Elastic wave propagation in a fluid‐filled borehole and synthetic acoustic logs

Geophysics ◽  
1981 ◽  
Vol 46 (7) ◽  
pp. 1042-1053 ◽  
Author(s):  
Chuen Hon Cheng ◽  
M. Nafi Toksöz
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Decay Rate ◽  
Elastic Waves ◽  
Guided Waves ◽  
Effective Radius ◽  
Dispersion Characteristics ◽  
Stoneley Waves ◽  
Full Wave ◽  
Shale Formation

The propagation and dispersion characteristics of guided waves in a fluid‐filled borehole are studied using dispersion curves and modeling full‐wave acoustic logs by synthetic microseismograms. The dispersion characteristics of the pseudo‐Rayleigh (reflected) and Stoneley waves in a borehole with and without a tool in the center are compared. Effects of different tool properties are calculated. The effect of a rigid tool is to make the effective borehole radius smaller. As an approximation, dispersion characteristics of the guided waves in a borehole with a tool can be calculated as a purely fluid‐filled borehole with a smaller effective radius. Theoretical waveforms (microseismograms) of elastic waves propagating in a borehole are calculated using a discrete wavenumber integration. With an appropriate choice of parameters, our results look similar to the acoustic waveforms recorded in a limestone and a shale formation. Several factors affect the shape of an acoustic log microseismogram. The effective radius of the borehole determines the relative amplitudes of the modes generated. Poisson’s ratio of the formation is the primary factor determining the relative amplitude of the leaky mode following the compressional arrival. Attenuation affects the duration and decay rate of the guided waves.

A CALIBRATED MODEL SEISMIC SYSTEM

Geophysics ◽  
1972 ◽  
Vol 37 (3) ◽  
pp. 445-455 ◽  
Author(s):  
C. N. G. Dampney ◽  
B. B. Mohanty ◽  
G. F. West
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Elastic Waves ◽  
Critical Examination ◽  
Two Dimensional ◽  
Linear Filtering ◽  
Analog Model ◽  
Basic Assumptions ◽  
Electronic Circuitry ◽  
Seismic System

Simple electronic circuitry and axially polarized ceramic transducers are employed to generate and detect elastic waves in a two‐dimensional analog model. The absence of reverberation and the basic simplicity. of construction underlie the advantages of this system. If the form of the fundamental wavelet in the model itself, as modified by the linear filtering effects of the remainder of the system, can be found, then calibration is achieved. This permits direct comparison of theoretical and experimental seismograms for a given model if its impulse response is known. A technique is developed for calibration and verified by comparing Lamb’s theoretical and experimental seismograms for elastic wave propagation over the edge of a half plate. This comparison also allows a critical examination of the basic assumptions inherent in a model seismic system.

scholarly journals Simulation of Dynamic Processes in Deformable Medium with the Grid-Characteristic Approach

2021 ◽  
pp. 74-81
Author(s):  
И.Б. Петров
Keyword(s):  
Neural Networks ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Elastic Waves ◽  
Elastic Wave Propagation ◽  
Seismic Survey ◽  
The Arctic ◽  
Dynamic Processes ◽  
Deformable Media ◽  
Direct Problems

Существует значительное количество прикладных задач, для решения которых применяется математическое моделирование динамических процессов в деформируемых средах. К таким задачам относят моделирование распространения упругих волн в геологических средах, в том числе с учетом ледовых образований, их рассеяния на зонах трещиноватости. Актуальность этих постановок обусловлена важностью решения обратных задач сейсмической разведки, обработки данных сейсмической разведки с целью уточнения запасов углеводородов и определения расположения углеводородов и других полезных ископаемых. Поэтому приобретает важность разработка высокоточных численных методов, позволяющих моделировать упругие волны в деформируемых средах. Одним из этих методов является сеточно-характеристический численный метод, примененный в данной работе. Этот численный метод применяется для решения прямых задач, то есть для расчета распространения упругих волн при известных параметрах рассматриваемой среды. А для решения обратной задачи по восстановлению параметров геологической среды по данным сейсмической разведки можно применять нейронные сети, для обучения которых можно использовать многократное решение прямых задач сеточно-характеристическим методом. В данной работе приведены примеры решения разнообразных прямых задач по распространению упругих волн в неоднородных геологических средах, в том числе в зоне Арктики, а также представлена постановка задачи по обучению нейронных сетей и графики, показывающие эффективность их обучения с использованием двух различных подходов. Many problems can be solved with the simulation of dynamic processes in deformable media. They are the simulation of elastic wave propagation in rocks including ice formations, and wave scattering on rock-fracture zones. Such studies are important for solving inverse problems of seismic exploration and seismic data processing to get a better estimation of hydrocarbon reserves, locate hydrocarbons and other minerals. Therefore, it is necessary to develop high-precision numerical methods used to simulate elastic waves in deformable media. One of such methods is the grid-characteristic approach used in this work. It is suitable for solving direct problems, i.e., to analyze the propagation of elastic waves in a medium with known properties. Neural networks can be applied to solve the inverse problem: reconstructing the geology from seismic survey data. Multiple solving of direct problems by the gridcharacteristic approach is used for network training. This paper contains some examples of solving a range of direct problems on the elastic wave propagation in heterogeneous rocks, also in the Arctic zone, and the problem statement for training neural networks and graphs is proposed to demonstrate the efficiency of training with two approaches.

