Elastic Property Estimations Of Phyllosilicate Minerals In Shale

Shale rocks are very significant for both unconventional and conventional hydrocarbon exploration and exploitation. The main constituents of shale are mica and clay minerals (which occupy 30-90% in volume fraction) and the remaining constituents are quartz, feldspar and carbonates. The orientation distribution of the clay minerals including mica significantly affects the elastic velocities and anisotropy of shales. For any type of rock physics modeling or anisotropy analysis, individual elastic moduli of clay minerals, their orientation distribution functions (ODF) and their volume fractions are imperative. The clay minerals are generally fine-grained and it is not possible to find a single large enough crystal for acoustic measurements. In this study, we use the orientation distribution data from published literature to devise an elliptical heuristic function relating bedding-normal P- and S-wave velocity in zero-interparticle-porosity clay aggregates to their preferred orientation. Then we compute elastic moduli for the most common phyllosilicate shale minerals such as muscovite, illite and illite/smectite aggregates. These results can be used for velocity modeling and accurate reservoir property estimations from seismic.