ABSTRACT

An integrated approach to detect new areas of potential interest associated with stratigraphic traps in mature basins is presented. The study was carried out in the Middle Magdalena Valley basin, Colombia. The workflow integrates outcrop and subsurface interpretations of facies, activity of faults, and distribution of depocenters and paleocurrents and makes use of them to construct a three-dimensional exploration-scale geocellular facies model of the basin. The outcrop and well log sedimentological analysis distinguished facies associations of alluvial fan, overbank, floodplain, and channel fill, the last one constituting the reservoir rock. The seismic analysis showed that tectonic activity was coeval with the deposition of the productive units in the basin and that the activity ended earlier (before the middle Miocene) along the western margin than along the eastern margin. Paleogeographic reconstructions depict transverse and longitudinal fluvial systems, alluvial fans adjacent to the active basin margins, and floodplain facies dominating the structural highs and the southwestern depositional limit. These reconstructions provided statistical data (lateral variograms) to construct the model. The exploration-scale facies model depicts the complete structure of the basin in three dimensions and the gross distribution of the reservoir and seal rocks. The predictive capability of the model was evaluated positively, and the model was employed to detect zones of high channel fill facies probability that form bodies that are isolated or that terminate upward in pinchouts or are truncated by a fault. Our approach can prove helpful in improving general exploration workflows in similar settings.

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