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The formation and development of fractures increase reservoir heterogeneity and improve reservoir performance. Therefore, it is of great research value to accurately identify the development of fractures. In this paper, two- and three-dimensional models are constructed based on the finite element method and compared with the real axis integration method. The influence of different geometric parameters on the Stoneley wave amplitude is studied to assess the propagation of Stoneley waves in the fracture zone in the well. The results show a significant positive correlation between the width and number of fractures and the attenuation coefficient of Stoneley waves. The fracture angle has a negative correlation with the attenuation coefficient and lesser impact on Stoneley waves. In addition, Stoneley waves are less sensitive to changes in fracture location, while the sensitivity to fracture spacing is significant in the range of 50 cm to 75 cm. The main propagation depth of Stoneley waves occurs 20 cm from the wall of the well. Quantitative analyses of the fracture width, number, location, spacing, depth, and angle are conducted to determine the influence of the fracture parameters on the Stoneley wave attenuation coefficient, clarify Stoneley wave propagation in wells, and provide a theoretical basis for the accurate evaluation of fractures. [ABSTRACT FROM AUTHOR]

This article reports on the successful downhole testing of the prototype permeability logging instrument, developed by the Li Ning Innovation Team of PetroChina. The test was carried out on 3 March 2024 in the Ren 91 standard well in Huabei (North China). In this article, we analysed the instrument characteristics of porosity logging measurement, saturation logging measurement, and permeability logging measurement in three stages of development, as well as the current research status of continuous depth-permeability measurement in the wellbore formations. We highlighted the basic principle of permeability logging measurement with Stoneley waves and pointed out the main challenges in the development of permeability logging measurement devices and on-site application research. [ABSTRACT FROM AUTHOR]

The layered structures of elastic solids have wide applications in various fields of engineering related to natural phenomena, foundations, composite structures, and ultrasonic devices, among others. To have a better understanding of the propagation characteristics of axisymmetric generalized Stoneley waves in a layered structure, the displacement is constructed using the Helmholtz decomposition method with the cylindrical formulation, and then the displacement and stress in the layered structure are presented with potential functions in the wave equations. The transfer matrix method is used to derive the equations of the axisymmetric Stoneley waves in layered elastic solids in the cylindrical coordinates for solutions of wave velocity and amplitudes. With a new formulation in cylindrical coordinates, numerical examples are presented for the dispersion and displacement characteristics of the generalized Stoneley wave of layered solids. The results show that if a low-speed interlayer is added between two semi-infinite media where Stoneley waves do not exist, a wave similar to the Stoneley wave, with displacement decaying exponentially in the semi-infinite direction, can exist. We refer to the Stoneley-like waves that exist in structures with several interlayers between two semi-infinite media as generalized Stoneley waves. [ABSTRACT FROM AUTHOR]

The current research concerns with the analysis of Stoneley waves propagation along an interface between two dissimilar homogeneous and isotropic halfspace having negative Poisson's ratios (auxetics). The main attention is paid to the case when both contacting media satisfy the Wiechert condition ensuring the existence of Stoneley wave. Closed form expressions are derived for derivatives of the Stoneley secular equation. The velocity of Stoneley waves is analyzed both theoretically and numerically in a broad range of the Wiechert parameter variation. [ABSTRACT FROM AUTHOR]

The results of seismoacoustic wave propagation modeling based on a numerical solution of a direct dynamic problem for a porous medium are considered. The propagation of seismic waves in a porous medium saturated with a fluid in the absence of energy loss is described by a system of first-order differential equations in a Cartesian coordinate system. The initial system is written as a hyperbolic system in terms of the velocities of the elastic host medium, the velocity of the saturating fluid, the components of the stress tensor, and the pressure of the fluid. For the numerical solution of the problem, a method of complexing the integral Laguerre transform in time with a finite-difference approximation in the spatial coordinates is used. The solution algorithm makes it possible to efficiently carry out calculations of modeling in a complexly constructed porous medium and investigate wave effects in such media. [ABSTRACT FROM AUTHOR]

Appearance of multiple Sezawa (M2,2) modes and the related interfacial Stoneley waves at propagation of Lamb wave in a stratified medium containing several layers obeying Wiechert condition is observed. Possible appearance of the multiple high frequency Stoneley and Sezawa modes may have importance in various applications starting from micro and nanomechanics to geophysics along with developing the nondestructive acoustic methods for qualitative and quantitative assessment of the high frequency asymptotics. The analysis is based on Cauchy sextic formalism. [ABSTRACT FROM AUTHOR]

Rayleigh-type waves are investigated in a layered model composed of thermoelastic medium with double porosity structure. Using appropriate boundary conditions, the dispersion relation is obtained, which provides multi-modes, dispersive and attenuating nature of Rayleigh-type waves. This dispersion relation reduces to the dispersion equation of Stoneley-type waves, when the thickness of the overlying layer is assumed to be large enough. Some new results along with earlier known ones are reduced from the present formulation. For a particular model, the phase speed and corresponding attenuation coefficient of Rayleigh-type waves are found to be affected by the presence of thermal, pores and layer thickness. Displacements and stresses generated by the fundamental mode are also depicted graphically. [ABSTRACT FROM AUTHOR]

Because natural cracks are not smooth cracks, in the process of identifying cracks by acoustic and electrical imaging, if cracks are regarded as smooth cracks, errors will be generated. Stoneley wave reflection coefficient has high sensitivity to crack width, and stoneley wave is often used to identify cracks. Physical experiment and numerical simulation were used to study the influence of rough fracture on acoustic response. In the aspect of experiment, the crack roughness experiment of model well was carried out, and the relationship between crack width and attenuation coefficient of rough crack was obtained. Numerical simulation of horizontal crack borehole model was carried out to study the influence of sinusoidal rough crack on stoneley wave. The roughness of crack surface was described by tortuosity. The experimental results show that the attenuation coefficient of stoneley wave will increase with the increase of notch on the crack surface. The simulation results show that the smaller the width of rough crack, the larger the gap between the attenuation coefficient of smooth crack and the same width. The relationship between stoneley wave attenuation coefficient and crack width and tortuosity is established by fitting. [ABSTRACT FROM AUTHOR]

Regions of existence for Stoneley waves are analyzed for the case when isotropic contacting media have different values of Poisson's ratios. The analysis is based on solving the secular equation in Scholte's form for Stoneley wave velocity. It reveals substantial similarity in shapes of regions of existence at all studied values of Poisson's ratio pairs. A recently observed gap in regions of existence for media with equal Poisson's ratios is also observed in cases when contacting media have different Poisson's ratios including both auxetic and non-auxetic media. [ABSTRACT FROM AUTHOR]

The process of propagation of the Stoneley wave at the "water–water saturated or gas hydrate-saturated sand" interface is considered. To describe the process, the equations of continuity, state of the liquid, of momenta, wave equations, equations for the displacement of particles and components of stress tensors are used. As a result of finding analytical solutions in the form of a harmonic traveling wave for pressure, displacements, potentials for the vectors of longitudinal and transverse waves, a dispersion equation was obtained for determining the Stoneley wave velocity. The values of Stoneley wave velocity are obtained for different saturations of sand with water and gas hydrate. The dependence of the depth of penetration of a sound wave, of longitudinal and transverse waves into a liquid and a solid medium on frequency is determined. The idea of determining the thickness of the hydrate-bearing layer by the degeneration of the Stoneley wave with an increase in the duration of the latter is proposed. [ABSTRACT FROM AUTHOR]

The sound field in porous media is affected by fluid flow governed by dynamic permeability. This macroscopic quantity is frequency dependent and can be connected with a relevant pore-scale estimation called the stochastic dynamic permeability (SDP) model. To further investigate the characteristics of the SDP model with different variables related to Biot relaxation frequency and envisage its potential applications in borehole acoustics, the influence of microstructures from a pore-scale image on dynamic permeability is studied. Then, the characteristics of dynamic permeability and a borehole Stoneley wave with different parameters are explored by sensitivity analysis. According to the influences of pore fluid parameters including density and viscosity, the velocity dispersion and attenuation of Stoneley waves in oil, gas and water-bearing formations are calculated. The results show that the dynamic permeability is affected by the microstructure of pores and the Biot relaxation frequency parameters have a crucial influence on the attenuation of the borehole Stoneley wave. Meanwhile, the attenuation coefficient can be used to identify the type of pore fluids. This is verified by an application to in situ acoustic logging data. The work provides a relatively comprehensive understanding of the features of the SDP dynamic permeability and indicates an approach to identify pore fluid by using a borehole Stoneley wave. [ABSTRACT FROM AUTHOR]

