Frequency-dependent S-wave splitting parameters analysis: A case study from azimuthal PS data, Sanhu area of the Qaidam Basin, China

Abstract

The Sanhu area, which is located in the eastern Qaidam Basin in China and formed of low-amplitude anticlinal and lithologic traps, is a favorable area for biogas exploration. The fracture systems in this area are characterized in detail with the use of frequency-dependent S-wave splitting parameters, which are sensitive to the size of the fractures. The results indicate that the delay time between slow and fast S-waves decreases rapidly with increasing frequency between 5 and 30 Hz, and then it slowly decreases to a stationary value at high frequencies. Moreover, the frequency-dependent delay times suggest that fractures of different scale have different 2D density distribution. The frequency-dependent orientation of the fractures suggests that large-scale fractures, which correspond to a low-frequency band (5–11 Hz), are oriented at approximately N48°E and have small random disturbances. The mesoscale fractures that correspond to the dominant frequency band (12–36 Hz) are oriented along approximately N54°E in the northeastern region and N45°E over the remaining area. As expected, the average fracture orientation and delay time of the dominant frequency band are consistent with previous results from conventional S-wave splitting analysis in the time domain, but the frequency-dependent fracture orientation and delay time indicate finer heterogeneity and spatial anomalies. In summary, the results show the potential for accurately characterizing fracture systems using frequency-dependent S-wave splitting parameters.

Anisotropy and fracture analysis for coalbed methane reservoir development in Bokaro coalfield, India

“…Though this method can effectively distinguish the fractures in coal, the limitations lie in discriminating the fracture, as the type of fracture could not be identified. The fracture is sensitive to the frequency spectrum as the time delay between fast and slow shear waves changes with variation in frequency (Wang et al ., 2019).…”

“…The occurrence of azimuthal anisotropy from fractures in coal was shown by De et al (1998), Gray et al (2002) and Vetri et al (2003) using seismic data. Wang et al (2019) have shown that shear wave splitting parameters and fracture orientation extracted from the full azimuth multi-component seismic data are frequency dependent. Also, it was observed that the travel time delay of the split shear waves decreases with increasing frequency.…”

“…Wang et al . (2019) have shown that shear wave splitting parameters and fracture orientation extracted from the full azimuth multi‐component seismic data are frequency dependent. Also, it was observed that the travel time delay of the split shear waves decreases with increasing frequency.…”

Seismic fluid identification method based on the joint PP‐ and SH–SH‐wave stochastic inversion

“…In addition, the S waves generated by vertical source excitation have a wider frequency band than those generated by horizontal source excitation, providing higher resolution for imaging subsurface structures. The pure S‐wave exploration test carried out by China National Petroleum Corporation in the Sanhu area of Qinghai has obtained high‐quality pure S‐wave seismic data (Deng et al., 2022; Wang et al., 2019; Wu et al., 2018). S‐wave splitting analysis using pure S‐wave seismic data has also achieved good application results in the Sichuan Basin, China (Yang et al., 2022).…”