Practical and robust experimental determination of c13 and Thomsen parameter

We analysed the complications in laboratory velocity anisotropy measurement on shales. There exist significant uncertainties in the laboratory determination of c(13) and Thomsen parameter . These uncertainties are primarily related to the velocity measurement in the oblique direction. For reliable estimation of c(13) and , it is important that genuine phase velocity or group velocity be measured with minimum uncertainty. The uncertainties can be greatly reduced if redundant oblique velocities are measured. For industrial applications, it is impractical to make multiple oblique velocity measurements on multiple core plugs. We demonstrated that it is applicable to make multiple genuine oblique group velocity measurements on a single horizontal core plug. The measurement results show that shales can be classified as a typical transversely isotropic medium. There is a coupling relation between c(44) and c(13) in determining the directional dependence of the seismic velocities. The quasi-P-wave or quasi-S-wave velocities can be approximated by three elastic parameters.