Measurements of seismic attenuation and transient fluid pressure in partially saturated Berea sandstone: evidence of fluid flow on the mesoscopic scale
Measurements of seismic attenuation and transient fluid pressure in partially saturated Berea sandstone: evidence of fluid flow on the mesoscopic scale
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DOI：
10.1093/gji/ggt259
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发表时间：
2013-10
影响因子：
2.8
通讯作者：
N. Tisato;B. Quintal
中科院分区：
文献类型：
--
作者：
N. Tisato;B. Quintal
苏明明，王瑞宇。提出了一种新的实验室技术，在细观尺度上研究波致流体流动作为部分饱和岩石地震衰减机制。该技术将频率范围从1到100 Hz的地震衰减测量与瞬态流体压力测量相结合，作为施加在样品顶部的阶跃应力的响应。我们使用了一个部分饱和水的Berea砂岩样本。实验结果表明，在部分饱和样品中，在介观尺度上，波动引起的流体流动占主导地位。采用三维数值模型对试验结果进行了验证。采用有限元法求解Biot固结方程。数值解中唯一考虑的衰减机制是介观尺度上的波动引起的流体流动。数值计算的瞬态流体压力与实验数据基本一致。此外，数值计算的衰减叠加到与频率无关的矩阵非弹性上，再现了在部分饱和样品中实验室测量到的衰减。实验-数值拟合表明，波致流体在细观尺度上的流动和基质非弹性是部分饱和伯里亚砂岩地震衰减的主要机制。
S U M M A R Y A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks. This technique combines measurements of seismic attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample. We used a Berea sandstone sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated samples. A 3-D numerical model representing the sample was used to verify the experimental results. Biot’s equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the attenuation measured in the laboratory in the partially saturated sample. This experimental—numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated Berea sandstone.