucial to understanding the potential harms, and the regulations have not yet addressed the risks that fracking poses to humans and the environment. I’d compare it to tanning on the beach: there’s nothing wrong with getting some sun, but if there’s a risk of skin cancer attached, you might want to use sunscreen.
Then what are some of the risks? Unfortunately, like many energy technologies, fracking comes with a long list of ‘side effects‘. So much so, that several European countries including France have banned the practice altogether. However, since the science is still young and many claims both for and against tend to be sensationalized by industry, media, and NGOs, it is difficult to gauge where the real threats are. Based on Professor Vengosh’s research, I will present two risks that are supported by strong science.
The first risk is the leakage of methane into drinking water. Contrary to many popular representations, it is rather unlikely that methane from the fractured rock 2 or 3 kilometers below the ground will make its way up through cracks into drinking water aquifers 200 meters deep or less. What Professor Vengosh’s study does, however, show is that methane from well casings can and does find its way into drinking water wells. The casing is the ‘tube’ that encloses the gas well, and when improperly installed and sealed, leaves channels for stray gas to escape.
The second risk is of fracking fluid (the mix of water and additives) contaminating surface water bodies such as rivers if carelessly collected and improperly treated. This is of particular concern since many US states and Canadian provinces do not yet have regulations that require companies to disclose the precise chemicals which they use. Professor Vengosh has shown that increased salinity, toxic compounds, and radioactivity can be measured in rivers downstream of fracking operations.
Now I use the word improperly in both cases to stress that unless appropriate regulations exist to hold industry to safe standards, there will undoubtedly be companies that cut corners to save time and costs, thereby endangering people and the environment. In my personal view, it is too early to tell whether the practice itself is at fault or if the blame falls on irresponsible and improper application. That said, uncertainty is not a justification for inaction. As the industry continues to grow it is therefore the responsibility of policy to make informed decisions on how this practice can be used and to what standards the industry must be held.
This has been your daily dose of mostly harmless science.
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Cover photo courtesy of Victor Brassinne, Flickr Creative Commons.