Geologic Interpretation of Compartmentalization in the Pliocene Shelf Edge Delta System at Amberjack, Gulf of Mexico

Joshua C. Turner¹, Evy Glorstad-Clark², Laura A. Banfield³, Stan G. Davis⁴, Jennifer L. Nelson⁵, Mick Casey⁶, and Kris E. Meisling^6
1 BP America Inc, Houston, TX
² EPTG, Houston, TX
³ BP Amoco, Houston, TX
⁴ BP America Inc,
⁵ BP, Houston, TX

Discovered in 1987, Amberjack field lies in 1,030 feet of water and began production in 1991. The field is composed of stacked shelf and deep-water reservoir sands. A new high-resolution 3D data set was used to re-examine the mature G reservoir interval in the Amberjack shelf edge delta system. Our work resulted in an updated framework, which was critical to improved understanding of the stratigraphic versus structural controls on field compartmentalization. The most important finding was the existence of numerous intra-reservoir growth faults, where shelf edge delta sands preferentially filled in accommodation space in the hanging walls.

Spectral Blueing and Color Inversion were applied to the seismic full stack reflectivity volume to match the seismic amplitude spectrum behavior to well log reflectivity and impedance, respectively. Advantages exist for both processes, but it was colored inversion data that provided the critical ability to detect the distribution of pay sands in the field area and wet sands outside the field area. An understanding of their distribution led to the interpretation of the intra-reservoir growth faults.

The depositional model is that of a shelf edge delta deposited in a relative structural low controlled by regional faults and salt movement on the outer shelf. Radial fault bands, marking the geometry of the delta front, provide an indication of sediment transport direction, as does distribution of sediment thicks associated with intra-reservoir growth faults. Reservoir heterogeneity and compartmentalization are interpreted as being controlled by a combination of paleotopography, intra-reservoir growth faults, and delta clinoforms.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005