Datapages, Inc.Print this page

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