Core-based evidence for sandy slump and sandy debris flow facies in the Pliocene and Pleistocene of the Gulf of Mexico: Implications for submarine fan models
- Mobil Exploration and Producing Technical Center, Dallas, TX (United States)
- Mobil Exploration and Producing U.S., Dallas, TX (United States)
Examination of nearly 3,500 feet of conventional core from Pliocene and Pleistocene deep-water reservoirs cored in 25 wells in 8 different areas covering the eastern, central and western Gulf of Mexico reveals that the reservoirs are predominantly composed of mass-transport deposits, mainly sandy slumps and sandy debris flows (60-100% of cored intervals). Bottom-current reworked sands are common (10-50%). Of importance to existing submarine fan models is that turbidities are extremely rare (<1 % of all cores). Sedimentary features indicative of slump and debris-flow origin include sand units with sharp upper contacts, slump folds, discordant, steeply dipping layers (up to 60[degrees]), glide planes, shear zones, brecciated clasts, rafted mudstone clasts, planar clast fabric, inverse grading of clasts, and moderate-to-high matrix content (5-20 %). These reservoirs have been interpreted by others to represent turbidite-dominated basin-floor fans and slope fans of the often used sequence stratigraphic model. However, our core data do not show a dominance of turbidities. Sandy debris flows exhibit a variety of log motifs (e.g., blocky, fining-up, and coarsening-up) due to changes in concentration of midstone clasts, and a variety of internal seismic facies (e.g., parallel-continuous, irregular-discontinuous, chaotic -discontinuous, and lateral pinch out) perhaps due to changes in stacking patterns of debris flows and slumps. Classic submarine-fan models, commonly advocated for these reservoirs, may not be appropriate. We propose a slump and debris-flow, dominated slope model in which sea-floor topography and depositional freezing (i.e., plastic flows) control sand distribution and geometry. Contrary to popular belief, sandy debris flows can be thick, areally extensive, and excellent reservoirs.
- OSTI ID:
- 6587921
- Report Number(s):
- CONF-960527-; CODEN: AABUD2
- Journal Information:
- AAPG Bulletin, Vol. 5; Conference: Annual convention of the American Association of Petroleum Geologists, Inc. and the Society for Sedimentary Geology: global exploration and geotechnology, San Diego, CA (United States), 19-22 May 1996; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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