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C. H. Cheng - One of the best experts on this subject based on the ideXlab platform.
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MODELING BOREHOLE Stoneley Wave PROPAGATION ACROSS PERMEABLE IN-SITU FRACTURES
2016Co-Authors: X M Tang, C. H. Cheng, F. L. PailletAbstract:The characterization of hydraulic transmissivity of permeable fracture reservoirs is a very important task in the exploration of water resources and hydrocarbons. Previ-ous studies that model the permeable structure as a single fluid-filled fracture failed to explain the observed significant Stoneley Wave attenuation across the permeable struc-ture. In this paper, the structure is modeled as a permeable fracture zone and synthetic Stoneley Wave seismograms in the vicinity of the structure are calculated. The results show that Stoneley Waves can be strongly attenuated or even eliminated without sig-nificant reflection, because of the dissipation of Wave energy into the permeable zone. Several field cases are also modeled and the theoretical results are compared with the field data. It is shown that low- and medium-frequency Stoneley Waves (1 kHz data from Moodus, Conneticut, and 5 kHz data from Monitoba, Canada) are very sensitive to the permeability of the fractures and can be used to assess permeability from in-situ logging data, if the fracture porosity and zone thickness can be measured. At high frequencies, however, Stoneley Waves are not very sensitive to permeability but are mainly affected by the sum of the fracture openings expressed as the product of fracture zone thickness 44 Tang et al. and porosity in the fracture zone. This finding is demonstrated by a logging data set (Monitoba, Canada) obtained using high-frequency Stoneley Waves at 34 kHz
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2016Co-Authors: X M Tang, C. H. ChengAbstract:This paper describes a fast algorithm for estimating formation permeability from Stone-ley Wave logs. The procedure uses a simplified Biot-Rosenbaum model formulation. The input to the inversion is the Stoneley Wave spectral amplitudes at each depth and re-ceiver, the borehole fluid properties (velocity and density), the borehole caliper log, the formation density and porosity (from log data), and the compressional and shear velocities for the interval of interest. The model uses the borehole caliper and elastic properties to compute the Stoneley Wave excitation (that is, predicted amplitude with-out permeability effects) as a function of frequency, and the porosity and permeability to compute the fluid flow amplitude reduction. This method also uses a reference depth of known permeability and compares amplitude variations at other depths relative to the reference depth. The permeability value obtained from the inversion represents the best fit over all receivers and all relevant frequencies. A processing example is shown to demonstrate the ability of this technique to extract formation permeability from Stoneley Wave logs
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Stoneley Wave PROPAGATION IN HETEROGENEOUS PERMEABLE POROUS FORMATIONS
2016Co-Authors: Xiaomin Zhao, M N Toksoz, C. H. ChengAbstract:The propagation of borehole Stoneley Waves is strongly correlated with permeability of the formation. Previous studies primarily focused on the situation where the per-meability is homogeneously distributed in the formation. In many in-situ situations, however, the permeability distribution of the formation is heterogeneous, due to effects such as a damaged zone around the borehole, random variation of the formation perme-ability, and layering, etc. This study investigates the effects of formation permeability heterogeneity on Stoneley Wave propagation. Using the theory of dynamic permeability and a finite difference technique in cylindrical coordinates, dynamic pore fluid flow in an arbitrarily heterogeneous porous medium surrounding