--> Development of the Opuama Canyon Complex, by William D. Wiggins, Pilar E. Garcia, Greg Schoenborn, Michael Roberts, Jacob Diedjomahor, and Joao Keller; #90037 (2005)

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Development of the Opuama Canyon Complex

William D. Wiggins1, Pilar E. Garcia1, Greg Schoenborn1, Michael Roberts2, Jacob Diedjomahor3, and Joao Keller1
1 ChevronTexaco, San Ramon, CA
2 ChevronTexaco, Bellaire, TX
3 ChevronTexaco, New Orleans, LA

The Opuama Canyon Complex is located in the Northwest Coastal area of Nigeria, near the Meren, Gbokoda, and Opuekaba fields. The Opuama Canyon, one of the largest Miocene-age canyons of the Niger delta, initially formed during a Late Oligocene drop in sea level (28.4 ma). It is coincident with the Benin Hinge Line, a basement shoulder which formed the northern margin of the Benue Rift System. An abrupt depositional thickening of the underlying Akata Shale unit against the Benin Hinge enhanced the conditions for growth faulting, which appears to have localized and maintained canyon development through time. The Akata Shale, a thick time-transgressive unit, acts as a regional detachment for growth faults in this area. Map patterns in the mid-Oligocene and Akata Shale intervals suggest that the canyon developed at the point of maximum growth on the underlying faults. This fairway of maximum extension and corresponding subsidence below regional elevation helped focus canyon development.

The position and longevity of the Opuama Canyon has obvious exploration significance in the Northern deepwater areas. The ability of the canyon to sustain itself from late Oligocene through Middle Miocene indicates that the canyon was primarily a sediment flume and not a depositional sink. Basinal equivalents of this major sediment point-source into deep water have recently been drilled with reported discoveries. Examination of receiving basin growth histories and stacking patterns outboard of the canyon are necessary to fully understand the prospectivity in this strongly channelized depositional environment.