Facies-driven correlations based on rock porosity for the assessment of geomechanical properties of carbonate rocks in Santos Basin

Abstract

Rock mechanical properties are essential for building reliable geomechanical models. Usually, such properties are assessed through laboratory tests. However, representative rock samples of deep formations are difficult to obtain owing to several issues. As an alternative, empirical correlations based on physical parameters such as rock porosity or the unconfined compressive strength, are commonly adopted. Yet, there is considerable data scattering, in particular for reservoirs from Brazilian pre-salt oil fields which are highly heterogeneous. In this study, we propose empirical correlations based on porosity for assessing mechanical rock parameters for carbonate rocks in the Mero field located in Santos Basin. First, a classification based on depositional processes was performed, identifying four carbonate facies: Coquinas, Reworked, Shrubs, and Laminites. The available data were collected from laboratory tests performed in samples taken from wells drilled in the Mero field. The data based on unconfined compressive strength and porosity were grouped for each proposed facies. Then, the corresponding elastic and strength parameters are assessed from triaxial compression tests. Finally, the obtained mechanical parameters are correlated to the porosity, establishing empirical correlations for each facies. The results show that such correlations can be used to assess rock mechanical properties in Pre-salt Brazilian carbonates, contributing to the building of more reliable geological reservoir models.