Fluid Migration in the Eugene Island Block 330 Area, Offshore Louisiana
Jeffrey A. Nunn, Sheila J. Roberts, Lawrence M. Cathles III,
and Roger N. Anderson
In a study funded by industry and the Department of Energy, the Global Basins Research Network has imaged fluid flow pathways that charged shallow, hydropressured, Plio-Pleistocene reservoirs in the Eugene Island 330 field, offshore Louisiana. Hydrocarbons appear to be derived from turbidite stacks within the salt withdrawal mini-basin buried deep within the geopressured zone. Fault zones, with pore pressure dependent permeability, provide conduits for episodic expulsion of fluids out of the geopressured zone.
Imaging of present day fluid migration was accomplished using multiple three-dimensional seismic surveys done several years apart. Volume processing and attribute analysis algorithms are used to identify seismic amplitude interconnectivity and changes over time that result from active fluid migration. Pressures and temperatures are used to provide rate and timing constraints. Geochemical variability in reservoirs is attributed to mixing of oils
Using detailed hydrostratigraphic information constructed from seismic and well data, we have simulated the episodic expulsion of fluids from the geopressured zone along faults into individual thin sand layers in the overlying hydropressured zone. Our finite element model, Akcess.BasinTM, realistically simulates fluid flow, heat and solute transport and pore pressure dependent permeability of faults and strata. Our results documenting the existence of past and present migration events connecting shallow reservoirs to deep source rocks implies that large, heretofore undiscovered hydrocarbon reserves exist deep within the geopressured zone along the deep water continental shelf of the northern Gulf of Mexico.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California