Study outlines risks of injecting waste into aquifer by Willow Belden, June 28, 2013, Wyoming Public Radio
A study found that if wastewater were injected into a deep portion of the Madison Aquifer, it could potentially contaminate drinking water supplies in other areas. Encana Oil and Gas has asked for permission to dispose of brine and drilling waste in the aquifer. The company says it would inject the waste into an area where water quality is already poor and which is so deep that it would be an impractical source for drinking water, regardless. But the new study suggested that Encana’s calculations may be inaccurate. Jill Morrison is an organizer with the Powder River Basin Resource Council, one of the groups that commissioned the study. She says the study found that the water quality at the proposed injection site is actually quite good. “More importantly, that waste injected at this location is not going to stay there,” Morrison said. “It’s going to flow away and likely move upwards.” Morrison says that means injected waste could pollute water in shallower portions of the aquifer, which could be future sources of drinking water. The Environmental Protection Agency is waiting for more information from Encana before deciding whether or not to approve their request. [Emphasis added]
[Refer also to:
Are Fracking Wastewater Wells Poisoning the Ground beneath Our Feet? Leaking injection wells may pose a risk–and the science has not kept pace with the growing glut of wastewater by Abrahm Lustgarten and ProPublica, June 21, 2013, Scientific American
Florida’s injection wells, for example, had been drilled into rock that was far more porous and fractured than scientists previously understood. “Geology is never what you think it is,” said Ronald Reese, a geologist with the United States Geological Survey in Florida who has studied the well failures there. “There are always surprises.” Other gaps have emerged between theories of how underground injection should work and how it actually does. Rock layers aren’t always neatly stacked as they appear in engineers’ sketches. They often fold and twist over on themselves. Waste injected into such formations is more likely to spread in lopsided, unpredictable ways than in a uniform cone. It is also likely to channel through spaces in the rock as pressure forces it along the weakest lines.
Petroleum engineers in Texas have found that when they pump fluid into one end of an oil reservoir to push oil out the other, the injected fluid sometimes flows around the reservoir, completely missing the targeted zone. “People are still surprised at the route that the injectate is taking or the bypassing that can happen,” said Jean-Philippe Nicot, a research scientist at the University of Texas’ Bureau of Economic Geology. Conventional wisdom says fluids injected underground should spread at a rate of several inches or less each year, and go only as far as they are pushed by the pressure inside the well. In some instances, however, fluids have travelled faster and farther than researchers thought possible.
In a 2000 case that wasn’t caused by injection but brought important lessons about how fluids could move underground, hydrogeologists concluded that bacteria-polluted water migrated horizontally underground for several thousand feet in just 26 hours, contaminating a drinking water well in Walkerton, Ontario, and sickening thousands of residents. The fluids travelled 80 times as fast as the standard software model predicted was possible.
According to the model, vertical movement of underground fluids shouldn’t be possible at all, or should happen over what scientists call “geologic time”: thousands of years or longer. Yet a 2011 study in Wisconsin found that human viruses had managed to infiltrate deep aquifers, probably moving downward through layers believed to be a permanent seal.
According to a study published in April in the journal Ground Water, it’s not a matter of if fluid will move through rock layers, but when. Tom Myers, a hydrologist, drew on research showing that natural faults and fractures are more prevalent than commonly understood to create a model that predicts how chemicals might move in the Marcellus Shale, a dense layer of rock that has been called impermeable. The Marcellus Shale, which stretches from New York to Tennessee, is the focus of intense debate because of concerns that chemicals injected in drilling for natural gas will pollute water. Myers’ new model said that chemicals could leak through natural cracks into aquifers tapped for drinking water in about 100 years, far more quickly than had been thought. In areas where there is hydraulic fracturing or drilling, Myers’ model shows, man-made faults and natural ones could intersect and chemicals could migrate to the surface in as little as “a few years, or less.” “It’s out of sight, out of mind now. But 50 years from now?” Myers said, referring to injected waste and the rock layers trusted to entrap it. “Simply put, they are not impermeable.” [Emphasis added]