To quantitatively determine the effect of different factors such as fracture width, dip angle, extension and filling material on Stoneley wave amplitude decreasing, the shock tube experiment method was changed from fixing the sample and vertically moving the sensor in the borehole to fixing the sensors along the shock tube wall and vertically moving the sample without drilling the borehole in it. The measurement accuracy and the signal-to-noise ratio of the first Stoneley wave were improved by the time corrections and amplitude corrections of Stoneley wave signals. At the same time, 21 sets of core models with different fracture parameters were processed for this measurement method by using full-diameter carbonate core, and relative amplitudes were defined to characterize Stoneley wave amplitude decreasing. The experimental results show that the relative amplitude of Stoneley wave exponentially decreases with increasing fracture width. The relative amplitude of Stoneley wave linearly decreases with increasing fracture dip angle. The relative amplitude of Stoneley wave exponentially decreases with increasing fracture extension. The relative amplitude of Stoneley wave decreases with increasing the permeability of filling material in the fracture. Under the above four conditions, the fracture width has the greatest effect on the decreasing of Stoneley wave amplitude, followed by the fracture extension and the permeability of filling material, and finally the fracture dip angle.

An interesting phenomenon observed in auxetics (materials with negative Poisson's ratio) relates to appearing anomalous velocity intersections of the interfacial Stoneley waves at varying acoustic properties of the contacting media satisfying Wiechert condition. Comparative analysis with the non-auxetics (materials with positive Poisson's ratio) revealed the absence of such intersections. The analysis is based on solving secular equation for Stoneley waves in the modified Scholte form. [ABSTRACT FROM AUTHOR]

Stoneley wave velocity variation is analyzed by solving the modified Scholte secular equation for velocity of Stoneley waves, allowing to find dependency of the Stoneley wave velocity on the Wiechert parameter and construct a set of inequalities that confines region of existence for the appropriate root of the secular equation. Numerical analysis for Stoneley wave velocity dependence on the Wiechert parameter for both auxetics (materials with negative Poisson's ratio) and nonauxetics revealed the presence of (i) asymptotes indicating degeneracy of Stoneley waves into the corresponding Rayleigh waves; and (ii) common extremums relating to degeneracy of Stoneley waves into the corresponding bulk shear waves. [ABSTRACT FROM AUTHOR]

It is shown that in auxetic materials (materials with negative Poisson's ratio), supersonic Stoneley waves travelling without attenuation with a velocity equal to or exceeding maximum bulk wave velocity, may exist. Analytical expressions for the relation between negative Poisson's ratio and Young's moduli of the contacting isotropic media ensuring the condition of propagation for supersonic Stoneley waves, are derived by solving a secular equation for Stoneley waves. [ABSTRACT FROM AUTHOR]

Introduction: For composite structures, delamination usually occurs at the interface. Ultrasonic guided waves have been widely used to detect the delamination. However, most researches focus on the measurement of the delamination length along the interface, and the measurement of the delamination thickness is less studied. Method: In this paper, based on the characteristic that the Stoneley wave only propagates along the interface, the reflection coefficient of interaction between Stoneley wave and delamination is used to measure the delamination thickness. The effects of delamination thickness and frequency on the reflection coefficient are investigated via dividing integral region and reciprocity theorem. Some experimental validations are carried out on two aluminum-steel bilayered composite plates with different delamination thickness. Results: It is found the reflection coefficient increases linearly at first, then its rate of increase slows down gradually, and finally becomes stable, in theory. And the experimental results can verify the theoretical relationship between the reflection coefficients and the delamination thickness. Conclusion: The variation of reflection coefficient provides a reference for the measurement of delamination thickness in Stoneley-wave-based non-destructive testing.

It is known that along an interface between two isotropic halfspace satisfying the widely used in geophysical applications Wiechert condition, Stoneley waves may propagate with speed of propagation that is independent from frequency. A recent proof on non-existence of Stoneley waves in functionally graded (FG) plates with continuous transverse inhomogeneity may indicate that in real situations, when there is no abrupt change of material properties, the Stoneley waves arise less frequently than it can be supposed. The current analysis is targeted to elucidate the situation of vanishing Stoneley waves, when the initially abrupt interface between elastic layers starts to diffuse. [ABSTRACT FROM AUTHOR]

