Seismic Sedimentology and 3-D Seismic Expression of High-Frequency Sequence Stratigraphy in Miocene, Starfak and Tiger Shoal Fields, Offshore Louisiana

Hongliu Zeng1

ABSTRACT

In Starfak and Tiger Shoal Fields, the framework of the Miocene sequence stratigraphy was constructed by wireline log analysis in 150 wells. The extrapolation of the well-based high-frequency (fourth-order) sequence framework into the expansive 3-D seismic survey is a major challenge that requires extracting 10-m geobodies from limited-bandwidth (5-60 Hz) seismic data.

Critical to this extrapolation is the recognition and interpretation of high-resolution depositional features. Emphasis needs to be shifted from interpreting vertical seismic data to developing new tools capable of extracting horizontal, seismic geomorphologic information.

This study shows that proportionally stratal slicing between maximum flooding surfaces provides sequential and accurate seismic imagery of depositional systems, which in turn serves as a basis for recognizing and mapping fourth-order systems tracts, sequence boundaries, and sequences in the geologic time domain. This presentation illustrates why stratal slices are generally better than time slices and horizon slices in interpreting depositional morphology. In a 1-s-traveltime interval, most of 31 fourth-order sequences derived from well-log analysis can be seismically mapped and visualized.

An easy-to-follow procedure to map a fourth-order sequence includes five steps: (1) recognize depositional systems on stratal slices, (2) separate mapping units by viewing depositional history, (3) digitize systems tracts, (4) visualize systems tracts and sequence boundaries in geologic time, and (5) visualize systems tracts and sequence boundaries in depth (traveltime).

1Bureau of Economic Geology, The University of Texas at Austin, University Station Box X, Austin, Texas 78713; e-mail: hongliu.zeng@beg.utexas.edu.