Characterization of Moon Rock Media With Elastic Waves

2003 ◽  
Author(s):  
Bernhard R. Tittmann
Keyword(s):  
Porous Media ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Frequency Band ◽  
Elastic Waves ◽  
Porous Ceramics ◽  
The Moon ◽  
Powder Metal ◽  
Device Applications

Elastic wave propagation in porous media will be introduced by a discussion of scattering to show the use of broad frequency band pulses in relating the attenuation, velocity and backscattering to information on porosity. Examples will be given for microporosity in castings and powder metal components. This will be followed by a discussion of the influence of volatiles within the pores on the absorption of elastic waves in porous ceramics and rocks. Implications of these findings will be given for ultrasonic device applications and for the interpretation of the lunar seismic experiments carried out as part of the Apollo missions to the moon.

scholarly journals Elastic Wave Propagation for Condition Assessment of Steel Bar Embedded in Mortar

2015 ◽  
Vol 20 (1) ◽  
pp. 159-170 ◽  
Author(s):  
M. Rucka ◽  
B. Zima
Keyword(s):  
Wave Propagation ◽  
Finite Elements ◽  
Elastic Wave ◽  
Elastic Waves ◽  
Condition Assessment ◽  
Elastic Wave Propagation ◽  
Longitudinal Waves ◽  
Numerical Investigations ◽  
Steel Bar ◽  
Steel Bars

Abstract This study deals with experimental and numerical investigations of elastic wave propagation in steel bars partially embedded in mortar. The bars with different bonding lengths were tested. Two types of damage were considered: damage of the steel bar and damage of the mortar. Longitudinal waves were excited by a piezoelectric actuator and a vibrometer was used to non-contact measurements of velocity signals. Numerical calculations were performed using the finite elements method. As a result, this paper discusses the possibility of condition assessment in bars embedded in mortar by means of elastic waves.

scholarly journals The Influence of Crack Modes on the Elastic Wave Propagation Characteristics in a Non-Uniform Rotating Shaft

2018 ◽  
Vol 8 (11) ◽  
pp. 2105 ◽  
Author(s):  
Yimin Wei ◽  
Xuan Shi ◽  
Qi Liu ◽  
Wenhua Chen
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Transfer Matrix ◽  
Elastic Waves ◽  
Transverse Crack ◽  
Propagation Characteristics ◽  
Mode Iii ◽  
Rotating Shaft ◽  
Rotating Speed ◽  
Local Flexibility

The transverse crack in a non-uniform shaft possesses different crack modes, and it can affect the propagation characteristics of the elastic waves in the shaft. The influence of the crack mode as well as the location and the depth of the crack and the rotating speed to the propagation characteristics is investigated in this paper. Firstly, the transfer matrix for the elastic wave in a non-uniform shaft is obtained by deducing the local flexibility coefficients of the three typical crack modes, in which the transverse crack is modeled as a local spring. After that, the influence of the crack mode to the propagation characteristics is studied both in a numerical and an experimental way. Finally, the influence of the location and the depth of the transverse crack as well as the rotating speed of the shaft is studied too. It is found that Mode III is the most suitable mode in this paper, the location of the crack will make the stopbands fluctuating, the depth mainly affects the bandwidth of the stopbands, and the increase of the rotating speed will shift up the stopbands without changing the bandwidths. The results can help to detect and locate a transverse crack.

Effective Models of PZT Actuators for Numerical Simulation of Elastic Wave Propagation

2014 ◽  
Vol 553 ◽  
pp. 705-710 ◽  
Author(s):  
Tian Wei Wang ◽  
Chun Hui Yang
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Health Monitoring ◽  
Elastic Waves ◽  
Elastic Wave Propagation ◽  
Finite Element Models ◽  
Engineering Structures ◽  
Analysis Techniques ◽  
Effective Models ◽  
Implicit And Explicit

In this study, to accurately identify the functions of piezoelectric actuators and sensors for the generation and collection of elastic waves in typical engineering structures, several effective models of surface-bounded flat PZT disks are further developed and validated for numerical modelling of elastic wave propagations. Based on these models, a series of finite element models of elastic waves in plates are devised using both implicit and explicit dynamics analysis techniques and those numerical simulations are conducted and verified one another. The results flowed from the present research is being used to study the elastic wave propagation in pipes and develop an online structural health monitoring (SHM) system with an integrated piezoelectric actuator-sensor network.

