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Formulation of the acoustically-induced electromagnetic field in a porous formation in terms of Hertz vectors and simulation of the borehole electromagnetic field excited by an acoustic multipole source

Guan Wei,Hu Heng-Shan,Chu Zhao-Tan,

物理学报 , 2006,
Abstract: The electromagnetic field induced by acoustic waves in a porous formation is investigated. By supposing the acoustic field is not influenced by its induced electromagnetic field, the governing equations for the coupled acoustic and electromagnetic fields are reduced to a set of Maxwell equations with a propagation current source. The Maxwell equations are then transformed into inhomogeneous vector Helmholtz equations by introducing Hertz vectors. Finally the electromagnetic field is formulated in terms of the solutions to the Helmholtz equations. This method is used to evaluate the electromagnetic field during seismoelectric logging in a porous formation. The full waveforms of the acoustic field and the electromagnetic field in the borehole are calculated when the borehole acoustic sources are respectively a monopole, a dipole and a quadrupole.
Monopole and multipole plasmons in a two-dimensional system  [PDF]
H. Pfnür,T. Langer,J. Baringhaus,C. Tegenkamp
Physics , 2011,
Abstract: Using monolayer graphene as a model system for a purely two-dimensional (2D) electron gas, we show by energy electron loss spectroscopy, highly resolved both in energy and momentum, that there is a significant probability for the excitation of not only one but two dispersing losses. The appearance of both losses is independent of the substrate (we tested graphene on the Si face of 6H-SiC(0001), and on Ir(111) without and with intercalated Na layer), and the ratio of the slope in the dispersion curves varies between 1.4 (SiC) and 2. While the lower dispersion curve can be attributed to the excitation of the monopole plasmon, in agreement with theoretical model calculations, the upper dispersion branch has not been identified before for plasmonic excitations in a 2D electron gas, and we assign it to the excitation of a multipole sheet plasmon.
Design and Analysis of Wideband Planar Monopole Antennas Using the Multilevel Fast Multipole Algorithm
Yikai Chen;Shiwen Yang;Shiquan He;Zai-Ping Nie
PIER B , 2009, DOI: 10.2528/PIERB09042002
Abstract: Two planar monopole antennas with wide impedance bandwidth are designed. A full-wave method of moment (MoM) based on the electric field integral equation (EFIE) is applied to analyze the impedance bandwidth and radiation performance of the monopoles. Meanwhile, the multilevel fast multipole algorithm (MLFMA) is employed to reduce the memory requirements and computational time. Experimental results such as the impedance bandwidth and radiation patterns are also presented. The good agreement between the experimental and numerical results well demonstrates the efficiency and accuracy of the MLFMA code. Both the experimental and numerical results show that the two planar monopole antennas possess good input impedance and radiation performance over the AMPS, GSM900, and DCS band. As the proposed antennas can achieve such wide impedance bandwidth with relatively low profile, they are very suitable for multi-band mobile communication systems.

REN Heng-Xin,HUANG Qing-Hua,CHEN Xiao-Fei,

地球物理学报 , 2010,
Abstract: A new method of numerical simulation of seismoelectric wave-fields in multi-layered porous media has been developed by extending Chen's technique of computing synthetic seismograms to coupled seismic and electromagnetic waves. However, the existence of an exponential growth factor leads to numerical instability for high-frequencies. A natural regularization approach eliminating the high-frequency instability is to create a fictitious thin flat layer including the source point in the numerical calculation, which requires an adequate thickness of the fictitious source layer as well as some extra computation cost. In this article, an analytical regularization approach is developed to deal with the high-frequency instability problem in numerical simulations of seismoelectric wave-fields in multi-layered porous media. The results show that the analytical regularization approach is much more effective in solving the above high-frequency instability problem than the natural regularization approach.
Monte Carlo simulation of nuclear logging detection systems
Silva, Jadir C. da;
Revista Brasileira de Geofísica , 2001, DOI: 10.1590/S0102-261X2001000300001
Abstract: the utmost challenge in nuclear logs interpretations and spectroscopy comes from the complex and dynamic structure of the radiation detectors response function. to interpret accurately such logs, the energy spectra for several dimensions of nuclear logging detectors must be satisfactorily known. in this work, different incident photon track and energies owing to events occurring into the gamma ray detector are simulated by the monte carlo method. the life of a particle within a nai(tl) scintillator crystal is computed by simulating the position, direction and energy of electrons and gamma-ray photons interaction by interaction. four types of photon interactions are computed, namely, photoelectric absorption, pair production, and rayleigh and compton scattering. the specific energy loss due to ionization and excitation for electron are also computed. these pulse high spectra are determined by collecting the radiation and transforming it into current pulses. the spectral distribution of these pulses results in a matrix of detector normalized response functions for multiple and complicated source geometry linked with all gamma ray incidence normally required on borehole environment. these data are displayed in such a way that they can be readily carried out into all nuclear log modeling processes with relevant detection effects.
Application of multipole array sonic logging to acid hydralic fracuring

