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着重研究了多孔介质BISQ模型中慢纵波的基本特性.给出了BISQ模型下慢纵波速度 和衰减的低频近似公式.与Biot理论对比,BISQ模型中慢纵波的衰减随频率降低急剧增大, 且随喷射流长度的减小而增加;相速度随喷射流长度的减小而增加,其低频极限值不是零; 孔隙流体位移与固相骨架位移之比的幅值随喷射流长度的增加而减小,其相位特点与Biot模 型预测的不同;在流体与孔隙介质的边界上可产生更大的渗流.为对比,同时也给出快纵波 的行为.依据BISQ模型可推断:非黏滞流体饱和孔隙介质中不存在喷射流机理;BISQ模型中
关键词:
多孔介质
喷射流
慢纵波
动力协调 相似文献
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Numerical Simulation of Shear-Horizontal-Wave-Induced Electromagnetic Field in Borehole Surrounded by Porous Formation 下载免费PDF全文
Seismoelectric fieM excited by purely torsional loading applied directly to the borehole wall is considered. A brief formulation and some computed waveforms show the advantage of using shear-horizontal (SH) transverseelectric (TE) seismoelectric waves logging to measure shear velocity in a fluid-saturated porous formation. By assuming that the acoustic field is not influenced by its induced electromagnetic field due to seismoeleetric effect, the coupling governing equations for electromagnetic field are reduced to Maxwell equations with a propagation current source. It is shown that this simplification is valid and the borehole seismoelectric conversion efficient is mainly dependent on the electrokinetic coupling coefficient. The receivers to detect the conversion electromagnetic field and to obtain shear velocity can be set in the borehole fluid in the SH-TE seismoelectric wave log. 相似文献
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Seismoelectric wave propagation modeling in a borehole in water-saturated porous medium having an electrochemical interface 下载免费PDF全文
Water-saturated porous media often exhibit a seismoelectric effect due to the existence of an electrical double layer and a relative flow of pore fluid. Here we consider the seismoelectric waves in an open borehole surrounded by water-saturated porous formation which exhibits discontinuity of electrochemical properties at a cylindrical interface. We carefully analyze the seismoelectric interface response since these signals show sensitivity to contrasts in electrochemical properties across an interface. Both coupled and approximate methods are used to compute borehole seismoelectric fields. The simulation results show that the radiated electromagnetic wave from the electrochemical interface is generated due to the change of salinity in pore fluid in the porous formation. However, the elastic properties of the formation remain unchanged across such an electrochemical interface. As a result it is difficult to recognize such a change in electrochemical properties using only elastic waves. Therefore, the seismoelectric interface response is potentially used to detect the changes of the electrochemical properties in the formation. 相似文献
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Theoretical and numerical study on the coupling acoustic field of the plane p-wave to a cased borehole is carried out. The medium outside the cased borehole is modeled as the porous medium. The scattering field characteristics in the cased borehole are investigated when a plane fast p-wave is incident in tilt to the cased borehole from the porous medium. The scattering fields inside and outside the cased borehole are analyzed and deduced by Biot's theory under the boundary conditions on each interface, and they are numerically studied. It is found that the scattering field has strong resonant characteristics and there exists a series of resonant frequencies and peaks. The effects of the frequency, radii of each interface, incident angle, porosity, and other parameters on the resonant acoustic field have been investigated in detail in the fast and slow formations respectively. The resonant characteristics of the scattering field are also analyzed from the physical sense. 相似文献
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On the basis of the acoustoelastic theory for elastic-plastic materials, the influence of statically deformed states including both the elastic and plastic deformations induced by applied uniaxial stresses on the Rayleigh wave in layered rocks is investigated by using a transfer matrix method. The acoustoelastic effects of elastic plastic strains in rocks caused by static deformations, are discussed in detail. The Rayleigh-type and Sezawa modes exhibit similar trends in acoustoelastic effect: the acoustoelastic effect increasing rapidly with the frequency-thickness product and the phase velocity change approaching a constant value for thick layer and high frequency limit. Elastic-plastic deformations in the Castlegate layered rock obviously modify the phase velocity of the Rayleigh wave and the cutoff points for the Sezawa modes. The investigation may be useful for seismic exploration, geotechnical engineering and ultrasonic detection. 相似文献
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Acousto-electric well logging by eccentric source and extraction of shear wave 总被引:1,自引:0,他引:1 下载免费PDF全文
The nonaxisymmetric acousto-electric field excited by an eccentric acoustic source in the borehole based on Pride seismoelectric theory is considered. It is shown that the acoustic field inside the borehole, converted electric and magnetic fields and coupled fields outside the borehole are composed of an infinitude of multipole fields with different orders. The numerical results show that both the electromagnetic waves and the seismoelectric field in the borehole, and the three components of both electric field and magnetic field can be detected. Measurements on the borehole axis will be of advantage to determining shear velocity information. The components of the symmetric and nonsymmetric acoustic and electromagnetic fields can be strengthened or weakened by adding or subtracting the two full waveforms logged in some azimuths. It may be a new method of directly measuring the shear wave velocity by using the borehole seismoelectric effect. 相似文献
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考虑孔隙流体中含有少量气泡,且气泡在声波作用下线性振动,研究声波在这种孔隙介质中的传播特性.本文先由流体质量守恒方程和孔隙度微分与流体压力微分的关系推导出了含有气泡形式的渗流连续性方程;在处理渗流连续性方程中的气体体积分数时间导数时,应用Commander气泡线性振动理论导出气体体积分数时间导数与流体压强时间导数的关系,进而得到了修正的Biot形式的渗流连续性方程;最后结合Biot动力学方程求得了含气泡形式的位移场方程,便可得到两类纵波及一类横波的声学特性.通过对快、慢纵波的频散、衰减及两类波引起的流体位移与固体位移关系的考察,发现少量气泡的存在对快纵波和慢纵波的传播特性影响较大. 相似文献
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Determination of the parameters of a linear-viscoelastic thin layer using the normally-incident ultrasonic waves 下载免费PDF全文
This paper proposes a method of simultaneous determination of the four layer parameters (mass density,longitudinal velocity,the thickness and attenuation) of an immersed linear-viscoelastic thin layer by using the normally-incident reflected and transmitted ultrasonic waves.The analytical formula of the layer thickness related to the measured transmitted transfer functions is derived.The two determination steps of the four layer parameters are developed,in which acoustic impedance,time-of-flight and attenuation are first determined by the reflected transfer functions.Using the derived formula,it successively calculates and determines the layer thickness,longitudinal velocity and mass density by the measured transmitted transfer functions.According to the two determination steps,a more feasible and simplified measurement setups is described.It is found that only three signals (the reference waves,the reflected and transmitted waves) need to be recorded in the whole measurement for the determination of the four layer parameters.A study of the stability of the determination method against the experimental noises and the error analysis of the four layer parameters are made.This study lays the theoretical foundation of the practical measurement of a linear-viscoelastic thin layer. 相似文献