the borehole is modeled. The effects of the flow on the borehole Stoneley Waves are calculated. The calculations were performed on various types of permeability heterogeneities. For a formation having ran-dom permeability variation with various heterogeneity scale lengths (smaller than the scale of the borehole), the Stoneley Wave attenuation and dispersion are only slightly higher than those calculated with a constant permeability (mean value of the random distributions). For a formation with permeability linearly increasing or decreasing away from the borehole, the Stoneley Wave behaviors are also similar to those calculated with a constant permeability. Significant effects are found for a damaged zone case where the zone has much higher permeability than the virgin formation. The attenuation exhibits a peak and the Stoneley Wave velocity is significantly decreased in the frequency range from 0 to 3 kHz. These features, if measured from the data, can be used as a diagnostic of the borehole condition. 44 Zhao et al
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EFFECTS OF A BOREHOLE ENVIRONMENT AND RESIDUAL HYDROCARBON ON Stoneley Wave AMPLITUDE AND REFLECTIVITY
2016Co-Authors: Guo Tao, C. H. ChengAbstract:In recent years, borehole Stoneley Wave amplitude and reflectivity have been used for estimating formation permeability based on the strong correlation between Stoneley Wave attenuation, reflectivity and formation fluid conductivity. There are other factors, however, that may cause substantial Stoneley attenuation and reflection in a borehole environment. To make better use of Stoneley measurements for formation permeability estimation, it is desirable to identify and quantify those causes of Stoneley attenuation and reflection that do not directly result from formation permeability. In this study, a simplified Biot-Rosenbaum model developed by Tang et at. (1991) is adopted to sys-tematically model Stoneley attenuation and reflection in various borehole environments and formation configurations. By changing pore fluid, formation porosity, lithology, bed boundaries and thickness in the modeling, the sensitivity of Stoneley Wave propa-gation to these conditions are quantitatively assessed. It is found that the presence of a light hydrocarbon in the formation, especially a natural gas residual in the immediate vicinity of the borehole wall, even with only 5 % contained in pore fluid, may also cause substantial Stoneley attenuation and reflection. This phenomenon, on the other hand, can be used to evaluate a nonfractured, low permeability gas reservoir when combined with shear Wave velocity data. For the full gas-saturated zone, Stoneley Wave reflection may be observed even when the permeability is as low as a few milliDarcies. Com-pared to the effects of pore fluid, the effects due to lithology contrasts at the boundaries and the changes of nonfracture porosity are insignificant in the cases studied here. For a residual gas-bearing zone of moderate permeability, Stoneley Wave attenuation and reflection may be observed if the zone is thicker than 0.5 meter
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INVERSION FOR PERMEABILITY FROM Stoneley Wave VELOCITY AND ATTENUATION
2016Co-Authors: N. Y. Cheng, C. H. Cheng, M N ToksozAbstract:The in situ permeability of a formation is obtained by the inversion of Stoneley Wave phase velocity and attenuation, which are evaluated by applying the Extended Prony's method to the array sonic logging data. The Maximum Likelihood inversion is used together with logarithmic parameterization of the permeabilities. Formation shear Wave velocity is also inverted for. This process is tested on both synthetic and field data. Logarithmic parameterization contributes to rapid convergence of the algorithm. Permeabilities estimated from field data are in good agreement with core measurments
X M Tang - One of the best experts on this subject based on the ideXlab platform.
