Innovative Seismic Techniques Applied to the Analysis of Submarine Channels, Lower Congo Basin, Angola

Luiz Empinotti¹, Chukwuemeka Phil-Ebosie¹, Fatima R. Dios¹, and Marco Morales^2
1Petrobras - International Business Área, Rio de Janeiro, Brazil
²Petrobras Research Center (CENPES), Rio de Janeiro, Brazil

The Lower Congo Basin, offshore Angola, is known for the occurrence of high and low-sinuosity channels within its Tertiary section. Current oil exploration in the basin is focused in the Oligocene and Miocene deep- and ultra-deep water sandy turbiditic deposits, formed by a prograding clastic wedge modulated by sea-level changes and episodes of coastal uplift, resulting a large network of submarine channels (Malembo Fm).

The channel deposits are characterized by complex geometries, with sandy deposits that at different scales reflect diverse episodes of channel and submarine valley entrenchment, downcutting and/or aggradation, filled by a variety of lithofacies. Each of these facies shows a distinct seismic response, which can be used to define lithology distribution and reservoir connectivity.

Even though the basic geometrical patterns of the channel systems are well known as a result of using conventional seismic analysis, much remains to be done in terms of refining the architectural element geometry and lithology distribution

This paper presents the results obtained by the utilization of seismic techniques aiming at obtaining a better visualization and understanding of Miocene channel systems architecture, which were examined in a 3D seismic dataset. The work shows the application of a variety of amplitude analysis techniques including: 3D geobody extractions, spectral decomposition and a Petrobras in-house technique named TECVA. This technique reveals small fluctuations of the dataset that, by a lateral trace to trace correlation, can enhance the observation of the different sismofacies within the channel complexes. The application of these techniques lead to a better definition of the geometry, architecture and lithology distribution of the channel complexes, significantly reducing the uncertainty of the volumetric estimations and reservoir quality predictions.

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