AAPG Bulletin, Vol.105, No.8, 1679-1720, 2021
Deep-water reservoir distribution on a salt-influenced slope, Santos Basin, offshore Brazil
Studies of near-seabed data sets show that salt tectonics controls the distribution and architecture of deep-water reservoirs inmany salt-influenced basins. It is typically difficult, however, to study the distribution and stratigraphic evolution of depositional systems preserved at deeper, economically significant depths, reflecting poor seismic imaging of steeply dipping strata flanking high-relief salt structures. Three-dimensional seismic and borehole data from the Santos Basin, offshore Brazil, allow us to identify a range of depositional elements that form the building blocks of three main tectono-stratigraphic phases. During the first phase, channel systems and lobes were confined within updip minibasins and to the hanging walls of salt-detached faults. During the second phase, channel systems and lobes filled updip minibasins leading to sediment bypass, with coarse clastic deposition then occurring in downdip minibasins, >100 km from the coeval shelf margin. Syndepositional seafloor relief caused (1) channel system deflection and diversion around salt-cored highs, (2) channel system uplift and rotation on the flanks of rising salt structures, and (3) lateral and frontal confinement of channel systems. During the final phase, rising salt walls dissected previously deposited deep-water systems, with mass-transport complexes deposition becoming increasingly important. Our results have important implications for postsalt prospectivity in the Santos Basin and other salt-influenced sedimentary basins, with a range of reservoirs and trapping styles present in this underexplored interval. More specifically, we show that large volumes of clastic sediment were not trapped behind the "Albian gap," a salt-controlled depocenter dominating the northwestern basin margin, but were instead delivered farther basinward.