?An oil-prone shale play in northeastern South Louisiana and southwestern Mississippi is gathering steam. The Cretaceous Tuscaloosa marine shale is a thick, black, highly organic source rock sandwiched between sands in the upper and lower Tuscaloosa. The shale is one of a number of such oil-prone unconventional plays in the forefront of exploration efforts in the Lower 48.


According to the Basin Research Institute at Louisiana State University in Baton Rouge, the Tuscaloosa marine shale may contain potential reserves of 7 billion barrels of oil, spread across some 5,900 square miles.


The shale thickness varies from 500 feet in southwestern Mississippi to more than 800 feet in southeastern Louisiana; most attention is on a highly resistive section at its base that can be up to 325 feet thick. Depths to the shale range from 11,500 to 13,500 feet in its prime target area in southeastern Wilkinson, southern Amite and southwestern Pike counties, Mississippi, and northern East Feliciana, St. Helena and Tangipahoa parishes, Louisiana.


Workers in South Louisiana have long believed that the marine shale sourced the hydrocarbons in such famed Lower Tuscaloosa sand fields as Port Hudson, Irene and False River, which lie much deeper and to the south. The Basin Research ­Institute has confirmed this relationship by geochemical analysis of oil from area wells.


Occasional vertical wells have produced oil from the Tuscaloosa marine shale. One well, #1 Winfred Blades in Section 42-1s-8e, Tangipahoa Parish, Louisiana, has made more than 24,000 barrels since 1978.


Attention now is on how the shale will respond to horizontal drilling and multi-stage fracturing techniques. Fort Worth-based Encore Acquisition Co. has been leading the effort to apply the industry’s up-to-date arsenal of technologies to the formation.


At a recent investment conference, Jonny Brumley, president and chief executive, said that Encore became interested in the Tuscaloosa shale because a number of wells in the area had suffered blowouts. It gathered records on more than 60 wells that had oil shows, generally oil over the shaker as the bit penetrated the shale.


Another positive was the shale’s pressure gradient of 0.60 psi per foot. Furthermore, the operator, experienced in the sizzling Bakken play in the Williston Basin, identified a siltstone within the shale that it believed had enough integrity to hold horizontal wellbores. The Bakken play is developed in such a zone, so it makes a strong analogy.


To date, Encore has drilled three wells. The #4-13H Joe Jackson, in Section 4-2n-3e, Amite County, Mississippi, was spudded last April in Enterprise West Field. The company pushed an 1,100-foot lateral into the Tuscaloosa marine shale. The well came on at about 150 barrels a day, and is still producing about 50 barrels a day.


The lateral on its second well, #1 Richland Plantation A, in irregular Section 69-1s-2e, East Feliciana Parish, Louisiana, reached 3,100 feet. The casing parted after the frac, but production from just 18 feet of perforations is about 50 barrels a day.


Encore’s latest test has been drilled and is waiting on completion. The #1 Weyerhaeuser, in irregular Section 60-1s-4e, St. Helena Parish, Louisiana, reached a total measured depth of 17,035 feet and features a 4,100-foot lateral. Casing has been run and cemented, and the entire region eagerly awaits results on this attempt.


The company’s fourth test for the program will be #1-H Board of Education, in Section 16-1n-5e, Amite County, Mississippi. Location has been staked; projected total depth is 17,500 feet.


Encore has accumulated 210,000 net acres in the Tuscaloosa play shale and figures it has acreage to support 300 gross wells. It is using ballpark figures of some 240,000 barrels of net reserves and average net cost of $7 million a well.


“There are still opportunities for companies to come into the play,” says Dan Collins, Baton Rouge-based mineral consultant. Through an informal landowners association, Collins has aggregated approximately 140,000 prospective acres. The Tuscaloosa marine shale landowners group has held discussions with more than two dozen companies.


“Interest is very high because the Tuscaloosa is oil-prone.”

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