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由岩石引起的地震波粘弹性响应取决于孔隙流体相对于固相运动。流体运动多半与内部波动引起的孔隙压力分布有关,而这种孔隙压力分布又取决于岩石孔隙的微观结构以及饱和度大小。我们在两种不同的尺度上讨论了波动引起的流体流动:(1)非均匀饱和度这一最小尺度上(如:在单孔中)的局部微观流动(喷流)。(2)饱和或干性区域大尺度内的宏观流动。本文的目的就是探索各种机理产生的多孔介质的粘弹性特性。我们在均匀围压(体积)条件下检测了这种流动,并将Gassmann’s公式做了动态推广,使其在各种频率和各种饱和度情况下适用于速度和衰减的估算。我们通过理论模得到的重要结果是:(1)在渗入和排出时地震速度的滞后现象随饱和度变化。(2)在声波衰减的两个峰值中,低频的波峰是由于全局喷流所致,高频的小峰是由于局部流动引起。这两种理论结果都已得到实验数据的证实。
The seismic wave-induced viscoelastic response due to rock depends on the pore fluid relative to the solid phase motion. The fluid movement is mostly related to the pore pressure distribution caused by the internal fluctuation. The pore pressure distribution depends on the microstructure of the pore and the saturation. We discuss the wave-induced fluid flow at two different scales: (1) Local micro-flow (jet) at the smallest scale of heterogeneous saturation (eg, in a single well). (2) Macroscopically large-scale flows in saturated or dry areas. The purpose of this paper is to explore the viscoelastic properties of porous media produced by various mechanisms. We examined this flow under uniform confinement (volume) conditions and introduced the Gassmann’s formula dynamically to make it suitable for estimation of velocity and attenuation at various frequencies and for various degrees of saturation. The important results we obtain from theoretical models are: (1) The hysteresis of the seismic velocity changes with the degree of saturation at infiltration and discharge. (2) Among the two peaks of sound attenuation, the low-frequency peak is due to the global jet, and the high-frequency small peak is caused by the local flow. Both theoretical results have been confirmed by experimental data.