Anisotropy measurements and characterization of the Qingshankou shale

Abstract

Qingshankou shale (Gulong area, China) exhibits strong acoustic anisotropy characteristics, posing significant challenges to its exploration and development. In this study, the five full elastic constants and multipole response law of the Qingshankou shale were studied using experimental measurements. Analyses show that the anisotropy parameters ϵ and γ in the study region are greater than 0.4, whereas the anisotropy parameter δ is smaller, generally 0.1. Numerical simulations show that the longitudinal and transverse wave velocities of these strong anisotropic rocks vary significantly with inclination angle, and significant differences in group velocity and phase velocity are also present. Acoustic logging measures the group velocity in dipped boreholes; this differs from the phase velocity to some extent. As the dip angle increases, the longitudinal and SH wave velocities increase accordingly, while the qSV-wave velocity initially increases and then decreases, reaching its maximum value at a dip of approximately 40°. These results provide an effective guide for the correction and modeling of acoustic logging time differences in the region.