Examples of Fluvial Stratigraphy in the Wilcox Group, Louisiana, as Revealed by High Resolution 3D Seismic Data

Jeanne S. F. Phelps, Jonathan L. Jee, Michael A. Fogarty, and R. David Phelps: Pennant Exploration, L.L.C., New Orleans, LA

Abstract

Following the marine deposition of the Austin Chalk and the overlying Midway Shale, the Laramide Uplift of the Rocky Mountains began a major regression. During the Eocene, a flood of sediments prograded towards the Gulf of Mexico and deposited the Rosita and Rockdale deltas of south and east Texas, and the Holly Springs delta of Louisiana and Mississippi. As it prograded across the stable shelf area, the Holly Springs delta laid down a remarkably uniform fluvial to shallow marine Wilcox sequence some 3,000 feet thick. Historically, both 2D and 3D seismic has proven to have little value for sequence stratigraphic interpretation of the Eocene of Louisiana. Conventional seismic processing of modern 3D seismic can be used to identify the major transgressive surfaces however it does not have the vertical and horizontal resolution needed for detailing the fluvial depositional patterns necessary to identify subtle stratigraphic features. Recent reprocessing of existing 3D seismic data using propriety software and processes indicate that 3D seismic can be a valuable tool for placing these fluvial sequences within an exploration context. Following reprocessing and calibration with other geological data, fluvial stratigraphic features such as differential compaction, sand and shale filled channels, and stratigraphic pinch outs can clearly be seen in the seismic data. When integrated with the extensive subsurface data set it is possible to create a sequence stratigraphic framework to use as part of a modern exploration program.