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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 26 (1976), Pages 10-16

Depositional Environments and Petroleum Potential of the Asphaltic Hartselle Sandstone in North Alabama (1)

Wendell M. Beavers, Peter A. Boone (2)

ABSTRACT

Asphalt and heavy oil occur in sandstone and limestone of Mississippian age in north Alabama. These petroliferous rocks occur in the Pride Mountain Formation, the Hartselle Sandstone, and the Bangor Limestone. Petroleum is more areally extensive in the Hartselle than in the Pride Mountain and the Bangor. The Hartselle Sandstone consists of two major lithofacies: (1) a clean, medium- to very thick-bedded, cross-laminated facies with little or no matrix associated with barrier-bar and upper coastal sands environments; and (2) a thin- to medium-bedded ripple-laminated to very thick-bedded muddy facies with significant terrigenous matrix and interbeds of mudstone associated with intertidal, lower coastal sands and transition zone environments. The Hartselle Sandstone was probably deposited under relatively stable conditions as a tidally influenced system of subparallel, northwest-southeast trending linear sand bodies characteristic of barrier-bar sedimentation and is a product of the lateral migration of morphologically defined depositional environments. The richest asphalt impregnation is in the clean facies; this facies also forms prominent sandstone ridges in the outcrop area.

Oil saturation in the impregnated intervals of the Hartselle ranges from 1 to 60 percent and averages about 27 percent. The porosity of the saturated zone of the Hartselle ranges from 0.4 to 24.0 percent and averages 13 percent. The impregnated interval ranges from 1 to 55 feet thick and has an average thickness of 21.3 feet.

Resource calculations indicate that average oil in-place is 285.5 barrels/acre-foot or 5,269.6 barrels/acre or 3.6 gallons of oil per ton of impregnated sandstone. The indicated-subeconomic petroleum resources of the Hartselle Sandstone are estimated as being 1.18 billion barrels of oil in 350 square miles where the Hartselle is more than 150 feet thick.


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