Seismic geomorphology and characterization of deep water architectural elements and its applications in 3D modeling. A case of study, North Carnarvon Basin Australia.

Abstract

Analysis of a high resolution 3D seismic volume from Cenozoic strata in the offshore of North Carnarvon basin, Australia has revealed fine details of deep water architectural elements, including their dimensions and position on the slope. Four main groups of architectural elements were identified and measured within eight stratigraphic sequences interpreted in the studied area: (1) erosive channel-fills, (2) channel-levee complexes, (3) mass transport deposits, and (4) sand fan lobes or sheets. Each depositional element exhibits a characteristic morphology and seismic response. The position of those elements on the shelf to slope area is a function of the morphology of the slope, and the equilibrium between accommodation space, sediment supply and sea level changes. The high resolution seismic allowed placement of the architectural elements within a sequence stratigraphic framework. Falling stage systems tracts are characterized by development of small erosive channels in the upper slope, channel-levee complexes in the middle and lower slope, and sand fan lobes on the lower slope. Variations in the sediment composition are related to early development of large mass transport deposits, slumps and debris flows. Lowstand systems tracts are characterized by the predominance of sand lobes and sheet sands on the lower slope and basin floor. Analysis of slope gradients allows comparison with other deep water sequences deposited on an ungraded-to-graded continuum of continental margins. The characterization of the stratigraphic grade of the margin showed the variations of the slope morphology and its consequences in the evolution of the margin from a graded margin to an out-of-grade margin. Compensational style deposition was clearly identified as a consequence of the interactions among accommodation space, sediment supply and subsidence of the area. Finally, the calculated seismic attributes are used to build a 3D geological interpretation. The extracted horizon-based attributes are used in the implementation of a simple methodology to construct probability maps for constraining the distribution of architectural elements within a 3D geocellular model. Measurements and spatial distribution of the mentioned elements are used as inputs for object-based model approach. Better results are observed using a Sequential Indicator simulation approach constrained by three dimensional probability volumes calculated from geobody extractions using multiple seismic attributes.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017