Reservoirs of the Augila oil field, Libya, are a carbonate and clastic unit as well as the underlying fractured and weathered granitic basement rock.

The Upper Cretaceous sedimentary reservoir rocks were deposited above the crest of a paleohigh composed of early Paleozoic or late Precambrian granitic rocks. The regional high extended across an area greater than 1,000 sq mi, had more than 2,000 ft of topographic relief, and was intensely fractured and weathered prior to burial.

A diachronous basal clastic unit, composed of basement-derived material deposited as the sea advanced across the high, grades upward and laterally into carbonates, forming a single sedimentary reservoir.

Petrographic and ecologic studies indicate that porosity and permeability in the sedimentary reservoir are the result of the environments of deposition and diagenesis. The Augila field is divided into the following environmental sectors: (a) low energy, well protected from the open sea; (b) low to moderate energy, shallow marine, slightly protected; (c) low to moderate energy, shallow open-marine shelf; and, (d) low energy, open marine.

These depositional environments were controlled by granitic ridges along the crest of the regional uplift and formed barrier islands during deposition of the sedimentary reservoir.

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