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Abstract: Stochastic Simulation of Deep Water Oligocene Turbidites (Campos Basin) Guided by a Stratigraphic Model Based Previous HitSeismicNext Hit Previous HitInversionNext Hit

Santos, Rogerio A.; Olinto G. Souza Jr.; Mauro R. Becker and Ricardo R. P. Alves - Petrobras/E&P/Cenpes

A stochastic model comprising a truncated Gaussian field has been used to generate an improved Previous Hit3-DNext Hit earth model, which attempts to represent a turbidite succession, in terms of lithotypes, which is the reservoir of a giant oil field in deep-water (600 - 1200 m) at SE Brazil. The goal of this Previous Hit3-DNext Hit reservoir characterization is to derive more realistic images of the inter-well heterogeneity using integrated geophysical and geological Previous HitdataNext Hit.

The reservoir is a dip-elongated Oligocene turbidite fan, NW/SE oriented, which were strongly cut by moderate to low sinuosity deep-sea channels. Reservoir fault systems have their main direction along and perpendicular to the fan orientation and are closely related to salt movement. This reservoir sandstone covers an area of 130 Km2, with thickness reaching 25 m. It shows average porosity of 30% and high permeability ( above 1000 mD).

The Previous HitseismicNext Hit volume was acquired in 1986 and reprocessed in 1996. This reservoir oriented reprocessing was done to improve the amplitude recovering, the well- Previous HitseismicNext Hit phase deconvolution and multiple attenuation, and also to obtain a more detailed velocity field for stacking and migration. The result of this reprocessing, which enhanced the vertical Previous HitseismicNext Hit resolution, allowed a better understanding of either the stratigraphic and Previous HitstructuralNext Hit model for the field (Fig. 1). Although there is an excellent correlation between amplitudes and sand thickness and a good correspondence between time and depth, due to a detailed velocity analysis, the individualization of each high resolution stratigraphic sequence can not be done Previous HitfromNext Hit the 3D Previous HitseismicNext Hit amplitudes. But using acoustic impedances derived Previous HitfromNext Hit constrained Previous HitseismicNext Hit amplitudes inversions, the correlation among the stratigraphic sequences and the Previous HitseismicNext Hit Previous HitdataNext Hit is improved. The Previous HitseismicNext Hit resolution after Previous HitinversionNext Hit is controlled not only by the time sampling of logs, but by a kind of "adjustable" Previous HitseismicNext Hit resolution for each stratigraphic sequence.

The stratigraphic model and the depositional elements of the turbidite system are the framework used to constrain the Previous Hit3-DNext Hit gridded geological model, which represents the reservoir architecture in terms of spatial distribution of the lithotypes. The stochastic model attempts to constrain Previous Hit3-DNext Hit earth models with 2-D Previous HitseismicNext Hit information related to the proportions of lithotypes. A Previous Hit3-DNext Hit proportion matrix is therefore required. This matrix is interpolated Previous HitfromNext Hit well Previous HitdataNext Hit constrained by Previous HitseismicNext Hit Previous HitdataTop (Fig. 2). The main philosophy behind this method is to establish a relationship between the spatial distribution model of the lithotypes proportions and the realization of a Gaussian random function in the analyzed stratigraphic interval.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil