A Simple Methodology for Carbonate Sequence Stratigraphic and Seismic Stratigraphic Interpretation: Examples from the Lower Cretaceous Section in Offshore Alabama and Mississippi

Marcello Badali`: Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama

Abstract

Carbonate sequence stratigraphic analysis requires a different approach than siliciclastic sequence stratigraphic interpretation. To-date, a methodology for integrating core data, well log information, and seismic data, and utilizing this integrated data set for recognizing and mapping third-order depositional sequences has not been published. This paper provides such a methodology by using the Lower Cretaceous carbonate section in offshore Alabama and Mississippi as an example. A carbonate rimmed shelf margin, characterized by periodic siliciclastic sediment input, and the correlative slope, represent the Early Cretaceous geologic setting in this area.

This study incorporates various kinds of data at different scales. Approximately 3,500 kilometers of 2D multi-channel seismic reflection data are interpreted and integrated with gamma ray, lithologic well log descriptions, and well log lithostratigraphic picks from more than 50 wells, and with 527 meters of core from wells in the study area and surrounding areas. Seven check-shot surveys are used to integrate the seismic and well log data, and software for PC is used to integrate and interpret the various data sets.

The interpretation includes several steps. The seismic attributes are first characterized, then the seismic data are interpreted without the support of the well log and core data. Once the seismic sequence boundaries, the systems tracts, and the seismic facies are recognized, they are projected onto the well-log signatures. The core data are matched with the well log signatures. The final interpretation includes the integration of seismic, well log, and core data for the carbonate sequence stratigraphic and seismic stratigraphic analysis.