A significant potential source of oil is found in sedimentary rocks containing heavy oil (less than API gravity 10°) called oil sands. The petroleum in oil sands are solid or semiliquid at reservoir conditions and can not be produced conventionally. Interest in oil sands has waxed and waned over the years, like all unconventional sources, depending primarily on the price of oil. While commercial production of oil sands has been ongoing in western Canada since the 1960s, little modern oil sand production has occurred in the U.S..
Alabama oil sands include the Mississippian age Hartselle Sandstone and, to a lesser degree, Pride Mountain Formation. The Hartselle Sandstone is the third largest oil sand resource in the United States. These rocks outcrop in a 70-mile long belt that extends from central Morgan County westward to far west-central Colbert County. Small-scale surface mining for road construction, concentrated in the Pride Mountain Formation in west-central Colbert County, is the only real commercial activity involving Alabama's oil sand to date.
Despite over a hundred years of scientific inquiry into the oil sands of Alabama, comprehensive studies are few and far between, and data and samples have been lost over time. In the mid-1980s, the Geological Survey undertook a wide-ranging study of the oil sands in northern Alabama culminating in the publication of Bulletin 111 (see Wilson, 1987 below), which incorporated data from new cores and samples with existing data, maps, other relevant information from both Survey records and private companies. This study calculate a total subsurface reserves of 7.5 billion barrels of oil and an additional 350 million barrels in outcrop and near surface (less than 50 feet deep) areas. Recovery potential is difficult to calculate as new technology can greatly enhance recovery.
A renewed interest in oil sands, in general, and the Hartselle, in particular, from both industry and government has led to the creation of the Alabama Oil Sands Program at the Geological Survey of Alabama. Check back for new information and further developments as the project gets underway.
Selected Resources and References
Download the presentation by the Geological Survey of Alabama and State Oil and Gas Board from the June 24, 2014, community meeting in Tuscumbia, AL, here.
Wilson, G.V., 1987, Characterisics and resource evaluation of the asphalt and bitumen deposits of northern Alabma, Geological Survey of Alabama, Bulletin 111, 110p.
Moftah, Ismail, 1973, Engineering Evaluation of Alabama Tar Sands, Geological Survey of Alabama, Circular 89, 58p., 5 plates.
Carroll, R.E., Pashin, J.C., and Kugler, R.L., 1995, Burial History and Source-Rock Characteristics of Upper Devonian Through Pennsylvanian Strata, Black Warrior Basin, Alabama, Geological Survey of Alabama, Circular 187, 30p.
Pashin, J.C,and Kugler, R.L., 1994, Outcrop characteristics of asphaltic Lewis Sandstone, Black Warrior Basin, Alabama: application to subsurface studies of reservoir heterogeneity, Geological Survey of Alabama, Reprint Series 98,259p.
Epsman, M.L., 1987, Subsurace Geology of Selected Oil and Gas Fields in the Black Warrior Basin of Alabama, Geological Survey of Alabama, Atlas 21, 255P.
Merrill, R.K., Gann, D.E., Jennings, S.P., 1988, Tishomingo County Geology and Mineral resources, Mississippi Dept. of Natural Resources, Bureau of Geology, Bulletin 127, 187p.