SUB-REGIONAL 3-D SEISMIC INTERPRETATION OF PLIO-PLEISTOCENE TURBIDITE SYSTEMS, NORTH-CENTRAL GREEN CANYON, NORTHERN GULF OF MEXICO
PETER VARNAI, PAUL WEIMER, 1996. "SUB-REGIONAL 3-D SEISMIC INTERPRETATION OF PLIO-PLEISTOCENE TURBIDITE SYSTEMS, NORTH-CENTRAL GREEN CANYON, NORTHERN GULF OF MEXICO", Stratigraphic Analysis Utilizing Advanced Geophysical, Wireline and Borehole Technology for Petroleum Exploration and Production, Jory A. Pacht, Robert E. Sheriff, Bob F. Perkins
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3-D seismic interpretation is now used routinely in the subregional analyses of the Gulf of Mexico turbidite systems. The detailed description and interpretation of these systems are essential for effective petroleum exploration and production. The objective of this study was to use 3-D seismic data to increase our understanding of Plio-Pleistocene turbidite systems in one mini-basin. Specifically, we interpreted a sub-regional 3-D seismic data set, and integrated it with available-well control in a major sediment fairway in north-central Green Canyon. We then described variations in slratal geometries using detailed reflection amplitude mapping and horizon slices. The patterns of the high-amplitude areas (anomalies) recognized on these maps and slices showed the three-dimensional distribution of the seismic facies of the vertical profiles and the different stratal geometries of turbidite systems. The integrated interpretation of the amplitude distribution with the seismic facies and well data resulted in a more detailed and reliable depositional environment interpretation.
Two turbidite depositional styles were interpreted in the selected upper Pliocene interval. In the 3.8 Ma sequence, roughly circular amplitude anomalies indicate laterally continuous, sheet-like deposition (lobe). Sand sheets were deposited in the lower part of the sequence, overlain by poorly preserved channel systems, and shale drapes were formed in the upper part. The younger sequences (3.0 to 1.9 Ma) have slightly sinuous amplitude anomalies, which were interpreted as channel-levee systems. The low amplitude areas of these sequences represent overbank deposits (channel and over-bank).
Comparing the results of our previous regional 2-D study to this subregional 3-D study shows the advantages of 3-D interpretation in sequence stratigraphy. The considerably closer line spacing of the subregional 3-D seismic data set allowed the correlation of individual seismic reflections, and therefore the mapping of their amplitude distribution. Using this amplitude mapping technique, we were able to study the seismic facies in three dimensions. Analyzing the stratal geometries helped to interpret the turbidite systems more reliably. Channel-levee systems were interpreted and mapped in an area where no distinct seismic reflection configuration associated with the channels is present. Only higher amplitudes indicate the presence of channels.