Seneca Resources Corp. has received federal approval to operate a new drilling wastewater injection well in Elk County, and more of those deep injection wells for the disposal of Marcellus and Utica shale gas drilling wastewater are on tap for Pennsylvania.
The U.S. Environmental Protection Agency announced last week that it had approved Seneca's proposal to convert one of its existing vertical gas wells into an injection well that will pump up to 60,000 gallons a day of drilling wastewater and salty brine about 2,400 feet below the surface into the Elk 3 Sandstone formation.
That formation is about 1,700 feet below groundwater aquifers that supply residential water to residents of the area, said Karen Johnson, chief of the EPA Region III groundwater and enforcement branch.
The EPA has permitted 30,000 Class II injection wells for drilling brine and wastewater disposal nationally -- about a third of those in Texas -- but the Seneca disposal well is just the ninth such well approved in Pennsylvania.
Ms. Johnson said more are in the offing for the state, including three more new disposal wells that could receive federal permits as early as this summer.
"We continue to have frequent meetings with [gas well] operators and a number of additional permits are under review," she said. "Independent companies and big operators are all saying they are going to need more capacity for disposal."
Drillers use about 4 million gallons of water and chemicals per well to hydraulically fracture or "frack" the deep Marcellus Shale gas formation with about a quarter of that eventually flowing back to the surface.
Drillers are no longer allowed to use municipal wastewater treatment facilities for disposal, Ms. Johnson said, and -- while many drillers recycle their water -- there is still a need for additional disposal locations.
"Drilling has changed," said Rob Boulware, a Seneca spokesman. "And the amount of activity in Pennsylvania is filling other water disposal areas, so we need to develop areas that others are not utilizing."
Seneca Resources, a subsidiary of Houston-based National Fuel Gas Co., operates primarily in Pennsylvania's northwest corner, where it has more than 3,000 shallow oil and gas wells and 170 deep shale gas wells, with more than 120 of those producing, said Mr. Boulware.
He said the Elk County well in Highland will accept brine and other wastewater from both the shallow conventional wells and deep shale gas wells. Although the EPA permit allows disposal of up to 15 tanker truckloads of water a day, he said he expects disposal of about four truckloads a day initially.
Seneca is still awaiting approval of the gas well's reclassification as a disposal well from the state Department of Environmental Protection.
Pennsylvania's existing deep injection disposal wells range in depths from 2,000 to 8,000 feet, usually discharging into porous limestone or sandstone formations, and can operate for several decades. Three of those wells, in Somerset, Erie and Beaver counties have been in operation since at least 1985, when the EPA began its permitting program.
Federal regulations require the disposal wells to have multiple pipe, casing and cement barriers to reduce the risk that drilling wastewater will contaminate shallow groundwater or surface water used for human consumption.
Although the EPA is not required to review Class II disposal well applications for seismic risks, a series of small earthquakes triggered by a 9,000-foot-deep wastewater disposal well near Youngstown, Ohio, two years ago has raised public awareness and concerns about that risk.
"In Ohio, the injection well was discharging into a formation that didn't have the permeability and porosity of this [Seneca] existing oil and gas formation," Ms. Johnson said. "But we take seismicity into account. In Pennsylvania that's very limited."
The Ohio well, which received most of its wastewater from Pennsylvania Marcellus Shale gas drilling operations, triggered tremors from a previously unknown and unmapped geologic fault line.
Don Hopey: email@example.com or 412-263-1983.