Textural classification of pre-salt carbonate rocks from the Santos Basin and analysis of the permoporous system: an approach based on the interpretation of X-ray computed tomography images

Abstract

Pre-salt lacustrine carbonates remain in evidence for being rocks of high complexity and responsible for the great economic potential of the Santos Basin. Aiming to contribute to studies in this field, the objective of this research was to define the key textures of the carbonate rocks in X-ray computed tomography (CT) images. For the execution of this study, core samples from two wells were used, and the adopted methodology comprises detailed geological description, characterization of the permoporous system, definition of the main textures in CT images, and analysis of the relationship between textures and their permoporous systems. The description of the main properties enabled the definition of six lithofacies and, through the analysis of CT images, a recurring pattern of certain textural attributes in specific lithofacies was identified. Thus, a representative proposal with four textural classes was established: laminated, shrubby, clastiform fragmented, and recrystallized. A direct relationship was observed between certain textures and the progression of diagenetic processes, as well as their corresponding permoporous systems. Finally, the proposed textural classification of CT images applied to Brazilian pre-salt lacustrine carbonate rocks demonstrates effectiveness in standard segmentation performed by expert technicians, enabling rapid identification of reservoir intervals of interest. For future work, it is recommended to employ this classification as an input base for training algorithms using machine learning techniques.