Print this pageBasin Floor Fans from Long-Offset, PSDM Data of East 
Africa
and New Exploration Areas Compared to the Great Fan Plains of Gulf of Mexico and Nigeria
Basin floor fan interpretations from a number of margins exhibit key criteria that advance their seismic recognition in new areas and understanding of how they are formed. Regional, long-offset PSDM seismic lines from selected margins highlight the seismic characteristics of several deep water areas where there are exceptional developments of deep water fans. The Miocene and Wilcox of Gulf of Mexico and Miocene of Nigeria give insight into seismic interpretation in new exploration areas including deep water East
Africa and Trinidad. The lower slope to basin floor fans have the highest potential for finding deep water reservoirs with commercial sizes and delivery rates, and are the sheet-form fans deposited at early lowstand times of sea level, a time of high energy depositional processes. The fan seismic response may show low-mounded to sheet-form morphologies with laterally continuous, high amplitudes of 10’s of kilometers or more in extent. Additional features are compensating lobe and pyramid stacking patterns of seismic geometries. The Wilcox in the Gulf of Mexico, major Miocene fields in offshore Nigeria, and the undrilled deep water East Africa and Madagascar show these criteria. In addition, East Africa
data demonstrate major down-cutting events and filling with stacked, shifting, seismic reflection packages interpreted as amalgamated fan events. As sea level rises, the depositional energy in the system falls. A seismic facies of mounded and discontinuous reflections indicates channels and levees and aggrades over the sheet-form seismic facies. This vertical stacking of different seismic facies is often the diagnostic criteria for interpretation of basin floor fans at the base of the sequence. These vertical stacking patterns repeat as sea level falls and rises many times, and are illustrated in the Miocene of the Gulf of Mexico and also in a new exploration area of the ultra-deep water of eastern Trinidad. The formation of repetitive, vertical stacking patterns in deep water, implies a matured, sediment staging area at the margin which would show an immediate response to changes in sea level, flushing sands into deep water at each sea level fall and trapping sediments in the margins and fluvial drainage patterns at each sea level rise. The mega-regional data show isopachs with broad, extensive sediment wedges that are characterized by multiple pathways of sediments into deep water, long depositional distances, and long-lived fairways. AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil