分层弹性与孔隙介质中弹性波场的互易关系

发布时间：2018-05-09 22:36

本文选题：互易性 + 孔隙介质　；参考：《哈尔滨工业大学》2016年博士论文

【摘要】：波动互易关系是同一介质或结构的两种波动状态之间的关系,常用于天然地震模拟与震源反演、地球物理测井、地震勘探等地学问题中,也可用于工业和医学的超声无损检测领域。前人建立了几种点源在均匀介质中的互易关系,但对于其在流固分区均匀介质中激发波场的互易关系,以及其他类型点源在均匀介质中激发波场的互易关系,研究得还不充分,这使得互易关系在工程中的应用受到阻碍。本文推导流固分层介质和孔隙介质中几类点源两两之间激发波场的互易关系,并采用数值实验阐释这些互易关系,论述其在波场计算方面的应用意义。地震矩张量是与互易性相关联、在地震学中有重要意义的物理量,但它是针对弹性介质推导的。考虑到震源位于孔隙岩石层,本文通过推导获得了孔隙介质位错辐射波场的等效地震矩张量表达式,计算并分析了波场的特性。论文在以下几个方面取得了进展:给出了声波测井中常用的偶极和四极声源的等效体力,在此基础上获得了流固分层介质中点源激发波场的互易关系,包括集中力、爆炸源、双力偶源、偶极源和四极源。采用三维时域有限差分(FDTD)算法,针对由弹性地层与流体井孔组合的介质模型,编程计算了声源分别位于井内和井外时的波场,通过数值结果阐释了互易关系。结果表明:无论发射源和接收点均位于井内流体中,还是分别处于井内流体或井外地层中,只要发射源和接收信号在类型和指向这两方面满足本文给出的互易条件,原状态和互易状态下的计算波形曲线就重合。数值实验还表明:当原状态与互易状态的发射源和接收器都位于井内时,互易物理量的井外界面微弱反射波的波形也重合。特别地,通过记录单极源激发声场在井轴上的水平位移(或记录水平偶极源激发声场在井轴上的声压),可以有效抑制接收信号中的井孔导波,加强对井外界面反射波的提取效果,这对于当前正在研制的井中远探测成像仪的设计有指导意义。论文通过算例阐明了互易关系在检验数值算法方面的适用性和局限性,指出:应用互易关系可在复杂模型中检验算法和源的施加的正确性,但不能检验界面处理的正确性;应用互易关系,可以简化波场模拟的计算量。基于孔隙介质Biot方程组推导了孔隙介质位错的等效地震矩张量,发现孔隙介质中的位错需要通过两个独立的地震矩张量描述,它们分别作用于孔隙单元整体和孔隙流体上。整体地震矩张量具有传统的弹性介质地震矩张量的意义,而流体地震矩张量则是孔隙介质特有的,引起二者的因素包括固相位错和经断层面向周围岩石的流体注入。对于张开位错,需两个地震矩共同描述;对于剪切位错,流体地震矩为零,剪切位错等效为孔隙单元整体上的双力偶;对于注入源,两个地震矩同为各向同性张量,且对角线元素比值由介质参数决定。给出了孔隙介质地震矩张量辐射位移场表达式,发现流体地震矩仅影响辐射纵波,不影响辐射横波。针对整体和流体地震矩同为单位张量的计算表明,流体地震矩仅对辐射慢纵波有较大影响,因此在计算无限大介质远距离辐射波场时流体地震矩可以忽略,但当计算近距离波场时或计算远距离长时间的流体扩散效应时,流体地震矩不可忽略。进一步的计算表明,对于非均匀孔隙介质,当源距离界面很近时,流体地震矩激发的慢纵波在衰减前就达到界面并转化为快纵波和横波,因此可以对远距离波场产生明显影响。考虑震电效应的计算还表明,流体地震矩对于辐射电磁波有较强影响。得到了孔隙介质中几类点源激发波场的互易关系,包括整体集中力、流体集中力、注入源、整体地震矩、流体地震矩和爆炸源。给出了流体-孔隙介质分层结构中体力形式和点源波场互易关系。采用孔隙地层井孔模型下三维FDTD数值实验阐释了互易关系。通过井内单极源和井外爆炸源的互易实验证明了简单地采用弹性介质互易关系代替孔隙介质互易关系会造成互易物理量波形不重合。在考虑孔隙介质震电效应的情况下,基于Pride震电耦合波控制方程组获得了孔隙介质中震源与电偶极子和磁偶极子激发波场的互易关系。通过格林函数法模拟无限大均匀孔隙介质中集中力和电偶极子的辐射震电耦合波场并阐释互易关系,发现如果互易关系中忽略孔隙介质特有的渗流位移项,将导致互易物理量波形在辐射电磁波部分不重合。采用解析方法模拟水平分层结构中地表集中力与电偶极子激发的震电波场,针对反射波阐释互易关系,互易物理量波形完全重合,这表明在地震勘探中震电和电震方法可以在一定程度上相互替代。计算了地下双力偶源与电偶极子、磁偶极子激发波场,其互易物理量波形完全重合。最后给出了流体-孔隙介质分层结构中震电波场互易关系。这一工作对于震电测井、震电勘探的波场分析、对于地震同震电磁场的模拟具有重要意义。
[Abstract]:The relationship between fluctuation and reciprocity is the relationship between the two wave states of the same medium or structure. It is often used in the field of natural seismic simulation and source inversion, geophysical well logging, seismic exploration and other geosciences, and can also be used in the field of ultrasonic nondestructive testing of industry and medicine. The reciprocity relation between the excited wave field in the fluid solid partition homogeneous medium and the reciprocity relation of the excited wave field of the other type point source in the homogeneous medium is not fully studied. This makes the application of the reciprocity in the engineering obstructed. This paper derives the interaction between the excited wave fields of several kinds of point sources 22 in the fluid solid layered medium and the porous medium. We use numerical experiments to explain these reciprocity relations and discuss its application significance in the field of wave field calculation. The seismic moment tensor is an important physical quantity associated with reciprocity and in seismology, but it is derived from the elastic medium. Considering the source in the pore rock layer, the pore medium is obtained by derivation. The equivalent seismic moment tensor expression of the dislocation radiation wave field is expressed and the characteristics of the wave field are calculated and analyzed. The paper has made some progress in the following aspects: the equivalent physical strength of the common dipole and quadrupole source in the acoustic logging is given. On this basis, the reciprocity relation of the excitation wave field of the point source in the fluid solid layered medium is obtained, including the concentrated force and the explosion. The source, double couple source, dipole source and quadrupole source are used to calculate the wave field of the sound source respectively in the well and outside the well by using the three-dimensional finite difference time domain (FDTD) algorithm. The results show that both the source and the receiving point are located in the well. In the fluid, in the fluid or in the well field respectively, as long as the source and the receiving signal can meet the reciprocity conditions given in the two aspects, the calculated waveform curves of the original state and reciprocity coincide. The numerical experiment also shows that the source and receiver of the original state and reciprocity are all located in the well. In particular, the horizontal displacement of the sound field on the well axis by recording monopole source (or recording the sound pressure on the shaft by recording the horizontal dipole source) by recording a monopole source, can effectively suppress the borehole guide wave in the received signal and strengthen the extraction effect of the reflection wave outside the well interface. The design of the remote detection imager is of guiding significance in the well developed well. This paper illustrates the applicability and limitation of the reciprocity relationship in the test of numerical algorithm through an example. It is pointed out that the application of reciprocity can test the correctness of the algorithm and source in the complex model, but it can not test the correctness of the interface treatment; and the application is interrelated. Based on the Biot equations of porous media, the equivalent seismic moment tensor of pore medium dislocation is derived. It is found that the dislocation in the porous medium is described by two independent seismic moment tensors, which are respectively acting on the whole and pore fluid of the pore unit. The seismic moment tensor of the elastic medium, while the fluid seismic moment tensor is unique to the pore medium, causes the two factors including the solid phase error and the fluid injection through the surrounding rock through the fault. For the open dislocation, two seismic moments are described together; for the shear dislocation, the fluid seismic moment is zero, and the shear dislocation is equivalent to the pore. The two seismic moment of the injection source is the same as the Isotropic Tensor, and the ratio of the diagonal element is determined by the medium parameters. The expression of the radiation displacement field of the seismic moment tensor of the porous medium is given, and it is found that the fluid seismic moment only affects the radiation longitudinal wave and does not affect the radiation transverse wave. The calculation of tensor shows that the fluid seismic moment has a great influence on the slow longitudinal wave of radiation, so the fluid seismic moment can be ignored when calculating the long distance radiation wave field of the infinite medium, but the fluid seismic moment can not be ignored when calculating the near distance wave field or the long long long distance fluid diffusion effect. Further calculation shows that the fluid seismic moment can not be ignored. When the source distance interface is very close, the slow longitudinal wave induced by the fluid seismic moment reaches the interface and turns into the fast longitudinal wave and the transverse wave before the attenuation. Therefore, it can have an obvious influence on the long distance wave field. The calculation of the seismic effect also shows that the fluid seismic moment has a strong influence on the radiation electromagnetic wave. Kong Xijie has been obtained. The reciprocity relation between several kinds of point sources excited wave field, including the whole concentration force, the fluid concentration force, the injection source, the integral seismic moment, the fluid seismic moment and the explosion source, is given. The reciprocity relation between the physical form and the point source wave field in the fluid porous media stratified structure is given. The reciprocity relation is explained by the three-dimensional FDTD numerical experiment under the pore formation hole model. Through the reciprocity experiments of the unipolar source and the explosion source outside the well, it is proved that the simple use of the reciprocity of the elastic medium instead of the reciprocity of the pore medium will result in the non coincidence of the waveform of the reciprocal matter. In the case of the seismic effect of the pore medium, the source and the couple in the pore medium are obtained by the control square of the coupled wave control of the Pride seismo electric coupling wave. The reciprocity relation between the excited wave field of the pole and the magnetic dipole is used. The Green function method is used to simulate the radiated seismic coupling wave field of the concentrated force and the electric dipole in the infinite homogeneous pore medium and explain the reciprocity relation. It is found that if the percolation displacement term peculiar to the pore medium is ignored in the reciprocity relation, the reciprocal physical wave wave will be caused by the radiation electromagnetic wave. The analytical method is used to simulate the seismic wave field of the surface concentrated force and the electric dipole excited by the electric dipole in the horizontal stratified structure. The reciprocity of the reciprocity is explained by the reflection wave. It shows that the seismic and electrical seismic methods can replace each other in a certain range in the seismic exploration. The dipole, magnetic dipole excitation wave field and the reciprocity physical wave wave form coincide completely. Finally, the reciprocity of the seismic wave field in the fluid porous media stratified structure is given. This work is of great significance for the seismic wave field analysis of seismogram and seismoelectric exploration, which is of great significance for the simulation of the electromagnetic field of the earthquake.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P631.4

【相似文献】