The Cadeville sand reservoir at Calhoun field, Jackson, Lincoln, and Ouachita Parishes, Louisiana, is a lenticular body of Upper Jurassic fine-grained quartz sandstone and quartzose limestone, which is enclosed vertically and laterally by impermeable carbonate mudrocks. This gas-condensate reservoir within the Schuler Formation is 11.5 mi long, 2.0 mi wide, and has a maximum thickness of 38 ft. It probably was deposited as a nonemergent bar in a shallow-marine environment.

There are progressive and systematic lateral changes in lithology within the reservoir. Both the size of detrital grains and the abundance of fossils are at a maximum along the east-west axis of the reservoir and decrease toward the north and south. The total percent carbonate is also greatest along the axis and decreases in the north and south. Moldic porosity is best developed along the reservoir axis, whereas intergranular porosity is dominant along the margins. Sorting of detrital grains is best north of the axis and poorest along and south of the axis.

Knowledge of these gradients in lithology was useful in locating the depositional axis of the Cadeville sand reservoir and was helpful in developing the west end of the field. In the event of a discovery of a similar reservoir, this knowledge would be useful in determining the probable position of the reservoir axis relative to the discovery well.