Direct scale comparison of numerical linear elastic moduli with acoustic experiments for carbonate rock X-ray CT scanned at multi-resolutions

Giant carbonate reservoirs hold almost 50-60% of the world's conventional hydrocarbons and are thus of major economic significance. The recently emerging Digital Rock Physics (DRP) based mechanical property predictions have been successful for sandstones when validated against laboratory results. For carbonates however the success has been limited due to their complex nature and heterogeneity. Typically experiments are conducted with core sample diameters in the order of several cm. Due to computational limitations numerical models are often of several orders of magnitude smaller than laboratory samples. In this study we used a standard carbonate rock called Silurian Dolomite to perform sonic wave experiments on two sample sizes: 1.5 in. and 0.5 in. diameter cylindrical cores. The latter unique size allowed us to compare our DRP based finite element method (FEM) simulations at a more compatible scale and higher image resolution. Through a multi-scale X-ray Micro-CT imaging of the same sample we studied the effect of resolution on elastic moduli simulation. We demonstrated the importance of determining Representative Volume Element (RVE) at each imaging resolution. Through determination of RVE as well as sampling of 40-55% volume fraction using non-overlapping cubes, we showed how our protocol leads to very satisfactory same scale validation of numerical linear elastic moduli predictions.