AAPG Bulletin, V. 82 (1998), No. 5B (May 1998 Part B), P. 918-960.

Sequence Stratigraphy of Pliocene and Pleistocene Turbidite Systems, Northern Green Canyon and Ewing Bank (Offshore Louisiana), Northern Gulf of Mexico¹

Paul Weimer,² Peter Varnai,³ Fadjar M. Budhijanto,² Zurilma M. Acosta,⁴ Rafael E. Martinez,⁴ Alonso F. Navarro,⁵ Mark G. Rowan,² Barry C. McBride,⁶ Tomas Villamil,⁷ Claudia Arango,⁸ Jennifer R. Crews,² and Andrew J. Pulham²

©Copyright 1998.  The American Association of Petroleum Geologists.  All Rights Reserved

¹Manuscript received December 12, 1996; revised manuscript received January 16, 1998; final acceptance January 20, 1998.
²Energy and Minerals Applied Research Center, Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399.
³Energy and Minerals Applied Research Center, Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399. Present address: Exxon Exploration Company, P.O. Box 9778, Houston, Texas 77210-4778.
⁴PDVSA Exploracion y Produccion, Gerencia de Planificacionde Exploracion, Edificio La Estancia, Oficina 1359, Chuac, Caracas, Venezuela.
⁵PDSVA Exploracion y Production, Piso 14, Ofic. 14115-C, Avenida La Estancia, Chuao-Caracas 1010A Venezuela.
⁶Energy and Minerals Applied Research Cent., Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399. Present Address: HS Resources Inc., 1999 Broadway, Suite 3600, Denver, Colorado 80202.
⁷Energy and Minerals Applied Research Center, Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399. Present address: Conoco, P.O. Box 2197, Houston, Texas 77252-2197.
⁸Energy and Minerals Applied Research Center, Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309-0399. Present address: Marathon Oil Company, P.O. Box 3128, Houston, Texas 77252-3128.

We thank the following companies and their representatives for their support and input as part of the Gulf of Mexico research consortium at the University of Colorado: Agip, Amoco, Anadarko, BP Exploration, BHP, Burlington Resources, Chevron USA, CNG, CXY, Conoco, Enterprise, Exxon, Marathon, Mobil, Occidental, PanCanadian, Pennzoil, Petrobras, Phillips, Shell, Texaco, Total, Union Pacific, and Unocal. Their support has been crucial for the success of this research. We extend special thanks to Halliburton Geophysical (now Western Geophysical), specifically to Bob Graebner, John Anderson, and Gary White, for the seismic data used in this project. We are indebted to PaleoData Inc. and Art Waterman for use of their biostratigraphic data. Digital logs were kindly provided by Marathon (Tricia Santogrossi). Software donations from GeoQuest, CogniSeis Development (Pat Poe, Roy Kligfield, Robert Ratliff), Landmark Graphics (Thom Fisher), Platte River Associates (Jay and China Leonard), and Zeh Graphics (Jerry Martin) are essential to the success of our study. We are grateful for the reviews by Laurie Lamar and M. S. Wacker, and AAPG reviewers Kevin Biddle, Robert Mitchum, Tor Nilsen, and George Ramsayer, all of whom improved the manuscript considerably. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this work.

ABSTRACT

Neogene turbidite systems are major reservoirs in the northern deep Gulf of Mexico. Few publications have described the stratigraphic variations or the three-dimensional geometries of these turbidite systems in detail; hence, an understanding of the stratigraphic characteristics of the producing sands is important for deep-water exploration in the Gulf of Mexico and similar basins worldwide.

This study focuses on the northern Green Canyon and central Ewing Bank protraction (lease) areas, where the Pliocene-Pleistocene turbidite systems were mapped using an integrated exploration database. Interpretation of 10,000 km of two-dimensional seismic, 185 well logs, and biostratigraphy from 180 wells allowed us to define the regional sequence stratigraphic framework for this area and potential areas for future exploration. A complex Pliocene-Pleistocene geologic evolution of the area is indicated by the seismic and geologic facies, depositional rates, nature of turbidite systems, and sand content.

Significant sand deposits (basin-floor fans) were deposited in most sequences and directly overlie sequence boundaries. Salt tectonics and faulting greatly influenced the loci of these fans’ deposition. Large, thick fans fill entire salt-withdrawal minibasins at the base of the Pliocene sequences. In the Pleistocene sequences, where the rate of salt withdrawal was less, smaller and thinner fans were deposited downdip of faults and adjacent to shallow salt bodies.

Channel systems, interbedded with overbank shales, constitute most of the sediments in the sequences. The older sequences contain more channels and sandier channel fills than the younger sequences. Analysis of all sequences indicates a complex depositional history where significant sands were deposited where abrupt decreases in bathymetric gradient are associated with salt tectonics or faulting.