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Stratigraphy and Sedimentation of the Paleocene-Eocene Deep-Water Section in the Central Campos Basin (Brazil Deep Seds—Deep-Water Sedimentation on the Southeast Brazilian Margin Project)


Souza Cruz, C.E.1, L.A.F. Sessegolo1, P.R. Blaskovski2, Eduardo B. Rodrigues3 (1) Petrobras, Rio de Janeiro, RJ, Brazil (2) Petrobras, Vitoria, ES, Brazil (3) PetrobrasResearch Center (CENPES), Rio de Janeiro, Brazil


     Tertiary deep-water sandstones are the most important petroleum reservoirs in the Campos Basin. The Paleocene-Eocene section comprise reservoirs in at least 16 oilfields, including Barracuda and Marlim Sul oilfields with 145 and 131 million m3 oil in place respectively. Cycle boundaries are the key elements in the sequence stratigraphy analysis of the Tertiary section, being identified in seismic profiles, well log correlation and biostrati­graphic data. The mapping of these sequences, separated by unconformities, has made it possible to understand the tectonic-sedimentary controls and the reservoir depositional architecture. The sedimentation of the Paleocene-Eocene section was controlled by strong halokinesis. The troughs that acted as conduits for the gravitational flows follow two main structural directions, NNW-SSE and WNW-ESE, inherited from the rift phase, reactivated during the Paleocene/Eocene due to the salt movements. Coeval depocentres, mainly locat­ed in the distal portion of the area, are characterized by NE-SW trending fault-related depres­sions and troughs, formed by the gravitational collapse of the sedimentary section above the salt. The depositional elements identified in our analysis comprise: 1) intra-slope, trough­confined amalgamated sandstones bodies (up to 120m thick), characterized by conglomer­ate and massive, coarse- to medium-grained sandstone, interbedded with bioturbated, medium- to fine-grained sandstone; 2) semi-confined, trough-front terminal lobes with medium- to fine-grained sandstone; 3) upper slope bottom current-reworked sandstone, characterized by cross-bedded glauconitic sandstone, interbedded with bioturbated muddy sandstone; and 4) wide-spread mud-supported cohesive debris-flows, rich in agglutinated red algae fragments.