HYDROCARBON POTENTIAL OF THE LOWER SMACKOVER FORMATION IN ARKANSAS, LOUISIANA, AND MISSISSIPPI

The Smackover Formation has historically been viewed as having two members: the Lower and the Upper members. The Lower Member consists of a basal laminated lime mudstone lithofacies which grades upward into the so called Brown Dense Limestone. The Lower Member is rich in organic carbon and commonly makes two-third of the 1200 feet thickness of the Smackover Formation. The Upper Member is composed of ooid grainstone and is porous and permeable forming prolific reservoirs. Traditionally, hydrocarbon exploration has been concentrated exclusively on the Upper Member. Recent successes in shale gas plays have put the Lower Member of the Smackover Formation in the spot light.

This study offers a new depositional system and sequence stratigraphic framework of the Smackover Formation and evaluates the hydrocarbon potential of its Lower Member. According to this synthesis, the Smackover Formation consists of four sequences which were deposited in a strongly progradational depositional system. From the oldest to the youngest, they are here referred to as Smackover Sequence-1 (SS-1) to Smackover Sequence-4 (SS-4).

The SS-1 and SS-2 were deposited in the inner shelf region. These two sequences do not posses the laminated lime mudstone and the Brown Dense Limestone lithofacies, have thin ooid grainstone layers, were influenced by microbial processes, their original mineralogy was aragonitic, and were exposed to extensive meteoric diagenesis.

SS-3 and SS-4 formed in the middle shelf to basinal areas. These two sequences have well-developed laminated lime mudstone and the Brown Dense Limestone which are rich in organic carbon, have turbidite-derived sandstones, and occasionally dolomitized. The ooid grainstone lithofacie of these two sequences are thick and were deposited as prograding shelf margin marine shoals.