Shelf-to-Slope Subsurface Petroleum Systems
2013. "Shelf-to-Slope Subsurface Petroleum Systems", Shelf Margin Deltas and Linked Down Slope Petroleum Systems–Global Significance and Future Exploration Potential, Harry H. Roberts, Norman C. Rosen, Richard H. Fillon, John B. Anderson
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Shelf-edge delta reservoirs of the paleo-Orinoco River are growth-fault expanded and stacked because of extremely rapid subsidence in the Columbus Basin growth fault province, offshore southeast Trinidad. Over 60 pay zones on the Trinidad shelf occur in deltaic reservoir intervals, each representing a fourth order sequence (40-100 Ka), and have been deposited within 6 mi (10 km) of the paleoshelf-edge. The resulting reservoirs are very thick (commonly 300 to 500 ft, up to 1000 ft), laterally extensive, highly continuous, and prolific producers. Six of BP’s best producing wells worldwide are situated in the Southeast Galeota (SEG) structural complex on the Trinidad shelf. Stacking of multiple, thick deltaic pay zones within large structural culminations result in very high reserve density. The SEG complex covers an area of ~60 mi2 (150 km2) and contains some 14 TCF of resources. Subsurface data, outcrop descriptions, and seismic images of the last lowstand delta beneath the modern Trinidad shelf-edge are combined to develop a better understanding of the depositional setting. Reservoir quality and well production data highlight the tremendous deliverability of these shelf-edge delta reservoirs. A tentative depositional model is proposed by way of an idealized fourth order sequence dip section across the shelf and by representative log profiles from the subsurface.