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MODELING BOREHOLE Stoneley Wave PROPAGATION ACROSS PERMEABLE IN-SITU FRACTURES
2016Co-Authors: X M Tang, C. H. Cheng, F. L. PailletAbstract:The characterization of hydraulic transmissivity of permeable fracture reservoirs is a very important task in the exploration of water resources and hydrocarbons. Previ-ous studies that model the permeable structure as a single fluid-filled fracture failed to explain the observed significant Stoneley Wave attenuation across the permeable struc-ture. In this paper, the structure is modeled as a permeable fracture zone and synthetic Stoneley Wave seismograms in the vicinity of the structure are calculated. The results show that Stoneley Waves can be strongly attenuated or even eliminated without sig-nificant reflection, because of the dissipation of Wave energy into the permeable zone. Several field cases are also modeled and the theoretical results are compared with the field data. It is shown that low- and medium-frequency Stoneley Waves (1 kHz data from Moodus, Conneticut, and 5 kHz data from Monitoba, Canada) are very sensitive to the permeability of the fractures and can be used to assess permeability from in-situ logging data, if the fracture porosity and zone thickness can be measured. At high frequencies, however, Stoneley Waves are not very sensitive to permeability but are mainly affected by the sum of the fracture openings expressed as the product of fracture zone thickness 44 Tang et al. and porosity in the fracture zone. This finding is demonstrated by a logging data set (Monitoba, Canada) obtained using high-frequency Stoneley Waves at 34 kHz
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2016Co-Authors: X M Tang, C. H. ChengAbstract:This paper describes a fast algorithm for estimating formation permeability from Stone-ley Wave logs. The procedure uses a simplified Biot-Rosenbaum model formulation. The input to the inversion is the Stoneley Wave spectral amplitudes at each depth and re-ceiver, the borehole fluid properties (velocity and density), the borehole caliper log, the formation density and porosity (from log data), and the compressional and shear velocities for the interval of interest. The model uses the borehole caliper and elastic properties to compute the Stoneley Wave excitation (that is, predicted amplitude with-out permeability effects) as a function of frequency, and the porosity and permeability to compute the fluid flow amplitude reduction. This method also uses a reference depth of known permeability and compares amplitude variations at other depths relative to the reference depth. The permeability value obtained from the inversion represents the best fit over all receivers and all relevant frequencies. A processing example is shown to demonstrate the ability of this technique to extract formation permeability from Stoneley Wave logs
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determining shear Wave transverse isotropy from borehole Stoneley Waves
Seg Technical Program Expanded Abstracts, 2001Co-Authors: X M TangAbstract:Many rocks in earth formations exhibit transversely isotropic (TI) characteristics. For determining the TI parameter using acoustic logging, Stoneley Waves are the only borehole Wave mode that has a significant sensitivity to the TI effects, especially when the formation is acoustically slow compared to borehole fluid. This study describes a method for deriving the formation shear-Wave TI parameter from the Stoneley Wave data acquired by a logging tool. The presence of the tool can substantially alter the Stoneley Wave characteristics and must be included in the analysis. In the inversion analysis, Stoneley Wave slowness is related to the weighted average of the Wave’s dispersion curve over the frequency range occupied by the Wave spectrum. This provides a fast method for the inversion. As a processing example, this method has been applied to estimate the shearWave TI parameter profile for the Lewis shale formation in Braggs, Wyoming. The resulting profile delineates the shear-Wave anisotropy magnitude and variation for this shale formation.
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Borehole Stoneley Wave propagation across permeable structures
Geophysical Prospecting, 1993Co-Authors: X M Tang, C. H. ChengAbstract:This study investigates the propagation of borehole Stoneley Waves across permeable structures. By modeling the structure as a zone intersecting the borehole, a simple 1D theory is formulated to treat the interaction of the Stoneley Wave with the structure. This is possible because the Stoneley Wave is a guided Wave, with no geometric spreading as it propagates along the borehole. The interaction occurs because the zone and the surrounding formation possess different Stoneley Wavenumbers. Given appropriate representations of the Wavenumber, the theory can be applied to treat a variety of structures, including a fluid-filled fracture. Of special interest are the cases of permeable porous zones and fracture zones. The results show that, while Stoneley Wave reflections are generated, strong Stoneley Wave attenuation is produced across a very permeable zone. This result is particularly important in explaining the observed strong Stoneley Wave attenuation at major fractures where it has been difficult to explain the attenuation in terms of the single planar fracture theory. In addition, by using a simple and sufficiently accurate theory to model the effects of the permeable zone, a fast and efficient method is developed to characterize the fluid transport properties of a permeable fracture zone.
