Analysis of seismic wave dispersion,attenuation and anisotropy of fractured media under anisotropic permeability
JIANG Xiaomin1,2, CHEN Xuehua1,2, WU Haojie2, LUO Xin1, LIU Junjie2
1. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China; 2. Key Lab of Earth Exploration & Information Techniques of Ministry of Education, Chengdu University of Technology, Chengdu, Sichuan 610059, China
Abstract：Permeability anisotropy and seismic anisotropy are the key characteristics of fluid-bearing fracture-pore rock. In this paper, fracture parameters (dip angle, azimuth angle, radius, etc.) are used to characterize the permeability of fractured media and analyze the anisotropy variation of permeability. The seismic anisotropy and dispersion-attenuation characteristics of seismic waves of orthogonal media under permeability anisotropy are studied based on Chapman's multi-group fracture equivalent medium model. The numerical simulation results show that:① The permeability anisotropy changes with fracture parameters and is symmetrically influenced by fracture azimuth angle;the variation of fracture radius and dip angle affects the permeability anisotropy, especially the fracture radius. ②In the case of permeability anisotropy, there are two different relaxation time for the dispersion and attenuation of seismic waves, and the characteristic frequency decreases first and then increases with the increase in gas content in the fluid-bearing fractured medium. ③ The two different characteristic frequencies produced by different permeability are related to the frequency corresponding to the extreme value of the seismic anisotropy coefficient. This indicates that permeability anisotropy can cause anisotropy of seismic dispersion and attenuation. The numerical analysis results in this paper can provide a powerful theoretical basis for the prediction of reservoir permeability and fluid identification in fractured reservoirs.
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