The often-repeated concern is that if a spill were to occur, responders would not be as well-prepared as they would have been if the fluid composition had been known beforehand, Wolske and Hoffman note.
Though groundwater contamination is often cited as a top concern, surface contamination from spills and improper disposal of waste fluids likely carries the greatest risk for harmful water-quality impacts, due to proximity to potable water resources, according to the geology/hydrogeology report written by Brian Ellis, assistant professor in the Department of Civil and Environmental Engineering.
When a well is fracked, the fluid is injected into rock formations to create cracks and to prop them open. Of the total volume of hydraulic fracturing fluids injected into a well, amounts varying from 10 percent to 70 percent may return to the surface as "flowback water" after the pressure is reduced and gas or oil begin to flow toward the wellhead.
In Michigan high-volume hydraulically fractured wells, the average amount of flowback water returning to the surface is about 37 percent of injected volumes, according to the Ellis report.
The flowback water is highly saline and can contain elevated levels of heavy metals and naturally occurring radioactive elements, in addition to methane and the original chemical additives in the fracturing fluids. In Michigan, common hydraulic fracturing fluid additives include ethylene glycol, hydrochloric acid, isopropyl alcohol, methanol and ammonium persulfate, according to the Ellis report.
"However, since in Michigan all flowback is disposed of by deep-well injection and it is not allowed to sit in open pits, the risk of this type of contam
|Contact: Jim Erickson|
University of Michigan