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Abstract: Classical Seismic Sequence Stratigraphic Interpretation of Intraslope Basin Fill: Deepwater Nigeria

Edward A. Duncan

Detailed interpretation of seismic facies patterns performed within the workstation environment provides an observation based methodology for constructing depositional models of turbidite and other reservoir bearing systems expected in deepwater Nigeria. The increased fidelity of the workstation allows greater detail and accuracy to be imposed onto depositional model construction by vastly improving the discrimination of depositional from structural seismic reflection geometries. In deepwater Nigeria intraslope basins, depositional cyclicity is clearly indicated by vertical seismic facies successions in the same way as can be recognised in bed thickness trends from outcrop or well log data. The recognition of the seismic facies successions appears to break the stratigraph into at least fourth and fifth order scale sequences.

Highly "zoomed", instantaneous phase displays enhance the reflection character so that near outcrop scale (resolution less than 50 meters) interpretations of depositional facies can be made. Common seismic facies and geologic interpretation include: 1) low angle erosional surfaces as channel scour or mass wasting detachment, 2) low relief mounds, often in compensation cycle overlapping stacks reflecting compacted channelbelt fill, 3) unidirectional, low angle clinoform sets suggesting lateral accretion within a channel belt or possible contourite mounds, 4) abrupt, shingled blocks illustrating tilted fault blocks of small scale intraformation slumping, and 5) high reflection amplitude and continuous, parallel reflections of pelagic and hemipelagic condensed sections. There are other s btle seismic facies resolvable given the increased fidelity of the workstation interpretation. Mapping and translation of these geometries into more robust stratigraphic predictions should have positive impact on exploration and development success.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France