Eugene J. Ferry1,
Harry H. Roberts2,
Richard H. Fillon3,
Elizabeth C. McDade3
(1) Texaco, Inc, Houston, TX
(2) Coastal Studies Institute, Louisiana State University, Baton Rouge, LA
(3) Texaco, Inc, New Orleans, LA
Abstract: An Investigation of Sea Floor Hydrocarbon Seeps and Related Subsurface Structures in the Mississippi Canyon Area, Northern Gulf of Mexico
Sea floor amplitude anomalies,
faults and topographic features in a 775 km3 (300 mi2) study area, located in
the southwestern corner of the Mississippi Canyon OCS lease area were
interpreted using exploration scale 3-D seismic attribute cubes and multibeam
bathymetry data. Amplitude anomalies and associated sea floor relief features
are not randomly located, they are confined to narrow belts surrounding large
minibasins with thick sedimentary sequences. Acoustic water-bottom anomaly
size, location, and intensity were analyzed relative to faulting, salt depth
,
and top of salt morphology. A direct relationship was observed between
water-bottom anomaly amplitude, salt, and faulting. Amplitude intensity appears
to be controlled to the first order by the number of faults reaching the sea
floor. However, not every fault reaching the sea floor is amplitude related.
Examination of the shallow subsurface and sea floor conditions in MC Block 885
was conducted on two positive relief, anomalous amplitude features using
high-resolution
2-D
seismic data, visual observations, and cores acquired from
a manned submersible. Sea floor conditions were cataloged and compared with
their
2-D
and 3-D geophysical attribute signatures. Notably different sea floor
conditions, represented by chemosynthetic communities, a mud volcano, and a
background environment were distinguished using phase, frequency, and
amplitude. Geochemical analysis of cores augmented differentiation of sea floor
conditions. Fluid and gas charging of sediments appears to occur along salt
related faults, with salt morphology focusing the fluid
migration
pathways.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana