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Macroscopic non‐Biot's material properties of sandstone with pore‐coupled wave‐induced fluid flows
Geophysical Prospecting ( IF 1.8 ) Pub Date : 2020-07-14 , DOI: 10.1111/1365-2478.13003
Shuna Chen 1, 2 , Xiaotao Wen 1, 2 , Igor B. Morozov 3 , Wubing Deng 3 , Zhege Liu 2
Affiliation  

Wave‐induced pore‐fluid flows are recognized as an important cause of seismic‐wave attenuation at frequencies below 1 kHz within heterogeneous rocks. By using Lagrangian continuum mechanics, wave‐induced pore‐fluid flow mechanisms can be classified strictly on the basis of macroscopic non‐Biot's material properties. In this classification, type I and II wave‐induced pore‐fluid flows are identified by local internal deformations being elastically coupled with either the whole Biot's rock or only with its pore fluid, respectively. Type III wave‐induced pore‐fluid flow is defined as a mixture of types I and II. For all types of wave‐induced pore‐fluid flows, the model predicts all rock properties observed in rock‐deformation experiments, such as the frequency‐dependent poroelastic moduli. The observed attenuation peaks and effective moduli can be used to invert for new, non‐Biot's material properties of porous rock. In data examples, we focus on the pore‐fluid coupled (type II) wave‐induced pore‐fluid flow mechanism and compare it to a previous analysis of type I. Non‐Biot's elastic and viscous rock properties are inverted for by fitting the effective drained bulk moduli measured in two previously published experiments: (1) with real sandstone including two saturating fluids and multiple confining pressures, and (2) a numerical experiment with heterogeneous sandstone containing mesoscopic‐ and microscopic‐scale wave‐induced pore‐fluid flows. Compared with a previous study of type I wave‐induced pore‐fluid flow, the data‐fitting method is improved by focusing on attenuation peaks and additional points in the observed spectra. For both of these experiments, both type I and II interpretations yield accurate fitting of the observed attenuation and dispersion spectra. Combinations of type I and II models (type III) yield a broad variety of acceptable mechanical models. This ambiguity of inversion shows that the different types of wave‐induced pore‐fluid flows cannot be differentiated in conventional attenuation/dispersion experiments. However, these WIFF types are physically meaningful and lead to rigorous equations of rock deformation that can be used in many applications.

中文翻译:

孔隙耦合波诱导流体流动的砂岩宏观非比奥材料特性

在非均质岩石中,低于1 kHz的频率,波诱导的孔隙流被认为是地震波衰减的重要原因。通过使用拉格朗日连续体力学,可以严格根据宏观非比奥材料的性质来对波诱导的孔隙流机制进行分类。在这种分类中,I型和II型波引起的孔隙流体流动是通过局部内部变形分别与整个毕奥特岩石或其仅与孔隙流体弹性耦合来识别的。III型波诱发的孔隙流定义为I型和II型的混合物。对于所有类型的波诱导的孔隙流,该模型都可以预测在岩石变形实验中观察到的所有岩石特性,例如与频率相关的孔隙弹性模量。观察到的衰减峰值和有效模量可用于反演多孔岩石的新的非比奥材料特性。在数据示例中,我们重点研究了孔隙-流体耦合(II型)引起的孔隙-流体流动机理,并将其与先前对类型I的分析进行了比较。非比奥的弹性和粘性岩石特性通过拟合有效值而得到反转。排水的体积模量是在之前发表的两个实验中测得的:(1)包含两种饱和流体和多种围压的真实砂岩,(2)包含介观和微观尺度的波浪诱发的孔隙流的非均质砂岩的数值实验。与先前研究的I型波引起的孔隙流体流动相比,通过关注观察光谱中的衰减峰和其他点,改进了数据拟合方法。对于这两个实验,I型和II型解释都可以精确拟合观察到的衰减谱和色散谱。I型和II型模型(III型)的组合产生了各种各样的可接受的机械模型。这种反演的含糊性表明,在常规衰减/弥散实验中无法区分不同类型的波诱导的孔隙流。但是,这些WIFF类型在物理上是有意义的,并导致可以在许多应用中使用的严格的岩石变形方程式。I型和II型模型(III型)的组合产生了各种各样的可接受的机械模型。这种反演的含糊性表明,在常规衰减/弥散实验中无法区分不同类型的波诱导的孔隙流。但是,这些WIFF类型在物理上是有意义的,并导致可以在许多应用中使用的严格的岩石变形方程式。I型和II型模型(III型)的组合产生了各种各样的可接受的机械模型。这种反演的含糊性表明,在常规衰减/弥散实验中无法区分不同类型的波诱导的孔隙流。但是,这些WIFF类型在物理上是有意义的,并导致可以在许多应用中使用的严格的岩石变形方程式。
更新日期:2020-07-14
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