What a surprise. There’s an emerging, oil-rich shale play in the United States, and it isn’t in the Permian Basin.
Don’t get too excited. It’s not far north of the Permian’s easternmost extent, on the Oklahoma-Texas border. This play is in the western Anadarko Basin, another prolific hydrocarbon basin in the U.S. Midcontinent.
At the upcoming 2025 Unconventional Resources Technology Conference in Houston, the play will be the subject of a June 10 luncheon presentation, “Small Operator in the Anadarko Basin: Highlights from the Cleveland Play in Dewey County and the ‘Cherokee’ Shale Play in Ellis County.”
Yes, “Cherokee” is in quotation marks.
Even though this shale play has been “emerging” (again, note the quotation marks) for a while, it isn’t exactly … nailed down. That includes knowing where it belongs, maybe, in the Cherokee Group stratigraphy of western Oklahoma.
History of Development
Presenters at the luncheon session will be Tiffany Stephens, exploration manager, and Bryan Hunt, senior geologist for Duncan Oil Properties Inc. Hunt said their presentation will focus on the Cherokee shale, a 200-400-foot section of black and gray shale in and around Ellis County, Okla. Most of the play drilling has taken place in that county, north of the Black Kettle National Grassland.
“It’s kind of the hot play in Oklahoma right now, the emerging play. We’ll start with a history of how it developed,” Hunt said.
“We’ll talk a little bit about depositional environments, the Anadarko Basin setting, where the wash is, where the reef is, and where the deeper water deposits are. We’ll talk about some rock data that we have,” he added.
The first true test of the new Cherokee play occurred in early 2020, Hunt noted, when it was opened by Mewbourne Oil Company, a Tyler, Texas-based, privately held independent operator with exploration offices in Texas and Oklahoma.
Mewbourne is the most active operator in the Cherokee shale, while Devon Energy is the largest publicly traded player, he said. SandRidge Energy made a significant acquisition in the play last year. Other operators are mostly small independents from Texas and Oklahoma.
Duncan Oil itself is a small Anadarko operator that has been in business for more than 80 years. Its offices are in a bank building on Broadway Avenue in Oklahoma City, not far from the city’s noted Bricktown area, and a short walk from the American Banjo Museum.
“We’ll get into, a little bit, what we think of as the drivers of the play. It’s maybe a little early in the play to say what’s the key,” Hunt said.
“The most obvious thing is pressure – pressure gradients. The higher-pressure areas are doing considerably better” in output, he noted.
“The total volumes are higher in the high-pressure area. Offhand, I’d say the GORs are probably slightly higher,” Hunt added.
Production reports show both oil and natural gas from Cherokee shale wells, with the main play mostly in southern Ellis County but edging into northern Roger Mills County, Okla.
Dewey and Custer counties are to the east, where a Cherokee gas play is evolving.
Oklahoma’s quarterly state lease sale in December brought multiple bids for tracts in the area. Chris Wiggers, state director of minerals management, said eastern Roger Mills, western Custer and southwest Dewey counties comprise the Cherokee shale gas play.
Hunt said more than 100 wells have been drilled in the original Cherokee shale play so far, almost all in Ellis County.
“I don’t think we know the full, true extent of the play yet. The original fairway is about 60-percent drilled up by now. It’s (the initial play extent) about four townships or so,” he said.
Cherokee development is typical of U.S. shale plays, with operators employing horizontal drilling and cased-hole, slick-water fracs. In recent years, longer laterals and improved techniques have boosted play efficiency and production.
Hunt said some early production-reporting glitches resulted in “instances of the public production databases doubling production on a few wells,” although those numbers might have been corrected by now, he added.
More Science Needed
Duncan Oil has researched production data, cores, cuttings, pressure and maturity data, mud logs and other geological data, and performed delta log R/Passey method total organic carbon calculations in the Cherokee shale.
“There’s not been a lot of science done. It’s mostly been figured out by the drill bit,” Hunt noted.
“It’s very poorly understood in the public sector what the play is – the players are mostly independents, small operators,” he said.
A certain number of Oklahoma geologists complain about inconsistent stratigraphic nomenclature in the U.S. Midcontinent – and that number sometimes seems to be close to 100 percent. In this part of the country, the formation designations in use for the strat column at one location might not be exactly the same names in effect five or ten miles away.
Hunt said the Red Fork is often mixed in with Cherokee in the shale play. Red Fork and Skinner formations within the Cherokee Group are additional drilling targets, particularly for fluvial-channel sandstones.
“The whole Cherokee group also includes several fluvio-deltaic sands that have been drilled and are often reported simply by the group name, ‘Cherokee,’” Hunt explained.
Multiple formations produce in the 50,000-square-mile Anadarko Basin, a longtime pillar of Midcontinent oil and gas development. In addition to Cleveland and Cherokee, possibilities include Woodford, Hunton, Springer, Morrow, Marmaton, Tonkawa and several others.
Cherokee shale exploration overlaps with the Cleveland tight sands horizontal play, in an area known for its stacked pay potential. The URTeC session also will examine two Cherokee horizontals drilled under Cleveland/Marmaton wells in Ellis County.
“Historically, that’s been our bread and butter. We still drill about five Cleveland wells a year,” Hunt said.
Both Stephens and Hunt have geology degrees, but Stephens also holds a law degree and Hunt has an MBA from the University of Oklahoma. Hunt said that’s given him a better perspective on engineering and money matters in oil and gas.
“It helped me understand the engineers a lot better, reservoir engineering and their perspective on well economics. It definitely helped me understand, ‘Geology is fun, it’s fun to do science – but ultimately, this is a business,’” he said.