Abstract The Mayaro Formation, which is exposed in SE Trinidad, is the key outcrop analogue for prolific hydrocarbon reservoirs in the Columbus Basin, offshore east Trinidad, because it was deposited in the same basin setting by the same depositional system (the palaeo-Orinoco) as the offshore reservoirs. Sequence and parasequence stacking patterns affect the distribution of different types of reservoir sand bodies and heterogeneities, with the potential to influence fluid flow in subsurface hydrocarbon reservoirs. Spectacular outcrops of successions of storm-wave-influenced sand bodies, tens to hundreds of metres thick, deposited in axial and medial delta-lobe settings are characterized by high sand–shale ratios (0.7–>0.95), and are analogues for many producing reservoirs in the basin. Fluvial- and tide-influenced sand bodies deposited in distal distributary settings are also recognized in the outcrops, but may be difficult to distinguish from medial delta-lobe deposits in subsurface data. More complex, thinly bedded distal delta-lobe deposits, with subsurface reservoir potential, exhibit lower sand–shale ratios (0.3–0.6). Complex depositional architectures, with a high proportion of thinly bedded sandstones, also occur in association with delta-front deposits. The distal delta-lobe and delta-front deposits are analogous to some of the most challenging to develop reservoirs in the Columbus Basin.

Abstract 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 mi 2 (150 km 2) 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.

Abstract The stops described herein are approximately 10 to 12 mi (16 to 20 km) north of Columbus, Georgia, on the east bank of the Chattahoochee River and on the west side of 1-185 (Fig. 1).

Abstract Uchee Belt rocks are well exposed in the vicinity of Columbus, Georgia. Stops A and B are on the banks of the Chattahoochee River in Phenix City, Alabama, and Stop C is located on the campus of Columbus College, Columbus, Georgia (Fig. 1).