Determined operators are slowly chipping away at a tough shale play that could add another layer of production to the Black Warrior Basin's unconventional resource mix.

The Upper Mississippian Floyd and Neal shales are two names for a formation that occurs in northwestern Alabama and northeastern Mississippi. Floyd is used in Alabama, and includes the Lewis sandstone; in Mississippi, the black shale between the Carter and Lewis sandstones is the Neal. Whatever the term, the Mississippian-aged rock is correlative to the Arkoma Basin's Fayetteville shale and the Fort Worth Basin's legendary Barnett.

The Black Warrior version of the shale is geologically complex. In the basin's northern portion, two dense limestone units sandwich the Floyd. Here, the shale attains more than 200 feet in thickness, contains more than 3% total organic carbon (TOC), and is thermally immature, according to work done by Matthew Totten and Albert Oko at Kansas State University. In the basin depths, the shale has similar TOC values but is 100 feet thicker and thermally mature. This slice of the play lacks the overlying limestone unit.

Early movers in the Floyd included Murphy Oil, Noble Energy and Wagner & Brown Ltd., and work centered in Pickens County, Alabama. In 2005 and early 2006, Murphy (reportedly partnered with Noble) drilled a handful of exploration wells in southeastern Pickens to depths around 7,500 feet. Results were uneven and no well was put on production.

Separately, Wagner & Brown drilled three wells in northwestern Pickens, but didn't get any producers either. Noble also drilled a 5,200-foot test in northeastern Pickens, but no activity has been reported at that site since mid-2005.

Denbury Resources drilled a pair of wells in Lamar County, Alabama, and one in Lowndes County, Mississippi. One Lamar County test was completed from Floyd for 80,000 cubic feet of gas per day and has made 10 million cubic feet in 10 months online. EOG Resources drilled a 9,500-foot well in Greene County, Alabama, but reported a subcommercial Devonian completion.

Certainly, results of the first round of drilling were lame. But it's a widespread play and work continues.

Today the focus of activity has shifted to Mississippi, where excitement was sparked last year by a Calhoun County discovery. Red Hills Resources reported a Floyd completion that made 818,000 cubic feet per day. (There is speculation that the well may be completed in a sand interval within the Floyd.) Cabot Oil & Gas has drilled a vertical test in the same county, but details have not been released. Both operators have additional wells planned or in progress in Chickasaw, Monroe and Yalobusha counties.

Furthermore, a number of high-profile horizontal ventures are under way in the Magnolia State. Carrizo Oil & Gas holds 137,000 acres prospective for Floyd, and is in progress on its first horizontal test in Clay County. The well encountered problems, was sidetracked and has now been drilled to total depth. Fracture stimulation of three zones should begin shortly.

Anadarko Petroleum is at work on two horizontal wells, in Oktibbeha and Lowndes counties, and David H. Arrington Oil & Gas Inc. has drilled one directional and one horizontal well, both in the same section in Lowndes County. Arrington recently staked four vertical wells in Lowndes, according to IHS Inc.

And, Alabama is seeing a couple of new vertical attempts near the basin's southeastern edge. Black Warrior Natural Resources recently set liner to 8,360 feet on a Greene County well, and Range Resources has spudded a 10,000-foot vertical well in Sumter County. The latter company, which holds 50,000 acres in the play, may drill a horizontal test this year.

Some firms have strong acreage positions but have not yet drilled wells. Edge Petroleum owns 44,000 acres in the southern part of the play. Bankers Petroleum has 95,000 acres, mainly in Alabama, that it considers prospective for both Pottsville tight-gas sands and Floyd. Both are watching activity.

"There have been mechanical issues, and the geology of the Floyd shale is complex," says Kent Bowker, president of Houston-based Bowker Petroleum. "It's going to take some deep pockets, patience and a lot of previous shale experience to make this play work. It's been frustrating, but I still have high hopes for it."

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