Scale and Architecture of Large Channel-Levee Systems and Ponded Sheets of the Foz do Amazonas Basin: Pleistocene Analogs for Deeper Exploration Targets

Mick Casey, Andrei V. Belopolsky, Kris E. Meisling, Mark Pasley, Jean-Paul van Gestel, Kevin Boyd, and David Shepherd
BP, Houston, TX

Analysis of the shallow Pleistocene section on 3-D seismic data from the structured, mid- to lower-slope of the Foz do Amazonas Basin, Brazil, provides exceptional images of the major depositional elements of one of the world's largest deep-water fan systems. These deposits comprise an alternation of large channel-levee complexes, ponded high amplitude reflection packages (HARPs), and chaotic mass transport complexes (MTCs). Channel trends and MTC distribution are strongly influenced by gravity-driven compressional structures. ODP coring has demonstrated that high amplitude reflections within the channels and the more sheet-like HARPs correspond to high net-to-gross sand intervals. The seismic geometries and architectures observed in these well-imaged shallow systems provide analogs for deeper exploration targets, as well as insights on dimensions and connectivity of deep-water reservoirs in similar depositional settings.

Broad (>20km), high-relief (>200m) channel-levee complexes are characterized by low-reflectivity levees flanking 6-7km wide channel belts containing stacked, high-amplitude reflections. Amplitude slices through these packages demonstrate an evolution from low-sinuosity, multilateral channel complexes (1-3km wide) upward into high-sinuosity, highly aggradational channels. The dimensions and stacking patterns observed in these channel systems are similar to many of the deep-water Angola reservoirs.

HARPs are characterized by extensive (10's km) high-amplitude reflection packages, which alternate with slump-disrupted mass-transport complexes (MTCs). HARPs exhibit onlap onto adjacent levees and structural highs providing clear evidence of ponding within bathymetric lows. HARPs are similar in scale to ponded sheet-sands associated with Gulf of Mexico salt-withdrawal minibasins.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005