Abstract
A conceptual depositional model was built for the Oligocene to lower Miocene Carbonera Formation just south of the giant Cusiana oil field in the Llanos Foothills of Colombia. Cross sections of normalized gamma-ray well logs tied to cuttings were constructed through the Carbonera Formation, displaying well-log stacking patterns and permitting the interpretation of depositional settings. Flattened time-domain seismic volumes were subjected to continuous wavelet transformation spectral decomposition and then linked to the well-log cross sections defining and mapping channel systems building a sequence stratigraphic framework. In plan view, various fluvial systems of the Carbonera Formation became visible. These included subtle stratigraphic features including point bars, crevasse splays, and other overbank phenomena undetectable in the time domain. A sequence stratigraphic framework of erosional and depositional surfaces subdivide the complex, sand-prone fluvial sediment cycles C1-C8 of the Carbonera Formation. A complex interplay of tectonics and eustasy was interpreted to control the sedimentary history of the Carbonera Formation on the eastern margin of the Eastern Cordillera of Colombia. Tectonic uplift was interpreted to be the dominant control on local accommodation and responsible for the great thickness of the Cenozoic sedimentary section. However, as the sedimentary section accumulated, there were occasional brief intervals when eustasy was a dominant factor. It is concluded that hydrocarbon exploration within the fluvial to marginal marine depositional systems of the Eastern Cordillera would be enhanced if normalized gamma-ray well logs, seismic cross sections and volumes, and frequency domain analysis using spectral decomposition are used to interpret this section.