Quantitative parameters of pore types in carbonate rocks

Abstract

Carbonate rocks are controlled by variable depositional systems and diagenetic process and have a wide variety of pore and grain shapes/sizes. Those characteristics imprint different petrophysical properties in carbonates, which are more difficult to predict than in siliciclastic rocks. Measurements on carbonates reveal that pore/rock type parameters are function of total porosity and play an important role in the relationship between porosity and P-wave velocity. In this research, the database consists of carbonate rock samples with a wide range of bulk porosities, pore types and rock textures, from different Brazilian areas in Southeast Continental Margin. We investigated the hypothesis that scatter values observed in velocity at a given porosity can be explained by pore types and pore shape characteristics. The quantification of pore shape/size distribution in each sample was based on four geometrical parameters from thin sections measurements - pore size, aspect-ratio, tortuosity and pore complexity. By multivariate analysis, those parameters were applied in the correlation between porosity and P-wave velocities in order to reduce scatter values normally observed.