3D Paleogeographic Reconstruction of the Cabiúnas formation lava flows in Campos basin, SE Brazil

Abstract

Hydrocarbon production from volcanic reservoir rocks in Brazil is rare but it was successfully achieved in the Badejo field, Campos Basin. The volcanic rocks are basalts of the Cabiúnas Formation, related with the voluminous lava flows that erupted prior and during the Gondwana breakup in the Early Cretaceous. Despite their widespread distribution in Campos Basin, volcanic facies architectures and studies of physical volcanology regarding the Cabiúnas basalts are still scarce. The cores recovered from wells BD-02, BD-04 and BD-08, drilled in the Badejo field, provided an excellent material to reconstruct the 3D geometries of the volcanic lava flows in the area. Two compound-braided sequences (Sequence 1 and 3) and a tabular-classic sequence (Sequence 2) were identified in the studied wells. Lithofacies associations or morphologies include classical, hummocky, sheet and rubbly pahoehoe lavas. Coherent, brecciated, peperites and volcanogenic lithofacies were also described in the well cores. Estimated vesicle deformation values (parameter D) for hummocky lavas are higher than those for classical pahoehoe lavas, pointing to porosities and permeabilities adequate to the best potential plays in Sequence 3. The compound-braided Sequence 3 have reach 89.5 m, much thicker than the 40 m thick tabular-classical sequence (Sequence 2). The volcanic paleoenvironment corresponds to subaerial lava flows interacting with wet sediments in all sequences. This information can be of great importance for better characterization of potential offshore volcanic reservoirs within Campos and other sedimentary basins associated with the Gondwana breakup in SE Brazil.