Outcrop and Subsurface Stratigraphic Models and Exploration Plays of Slope and Basin Floor Carbonates

Xavier Janson¹, Charles Kerans², Ted Playton², Jason Clayton², Peter Winefield³, and Peter Burgess^4
1Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX
²Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX
³Shell International E&P, Houston, TX
⁴Shell International E&P, Rijswijk, Netherlands

Exploration for carbonate-slope and basin-floor reservoirs involves an underdeveloped play type. Significant risks include reservoir quality prediction and top and lateral seal development, but risk can be reduced by improving conceptual models developed using detailed outcrop studies and careful examination of core, log, and 3D seismic data within a sequence framework. New conceptual models for carbonate-slope and basinal-deposit stratigraphic architecture and several exploration plays have been developed using extensive literature review and several detailed outcrop studies. Six stratigraphic play types can be defined for toe-of-slope and basinal carbonate sediments: (1) Reefal upper slope; (2) toe-of-slope apron; (3) channelized fan; (4) basin-floor fan; (5) drift, contourite; and (6) collapse/olistostrome. These plays will be documented using outcrop and subsurface examples ranging from the Carboniferous to modern-day carbonate depositional systems. Hydrocarbon production comes from the first three types of play and possibly also from true carbonate basin-floor fans. Contourites and margin-collapse plays remain hypothetical. In addition to these pure stratigraphic-trap plays, tectonic deformation, fracturations, and late diagenesis can greatly enhance the potential for accumulation of hydrocarbon in the toe of slope and basin adjacent to shallow-water carbonate platforms.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery