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Play Opportunities for the Eastern Gulf of Mexico
The eastern part of the Central Gulf Outer Continental Shelf (OCS) Planning Area and the Eastern Gulf OCS Planning Area comprise one of the most attractive exploration opportunities now and soon to be available in the Gulf of Mexico. Recent industry activity in eastern Mississippi Canyon, Main Pass, Viosca Knoll, and Mobile offshore areas have produced successes that have identified significant hydrocarbon accumulations in the eastern part of the Central Gulf OCS. There is also a large amount of industry interest in the Eastern Gulf OCS region. The current focal point in the Eastern Gulf OCS is comprised of the areas to be contained in the planned OCS Sale 181 leases to be offered in December 2001. These areas are located in the westernmost extents of the Destin Dome, Desoto Canyon, and Lloyd areas (Fig. 1).
Areas within the Eastern Gulf Planning Area are under-explored relative to the traditional exploration areas of the Western and Central Gulf. Fewer scheduled lease sales, a more diverse geology, and absence of producing infrastructure are among the factors that have led to sporadic development in this area. Only eight previous lease offerings have been made in the Eastern Gulf OCS region. The last federal lease sale (Sale #116) occurred in 1988 and resulted in only 114 tracts being awarded. The low density of leases in the region is in itself attractive to an industry always in search of new opportunities.
In preparation for upcoming lease sales, analyses of newly acquired 2-D and 3-D seismic data tied to existing well control provide a look at some interesting play opportunities for these areas. Approximately 23,000 miles of new 2-D seismic have been acquired for evaluation of these tracts along with 450 blocks of new 3-D seismic. These new data, when combined with the relatively sparse drilling record, illustrate both old and new play opportunities for these areas.
Three broad areas of interest may be discerned: allochthonous salt related features, autochthonous salt related features, and Mesozoic shelf carbonate plays. These plays are within the eastern Mississippi Fan and the Florida carbonate shelf. Allochthonous salt-related plays are largely of early Pliocene or middle to late Miocene age and occur in proximity to and beneath horizontal salt features largely restricted to the upper Mississippi Fan. Good examples of discoveries associated with the allochthonous salt are Mississippi Canyon 211, 292, and 778, each structurally positioned beneath a salt sill. Additional undrilled opportunities remain to be tested in this play, but they often require high-effort seismic acquisition and processing to be delineated sufficiently for an exploration test.
Middle to upper Miocene plays are associated with autochthonous features within the middle to outer fan. Examples of discoveries associated with autochthonous salt are at Mississippi Canyon 84, 305, and 657, and Viosca Knoll 915. This play is characterized by lower Pliocene to middle Miocene slope fans and their associated channel levee and fan deposits. Often these features are developed above or adjacent to salt deformation features and associated faulting, some having been subjected to post-depositional basin inversion due to salt movement and withdrawal.
The deep Cretaceous section also represents a play within this part of the fan, pending the confirmation of reservoir section. Recent activity along the buried Cretaceous shelf edge has turned up a significant play with several sizable gas discoveries reported from grain shoal carbonate reservoirs in Viosca Knoll and Mobile areas. The Cretaceous section has been proven gas-productive from Aptian and possibly Albian formations that may extend into the west Florida shelf. Examples of discoveries along this trend are in Viosca Knoll 252, 114, and Mobile 991. Evaluation of multiple seismic attributes have proven useful for identification of porous zones along this trend.
Additional opportunities may also be available from the downdip Jurasic Norphlet Formation beneath the shelf. A discovery at Destin Dome 56 as well as prior discoveries in the Mobile Bay area have drawn appreciable interest to the trend. Precise evaluation and ranking of opportunities within these new plays will be highly dependent on detailed evaluations of the new seismic data and understanding of the stratigraphic and sedimentologic framework within these regions.
Basinal equivalents of the Mesozoic section have yet to be tested with the presence of reservoir rock
being the main concern. This section sources much of the hydrocarbons for the shallower section in the region and may still contain appreciable trapped reserves yet to be systematically identified. Development of significant structural trapping opportunities due to an abundance of salt structures is observed within the deep water Mesozoic section.
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