Impact of Clay Content on Elastic Anisotropy of Synthetic Shale

Abstract

Clay minerals are important components in shale, controlling elastic properties and anisotropy of shale. Since the mineral components of the natural shale are very complex and vary greatly with different origins, it is impossible to find the shale for which clay content is a single variable factor. In this study, we made 8 synthetic shale samples with different clay content to reduce the number of unknown factors caused by multiple minerals and diagenetic environment. Ultrasonic measurements were performed to investigate the impact of clay content on elastic anisotropy of synthetic shale. The results show that both P- and S-wave velocities of samples increase with the increase of clay content, but the P-wave velocity gradient is larger than the S-wave velocity gradient, which suggest that P-wave velocity is more sensitive to soft component (clay mineral). Additionally, there are negative correlation between Vp/Vs ratio and clay content. Finally, P- and S-wave anisotropy of samples are calculated, both P- and S-wave anisotropy of samples increase with the increasing of clay content, and we built the relationship between the P-and S-wave anisotropy ratio and weight percent of clay mineral indirectly.