The Grès d’Annot as an analogue for Brazilian Cretaceous sandstone reservoirs: comparing convergent to passive-margin confined turbidites

Abstract

Abstract The Eocene deep-water sand-rich deposits of the Grès d’Annot of southern France have been used as outcrop analogues for offshore Cretaceous reservoirs of Campos Basin, southeastern Brazil. The analogy is chiefly based on the sand-rich, confined nature of the two systems. Such application can be questioned as the contrasting geological settings, i.e. convergent versus passive margin, could produce rather different depositional scenarios. Detailed comparison between the two systems permits, however, recognizing additional similarities, and also some differences, whose recognition is important to ensure the correct application of the Grès d’Annot as an analogue for this and other passive-margin reservoirs. Comparative analysis of channel dimensions, facies continuity, and three-dimensional expression suggests that confined sand-rich systems show many similarities in terms of critical reservoir heterogeneity, providing that palaeotopographic control was similar, regardless of the tectonic environment in which they were formed. In addition, contrasts found among sequences in the same tectonic setting suggest that other factors (such as, for example, sand/shale ratio of the sediment input) play an important role in defining reservoir architecture. These observations further suggest that, once similarities and differences are correctly understood, analogue data, even from quite different tectonic settings, may provide a powerful tool for improving subsurface reservoir models.