(1) C & C Reservoirs Ltd, London, United Kingdom
ABSTRACT: Trapping Styles and Reservoir Characterization of Deepwater Reservoirs: Comparison of 33 Field Examples from Gulf of Mexico, West Africa and Brazil
A comparison of 33 deep-water turbidite fields in seven basins from West Africa, Brazil and Gulf of Mexico reveals recurring patterns of trapping and reservoir architectural styles that have implications for exploration drilling and development plans in passive-margin basins. The fields are contained mainly in combination structural-stratigraphic traps, with 80% showing some element of stratigraphic closure, principally depositional pinch-out, which generally tends to diminish in importance upslope with increasing structuration and sand occurrence. Basinwide mobile substrate (salt or shale) thickness controls regional deformation style, the likelihood of structural trapping and the location of reservoirs. Six principal deep-water reservoir types are recognized, whose abundance varies across the continental slope: (1) channel-dominated reservoirs, which are commonest on the middle slope; (2) sheet-dominated reservoirs, commonest on the middle-lower slope; (3) leveed-channel reservoirs on the upper slope; (4) canyon-fill reservoirs on the upper slope-shelf; (5) debrite reservoirs on the upper slope; and (6) contourite reservoirs, commonest on the lower slope-basin floor. The case histories provide a series of guidelines for predicting sand-body dimensions and stacking patterns, together with their influence on aquifer support, well spacings and development options. Pre-drill reserves estimates should take into account the upside potential for deeper hydrocarbon pools as virtually all the passive-margin case studies have at least 2-5 separate payzones. Passive-margin turbidite fields are generally of Paleogene age or younger, so the reservoirs are weakly consolidated/cemented, porosities exceed 25% in most cases and excellent well deliverabilities are common.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.