Petrophysical properties of porous medium from Petrographic Image Analysis data

Petrographic Image Analysis (PIA) is a well-established rapid two-dimensional (2D) method to quantify pore and solid space in reservoirs and different porous materials. This paper aims to describe a method of characterization and quantification of petrophysical properties in carbonate pore systems using Petrographic Image Analysis over more than three orders of magnitude, from a submicron to a millimeter scale. We integrated two kinds of multiscaled digital image: the transmitted-light-colored petrographic images which allowed us to characterize the macroporosity; the Back-Scattered Electrons (BSE) grey level images which gave us information about microporosity. This technique enabled us to measure different classical petrophysical properties such as pore area, specific surface area, average pore diameter, distribution of pore size, pore shape factor, macroporosity and microporosity. We used image parameters in order to obtain the model of capillary pressure curve versus saturation (Pc–S). On the other hand, using empirical equations of permeability derived from Carman–Kozeny expression and a bundle of capillary tubes model, we were able to calculate the permeability of carbonate pore systems from different image parameters. The same petrophysical parameters were directly measured on core through classical three-dimensional petrophysical techniques (3D), such as Hg-injection porosimetry, permeametry and the BET technique. Finally, we compared the values different petrophysical properties of carbonate pore systems, obtained from 2D image analysis (PIA) and 3D classical petrophysical techniques.