ABSTRACT

Smackover sandstones in Thomasville field represent turbidite channel deposits. These sandstones are interbedded with a few thin beds of oolitic grainstones. A total of 969 ft (296 m) of core from three wells was examined, of which 820 ft (252 m) were sandstone. Depths ranged from 20,100 to 20,649 ft (6,131 to 6,298 m). Electric logs and cores from the three wells show abrupt facies changes, which may be expected from a shifting channel deposition. Correlations were made between the wells and environments of deposition determined from an examination of core composition, texture, and sedimentary structures.

Thick, massive bedsets and massive to laminated bedsets (A and AB units, respectively) are common in all cores, although massive (A) units dominate. Quartz grain sizes decrease upward in most bedsets. Sandstones have a mean grain size of 0.23 mm (fine grained). Carbonates exhibit similar textural trends and sedimentary structures.

Porosity and permeability average 5.1% and 0.32 md for sandstone, and 1.2% and 0.01 md for carbonates. A black, opaque residue, ubiquitous in the cores, represents residue of a former oil pool. Resistivity plotted against bulk density shows distinct groups for each rock type. A plot of resistivity versus porosity suggests a gas-water contact farther down the section at a depth of about 20,500 ft (6,253 m). Based on this study, the gas column is on the order of 300 ft (92 m) for about 50% water saturation.

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