Application of seismic attributes and spectral decomposition for reservoir characterization of a complex fluvial system: Case study of the Carbonera Formation, Llanos foreland basin, Colombia

Hydrocarbon exploration in the Llanos foreland basin of eastern Colombia has traditionally focused on structural traps. However, in the past decade, the country’s oil demand has generated an increased interest in exploration for stratigraphic traps. We integrated 700 km² of 3D seismic data volumes with eight wells in the Central Llanos area to assess the reservoir potential of the fluvial channel deposits of the Late Eocene–Oligocene Carbonera Formation in the Casanare Province. Distinguishing nonproductive, mud-filled channels from productive sand-filled channels is of economic importance for hydrocarbon exploration because both channel types can exhibit a similar seismic character. Our interpretation of the fluvial sandstone and the reservoir identification was based on 3D seismic attributes, including coherence, curvature, and spectral decomposition, and the analysis of fluvial geomorphology. Analysis of stratal slices through coherence, isofrequency amplitude cubes, and curvature cubes revealed (1) a northeast-trending meandering fluvial system with changes in the rivers’ paleoflow direction from southwest to northeast during the period of the Late Eocene to the Early Miocene, (2) development of prospective sandy point bars, scrolls, and sand bar deposits, and (3) channel ridges and bases accentuated by differential compaction dependent on the channel’s filling material. Based on our attribute analysis, we were able to characterize nonprospective mud-filled channels versus prospective sand-filled channels.