DELINEATION OF AN OIL AND GAS FIELD WITHIN A TURBIDITE SYSTEM: BREDASDORP BASIN, SOUTH AFRICA
Published:December 01, 1994
S.J. WINTERS, S. KUHLMANN, 1994. "DELINEATION OF AN OIL AND GAS FIELD WITHIN A TURBIDITE SYSTEM: BREDASDORP BASIN, SOUTH AFRICA", Submarine Fans and Turbidite Systems—Sequence Stratigraphy, Reservoir Architecture and Production Characteristics Gulf of Mexico and International, Paul Weimer, Arnold H. Bouma, Bob F. Perkins
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A sequence stratigraphic approach applied to the central Bredasdorp basin has delineated a eustatic third-order Aptian sequence in which several hydrocarbon discoveries have been made to date. The sequence consists of a lowstand sequence set within which higher-order sequences are developed, a transgressive systems tract with a thick marine condensed section, and a progradational highstand systems tract. The fourth-order simple sequences within the lowstand sequence set are associated with basin floor fans which have been deposiited retrogradationally within the confines of a fault-controlled erosional valley. The basin floor fans are characterized by stacked deep-marine channel deposits and form combination traps through stratigraphic pinch-outs and local inversion tectonics.
The channel-fill sandstones comprise the primary reservoirs and are characterized by high amplitude seismic anomalies. Mapping of these anomalies, facilitated by a 3-D seismic survey, forms a critical part of the interpretation process as the amplitude variations signify changes in sandstone thickness, porosity, net-to-gross ratios, and fluid content Seismic modelling has been applied in an attempt to calibrate these amplitude responses.
Appraisal drilling has confirmed the sequence stratigraphic model of two retrogradationally stacked basin floor fans which contain significant oil and gas accumulations.