Norphlet Formation (Upper Jurassic) Sand Erg: Depositional Model for Northeastern De Soto Salt Basin, Eastern Gulf of Mexico

David A. Kemmer, Roger L. Reagan

Available well control, seismic reflection geometries, and seismic modeling suggest the interpretation of a Norphlet Formation (Upper Jurassic) sand erg in the northeastern De Soto salt basin.

Ranging in thickness from less than 100 ft to nearly 1,000 ft, the Norphlet erg encompasses an area of approximately 700 mi². Separated from the major gas accumulations in the Norphlet in the Mobile Bay area by the offshore extension of the Pensacola arch, the Norphlet erg appears to be oriented transverse to the axis of the De Soto salt basin.

Seismic signatures for the Smackover carbonate, Norphlet sand, and Louann Salt intervals are investigated using synthetic seismograms generated from six wells in the eastern Gulf of Mexico. General characteristics about the reflection coefficients from the major units in the interval are noted.

The reflection coefficient information and synthetic seismograms are used to interpret seismic data on a regional basis. Two-dimensional, vertical-incidence, ray-trace modeling of the seismic data is done to aid the interpretation on a detailed basis. Interpreted Norphlet sandstone thicknesses and Louann Salt structures are combined to support the Norphlet Formation sand erg hypothesis.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.