Analytical Sciences

Layer Caused an Anisotropic Terahertz Response of a 3D-printed Simulative Shale Core

Xinyang MIAO,*,** Limei GUAN,** Rima BAO,*,** Yizhang LI,** Honglei ZHAN,** Kun ZHAO,*,** Xiaodong WANG,*** and Fan XU***

*State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
**Beijing Key Laboratory of Optical Detection Technology for Oil and Gas, China University of Petroleum, Beijing 102249, China
***School of Physics and Optoelectronic Engineering, Yangtze University, Jingzhou 434023, China

Energy demands have motivated the development of shale formations as significant unconventional reservoirs. The anisotropy of shales plays a significant role in both the mechanical behavior and engineering activities. Alternating layers presented in shales affect the propagation of waves, causing anisotropy at various frequencies. Simplifying the complicated interior structures of shales is conducive to characterize the anisotropic properties. Therefore, simulative shale core samples were designed and fabricated using additive manufacturing processes, and layer-caused dielectric anisotropy was investigated by terahertz (THz) time-domain spectroscopy. On the basis of effective medium theory, the change of the optical length caused by refraction of rays was discussed and modeled. It is believed that the refraction of rays at the interfaces is the source of THz propagation anisotropy in the multilayered structure, and the anisotropy degree is mainly influenced by the layer thickness as well as the refractive index.

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