The Marcellus Shale put Pennsylvania on the map as a gas-producing state, but other rock layers have the potential to keep it there far into the future.
Drillers have sought unconventional well permits for 12 geological formations other than the Marcellus, according to state records compiled and organized by MarcellusGas.org. The state Department of Environmental Protection has issued permits for about 900 wells, site developer Carl Hagstrom said. Most of those are in the western part of the state; about 520 of those have been drilled.
Other than the Marcellus, which has more than 15,000 well permits, the most popular target formations in Pennsylvania are the Utica Shale with 258 permits, the Burket/Geneseo Shale with 246 permits and the Point Pleasant Shale with 159 permits. Although sometimes listed separately, the Point Pleasant is technically considered part of the Utica, according to a presentation by the Pennsylvania Geological Survey.
“They are all classic formations that have new life due to horizontals with classic hydraulic fracturing,” Lackawanna College School of Petroleum and Natural Gas dean Richard Marquardt said in an email. “They are all basically silty shales.”
These black shales with high organic content were formed over hundreds of millions of years ago when organisms, most likely algae, died then settled to the bottom of the ocean, said Allegheny County petroleum geologist Gregory Wrightstone, who has more than 35 years’ experience with unconventional formations in the Appalachian Basin.
Over millenia, heat and pressure broke down this organic material and formed natural gas.
The amount of oil and gas in a rock layer is dependent in part on how much heat or pressure affected it, a trait known as “thermal maturity.” Gas companies have to drill exploratory wells to learn how thermally mature a formation is in certain sections.
Though the Utica/Point Pleasant and Burket/Geneseo formations lie under most of the state, including all of Northeast Pennsylvania, most of the recent exploration has focused on the west and southwest.
Still, companies such as Seneca Resources Corp. and Shell have drilled into them as far east as Tioga and Lycoming counties.
“The question is how far east can you push the Utica in terms of thermal maturity,” Mr. Wrightstone said. “That’s a multibillion-dollar question.”
Although persistently low gas prices have driven down profits and forced many gas companies to cut back on drilling new Marcellus wells, they may try exploring some of these other formations, Pennsylvania Independent Oil and Gas Association president Louis D’Amico said in an email.
“They would like to see what potential for the future lies with these formations,” he said. “It’s one way to justify not further reducing their staffs during these tough times.”
With massive amounts of gas locked up in the Marcellus, Utica/Point Pleasant and Burket/Geneseo, Pennsylvania has many decades of production to come, Mr. Wrightstone said.
The industry considers the threshold for a “supergiant” gas field to be 30 trillion cubic feet, he said. The Marcellus holds more like 800 trillion cubic feet, he said.
“We should really coin a new term for the Marcellus,” he said. “We should probably call it something like a megagiant.”
The Utica/Point Pleasant is also a world-class reservoir and, while the Burket/Geneseo is like the Marcellus’s “little brother,” it still likely holds more than 30 trillion cubic feet , he said.
“In any other time it would have been this absolutely incredible field, and it’s a yawner,” he said.
One secret to the productivity of East Coast shales relative to others lies in their brittleness, said independent completions consultant Larry Fulmer, who has worked on naturally fractured oil and gas reservoirs for 40 years.
“The East Coast is blessed with ancient, ancient rock,” he said.
While hydraulic fracturing does create new cracks in the target rock, unconventional well production is tied to existing fractures, he said. An old, brittle shale holds more existing fractures than the pliable shales seen in many other parts of the world.
“Shales are barriers in a lot of the rest of the world,” he said. “On the East Coast, shales are formations.”
Searching for wells by formation is now available on MarcellusGas.org. Mr. Hagstrom plans to add new information that will help users compare production from various layers.
This article was written by Brendan Gibbons from The Times-Tribune, Scranton, Pa. and was legally licensed through the NewsCred publisher network.