Stratigraphy and Depositional Systems in the Deepwater
Zarra, Larry1 (1) Chevron,
Deep basin components of
Post-depositional structuring and
variable sand content complicated initial stratigraphic interpretations.
Correlations were facilitated by developing an integrated sequence
stratigraphic interpretation. Key components incorporate biostratigraphic data,
revised chronostratigraphic models, and detailed mapping of local sequence
boundaries. Lower slope reservoir sands and uncharged reservoir quality
sandstones are almost entirely limited to the 29.4-32 Ma sequence. The older
32-33.7 Ma sequence (
Depositional setting of the 29.4-32 Ma sequence includes weakly confined toe-of-slope turbidite fairways and adjacent thin-bedded overbank deposits. Characteristic turbidite lithofacies associations were interpreted from conventional cores. Core control was calibrated to OBMI (Oil Based Microresistivity Imager) logs, and extrapolated away from the cored interval.
Detailed mapping of sequences and turbidite sand packages within sequences enabled construction of horizon relative volumes that display distinct depositional features. Reservoir architectural styles include high to low sinuosity channels, anastomosing channel complexes, and discrete distributary lobes. While many of the seismic images of depositional features are un-calibrated, some images are calibrated to well data and conventional core.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California