1. State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China; 2. Key Laboratory of Earth Exploration & Information Techniques, Ministry of Education, Chengdu University of Technology, Chengdu, Sichuan 610059, China
Abstract：When seismic wave propagates through pores with different sizes and shapes,it will lead wave-induced local flow,which causes frequency-dependent dispersion and attenuation.In this paper,we analyze the effects of fluid substitution in fractured porous media based on the Collet squirt flow model.First we calculate the velocity of P-wave and inverse quality factor of the media at different incident angles.The velocity dispersion and attenuation vary with the frequency.There is no change in velocity at the low-and high-frequency limits,and the inverse quality factors increase and then decrease with the increase of frequency.Then we analyze effects of the background porosity variation on the P-wave velocity and anisotropic parameters.The obvious decrease occurs in velocity with the increase of porosity at lower frequencies (<1kHz) while no obvious change occurs at higher frequencies (>100kHz),and the attenuation increases with the frequency and media anisotropy becomes stronger.In addition,fluid types also affect the P-wave velocity.The velocity dispersion and attenuation are not obvious when the media filled with gas.The velocity dispersion and attenuation become stronger within brine-bearing media,and they are the strongest within oil-bearing media at the whole frequency band.Finally,we analyze the effects of the fracture density on the velocity and anisotropic parameters.The increasing fracture density can increase the P-wave velocity attenuation and media anisotropy.
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