The present article attempts to study the propagation of surface seismic waves (Stoneley waves) in the layered structure composed of rock and ice medium. The interface between the two media (ice and rock) is considered to be frictional. Mathematical model of the present problem is formulated by adapting the Coulomb frictional boundary conditions. The frequency relation is obtained in the determinant form. The non-dispersive nature of the Stoneley wave is observed through the frequency relation. The non-dimensional phase velocity and damping parameter curves have been plotted against the non-dimensional angular frequency. Effect of different parameters (viscoelastic coefficient of the rock medium, frictional interface parameter, anisotropy parameter and initial stress of both the media) on the phase velocity and damping has been distinctly marked and shown graphically. [ABSTRACT FROM AUTHOR]

The target stratum of gas reservoirs in the Ku-che area, Western China, is a fractured tight sandstone reservoir with a fracture width of less than 100 jam, which are difficult to identify with conventional and imaging logging methods. The sensibility of Stoneley wave energy to fluid motion in a well makes it possible to evaluate the effectiveness of fractures through Stoneley wave energy (amplitude) information. In this study, the 3-D staggered grid stress-velocity finite difference (FD) method was applied to simulate the acoustic fields of the borehole in the formation with tilt fractures. The effects of different fracture widths and tilt angles on the amplitude of the Stoneley wave were investigated. The results show that the existence of fractures causes the attenuation of Stoneley waves, which is well correlated with the fractures' width. Accordingly, the Stoneley wave energy extracted from the array acoustic data was normalised, and its attenuation coefficient was calculated. According to the simulation results, the fracture width and permeability can be inverted. This method was applied to evaluate the ef-fectiveness of the fractured tight sandstone reser-voirs in the Kuche area, and good results were ob-tained. [ABSTRACT FROM AUTHOR]

It is shown that in auxetic materials (materials with negative Poisson’s ratio), supersonic Stoneley waves travelling without attenuation with a velocity equal to or exceeding maximum bulk wave velocity, may exist. Analytical expressions for the relation between negative Poisson’s ratio and Young’s moduli of the contacting isotropic media ensuring the condition of propagation for supersonic Stoneley waves, are derived by solving a secular equation for Stoneley waves.

for the enhancement and improvement of ultrasonic methods evaluation and measurements. The purpose of this work is to determine the influence of the geometric parameters of the acoustic load body and its position on the coefficients of reflection and propagation of the Stoneley and Rayleigh waves and to identify the possibility of using the results of the study for practical applications.Based on the analysis of the acoustic path and the experimental data, the relationship between the measured amplitude parameters and the coefficients of the propagation and reflection of surface waves, as well as the reflectivity of the contact region of the load body in the form of a prism through the sliding boundary, which reaches up to ≈ 32–34 дБ, is established. For the first time, the dependence of these coefficients on the inclination angle of one of the prism lateral faces in the range of 0 ± 45°, dimensionless thickness of the contact layer (0–0,05) and its orientation relative to the acoustic axis.It is established that these coefficients are mainly maximal when the prism is rectangular. The coefficient of reflectivity in the hard contact of bodies is more than an order of magnitude less, and the coefficients of wave propagation – comparable in magnitude. The prospects of using the results of the study to evaluate the quality of adhesion of materials during welding, soldering, gluing, detection of defects in hardto-reach places, as well as to determine the physical and mechanical properties of metals by the proposed method of creating a reference signal are shown.

The interfacial Stoneley waves at the Wiechert condition imposed on physical properties of the adjacent isotropic and homogeneous halfspaces are analyzed. It is shown both theoretically and numerically that the speed of propagation of Stoneley waves along the Wiechert line is a monotonically decreasing function of the dimensionless Wiechert parameter. It is also found that such a monotonic behavior takes place at the nonnegative values of Poisson's ratio. The observed monotonic behavior delivers the unique possibility for applying acoustic methods to nondestructive evaluation of physical parameters of media satisfying the Wiechert condition. [ABSTRACT FROM AUTHOR]

Observance of Stoneley waves at the guided wave dispersion in stratified plates containing layers with alternating contrast physical properties is analyzed by applying Cauchy sextic formalism coupled with the exponential fundamental matrix method. Additional high-frequency asymptotes related to appearing interfacial Stoneley waves are detected and analyzed. Comparison with the case when Stoneley waves do not exist is presented. [ABSTRACT FROM AUTHOR]

