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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 36 (1986), Pages 295-304

Exploration Models for Submarine Slope Sandstones

Roger M. Slatt (1)

ABSTRACT

Recent published studies have demonstrated a far greater potential than previously recognized for submarine slope sandstones to contain significant oil and gas reserves in the Gulf Coast and elsewhere. Comparison of modern slopes with outcrop and subsurface analogs from several areas has provided the framework for developing the following submarine slope sandstone exploration models: submarine canyon fill, slope gully/channel fill, slope "spillover" sand sheets and intraslope basin fill.

Submarine canyon fill is mainly shale, but sandstone beds that form stratigraphic traps may be present; canyon shale-fill juxtaposed against older sandstones can also form stratigraphic traps. Gully/channel fills are sandstones deposited on shallow-gradient slopes or ramps. Proximity of these sandstones to slope shales provide opportunities for development of stratigraphic traps. "Spillover" sand sheets are resedimented from a shelf to a shallow-gradient slope, and are associated with gully/channel fills. Intraslope basin fill is mainly shale, but elongate, sheetlike, or fan-shaped turbidite sandstones can provide stratigraphic traps. In all of the above cases, slope shales may be sufficiently enriched in organic carbon to be potential hydrocarbon source rocks; the potential for organic-rich shales to accumulate is highest in intraslope basin fill.

These types of deposits exhibit certain geophysical and geological criteria which can be utilized for their detection in the subsurface. These criteria, coupled with an understanding of slope depositional processes, dimensions of depositional sites, and geometries of sandstones, can lead to improved exploration play development and prospect generation in the transition zone from shallow to deep parts of the Gulf Coast basin, and elsewhere.


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