ABSTRACT: Smackover Exploration Along the Flanks of Intermediate Salt Ridges, Central Mississippi Salt Basin

REQUARTH, JEFFREY S., and JOHN J. MORRIS, no affiliation

Recent Smackover fields discovered in the Central Mississippi Salt basin can be characterized by their positions along the flanks of a series of northwest to southeast trending salt ridges. The majority of the Smackover production discovered in Mississippi during the 1960s and 1970s was in structural/stratigraphic traps associated with low relief salt anticlines. These discoveries were located along the basin margin and typified by such fields as Prairie Branch, Nancy, West Nancy, East Nancy and Pachuta Creek. Recent discoveries along the flanks of intermediate-size salt ridges indicate that significant additional Smackover reserves remain untapped. New and rejuvenated fields, such as West Chaparral, Clear Creek, Tallabogue Creek, Shubuta and Winchester were located or extended by a c mbination of methods including salt deformation modeling, high quality, multi-fold seismic acquisition and interpretation and subsurface analysis of existing well control.

"Upthrown" Smackover fields in Mississippi range in size from 100,000 to 10,000,000 bbl of oil and from one to ten wells. Many of the fields exhibit steep Smackover dips (10 to 50 degrees), thick pay columns and limited aerial extent. Lateral and vertical seals are of critical importance in evaluating "upthrown" traps. Existing field evidence suggest that the best "upthrown" fields exhibit lateral and vertical reservoir seals formed by Lower Haynesville (Buckner) anhydrites.

Relatively few "downthrown" Smackover fields have been exploited to date. West Chaparral Field, discovered in 1989, has made one million barrels of oil through December 1991 from seven wells, and may ultimately produce five million barrels of oil. A generalized "downthrown" trap model shows the Smackover to be terminated updip by Louann Salt with the vertical seal provided by a thick Lower Haynesville section. Bed dips in the Smackover should be lower than those found in the "upthrown" trap due to the absence of late salt movement. Thick pay columns and larger closures may be expected in future "downthrown" fields as a result of excellent lateral and vertical reservoir seals and the lack of late structural movement.

AAPG Search and Discovery Article #91014©1992 AAPG GCAGS and GC-SEPM Meeting, Jackson, Mississippi, October 21-23, 1992 (2009)