Inverted Basin Petroleum Systems, Eastern Salt Canopy Trend: Deepwater Gulf of Mexico

Eisenberg, Richard¹, Matthew Johnson², Wes Combs², Kevin Eastham² (1) ChevronTexcao, Houston, TX (2) ChevronTexaco, New Orleans, LA

Since the initial drilling at Metallica and subsequent discoveries at Thunder Horse there has been a significant increase in wildcat drilling activity in the Eastern Salt Canopy Trend of the Deepwater Gulf of Mexico. Our understanding of these petroleum systems and our abil­ity to accurately assess the geological risk of prospects of this play type has evolved rapid­ly over the past 5 years as a result of deeper exploratory drilling and public availability of data from these wells. Regional and prospect scale structural mapping of proprietary pre­stack depth migrated seismic data, analysis of well logs and interpretation of the stratigraph­ic relationships between inverted mini-basins provide the framework for this comprehensive summary and comparison of the petroleum systems characterizing this play type.

Structural and stratigraphic analysis of the Miocene inverted mini-basins in the Eastern Salt Canopy Trend reveals significant patterns with respect to reservoir, hydrocarbon charge and focus, seal and structural geometry. Discoveries in the trend are found within aerially restricted 4-way closures produced by structural inversion of primary depocenters and with­in related 3-way closures along the margins of the mini-basins against the allochthonous salt canopy. Variability in reservoir quality with depth is related to complex burial/diagenet-ic histories and the proximity to thick salt. Structural inversion in the Middle Miocene sub­sequent to significant periods of lowstand creates the laterally extensive top seal for these hydrocarbon systems during ensuing transgressive periods. Although our understanding of these petroleum systems has come along way since the first hydrocarbon discovery at Thunder Horse, a large degree of geological uncertainty still exists. The ability to adapt to these evolving challenges and integrate new data as it becomes available will ultimately determine the long-term exploration success within this trend.