Terahertz Time-Domain Spectroscopic Imaging Of Diverse Shale

Using terahertz time-domain spectroscopy (THz-TDS) to characterize the shale is significant for geological research. This paper adopts the transmission THz-TDS system which is composed of a femtosecond laser, terahertz radiation generation device, corresponding detection device, and time delay control system. It can also further explore the application potential of THz-TDS in rock mineralogy. The method of shale powder tablet is used to make sample suitable for test and confirm the appropriate proportion that the shale mixed with PTFE under the condition of THz-TDS. Matlab software is used to extract the phase shift and amplitude curve of the sample, and then the refractive index and absorption coefficient of the sample are extracted from the time domain data. In addition, it is feasible to use the characteristic peak in the absorption coefficient to identify minerals in similar shales. The mineral composition of shales which cannot be directly determined by THz-TDS is determined by X-ray fluorescence (XRF) and X-ray diffraction (XRD). The experimental results show that the refractive index can be used to distinguish two kinds of similar black shales: oil shale which is rich in organic matter and ordinary shale. THz-TDS can be used as a supplement to traditional testing methods, which provide a new method for the study of the rock mineralogical characteristics of shale and make the characterization system of shale more perfect.