LAUSR

Petrofacies and taphofacies defined for the Morro do Chaves Formation (Late Barremian/Early Aptian) outcropping in the Sergipe-Alagoas Basin (NE Brazil) enable the interpretation of the biostratinomic and fossil-diagenetic processes that acted on the abundant bivalve shells and enclosing sediments. Such processes played an important role in the circulation of fluids within the coquina deposits and therefore on the resulting porosity–permeability of the rocks. Ten taphofacies and four lithofacies are recognized, allowing 36 petrofacies to be defined, based on the nature of the sedimentary and taphonomic processes. Five of these petrofacies are distinguished for those showing almost total replacement of the original constituents. The relationship between petrofacies with the geometry of sedimentary bodies and their lateral and vertical variations, forms the basis of a stratigraphic model for the depositional system of the coquinas of the Morro do Chaves Formation that reflects the spatial and temporal distribution of the identified petrofacies. The integration of the evolutionary taphonomic analysis of the unit with the analysis of multiscale properties through the CAMURES Methodology allowed us to develop a theoretical model for the alteration and modification of taphonomic elements and coquinas, which reflect the rise and fall of the relative base level in a lacustrine to the restricted marine setting. This model leads to more accurate identification and classification of coquina reservoir facies, as well as the delimitation of reservoir zones for 3D geocellular modeling and flow simulation of hydrocarbon-producing reservoirs, thus improving predictive analyses.