EGU21-1485
https://doi.org/10.5194/egusphere-egu21-1485
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Experiment and simulation of stress-dependent P-wave velocity anisotropy in sandstone

Haimeng Shen1,2, Xiaying Li1,2, and Qi Li1,2
Haimeng Shen et al.
  • 1State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China (qli@whrsm.ac.cn)
  • 2University of Chinese Academy of Sciences, Beijing 100049, China

Velocity anisotropy is particularly important in field applications of seismic monitoring or exploration [1]. We investigate the stress-dependent P-wave velocity anisotropy of sandstones with triaxial experiments and PFC based numerical simulation [2-3]. The sandstone sample was taken from the lower Shaximiao formation, Sichuan Basin, China [4]. The evolution of anisotropy is discussed with the ellipse least-squares fitting method. The results show that the P-wave velocity is affected by both the bedding plane and loading conditions. As confining pressure increases, the anisotropy magnitude decreases for each sample. The direction of anisotropy is along with the direction of the bedding plane. Under deviator loading, the anisotropy is strengthened for the sample with bedding parallel to the maximum principal stress. The direction of anisotropy reversal occurs in the sample with bedding normal to the maximum principal stress. And the anisotropy magnitude of that sample is reduced firstly and then improved. The P-wave velocity anisotropy is originated from preferred mineral orientation and aligned cracks in these samples. The stress has little effect on the mineral orientation. The evolution of P-wave velocity anisotropy is related to closing and reopening of microcracks.

 

Keywords: Velocity anisotropy; Anisotropy reversal; Triaxial experiment; PFC2D; Sandstone

 

[1] Li, X., Lei, X. & Li, Q. 2018. Response of Velocity Anisotropy of Shale Under Isotropic and Anisotropic Stress Fields. Rock Mechanics and Rock Engineering, 51, 695-711, http://doi.org/10.1007/s00603-017-1356-2

[2] Li, X., Lei, X. & Li, Q. 2016. Injection-induced fracturing process in a tight sandstone under different saturation conditions. Environmental Earth Sciences, 75, 1466, http://doi.org/10.1007/s12665-016-6265-2

[3] Shen, H., Li, X., Li, Q. & Wang, H. 2020. A method to model the effect of pre-existing cracks on P-wave velocity in rocks. Journal of Rock Mechanics and Geotechnical Engineering, 12, 493-506, http://doi.org/10.1016/j.jrmge.2019.10.001

[4] Li, X., Lei, X., Li, Q. & Chen, D. 2021. Influence of bedding structure on stress-induced elastic wave anisotropy in tight sandstones. Journal of Rock Mechanics and Geotechnical Engineering, -, http://doi.org/10.1016/j.jrmge.2020.06.003

How to cite: Shen, H., Li, X., and Li, Q.: Experiment and simulation of stress-dependent P-wave velocity anisotropy in sandstone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1485, https://doi.org/10.5194/egusphere-egu21-1485, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.