New integrated 2D-3D physical method to evaluate the porosity and microstructure of carbonate and dolomite porous system

摘要

We propose here a method which concerns the characterization of carbonate porous systems from image analysis of wood's metal intrusion. The wood's metal is an alloy which at a low melting point (70 °C) and in fact in fusion phase (liquid phase) this alloy can be injected into the geological porous space of materials with the aim of making a quantification by microscopic image. It is thus possible to solidify the pores and the cracks in various conditions of fluid pressure. The study of numeric images of this preparation on a scanning electron microscope has the advantage of presenting a strong contrast and thus facilitating the image segmentation in three phases (substance, empty porous space and pores filled with wood's metal). We show the results of this new method of investigation on samples of the carbonates types and for various pressures of injection. These results are then compared with traditional measurements of porosity mercury. We obtain a very good correlation between physical measurements (porosity, pore-throat size) given in porosity mercury and measurements resulting from the image processing. We have moreover the possibility to visualize in 2D and thus to determine the proportion of closed pores i.e. pores which are found insulated without connection. The proportions of these pores do cannot be given with traditional methods and they represent an increasingly important data for many properties.