scholarly journals On the Failure of Classic Elasticity in Predicting Elastic Wave Propagation in Gyroid Lattices for Very Long Wavelengths

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1243
Author(s):  
Giuseppe Rosi ◽  
Nicolas Auffray ◽  
Christelle Combescure
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Circular Polarization ◽  
Elastic Waves ◽  
Rotational Symmetry ◽  
Dispersion Relations ◽  
Point Of View ◽  
Elastic Wave Propagation ◽  
Transverse Waves

In this work we investigate the properties of elastic waves propagating in gyroid lattices. First, we rigorously characterize the lattice from the point of view of crystallography. Second, we use Bloch–Floquet analysis to compute the dispersion relations for elastic waves. The results for very long wavelengths are then compared to those given by classic elasticity for a cubic material. A discrepancy is found in terms of the polarization of waves and it is related to the noncentrosymmetry of the gyroid. The gyroid lattice results to be acoustically active, meaning that transverse waves exhibit a circular polarization when they propagate along an axis of rotational symmetry. This phenomenon is present even for very long wavelengths and is not captured by classic elasticity.

PROPAGATION OF ELASTIC WAVES IN THE EARTH

Geophysics ◽  
1940 ◽  
Vol 5 (1) ◽  
pp. 1-14 ◽  
Author(s):  
L. G. Howell ◽  
C. H. Kean ◽  
R. R. Thompson
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Elastic Waves ◽  
Single Frequency ◽  
Near Surface ◽  
Proper Understanding ◽  
The Earth ◽  
Considerable Research ◽  
Continuous Waves ◽  
Propagation Of Elastic Waves

An investigation of elastic‐wave propagation in near‐surface materials using single‐frequency continuous waves and pulses, over a range of 20 to 1400 cycles, is described. While only touching upon the diverse problems involved in a study of this kind the results indicate a complexity requiring considerable research if a proper understanding, commensurate with the importance of the problem, is to be attained.

Application of Ultrasonic Guided Waves Testing Method in Coiled Springs

2011 ◽  
Vol 127 ◽  
pp. 449-454
Author(s):  
Fang Jun Zhou ◽  
Yue Min Wang ◽  
Chuan Jun Shen ◽  
Feng Rui Sun ◽  
Hong Tao Zhang
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Theoretical Calculation ◽  
Guided Waves ◽  
Theoretical Calculations ◽  
Field Testing ◽  
Elastic Wave Propagation ◽  
Ultrasonic Guided Waves ◽  
Elastic Wave Equation ◽  
Testing Method

In this paper,application of defect detection by ultrasonic guided waves in springs has been studied in three aspects,which are theoretical calculation, simulation modeling and experiments.For the springs structure is helix and it can not be directly described easily,less work has been done on theoretical calculation of elastic wave propagation in the springs.The elastic wave equation of the spiral structure is established and calculated numerically here,considering the theoretical calculation helps to quantitative analyze the law of elastic wave propagation in the springs.Then guided waves dispersion relations corresponding is achieved.The experimental results of spring field testing agree well with the theoretical calculations and simulations,indicating the effectiveness of ultrasonic guided waves inspection in springs.

A rectangular-grid lattice spring model for modeling elastic waves in Poisson’s solids

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. T69-T86 ◽  
Author(s):  
Muming Xia ◽  
Hui Zhou ◽  
Hanming Chen ◽  
Qingchen Zhang ◽  
Qingqing Li
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Elastic Waves ◽  
Heterogeneous Media ◽  
Elastic Wave Propagation ◽  
P Wave ◽  
Numerical Dispersion ◽  
Spring Model ◽  
Rectangular Grid ◽  
Lattice Spring Model

The lattice spring model (LSM) combined with the velocity Verlet algorithm is a newly developed scheme for modeling elastic wave propagation in solid media. Unlike conventional wave equations, LSM is established on the basis of micromechanics of the subsurface media, which enjoys better dynamic characteristics of elastic systems. We develop a rectangular-grid LSM scheme for elastic waves simulation in Poisson’s solids, and the direction-dependent elastic constants are deduced to keep the isotropy of the discrete grid. The stability condition and numerical dispersion properties of LSM are discussed and compared with other numerical methods. The 2D and 3D numerical simulations are carried out using the rectangular-grid LSM, as well as the second- and fourth-order accuracy staggered finite-difference method (FDM). Wavefields obtained by LSM are fairly similar with those by analytical solution and FDM, which demonstrates the correctness of the proposed scheme and its capability of modeling elastic wave propagation in heterogeneous media. Moreover, we perform plane P-wave simulation through a semi-infinite cavity model via LSM and FDM, the recorded wavefield snapshots indicate that our proposed rectangular-grid LSM obtains more reasonable wavefield details compared with those of FDM, especially in media with high compliance and structure complexity. Our main contribution lies in offering an alternative simulation scheme for modeling elastic wave propagation in media with some kinds of complexities, which conventional FDM may fail to simulate.

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