An experimental study of solid matrix weakening in water saturated Savonnières limestone

Petrophysical properties of carbonate reservoirs are less predictable than that of siliciclastic reservoirs. The main reason of this situation is physical and chemical interactions of carbonate rocks with pore fluids. Such interactions can significantly change elastic properties of rock matrix and/or grains making applicability of Gassmann’s fluid substitution procedure debateable. This study is an attempt to understand the mechanisms of fluid-rock interactions and the influence of these interactions on elastic parameters of carbonates. We present the results of the precise indentation tests conducted on Savonnières limestone at a microscale level under dry and water saturated conditions Our experiments display softening of the rock matrix after water saturation. We also observed an effect of shear modulus reduction in Savonnières limestone in our ultrasonic measurements.