Characterisation of pore structure by combining mercury porosimetry and micrography

Savonnières, a French layered oolithic limestone, shows important ink-bottle effects. As a consequence, a great discrepancy is observed between the results of different techniques to determine the pore volume distribution. It is shown that mercury intrusion porosimetry results can be considered as the main drainage curve and are, for this kind of materials, not convenient to determine the apparent pore volume distribution due to hysteresis phenomena. The main wetting curve is obtained using image analysing techniques on SEM-micrographs, combined with pressure membrane apparatus results on capillary saturated samples. A simple structural hysteresis model is developed to predict the mercury intrusion porosimetry results, starting from the main wetting curve. The good agreement between theory and experiment verifies that the large difference between main wetting and main drainage curve can indeed be attributed to structural hysteresis. In this way, the presented technique gives, in addition to a better knowledge of the pore volume distribution, insight in the pore geometry and connectivity, which can serve as input for microstructure-based transport models.