The Smackover limestone is the primary exploration target in the updip part of the entire Gulf Coast area, extending from East Texas to Florida. Accordingly, the Smackover provides most of the new reserves being found in this area and most major companies and many independents have virtually stopped Cretaceous exploration to concentrate on the Jurassic reservoirs (Smackover and Cotton Valley).

Smackover exploration started on a major scale during the 1940s in southern Arkansas where relatively shallow (above 9,000 ft) oil was found. Production was predominantly from oolitic limestones on relatively simple anticlinal structures that were located by reflection seismograph. Nearly 20 years later, in the 1960s, major Smackover exploration began in East Texas. There, a different set of problems confronted explorationists--more radical facies changes, predominantly dolomite reservoirs, gas condensate-sulfur rather than oil pays, abundant inert gases, complex salt intrusions, greater depths (over 12,000 ft), and erratic porosity developments!

Nearly 5 years later, in the late 1960s, Smackover exploration expanded to Mississippi, Alabama, and most recently, to Florida. There, producing rates are higher and multipays of both oil and gas are common in the Cotton Valley and Norphlet sandstones, in addition to the Smackover. Broad limits of the favorable producing facies in the Smackover are fairly well recognized in Mississippi and presently are being extended eastward into Alabama and Florida where recent discoveries by Humble have started "hot" lease plays.

Although local structure and stratigraphic variations are extremely complex, the regional picture of Smackover deposition is viewed as a simple "wedge" of predominantly carbonate rocks rimming the Gulf Coast, and underlain by salt along the downdip area and an old Paleozoic landmass on the north in the updip area. Most Smackover fields have been round in areas of post-Smackover (Buckner anhydrite) "thins," seismic "salt swells," and very low relief Lower Cretaceous structures. Most of the recently discovered fields cover less than 1,200 acres; however, pay sections of more than 100 ft are not uncommon, yielding large reserves over small geographic areas. Consequently, several tests commonly are required to pinpoint the accumulation.

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