Roy H. Wilty¹

(1) University of Louisiana Energy Institute, Lafayette, LA

ABSTRACT: Depositional Sequence Architecture And Seismic Facies Heterogeneity in Late Miocene Deltaic And Incised Valley Fill Sands, Offshore Louisiana, Gulf of Mexico

West Delta 79-86 field is a mature oil and gas field located approximately 25 miles south of Venice, Louisiana. The field consists of multiple reservoir compartments, ranging in age from Late Miocene to Pliocene. The general depositional framework consists of multiple, stacked, upward coarsening packages of highstand, early-lowstand, and transgressive, mid-shelf to shelf-edge deltaic sands. These sands were deposited from a Late Miocene depocenter located to the north and northeast of the study area. The deltaic sands are truncated by multiple, individual and coalesced incised valleys, which formed as a result of shelf exposure during relative lowstands of sea level. The incised valley fill consists of fining upward sediments deposited during incision by lateral accretion, and during transgression and flooding of the exposed shelf surface. The result is a complex depositional system, which has yet to be interpreted on 3D seismic using modern processing, visualization, and interpretation techniques.

The goal of this project is to better define the depositional architecture of these sand bodies by using 3-D seismic facies mapping and visualization techniques. The vertical sequence boundary architecture is determined from well log and biostratigraphic data, and then interpreted laterally throughout a 3-D seismic data set. These bounding surfaces are then used to flatten the seismic volume, allowing for a detailed interpretation of the internal sequence heterogeneity. The well bores provide the necessary data to properly calibrate the seismic facies to litho-facies. Preliminary results using amplitude horizon slices and opacity filtering suggest an incised valley system with a considerably higher degree of complexity than previous 2-D seismic and log-based interpretations have proposed.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado