Abstract We utilize 3D seismic data and robust rock-physics models, combined with a well dataset, to investigate the subsurface of the Mundaú sub-basin, Brazil. Seismic attributes analysis and unsupervised machine-learning approaches were able to produce high-resolution images to allow the mapping of the 3D geometry of ancient geomorphological features across stratigraphic levels, from the Albian to the Turonian interval. Significant deep-water elements were identified using seismic attributes and machine-learning techniques (i.e. channel complex, point bars, feeder channels, faults, depocentres, dendritic lobes, smaller channels and distributaries). In addition, the petrophysical analysis enhanced the subsurface characterization by employing a deep convolutional network that allowed S-wave modelling and synthetic seismic generation. The well-log data analysis validated interpretation of sand-prone deposits; in addition, the rock-physics modelling provided insight into the deposited lithologies. After the petrophysical analysis, seismic facies classification was performed using machine-learning techniques, including self-organizing maps and independent component analysis, which provided valuable insights into the geomorphology of this under-researched basin. The enhancement of seismic and petrophysical data with machine learning proves to be a useful technique for better characterizing this basin. This approach may be used on similar frontier hydrocarbon basins to help de-risk petroleum exploration.

Abstract The Upper, Middle and Lower Amazon basins are large elliptical, elongated syneclises located between the Guyana and the Brazilian Precambrian shields, covering a total area of about 850,000 sq km (327,000 sq mi). These basins, or sags, contain multiple cycles of Phanerozoic sediments interrupted by unconformities. Sediments are predominantly Paleozoic with minor Cretaceous covering. Regional, positive elements include upwarps, swells, platforms, structural terraces, and major interbasinal arches, entirely caused by basement tectonics. Crustal stretching also caused widespread rifting and associated basic volcanism. Tectonic modifiers comprise mostly wrenching, within or at basin margins, especially in the Upper Amazon basin, where folds and reverse faults trap large gas accumulations.