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Characterization of Deepwater Channel Systems in the Wilcox Formation, Offshore GoM

Abstract

Large quantities of hydrocarbons have been discovered in the Paleogene Wilcox Formation, deep-water Gulf of Mexico. Although the general depositional environment with large submarine fans was agreed upon already about 10 years ago, few details have been published regarding smaller scale architectural elements. Most of the prospective areas are situated deep below the vast and several thousand feet thick salt canopy, severely limiting seismic imaging and geological characterization of the main depositional elements. However, some areas offer seismic geomorphology observation and interpretation opportunities. Through detailed interpretation of seismic datasets, 100s of channel segments from the distal Wilcox Fm. have been visualized and characterized. Dimensions, sediment distribution patterns and influence of evolving substrate relief (associated with salt dynamics) on channel directions have been analysed. Seismic geomorphology patterns related to channels show significant variability in sinuosity, bifurcation, and sediment dispersal directions through time. Evenly spaced wells allow for detailed correlation of sheet-like sub units (interpreted as lobes) and suggest a relatively flat basin floor with large-scale compensational stacking of units. Conventional core data from wells have also provided sedimentological evidence for channelized facies, corresponding to channel-form seismic geomorphology. The observed channels have relatively consistent widths which together with the long correlation lengths and uniform thickness of lobes point towards an organized, repeated pattern in the build-up of the distal Wilcox Fm. Important analogous datasets for the deep-water Wilcox Fm. can be found in the distal parts of the Mississippi and Zaire fans, where published studies of the seabed have revealed highly sinuous to semi-straight feeder- and distributary channel networks with bifurcation in addition to lobes. Lobes are virtually impossible to characterize from seismic datasets in the GoM, hence recognition and mapping of channels in the distal basin floor fans of the Wilcox Fm. offers guidance to prediction and calibration of lobe architecture (dimension and orientation) at local to semi-regional scale. Improved understanding of the lobes that dominate the distal Wilcox Fm. is fundamental to the development of predictive reservoir models addressing reservoir presence and quality.