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Abstract: Drilling into a Present-Day Migration Pathway for Hydrocarbons within a Fault Zone Conduit in the Eugene Island 330 Field, Offshore Louisiana

R. N. Anderson

Within the Global Basins Research Network, we have developed 4-D seismic analysis techniques that, when integrated with pressure and temperature mapping, production history, geochemical monitoring, and finite element modeling, allow for the imaging of active fluid migration in the subsurface. We have imaged fluid flow pathways that are actively recharging shallower hydrocarbon reservoirs in the Eugene Island 330 field, offshore Louisiana. The hydrocarbons appear to be sourcing from turbidite stacks within the salt-withdrawal mini-basin buried deep within geopressure. Fault zone conduits provide transient migration pathways out of geopressure.

To accomplish this 4-D imaging, we use multiple 3-D seismic surveys done several years apart over the same blocks. 3-D volume processing and attribute analysis algorithms are used to identify significant seismic amplitude interconnectivity and changes over time that result from active fluid migration. Pressures and temperatures are then mapped and modeled to provide rate and timing constraints for the fluid movement. Geochemical variability observed in the shallow reservoirs is attributed to the mixing of new with old oils.

The Department of Energy has funded an industry cost-sharing project to drill into one of these active conduits in Eugene Island Block 330. Active fluid flow was encountered within the fault zone in the field demonstration experiment, and hydrocarbons were recovered. The active migration events connecting shallow reservoirs to deep sourcing regions imply that large, heretofore undiscovered hydrocarbon reserves exist deep within geopressures along the deep continental shelf of the northern Gulf of Mexico.

AAPG Search and Discovery Article #90953©1995-1996 AAPG Distinguished Lecturers