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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]

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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]

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 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]

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]

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 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]

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]

This paper is concerned with the study of propagation of Stoneley waves at the interface of two dissimilar transversely isotropic thermoelastic solids without energy dissipation and with two temperatures. The secular equation of Stoneley waves is derived in the form of the determinant by using appropriate boundary conditions i.e. the stresses components, the displacement components, and temperature at the boundary surface between the two media are considered to be continuous at all times and positions. The dispersion curves giving the Stoneley wave velocity and Attenuation coefficients with wave number are computed numerically. Numerical simulated results are depicted graphically to show the effect of two temperature and anisotropy on resulting quantities. Copper material has been chosen for the medium M1 and magnesium for the medium M2. Some special cases are also deduced from the present investigation. [ABSTRACT FROM AUTHOR]

The present work aims to study the propagation of Stoneley wave at the common interface of two distinct homogeneous viscoelastic semi-infinite media. The closed-form expression of the velocity equation has been obtained. The real part of the velocity equation corresponds to the phase velocity of Stoneley wave, whereas the imaginary part corresponds to the damped velocity associated with the Stoneley wave. The Lamé ratio associated with Lamé's first constant for the upper/lower viscoelastic semi-infinite medium and the frictional parameter associated with the shear strain for the upper/lower viscoelastic semi-infinite medium have significant effects on the phase velocity and the damped velocity of Stoneley wave associated with a longitudinal/transversal wave in the upper/lower viscoelastic semi-infinite medium. Numerical computation and graphical illustration were carried out to highlight the important peculiarities of the problem. Moreover, as a special case, it was observed that the velocity equation of propagation of Stoneley wave in the present problem is in good agreement with the velocity equation obtained earlier for the Stoneley wave propagation at the common interface of two distinct homogeneous isotropic semiinfinite media. [ABSTRACT FROM AUTHOR]

Fracture detection and evaluation in carbonate reservoirs plays an important role in reservoir development and cost optimization. The majority of Iranian hydrocarbon reservoirs are carbonates for which the detection and evaluation of fractures is crucial. Cores and image logs are usual tools of fracture studying; however, it is both technically and financially impossible to core or image the whole thickness of the reservoir and in the whole wells. Other tools of fracture detection exploit the information conveyed by well log data. One application for dipole sonic imager (DSI) is its capability to evaluate fractures by measuring Stoneley wave. In this study, the DSI was used as a tool to position fractures and evaluate its intensity in the fractured bearing Darian formation. For this, the Stoneley wave data were analyzed using a commercial software. The direct and reflected Stoneley waves were subtracted from the original data and reflection coefficients were calculated afterwards. From the calculated reflection coefficients, positions and intensities of fracture were determined. The results were validated by the formation micro imager (FMI) log data. The reason of doing this project using Stoneley wave analysis obtained by acoustic tool in objective field is that core data and FMI data-which are direct method in fractures evaluating-are not accessible because of economical and technical reasons. In this project, a DSI is used for propagating Stoneley wave in a fractured zone in the Dariyan Formation. The Stoneley wave data were analyzed using commercial software. Then, reflected and direct waves were subtracted from the original data. As a result, reflection coefficients were calculated. According to calculated RC, position and intensity of fractures were detected. Finally, the results were validated by FMI image log data. [ABSTRACT FROM AUTHOR]

A fluid-saturated flat channel between solids, such as a fracture, is known to support guided waves--sometimes called Krauklis waves. At low frequencies, Krauklis waves can have very low velocity and large attenuation and are very dispersive. Because they propagate primarily within the fluid channel formed by a fracture, Krauklis waves can potentially be used for geological fracture characterization in the field. Using an analogue fracture consisting of a pair of flat slender plates with a mediating fluid layer--a trilayer model--we conducted laboratory measurements of the velocity and attenuation of Krauklis waves. Unlike previous experiments using ultrasonic waves, these experiments used frequencies well below 1 kHz, resulting in extremely low velocity and large attenuation of the waves. The mechanical compliance of the fracture was varied by modifying the stiffness of the fluid seal of the physical fracture model, and proppant (fracture-filling high-permeability sand) was also introduced into the fracture to examine its impact on wave propagation. A theoretical frequency equation for the trilayer model was derived using the poroelastic linear-slip interface model, and its solutions were compared to the experimental results. [ABSTRACT FROM AUTHOR]

The interlaminar defect is a major form of damage in metal layer composite pipes which are widely used in petroleum and chemical industry. In this paper, a Stoneley wave method is presented to detect interlaminar damage in laminated pipe structure. Stoneley wave possesses some good characteristics, such as high energy and large displacement at the interface and non-dispersive in the high-frequency, so the sensitivity of detecting interlaminar damage can be improved and the higher frequency can be used in damage detection compared with Lamb waves. Additionally, as the frequency increases, the wavelength of the Stoneley wave reduces. Thus, its ability to detect small defects at the interface is enhanced. Finite element model of metal layer composite pipe with interlaminar damage is used to simulate wave propagation of Lamb waves and Stoneley wave, respectively. The damage location is calculated by using the Stoneley wave signal obtained from finite element model, and then the results are compared with the actual damage locations. The simulation examples demonstrate that the Stoneley wave method can better identify the interlaminar damage in laminated pipe structure compared with Lamb waves. [ABSTRACT FROM AUTHOR]

New nonlinear wave equations describing the propagation of a surface wave along the interface between two half-spaces with different densities and elastic properties (Stoneley wave) are proposed. Nonlinearity is introduced by the five-constant Murnaghan potential, which includes both geometrical and physical nonlinearities. The nonlinear equations are solved in two iterations of the method of successive approximations. The solution includes second harmonics [ABSTRACT FROM AUTHOR]