GAO Kun,TAO Guo,MA Yong,

地球物理学进展 , 2006,
Abstract: Multipole array sonic logging tools have widely been employed in Chinese oilfields in recent years.We developed a software package for rock mechanical analysis with multipole array sonic logs.This advanced data processing method and software have been applied to Tahe oilfield in Northern West China to provide guidance to acid hydraulic fracturing design and evaluation.In this paper,we present the field examples of such data processing and applications to demonstrate the validity and advantages of our method and software package.
The converted electromagnetic wave characteristics of seismoelectric conversion effect in borehole

ZHANG Yuan-Zhong,XIAO Li-Zhi,CHU Ze-Han,LI Jian-Hao Faculty of Nature Resource & Information Technology,University of Petroleum,Beijing,China China Petroleum Logging CoLtd,Xi'an,China,

地球物理学报 , 2005,
Abstract: Acoustic wave and electromagnetic wave signals were recorded in the model borehole on the condition of different salinity by using the weak signal detection technology for investigating the seismoelectric conversion effect and exploring its potential application in well logging. The characteristics of the electromagnetic wave were analyzed by comparing with the acoustic wave. The results show that the electromagnetic wave is the converted electromagnetic wave induced by the acoustic wave when it propagates along the borehole. We found that the converted electromagnetic wave has symmetrical two dominant frequency crests in the spectrum. Pseudo-Rayleigh wave induces the seismoelectric conversion and radiates the converted electromagnetic wave in the borehole.
Seismoelectric effects due to mesoscopic heterogeneities  [PDF]
D. Jougnot,J. G. Rubino,M. Rosas Carbajal,N. Linde,K. Holliger
Physics , 2014, DOI: 10.1002/grl.50472
Abstract: While the seismic effects of wave-induced fluid flow due to mesoscopic heterogeneities have been studied for several decades, the role played by these types of heterogeneities on seismoelectric phenomena is largely unexplored. To address this issue, we have developed a novel methodological framework which allows for the coupling of wave-induced fluid flow, as inferred through numerical oscillatory compressibility tests, with the pertinent seismoelectric conversion mechanisms. Simulating the corresponding response of a water-saturated sandstone sample containing mesoscopic fractures, we demonstrate for the first time that these kinds of heterogeneities can produce measurable seismoelectric signals under typical laboratory conditions. Given that this phenomenon is sensitive to key hydraulic and mechanical properties, we expect that the results of this pilot study will stimulate further exploration on this topic in several domains of the Earth, environmental, and engineering sciences.
Numerical study on acoustic multipole logging in the gas-bearing reservoir with low porosity and permeability

CHEN Xue-lian,WANG Rui-jia,

地球物理学进展 , 2007,
Abstract: The logging responses to complex gas reservoir with low porosity and low permeability are not obvious,so it is difficult to evaluate the gas reservoir with conventional logging data and methods.So a new method that is validated by numerical calculations is introduced in this paper.The reservoir is modeled by isotropic porous medium based on Biot and homogenization theories,and the propagation characteristics of the mode waves excited by the multipole sources(dipole and quadrupole)in a fluid-filled borehole are numerically simulated.The results show that the attenuation of mode waves is more sensitive to the reservoir pore parameters than the phase velocity;and the sensitivity of the attenuation to the gas saturation can be improved with the increase of the multipole series or the excitation frequency.It is much better to apply the attenuation coefficient than the phase velocity in identifying gas reservoir.
Component wave analysis of borehole seismoelectric wavefields in a porous formation

Wang Zhi,Hu Heng-Shan,Guan Wei,He Xiao,

物理学报 , 2012,
Abstract: In this work, the axisymmetric seismoelectric logging response excited by a point-pressure source is formulated as an integral in the frequency-wavenumber domain. To analyze the properties of each constituent wavepacket in the seismoelectric logs, the poles and the branch points of the integrands are examined by the complex analysis. The electromagnetic wavenumber in the borehole fluid proves to be a removable branch point. The argument principle is used to search for the complex poles. After the excitation intensity as well as the dispersion curves has been obtained for each component wave for a typical sandstone formation, the ratio of the electric excitation intensity to the acoustic excitation intensity is evaluated. Especially it is found that the argument of this ratio of the Stoneley wave is sensitive to the permeability. The excitation curves corresponding to the branch points show that the compressional wave has a higher seismoelectric conversion efficiency than the shear wave and the mode waves.
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