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Stoneley Wave propagation in a fluid filled borehole with a vertical fracture
International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1991Co-Authors: X M Tang, C. H. Cheng, M N ToksozAbstract:The propagation of Stoneley Waves in a fluid‐filled borehole with a vertical fracture is investigated both theoretically and experimentally. The borehole propagation excites fluid motion in the fracture and the resulting fluid flow at the fracture opening perturbs the fluid‐solid interface boundary condition at the borehole wall. By developing a boundary condition perturbation technique for the borehole situation, we studied the effect of this change in the boundary condition on the Stoneley propagation. Cases of both hard and soft formations have been investigated. The fracture has minimal effects on the Stoneley velocity, except in the very low frequency range in which the Stoneley velocity drastically decreases with decreasing frequency. Significant Stoneley‐Wave attenuation is produced because of the energy dissipation into the fracture. The quantitative behavior of these effects depends not only on fracture aperture and borehole radius, but also on the acoustic properties of the formation and fluid. ...
M N Toksoz - One of the best experts on this subject based on the ideXlab platform.
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Stoneley Wave PROPAGATION IN HETEROGENEOUS PERMEABLE POROUS FORMATIONS
2016Co-Authors: Xiaomin Zhao, M N Toksoz, C. H. ChengAbstract:The propagation of borehole Stoneley Waves is strongly correlated with permeability of the formation. Previous studies primarily focused on the situation where the per-meability is homogeneously distributed in the formation. In many in-situ situations, however, the permeability distribution of the formation is heterogeneous, due to effects such as a damaged zone around the borehole, random variation of the formation perme-ability, and layering, etc. This study investigates the effects of formation permeability heterogeneity on Stoneley Wave propagation. Using the theory of dynamic permeability and a finite difference technique in cylindrical coordinates, dynamic pore fluid flow in an arbitrarily heterogeneous porous medium surrounding the borehole is modeled. The effects of the flow on the borehole Stoneley Waves are calculated. The calculations were performed on various types of permeability heterogeneities. For a formation having ran-dom permeability variation with various heterogeneity scale lengths (smaller than the scale of the borehole), the Stoneley Wave attenuation and dispersion are only slightly higher than those calculated with a constant permeability (mean value of the random distributions). For a formation with permeability linearly increasing or decreasing away from the borehole, the Stoneley Wave behaviors are also similar to those calculated with a constant permeability. Significant effects are found for a damaged zone case where the zone has much higher permeability than the virgin formation. The attenuation exhibits a peak and the Stoneley Wave velocity is significantly decreased in the frequency range from 0 to 3 kHz. These features, if measured from the data, can be used as a diagnostic of the borehole condition. 44 Zhao et al
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INVERSION FOR PERMEABILITY FROM Stoneley Wave VELOCITY AND ATTENUATION
2016Co-Authors: N. Y. Cheng, C. H. Cheng, M N ToksozAbstract:The in situ permeability of a formation is obtained by the inversion of Stoneley Wave phase velocity and attenuation, which are evaluated by applying the Extended Prony's method to the array sonic logging data. The Maximum Likelihood inversion is used together with logarithmic parameterization of the permeabilities. Formation shear Wave velocity is also inverted for. This process is tested on both synthetic and field data. Logarithmic parameterization contributes to rapid convergence of the algorithm. Permeabilities estimated from field data are in good agreement with core measurments
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Stoneley Wave propagation across borehole permeability heterogeneities
Seg Technical Program Expanded Abstracts, 1994Co-Authors: Xiaomin Zhao, M N Toksoz, C. H. ChengAbstract:An important application of borehole acoustic logging is the determination of formation permeability using Stoneley Waves. Heterogeneous permeable structures, such as fractures, sand-shale sequences, etc., are commonly encountered in acoustic logging. The purpose of this study is to investigate the effects of the permeability heterogeneities on the borehole Stoneley Wave propagation, We have studied the effects of formation permeability heterogeneities on the Stoneley Wave propagation when the heterogeneity changes in radial and azimuthal directions (Zhao et aL, 1993). To further study the problem of acoustic logging in heterogeneous porous formations, we study the case where the formation permeability varies in the