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Combined Effects of Pressure and Water Saturation on the Seismic Anisotropy in Artificial Porous Sandstone With Aligned Fractures
Author(s) -
Han Tongcheng,
Gurevich Boris,
Fu LiYun,
Qi Qiaomu,
Wei Jianxin,
Chen Xingyu
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb019091
Subject(s) - anisotropy , saturation (graph theory) , geology , seismic anisotropy , overburden pressure , pore water pressure , porosity , mineralogy , water saturation , geotechnical engineering , geophysics , petrology , soil science , optics , physics , mathematics , combinatorics , mantle (geology)
Fractures are commonly existing in the subsurface rocks, and understanding the seismic anisotropy in fractured rocks is of great importance in a range of geophysical applications. However, although all the fractured rocks are suffering from geological stresses and most of them are experiencing partial water saturation, the combined effects of confining pressure and water saturation on the seismic anisotropy in fractured rocks remain poorly understood. To obtain such knowledge, we measured and compared the anisotropic velocities and corresponding seismic anisotropy in two artificial porous sandstone samples with and without aligned fractures, respectively, as functions of varying confining pressure and degree of water saturation. We showed that the existence of aligned fractures significantly reduced the five measured velocities but dramatically enhanced the seismic anisotropy in the fractured sample. We also showed that confining pressure and water saturation had an interdependent complex effect on the seismic anisotropy of the fractured sample. The seismic anisotropy of the dry sample showed the highest‐pressure sensitivity, and the saturation effect was most significant at low confining pressure. Integrated interpretation of the experimental data indicated that wave‐induced fluid flow due to pore‐scale and mesoscale fluid distribution in the rocks is responsible for most of the observed pressure and saturation‐dependent anisotropic behaviors in the rocks. The results have helped to gain new knowledge on the seismic anisotropy in partially saturated fractured rocks subject to varying pressures and suggest the requirement for advanced theoretical models to fully understand the acquired data.