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本文以中观孔隙结构的White模型为基础,构建了部分饱和孔隙介质模型,利用Biot方程的建立思路和Johnson推导的体变模量,推导了部分饱和孔隙介质中的纵波方程,并以平面波为例,求取了方程的衰减系数,分析了地震勘探频带范围内地震波的衰减特性。结果表明:在部分饱和孔隙介质中,地震波在低频段也会发生明显的衰减和频散现象,频率越大,衰减越大;且第二纵波的衰减比第一纵波更为明显;这一结论弥补了Biot理论在描述地震勘探频带范围内波的衰减现象的不足。文中还研究了孔隙度、饱和度和模型内径尺寸对第纵波衰减特性的影响机理,主要表现在在地震勘探频带范围内,波的衰减随孔隙度的增大而增大,随含油气饱和度的增大而减小,当孔隙内径尺寸小于二分之一外径尺寸时,波的衰减随内径尺寸的增大而增大,当内径尺寸大于二分之一外径尺寸时,波的衰减随内径尺寸增大而减小。
Based on the White model of Mesozoic pore structure, a partially saturated pore media model is constructed. Based on the idea of Biot equation and the body moduli deduced by Johnson, the compressional wave equation in partially saturated porous media is deduced, For example, the attenuation coefficient of the equation is obtained, and the attenuation characteristics of the seismic waves in the seismic exploration frequency band are analyzed. The results show that, in the partially saturated porous media, the seismic wave will obviously attenuate and disperse in the low frequency band. The larger the frequency is, the larger the attenuation is; and the second longitudinal wave attenuation is more obvious than the first longitudinal wave Make up for the shortcomings of the Biot theory in describing the wave attenuation phenomenon in the seismic exploration band. The mechanism of the effect of porosity, saturation and inner diameter of the model on the attenuation characteristics of the P-wave is also studied. The attenuation of the wave increases with the increase of the porosity in the seismic exploration band, When the pore size is less than one half of the outer diameter, the attenuation of the wave increases with the increase of the inner diameter. When the inner diameter is larger than one half of the outer diameter, the attenuation of the wave With the diameter size increases and decreases.