borehole axial and radial directions. This is a very important problem because vertical heterogeneity variations are commonly encountered in acoustic logging applications. Using the finite difference approach, such heterogeneities as random heterogeneous permeability variations, multiple fracture zones, permeable (sand) non-permeable (shale) sequences, can be readily modeled, and the results are presented. Our numerical simulation results show that the continuous permeability variations in the formation have only minimal effects on the Stoneley Wave propagation. Whereas the discontinuous variation (e.g., permeable sand and non-permeable shale sequences) can have significant effeces on the Stoneley Wave propagation. However, when the Stoneley Wavelength is considerably large compared to the scale of heterogeneity variations, the Stoneley Wave is sensitive only to the overall fluid transmissivity of the formation heterogeneity, To demonstrate the effects of heterogeneity on the Stoneley Wave propagation. an experimental data set (Winkler et aI., 1989) has been modeled using a randomly layered permeability model. The heterogeneous permeability model results agree with the data very well, while the data disagree with the results from homogeneous permeability models. The numerical technique for calculating Stoneley Wave propagation across permeability heterogeneities has been applied to interpret the acoustic logging data across a heeerogeneous fraceure zone (paillet. 1984). The modeling technique, in conjunction with a variable permeability model, successfully explains the non-symmetric patterns of the Stoneley Wave attenuation and reileceion at the top and bottom of the fracture
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Stoneley Wave propagation in heterogeneous permeable porous formations
Seg Technical Program Expanded Abstracts, 1993Co-Authors: Xiaomin Zhao, M N Toksoz, C. H. ChengAbstract:The propagation of borehole Stoneley Waves is strongly correlated with permeability of the formation. Previous studies primarily focused on the situation where the permeability is homogeneously distributed in the formation. In many in-situ situations, however, the permeability distribution of the formation is heterogeneous, due to effects such as a damaged zone around the borehole, random variation of the formation permeability, and layering, etc. This study investigates the effects of formation permeability heterogeneity on Stoneley Wave propagation. Using the theory of dynamic permeability and a finite difference technique in cylindrical coordinates, dynamic pore fluid flow in an arbitrarily heterogeneous porous medium surrounding the borehole is modeled. The effects of the flow on the borehole Stoneley Waves are calculated. The calculations were performed on various types of permeability heterogeneities. For a formation having random permeability variation with various heterogeneity scale lengths (smaller than the scale of the borehole), the Stoneley Wave attenuation and dispersion are only slightly higher than those calculated with a constant permeability (mean value of the random distributions). For a formation with permeability linearly increasing or decreasing away from the borehole, the Stoneley Wave behaviors are also similar to those calculated with a constant permeability. Significant effects are found for a damaged zone case where the zone has much higher permeability than the virgin formation. The attenuation exhibits a peak and the Stoneley Wave velocity is significantly decreased in the frequency range from 0 to 3 kHz. These features, if measured from the data, can be used as a diagnostic of the borehole condition.
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Stoneley Wave propagation in a fluid filled borehole with a vertical fracture
International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1991Co-Authors: X M Tang, C. H. Cheng, M N ToksozAbstract:The propagation of Stoneley Waves in a fluid‐filled borehole with a vertical fracture is investigated both theoretically and experimentally. The borehole propagation excites fluid motion in the fracture and the resulting fluid flow at the fracture opening perturbs the fluid‐solid interface boundary condition at the borehole wall. By developing a boundary condition perturbation technique for the borehole situation, we studied the effect of this change in the boundary condition on the Stoneley propagation. Cases of both hard and soft formations have been investigated. The fracture has minimal effects on the Stoneley velocity, except in the very low frequency range in which the Stoneley velocity drastically decreases with decreasing frequency. Significant Stoneley‐Wave attenuation is produced because of the energy dissipation into the fracture. The quantitative behavior of these effects depends not only on fracture aperture and borehole radius, but also on the acoustic properties of the formation and fluid. ...
Xiao Ming Tang - One of the best experts on this subject based on the ideXlab platform.