In this paper, the finite difference method is used to model the Stoneley wave reflection by a horizontal fracture in a borehole. The fracture shape is described by some finite difference grids. Therefore, the fracture aperture can be varied in the radial direction, thus extending previous researches on the assumption that the fracture aperture is constant throughout the fracture. Finite difference grids can also be used to describe a fracture which extends a finite distance in the radial direction. In addition, the finite difference algorithm can deal with the problem of inhomogeneous formation. Therefore, it allows the variation of formation elasticity in the model. Fine grids are needed to describe the small fracture aperture, and variable grid spacing is employed by finite difference method to improve computational efficiency. The Stoneley wave propagation is simulated by the variable grid spacing finite difference method in several models with variable fracture aperture, finite extension fracture and models with heterogeneous formation. The variable grid spacing finite difference method is validated through a comparison with real axis integration method and the analytical method. We get some conclusions by simulating and investigating effects of the variation of fracture aperture, the fracture of finite extension and inhomogeneity of formation on the Stoneley wave reflection. Although the fracture aperture changes along the fracture extension direction, the reflection coefficient of Stoneley wave is mainly controlled by the fracture aperture near the borehole. The Stoneley wave in the fracture is reflected back into the borehole, by the tip of finite extension fracture, which results in some notches in the reflection coefficient curve. If the Stoneley wave propagates from the formation with small elastic modulus to the formation with large elastic modulus, the reflection coefficient of Stoneley wave will be larger than that of homogeneous model with small elastic modulus. And if Stoneley wave propagates from the formation with large elastic modulus to the formation with small elastic modulus, the reflection coefficient of Stoneley wave will be smaller that of homogeneous model with large elastic modulus. These results provide some basis for the use of Stoneley wave to detect the fracture properties in formation. [ABSTRACT FROM AUTHOR]

The present paper deals with the propagation of surface waves (Stoneley and Rayleigh waves) in thermoelastic materials with voids. The frequency equations of the Stoneley waves at the bonded and unbonded interfaces between two dissimilar half-spaces of thermoelastic materials with voids are obtained. The numerical values of the determinant for bonded and unbonded interface are calculated for a particular model. We also derived the frequency equation of the Rayleigh wave in thermoelastic materials with voids. The phase velocity and attenuation coefficients have shown that there are two modes of vibration. These two modes are computed and they are depicted graphically. The effect of thermal parameters in these surface waves is discussed. [ABSTRACT FROM AUTHOR]

The finite difference (FD) method of monopole source is used to simulate the response of full-wave acoustic-logging in cave formations. The effect of the cave in the formation of borehole full-waves was studied. The results show that the radius of cave is not only linearly related to the first arrival of the compressional wave (P-wave), but also to the energy of the shear wave (S-wave). The converted S (S–S wave) and P-waves (S–P wave) are formed when the S-wave encounters the cave. If the source distance is small, the S–S and S–P waves are not separated, and the attenuation of the S-wave is not large, due to superposition of the converted waves. The S–P wave has been separated from the S-wave when the source distance is large, so the attenuation of the S-wave increases. The amplitude of the P and S–waves changes most when the distance of the cave to the borehole wall reaches a certain value; this value is related to the excitation frequency. The amplitude of the Stoneley wave (ST wave) varies directly with the radius of cave. If the radius of the cave is large, the energy of ST wave is weak. The scattered wave is determined by the radius and position of the cave. The investigation depth of a monopole source is limited. When the distance of the cave to the borehole wall exceeds the maximum investigation depth, the borehole acoustic wave is little affected by the cave. In actual logging, the development of the cave can be evaluated by using the first arrival of the P-wave and the energy of the S and ST waves.

Featured Application: Shortcut to wave-structure calculation for elastodynamic guided waves and prediction of acoustic leakage behavior. The partial-wave method takes advantage of the Christoffel equation’s generality to represent waves within a waveguide. More specifically, the partial-wave method is well known for its usefulness when calculating dispersion curves for multilayered and/or anisotropic plates. That is, it is a vital component of the transfer-matrix method and the global-matrix method, which are used for dispersion curve calculation. The literature suggests that the method is also exceptionally useful for conceptual interpretation, but gives very few examples or instruction on how this can be done. In this paper, we expand on this topic of conceptual interpretation by addressing Rayleigh waves, Stoneley waves, shear horizontal waves, and Lamb waves. We demonstrate that all of these guided waves can be described using the partial-wave method, which establishes a common foundation on which many elastodynamic guided waves can be compared, translated, and interpreted. For Lamb waves specifically, we identify the characteristics of guided wave modes that have not been formally discussed in the literature. Additionally, we use what is demonstrated in the body of the paper to investigate the leaky characteristics of Lamb waves, which eventually leads to finding a correlation between oblique bulk wave propagation in the waveguide and the transmission amplitude ratios found in the literature. [ABSTRACT FROM AUTHOR]