薄层结构的动态多孔弹性——Gelinsky理论结果分析与讨论
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摘要
在多孔流体饱和状态下的层状沉积物中,由于介质的非均匀性,地震波的传播速度和能量会受到一定的影 响。在非均匀介质中,阻抗的起伏会导致多孔弹性散射,介质各层压缩系数的变化会引起层内流动(宏观上的一 维局部流动)。利用Gelinsky等人提出的理论模型,编制了相速度和衰减的计算程序,探讨了弹性波速度及衰减 与介质参数(相关长度)的关系。结果表明,当相关长度增大时,相速度的过渡带向低频方向移动,衰减的弛豫峰 随相关长度的增大向低频方向移动,且幅度逐渐减小。
Compressional seismic P-waves, propagating in poroelastic, fluid saturated, laminated sediments are strongly affected by the medium heterogeneity. In heterogeneous media, impedance fluctuations lead to poroelastic scattering, variations of layer compressibility cause inter-layer flow (a 1-D macroscopic local flow). Codes for estimation of phase velocity and attenuation was written based on the expressions proposed by Gelinsky and others. The relations between the elastic wave velocity and attenuation with medium parameters, especially with correlation length were investigated. The results show that the velocity and the relaxation peak of the attenuation moved to low frequencies, and the amplitude of the attenuation decreases, as the correlation length increases.
Compressional seismic P-waves, propagating in poroelastic, fluid saturated, laminated sediments are strongly affected by the medium heterogeneity. In heterogeneous media, impedance fluctuations lead to poroelastic scattering, variations of layer compressibility cause inter-layer flow (a 1-D macroscopic local flow). Codes for estimation of phase velocity and attenuation was written based on the expressions proposed by Gelinsky and others. The relations between the elastic wave velocity and attenuation with medium parameters, especially with correlation length were investigated. The results show that the velocity and the relaxation peak of the attenuation moved to low frequencies, and the amplitude of the attenuation decreases, as the correlation length increases.
引文
1 Gelinsky S,Shapiro S A,Muller T, et al. Dynamic po-roelasticity of thinly layered structures[J]. International Journal Solids and Structures, 1998, 35(34) :4 739-4 751
2 Biot A M. Mechanics of deformation and acoustic propagation in porous media[J]. Journal of Applied Physics, 1962, 33(4):1 482-1 498
3 Piona T J. Observation of a second bulk compressional wave in a porous medium at ultrasonic frequencies[J]. Applied Physics Letters,1980,36(4) :259-261
4 Shapiro S A, Hurbal P. Elastic waves in thinly layered sediments: The equivalent medium and generalized O'Doherty-Anstey formulas[J]. Geophysics, 1996, 61 (5):1 282-1 300
5 Gelinsky S, Shapiro S A. Porelatic Backus-averaging for anisotropic layered fluid and gas saturated sediments [J]. Geophysics, 1997,62(6):1 867-1 878
6 Norris A N. Low-frequency dispersion and attenuation is partially saturated rocks[J]. Journal of the Acoustical Society of America,1993,94(1) :359 -370
7胡恒山,王克协,刘家琦．孔隙介质中快纵波的衰减特性 和动力协调现象[J]．计算物理,2002,19(3):203-207
8杨顶辉,陈小宏．含流体多孔介质的BISQ模型[J]．石 油地球物理勘探,2001,36(2):146～159
2 Biot A M. Mechanics of deformation and acoustic propagation in porous media[J]. Journal of Applied Physics, 1962, 33(4):1 482-1 498
3 Piona T J. Observation of a second bulk compressional wave in a porous medium at ultrasonic frequencies[J]. Applied Physics Letters,1980,36(4) :259-261
4 Shapiro S A, Hurbal P. Elastic waves in thinly layered sediments: The equivalent medium and generalized O'Doherty-Anstey formulas[J]. Geophysics, 1996, 61 (5):1 282-1 300
5 Gelinsky S, Shapiro S A. Porelatic Backus-averaging for anisotropic layered fluid and gas saturated sediments [J]. Geophysics, 1997,62(6):1 867-1 878
6 Norris A N. Low-frequency dispersion and attenuation is partially saturated rocks[J]. Journal of the Acoustical Society of America,1993,94(1) :359 -370
7胡恒山,王克协,刘家琦．孔隙介质中快纵波的衰减特性 和动力协调现象[J]．计算物理,2002,19(3):203-207
8杨顶辉,陈小宏．含流体多孔介质的BISQ模型[J]．石 油地球物理勘探,2001,36(2):146～159
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