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Inversion of Shear Wave Anisotropic Parameters in Strongly Anisotropic Formations
2016Co-Authors: Shihong Chi, Xiao Ming Tang, Zhenya ZhuAbstract:Deepwater reservoirs use highly deviated wells to reduce cost and enhance hydrocarbon recovery. Due to the strong anisotropic nature of many of the marine sediments, anisotropic seismic imaging and interpretation can improve reservoir characterization. Sonic logs acquired in these wells are strongly dependent on well deviations. Cross-dipole sonic logging provides apparent shear Wave anisotropy in deviated wells, which can be far from the truth. Although anisotropic parameters have been successfully obtained using data from wells of several deviations or using single well data based on weak anisotropy approximation, estimation of strong shear Wave anisotropy from single well data remains a challenge. Using sensitivity analysis, we find Stoneley Wave velocity has good sensitivity to qSV and SH Wave velocities in deviated wells. We create a linear inversion scheme to estimate shear Wave anisotropy using SH, SV, and Stoneley Wave velocities logged in one well. We first apply the method to laboratory measurements from boreholes of various deviations relative to the symmetry axis of an anisotropic material. We then apply the method to a field data set acquired in a deviated well. We also compute the vertical and horizontal shear Wave velocity logs in this well using the inverted elastic shear Wave constants
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Stoneley Wave speed modeling in general anisotropic formations
Seg Technical Program Expanded Abstracts, 2004Co-Authors: Shihong Chi, Xiao Ming TangAbstract:For determining anisotropy using acoustic logging data, Stoneley Waves are the only Wave modes that are sensitive to formation properties transverse to the borehole axis. We derive Stoneley-Wave speeds in deviated and horizontal wells penetrating anisotropic formations. We first apply the elastic theory of an anisotropic body to find the radial displacement of a borehole cross section under uniform pressure. We then derive the effective formation modulus based on quasistatic analysis. Finally, we derive a two-dimensional analytical solution for low-frequency Stoneley-Wave speed in a horizontal well penetrating a transversely isotropic formation with a vertical symmetry axis. For deviated wells, we derive a 3D analytical solution that is also valid for general anisotropic formations. Our analytic solutions agree with the finite-difference modeling results and are particularly suited for strongly anisotropic formations. With increasing well deviation the sensitivity of Stoneley-Wave speed to horizontal shear-Wave velocity decreases and the sensitivity to vertical shear-Wave velocity increases.
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determining formation shear Wave transverse isotropy from borehole Stoneley Wave measurements
Geophysics, 2003Co-Authors: Xiao Ming TangAbstract:Many rocks exhibit transversely isotropic (TI) characteristics. For determining the TI property using acoustic logging, Stoneley Waves are the only borehole Wave mode that has a significant sensitivity to TI effects, especially when the formation is acoustically slow compared to the borehole fluid. This study describes a method for deriving the formation shear-Wave TI parameter from the Stoneley Wave data acquired by a logging tool. It is shown that the presence of the tool in the borehole can substantially affect the Stoneley Wave propagation. Fortunately, for low-frequency Stoneley Waves, the tool effect can be satisfactorily modeled using an effective modulus, regardless of the actual structure of the tool. The modulus can be determined from a calibration procedure. In the inversion processing of the Stoneley Wave data, the Stoneley Wave slowness is related to the weighted average of the Wave's dispersion curve over the frequency range occupied by the Wave spectrum. This provides a fast method for the inversion. As a processing example, this method has been applied to estimate the shear-Wave TI parameter profile for the Lewis shale formation in Braggs, Wyoming. The resulting profile delineates the shear-Wave anisotropy magnitude and variation for this shale formation.
