Smackover Formation Essay

The Smackover Formation is a carbonate reservoir rock overlain by the sealing anhydrite Buckner Formation and establishes a reservoir-seal relationship between the formations. Carbonate carriers at the shelf margin produce environments of restriction where Buckner evaporites, terrigenous clastics, and evaporites accumulate. With increasing sea level rise, up-dip deposits of Gilmer beds consisting of ooids, peloids, and fossil limestones can be seen in the present day Mexia-Talco fault system (Stewart, 1984). The Smackover Formation contains “type I kerogen, an algal-derived kerogen found and preserved in anoxic environment conditions” (Sassen, 1990, p.265).
Traps can be stratigraphic, structural, or a combination of the two. A large percent of crude oil is present in stratigraphic traps, and combination traps are responsible for the largest amounts of natural gas (Foote et al., 1988). In a petroleum system like the Smackover Formation, it is important for traps to be present so that the hydrocarbons are unable to escape. However, Locklin, 1984, page 41, makes a clear argument why "apparent Upper Jurassic reservoir rocks have not trapped hydrocarbons more frequently." He reasons that potentially “large faults have caused breaking of mineralized seals and created excessive fracturing along a fault plane, which allowed for the
Migration occurred after pre-compaction and before the later, deeper cement precipitation (Moore, 1984). Based on this, Moore deciphers that the source rocks in east Texas reached maturity earlier than those source rocks in other basins (Arkansas, Mississippi, Louisiana) (Foote et al., 1988). The swift thinning of strata to the northern part of the basin and the regional fluid migration from its source at the basin margin towards the shelf is essential for hydrocarbon accumulation in the reservoir (Foote et al.,