Using gOcad to improve structural mapping in the Lower Congo Basin.

@inproceedings{LingreyGM2013,
 abstract = { Accurate mapping of field segmentation in a West African Basin hydrocarbon field requires a mix of careful 3D seismic interpretation and 3D faulted-framework modeling using gOcad. The trapping structure formed above a north-northwest trending extensional salt wall during mid-Tertiary west-directed downslope sliding above the extensive Aptian salt layer. In the mid-Miocene (Seravallian-Tortonian) as adjacent withdrawal synclines began to ground onto a salt weld, the extensional expansion of the salt wall ceased and changed to a contractional closing. Upper Oligocene through mid-Miocene sediments shortened by folding and thrust faulting above the closing salt wall. Most earlier formed normal growth faults ceased motion and some were deformed and tilted to low angles. A few normal faults situated at the crest of the emerging anticline continued with fold localized Late Tertiary extensional slip. Lower Miocene (Aquitanian) slope channel complex sandstone reservoirs form a structuralstratigraphic trap across the Late Miocene anticline. The trap is segmented into two obvious trap elements (western and eastern) by three north-striking faults (350° + 10°). Younger down-flank thrust faults (west-vergent on the west, east-vergent on the east) frame the aggregate trap and an older, large offset down-to-the-east normal growth fault isolates the two reservoir elements. An enigmatic north-trending zone of conjugate normal faulting disrupts the eastern structural trap on its west-dipping anticlinal flank. While portions of the gently east-dipping and steeply west-dipping normal faults can be identified and traced in the 3D seismic data, other portions of these faults are poorly constrained by uncertain/incomplete reflection images. This is particularly true near conjugate intersection traces (~horizontal branchlines) with other faults. Using gOcad software enables a logical connection for a system of branclines to be developed. The completed fault-framework can be taken back into the seismic data for corroboration. The completed fault-framework identifies a conjugate fault intersection (X-fault) geometry located at the stratigraphic position of the Aquitanian reservoir. With this greater mapping detail, the enigmatic zone becomes clear and the mapview structural segmentation can be crisply defined. 2D structural profiles using the gOcad fault traces have been palinspastically restored to verify the kinematic feasibility of the structural interpretation. },
 author = { Lingrey, Steven },
 booktitle = { Proc. 33rd Gocad Meeting, Nancy },
 title = { Using gOcad to improve structural mapping in the Lower Congo Basin. },
 year = { 2013 }
}