Members of Winona State University’s (WSU) geology department discussed the geology of frac sand and its relation to Winona, Minn., and larger areas as part of WSU’s athenaeum series, according to a report in the Winona Daily News.
“We wanted to provide context to the whole sand issue that’s been affecting our area,” said geoscience professor Toby Dogwiler.
The Jordan and St. Peter sandstones laid down hundreds of millions of years ago and the source of the hard, round, uniform sand grains prized by oil and natural gas drillers, underlie much of the region, Dogwiler explained. However, these sandstone layers are covered by and sandwiched among layers of limestone, shale, silt, clay and soil – making all but a very small portion accessible to frac sand miners.
The only areas where mining is economically feasible are in the valleys, where natural forces or erosion have exposed the sandstone, he said. And a number of additional factors further limit the locations where mining is likely to occur, like limitations on mining on publicly owned lands, laws protecting streams, transportation costs, land reclamation costs and other factors.
The mining process, however, does not come without side effects. “There’s no doubt it will affect groundwater resources,” Dogwiler said. “What it boils down to is not if there’s frac sand mining, but how much.”
Frac sand is used in hydraulic fracturing, a relatively new method of mining oil. “With oil prices going up, gas prices going up, this has become more economically feasible,” said WSU geoscience professor Candace Kairies-Beatty.