AKRON, Ohio -- The volume of drilling wastes from Pennsylvania's Marcellus Shale is growing and threatening to overwhelm existing waste-handling infrastructure in Ohio and other states, according to a study released Tuesday.
Ohio's 179 injection wells for disposing of briny waste might not be sufficient for the Pennsylvania waste, plus wastes from Ohio's developing Utica Shale, said Brian Lutz, assistant professor of biogeochemistry at Kent State University, who led the analysis while he was a postdoctoral research associate at Duke University.
"The overall volume of water that now has to be transported and treated is immense," he said. "It threatens to overwhelm the region's wastewater-disposal infrastructure capacity."
The wastes in play include flow-back water, produced immediately after hydraulic fracturing, or fracking, plus brine, or production water, generated after the fracking is done and the well goes into production. Such wastes generally are similar with a few key differences.
The liquid wastes can contain significant amounts of salts and total dissolved solids; low-level radiation and toxic heavy metals picked up from underground rocks; oils and grease; leftover toxic chemicals used in fracking; and certain volatile organic compounds, including benzene.
Pennsylvania has about 6,400 Marcellus Shale wells that have been drilled and another 3,500 that have been permitted. In comparison, Ohio has about 500 wells permitted in the Utica Shale, of which 200 have been drilled.
Mr. Lutz said Pennsylvania generated about 20 million barrels (each holding 42 gallons) of wastewater in 2011. About 7 million barrels were shipped to Ohio injection wells.
Ohio is projecting that its injection wells handled nearly 14 million barrels in 2012, up from 12.8 million barrels in 2011. (Final figures have not been compiled). More than half of that volume came from Pennsylvania and West Virginia.
Ohio cannot ban such wastes because they are interstate commerce protected under the U.S. Constitution. It is unknown exactly how much injection capacity the state can handle.
"This is the reality of increasing domestic natural gas production," said Martin Doyle, a professor of river science at Duke. "There are significant trade-offs and environmental impacts whether you rely on conventional gas or shale gas."
Mr. Lutz reported that Marcellus Shale horizontal wells that have been fracked are producing less wastewater per unit of gas than conventional wells would produce.
Fracked natural gas wells in the Marcellus Shale produce only about 35 percent as much wastewater per unit of gas recovered as conventional wells, according to the analysis that appears in the journal Water Resources Research.
"We found that on average, shale gas wells produced about 10 times the amount of wastewater as conventional wells, but they also produced about 30 times more natural gas," said Mr. Lutz, who only recently came to Kent State. "That surprised us, given the popular perception that hydraulic fracturing creates disproportionate amounts of wastewater."
The researchers at Kent State and Duke analyzed gas production and wastewater generation for 2,189 gas wells in Pennsylvania, using data reported by the industry to the state's Department of Environmental Protection.
Mr. Doyle said the researchers were surprised that drillers classified most of the wastewater as brine, not fracking flowback water.
Studies have shown that brine can be as difficult to treat as many of the chemicals used in fracking fluids, he said.