Understanding the relationship between acoustic impedance and porosity in a presalt carbonate reservoir of the Santos Basin

Abstract

The carbonate reservoirs in the Santos Basin presalt are of great importance in the national oil production scenario, being currently the most prolific source of oil in Brazil, with accumulations of excellent production, quality and high commercial value. Quantitative seismic interpretation assists in the characterization of these reservoirs of high geological complexity and in the challenges related to seismic imaging, making the bridge between variations in seismic amplitude and changes in rock properties. The present work aims to understand the relationships between acoustic impedance, porosity and clay volume through the definition of electrofacies. The crossplots and probability density functions (PDF) built for the electrofacies from the well data with the upscale showed a good correlation between the values of acoustic impedance and effective porosity when considering the reservoir, tight carbonate and igneous electrofacies, but it is difficult to distinguish between muddy and reservoir electrofacies. This work intended to evaluate the feasibility of using an acoustic impedance volume for future modeling of reservoir properties, and to evaluate the types of electrofacies that can be distinguished in a future classification of multiattribute seismic facies.