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Decoding the Sedimentary Evolution of the Marlim Complex: The Richest Oligo-Miocene Deep-Water Oil-Bearing System in Campos Basin (Brazil Deep Seds—Deep-Water Sedimentation on the Southeast Brazilian Margin Project)


Arienti, Luci M.1, Eduardo B. Rodrigues1, H.E. Voelcker2, R.C. Gontijo1, Waldemar de Almeida2 (1) Petrobras Research Center (CENPES), Rio de Janeiro, Brazil (2) Petrobras, Macaé, RJ, Brazil


The Marlim Complex comprises an area of around 500 Km2, from deep to ultra-deep water, including 4 proved oil fields: Voador, Moréia, Marlim and Marlim Leste. These fields are responsible for about 1,5 billions m3 of oil in place of Campos Basin. Integration of regional 3D seismic, well logging profiles and biostratigraphic data gathered under a sequence stratigraphy approach provided a base for interpreting the system as a whole. The Marlim Complex can be divided into 4th order sequences. Despite the large diversity of seis­mic geometry, the major part of the Complex presents facies associations with an intriguing similarity from the inner to the distal portions. The most common lithologic facies comprise rare thin beds of extraformational conglomerates, with common shallow water bioclasts; apparently massive medium-to fine-grained sandstones with dispersed or locally concen­trated granules and punctual coal fragments, corresponding to 90% of the bulk; intraclastic sandstones; and, fine-grained laminated sandstones (usually occurring at the top of individ­ual cycles). Heterolithes were observed at the very end of the sequences. Inferred deposi­tional geometries sometimes visible in seismic attribute maps are: 1.braided-like channels; 2.long, deeply incised, linear 1 km-wide conduits infilled by braided channels; 3.discrete channels; and, 4.sheet-like unconfined deposits. Hyperpycnal flows, related to a strong 3rd order prograding fluvio-deltaic system, are assumed as the main process responsible for transferring the large amount of sediments retrieved in the Marlim Complex. The denudation of an uplifting source area provided the high sedimentation rate and inherited basement structures and halokinesis ultimately controlled the accommodation space.