Print this pageBasement Fabric from 3-D Seismic, Offshore Deepwater Colombia
Abstract
Abstract
In 2013, the ANH acquired a 5000 km regional 50X80 km grid of high quality 2D data in the deepwater Colombia Basin. It was the first high resolution modern seismic data in a 200,000 km2 area stretching from the Hess Escarpment to the Northwest, the upper slope of the Magdalena Fan to the Southeast, the offshore Panama border to the Southwest, and the Beata Ridge to the Northeast. The data confirmed the area contains greater than 10 kms of possible Miocene to Holocene Magdalena Fan turbidites overlying a distinctly different seismic facies of unknown age and lithology.
The seismic data show very intriguing amplitude and flatspot anomalies over a wide area and thick interval of Magdalena Fan turbidites. Geophysical analysis and seismic response modeling of the data show the anomalies are consistent with direct hydrocarbon indicators.
Anadarko has assembled an 8.5 MM acre position in the basin. Beginning in 2015, the first phase of a 29,300 km2 mega 3D survey was shot covering 16,300 km2 with an 8.1 km cable and 15 second record length. The complete fast-track onboard-processed time migrated volume was received and loaded in December.
The data show a basement fabric consisting of parallel ridges and troughs 15-30 kms wide striking N70degW with a ridge peak to base trough amplitude of approximately 1.2 seconds TWT. The ridges look to be volcanic and show differential compaction in the sediments above them. There is also a prominent reflector about 1.8 seconds below the top of the ridge and trough system underlying the entire area.
The troughs are about 2/3 filled with high amplitude low frequency reflectors. The trough reflectors show significant post depositional compaction thinning onto the ridges, and time slices through the top of trough fill show polygonal faulting and thin-skinned bedding-plane thrusting. These ridges and troughs stop abruptly at an orthogonal ridge-trough system on the east side of the 3D survey.
The ridge and trough system are interpreted to be the flow lines of a preserved fragment of thin oceanic crust emplaced during the separation of North and South America and the orthogonal system marks the South America COB. The anomalous trough fill facies may be the time equivalent of the prolific Jurassic source rocks found in the GOM. The fill is sufficiently buried to be mature for petroleum generation and is the likely source of the abundant potential direct hydrocarbon indicators seen in the overlying Magdalena Fan turbidites.
AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016