Cenomanian channel system evolution of Mundaú Sub-basin deepwater, Brazilian Equatorial Margin: Reservoir characterization using machine learning techniques

Abstract

Submarine channel systems have garnered significant attention in recent years due to their importance in petroleum exploration and favorable reservoir characteristics. Specifically, the Brazilian Equatorial Margin basins have attracted considerable interest from various sectors because of substantial hydrocarbon discoveries in adjacent basins. In the Mundaú Sub-basin (Ceará Basin, NE Brazil), recent studies have identified a series of sand-rich structures associated with a Cenomanian submarine channel system. However, despite these advancements, the depositional elements, sedimentary architecture, and stratigraphic sequences remain poorly understood. This paper aims to integrate robust quantitative geophysical techniques, including unsupervised machine learning methods, multi-attribute analysis, and RGB blending, to clarify the main evolutionary stages of the Cenomanian submarine channel-lobo system in the central portion of the aforementioned Sub-basin and their controlling factors. We utilized data from four exploration wells drilled in the deep waters of the Mundaú Sub-basin, along with a 2200 km² seismic volume covering the study area. Our integrated approach identified three main evolutionary stages. The first stage is characterized by straight to low-sinuosity confined channels on the upper to middle slope, alongside poorly confined channels and splays on the lower slope to basin floor, primarily comprising sand-prone layers developed during a Falling Stage System Tract. The second stage exhibits low to moderate sinuosity confined channels in the upper to middle slope, with significantly poorly confined channels and splays on the lower slope to basin floor, also dominated by sand-prone layers developed in a Lowstand Tract System. The final stage features a high-sinuosity confined channel with dominant sand-prone and sand/mud-prone layers developed in a Transgressive System Tract. all stages and across almost the whole region, sand-prone and sand/mud-prone facies were identified and associated with various depositional elements at different scales. the presence of sand-prone layers in all stages is thought to result from high-density turbidity currents driven by a narrow shelf and stepped slope. The mapped features and predicted facies indicate an unexplored area with sand-rich layers likely possessing good lateral and vertical connectivity. Important structures that may facilitate oil migration were identified, highlighting the high exploration potential of the Cenomanian submarine channel system in the Mundaú Sub-basin.