Direct shear-wave seismic survey in Sanhu area, Qaidam Basin, west China

The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterizati...

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Bibliographic Details
Published in:	Leading edge (Tulsa, Okla.) Vol. 41; no. 1; pp. 47 - 53
Main Authors:	Deng Zhiwen, Deng Zhiwen, Zhang, Rui, Gou Liang, Gou Liang, Zhang Shaohua, Zhang Shaohua, Yue Yuanyuan, Yue Yuanyuan, Chang Xuejun, Chang Xuejun, Wu Yongguo, Wu Yongguo, Wang Yan, Wang Yan, Ni Yudong, Ni Yudong, Yan Zhihui, Yan Zhihui, Gong Ting, Gong Ting, Wang Haili, Wang Haili, Feng Faquan, Feng Faquan, Liu Zhigang, Liu Zhigang, Wu Long, Wu Long
Format:	Journal Article
Language:	English
Published:	Society of Exploration Geophysicists 2022
Subjects:	applied (geophysical surveys & methods) Asia body waves Cenozoic China data acquisition data processing Economic geology elastic waves energy sources Far East geophysical methods Geophysics guided waves Holocene image analysis interpretation inverse problem oil and gas fields petroleum petroleum exploration Pleistocene Qaidam Basin Quaternary reservoir properties S-waves Sanhu China Sanhu Depression Sanhu Field seismic attributes seismic methods seismic waves signal-to-noise ratio surface waves velocity vibrators
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Summary:	The formation containing shallow gas clouds poses a major challenge for conventional P-wave seismic surveys in the Sanhu area, Qaidam Basin, west China, as it dramatically attenuates seismic P-waves, resulting in high uncertainty in the subsurface structure and complexity in reservoir characterization. To address this issue, we proposed a workflow of direct shear-wave seismic (S-S) surveys. This is because the shear wave is not significantly affected by the pore fluid. Our workflow includes acquisition, processing, and interpretation in calibration with conventional P-wave seismic data to obtain improved subsurface structure images and reservoir characterization. To procure a good S-wave seismic image, several key techniques were applied: (1) a newly developed S-wave vibrator, one of the most powerful such vibrators in the world, was used to send a strong S-wave into the subsurface; (2) the acquired 9C S-S data sets initially were rotated into SH-SH and SV-SV components and subsequently were rotated into fast and slow S-wave components; and (3) a surface-wave inversion technique was applied to obtain the near-surface shear-wave velocity, used for static correction. As expected, the S-wave data were not affected by the gas clouds. This allowed us to map the subsurface structures with stronger confidence than with the P-wave data. Such S-wave data materialize into similar frequency spectra as P-wave data with a better signal-to-noise ratio. Seismic attributes were also applied to the S-wave data sets. This resulted in clearly visible geologic features that were invisible in the P-wave data.
ISSN:	1070-485X 1938-3789
DOI:	10.1190/tle41010047.1