Abstract: The aim of the study is to increase the reliability of estimation of the acoustic parameters of a layered permeable formation using new software, based on two-velocity continuum equations for 2D numerical simulation of acoustic waves propagating in a borehole. The key method is the method of finite differences as applied to solving equations of the continuum filtration theory. The dissipative characteristics of Stoneley waves have been identified for the case of their propagation in a layered formation. These aspects should be taken into account when using Stoneley waves to estimate the permeability of geologic media. [Copyright &y& Elsevier]

ABSTRACT The dynamic response of a semi-infinite fluid-filled borehole embedded in an elastic half-space under a concentrated normal surface load is analysed in the long-wavelength limit. The solution of the problem is obtained with integral transforms in the form of a double integral with respect to the slowness and frequency. The partial P- and SV -wave responses are further transformed to path integrals along Cagniard paths in the complex slowness plane. Unlike the traditional Cagniard-de Hoop technique based on the Laplace transform of time dependence, this paper is based on the Fourier transform. The tube-wave response is presented as a causal integral over a slowness range. The resultant representation in the time-domain is suitable for the numerical evaluation of the complete response in the fluid-filled borehole, especially at large distances. Asymptotic analysis of seismic phases arising in the borehole is performed on the basis of the obtained solution. The complete asymptotic wavefield consists in P - and SV -waves, the Rayleigh wave and the low-frequency Stoneley (tube) wave. Pressure synthetics obtained by the use of the asymptotic formulas are shown to be in good agreement with straightforward calculations. [ABSTRACT FROM AUTHOR]

The analysis of lithological composition was carried out. Reservoir elastic moduli were estimated with the lithological composition taken into account. The technique for permeability prediction according to the Stoneley wave parameters and a calculation example are presented. The comparison of permeability calculation with the proposed technique and other technologies is demonstrated. The application of the developed technique for permeability calculation provides theoretically proven outcomes. [ABSTRACT FROM AUTHOR]

Abstract: The dependence of the Stoneley attenuation length on the concentration and composition of salt in pore fluid observed in experiments may be associated with osmosis. The salinity dependence is relevant to methods in which the permeability of porous formations is estimated from its relationship with the Stoneley attenuation length. [ABSTRACT FROM AUTHOR]

We investigated the propagation properties of Stoneley waves between two magneto-electro-elastic half planes. Magneto-electro-elastic materials are assumed to possess hexagonal (6 mm) symmetry. Twenty-five sets of magneto-electrical interface conditions were adopted and generalized frequency equations were derived and solved numerically. It was found that, for each set of interface conditions, existing Stoneley waves are always non-dispersive. Numerical results further show that material properties have a significant effect on both the number and velocity of Stoneley waves, and that, although different magneto-electrical interface conditions could influence the existence of Stoneley waves, they have no effect on wave velocities. [ABSTRACT FROM AUTHOR]

The properties of harmonic surface waves in an elastic cylinder made of a rigid material and filled with a fluid are studied. The problem is solved using the dynamic equations of elasticity and the equations of motion of a perfect compressible fluid. It is shown that two surface (Stoneley and Rayleigh) waves exist in this waveguide system. The first normal wave generates a Stoneley wave on the inner surface of the cylinder. If the material is rigid, no normal wave exists to transform into a Rayleigh wave. The Rayleigh wave on the outer surface forms on certain sections of different dispersion curves. The kinematic and energy characteristics of surface waves are analyzed. As the wave number increases, the phase velocities of all normal waves, except the first one, tend to the sonic velocity in the fluid from above [ABSTRACT FROM AUTHOR]

Frequency equations for Stoneley waves at unbonded and bonded interfaces between two dissimilar microstretch elastic half-spaces have been derived. Eringen's theory of microstretch elastic solid material is employed for mathematical analysis. It is found that Stoneley waves in a microstretch elastic solid medium are dispersive. Numerical computations are performed for a particular model to study the variation of phase velocity with respect to wavenumber, and reveal that for small values of non-dimensional wave number, the effect of microstretch property of the medium has a significant effect on dispersion curves, while no effect is observed for higher values of the non-dimensional wavenumber. The results of Tajuddin, Murty and Stoneley have been derived as particular cases of the present problem, and some other interesting particular cases have also been discussed. [ABSTRACT FROM AUTHOR]

A generalization of the Wiechert condition by introducing two independent dimensionless parameters instead of one parameter in the original Wiechert condition is proposed. Variation of Stoneley wave velocity at varying two parameters of the generalized Wiechert condition at different Poisson's ratios is studied revealing a substantial discrepancy in Stoneley wave velocity profiles. [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. [ABSTRACT FROM AUTHOR]

A 3D seismic survey was done on a near surface karstic reservoir located at the hydrogeological experimental site (HES) of the University of Poitiers (France). The processing of the 3D data led to obtaining a 3D velocity block in depth. The velocity block was converted in pseudo porosity. The resulting 3D seismic pseudo-porosity block reveals three high-porosity, presumably-water-productive layers, at depths of 30–40, 85–87 and 110–115 m. This paper shows how full wave acoustic logging (FWAL) can be used to validate the results obtained from the 3D seismic survey if the karstic body has a lateral extension over several seismic. If karstic bodies have a small extension, FWAL in open hole can be fruitfully used to: detect highly permeable bodies, thanks to measurements of acoustic energy and attenuation; detect the presence of karstic bodies characterized by a very strong attenuation of the different wave trains and a loss of continuity of acoustic sections; confirm the results obtained by vertical seismic profile (VSP) data. The field example also shows that acoustic attenuation of the total wavefield as well as conversion of downward-going P-wave in Stoneley waves observed on VSP data are strongly correlated with the presence of flow. [ABSTRACT FROM AUTHOR]