ABSTRACT: Miocene Stratigraphic Study in East and West Cameron OCS Areas, Gulf of Mexico

DU XIAOTAO and JOEL S. WATKINS, Texas A&M University, College Station, TX

As part of the Gulf of Mexico Structural and Stratigraphic Synthesis project, we have undertaken a detailed stratigraphic study of the Miocene of the East and West Cameron OCS areas. The study includes sea level studies using nannofossil data from 10 wells, detailed sequence and systems tract mapping from seismic data and net sand thickness from well logs. Our study maps on a sand-by-sand basis sand transport fairways and identifies previously undetected sands. This approach improves predictability of regional sand distribution and serves as an example for integrated sequence analysis.

The Miocene stratigraphic framework is based on condensed sections. Condensed sections are marked by peaks of nannofossil abundance and diversity and diagnostic transgressive patterns on well logs. The framework consists of eight sequences ranging in age from S. belemnos to D. berggrenii. Condensed sections interpreted from nanno reports are tied to seismic data for regional mapping.

Unconformities are interpreted from nanno biozones as tentative sequence boundaries. In the D. kugleri sequence, we found erosional features on seismic data corresponding to nanno unconformities but in the D. deflandrei sequence, we found no evidence of erosion in seismic data. Three wells detect the missing nanno zones, however. After putting condensed sections and tentative sequence boundaries on well logs, log characteristics are used to refine sequence boundaries.

Noteworthy results of our study include: (1) highstand deltaic sands occur in most sequences; (2) prograding complexes comprise most of the lowstand systems tracts; (3) sequences and systems tracts can be traced across the entire area without pronounced thickness changes; (4) dramatic changes of lithofacies occur only when crossing faults; and (5) shelf-slope breaks tend to coincide with faults.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)