K-Image - Permeability Characterization Integrating Matrix and Non-Matrix Pore Scales on Pre-Salt Reservoirs

Abstract

Summary Several oil fields on the pre-salt have high heterogeneity in terms of pore types and scale, with the occurrence of non-matrix pore systems displaying important impact on productivity. Not surprisingly, discrepancies were verified between matrix permeability in 1D petrophysical models and the permeability scale estimated by DST measurements, which are generally understood as related to the presence of dissolution structures formed by karstification processes. Intending to represent the non-matrix permeability scale in our petrophysical models, Petrobras’s researchers began the development of techniques for permeability estimation, where it is possible to separate the matrix pore systems from the non-matrix and to assign different parameters to each distinct medium. This technique is known as K-image, where attributes extracted from image logs are combined with porosity logs in algorithms that calibrate the models, both with the matrix absolute permeability and DST estimated permeability, and then they are used in a permeability equation which has terms representing matrix with different flow capacities and a term that represents the extra-matrix pore systems. The application of this technique brought a significant gain in the ability to characterize permeability of non-matrix pore systems on pre-salt oil fields where the dynamic impact of these systems has been observed.