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Modeling of low-frequency Stoneley-Wave propagation in an irregular borehole
Geophysics, 1997Co-Authors: Kazuhiko Tezuka, Chuen Hon Cheng, Xiao Ming TangAbstract:A fast modeling method is formulated for low-frequency Stoneley-Wave propagation in an irregular borehole. This fast modeling method provides synthetic Waveforms which include the effects of two borehole irregularities, diameter changes (washout), and formation property changes. The essential physics of the low-frequency Stoneley Waves are captured with a simple 1-D model. A mass-balance boundary condition and a propagator matrix are used to express Stoneley-Wave interactions with the borehole irregularities. The accuracy of the proposed method was confirmed through comparison with existing finite-difference and boundary integral modeling methods that yielded cross-correlations greater than 0.98. Comparison of synthetic records calculated for an actual borehole with field records showed qualitative agreement in the major reflections because of the washout zones, but showed some disagreements in the reflections caused by the fractures. Since the synthetic records include only information relating to the borehole geometry and the elastic properties of formation, the reflection caused by the fracture will appear only in the field record. These results suggest the possibility of distinguishing Stoneley-Wave reflections caused by fractures from those caused by borehole irregularities. Further, the fast computational speed of this method--over 300 times faster than either boundary integral or finite-difference methods--makes it quite suitable for field application.
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fast inversion of formation permeability from Stoneley Wave logs using a simplified biot rosenbaum model
Geophysics, 1996Co-Authors: Xiao Ming Tang, C. H. ChengAbstract:This paper describes a fast algorithm for estimating formation permeability from Stoneley Wave logs. The procedure uses a simplified Biot-Rosenbaum model formulation. The input to the inversion is the Stoneley-Wave spectral amplitudes at each receiver position, the bore-hole fluid properties (velocity and density), the borehole caliper log, the formation density and porosity (from log data), and the compressional and shear velocities for the interval of interest. The model uses the borehole caliper and elastic properties to compute the Stoneley Wave excitation (that is, predicted amplitude without permeability effects) as a function of frequency, and the porosity and permeability to compute the fluid flow amplitude reduction. This method also uses a reference depth of known permeability and compares amplitude variations at other depths relative to the reference depth. The permeability value obtained from the inversion represents the best fit over all receivers and all relevant frequencies. A processing example is shown to demonstrate the ability of this technique to extract formation permeability from Stoneley Wave logs.
M Markov - One of the best experts on this subject based on the ideXlab platform.
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squirt flow influence on sonic log parameters
Geophysical Journal International, 2014Co-Authors: I Markova, Ronquillo G Jarillo, M Markov, Boris GurevichAbstract:S U M M A R Y Most sedimentary rocks contain movable fluid in the pores. Hydrodynamic effects due to Waveinduced oscillatory fluid flow can lead to significant changes of velocities and attenuations of elastic Waves in these rocks. In this paper, we consider the influence of a squirt flow (local flow between the pores of different compressibility) on the sonic log response. The calculations are performed using a unified model describing the joint influence of squirt flow and Biot’s global flow. The results show that the influence of the squirt flow increases with increase of a signal frequency. This influence is relatively small in the case of the Stoneley Wave but it is significant in the case of P and S Waves.
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low frequency Stoneley Wave propagation at the interface of two porous half spaces
Geophysical Journal International, 2009Co-Authors: M MarkovAbstract:SUMMARY The Frenkel-Biot theory is used to study a propagation of Stoneley elastic Wave at the boundary of two fluid-saturated porous media. The velocity and attenuation of the Stoneley surface Wave are determined. I show that the dispersion equation coincides with the equation for the Stoneley Wave at the interface of two elastic half-spaces in the low-frequency range. Numerical examples of calculations are presented for two important cases: two different fluids lying in the same viscoelastic skeleton (gas–water interface) and two poroelastic half-spaces with different porosity and permeability containing the same fluid. To take into account the absorption in the solid matrix, I use well-known Stoll’s model. Our calculation results have shown that the Stoneley Wave absorption is determined by the energy dissipation in the solid matrix for consolidated rocks. As the frequency is increased, hydrodynamic effects connected with the presence of a movable fluid in the pores begin to play a significant role.