Seismogram synthesis for radially layered media using the generalized reflection/transmission coefficients method: Theory and applications to acoustic logging

Geophysics ◽  
1996 ◽  
Vol 61 (4) ◽  
pp. 1150-1159 ◽  
Author(s):  
Xiaofei Chen ◽  
Youli Quan ◽  
Jerry M. Harris
Keyword(s):  
Seismic Profiles ◽  
P Waves ◽  
Transmission Coefficients ◽  
Full Waveform ◽  
Hankel Functions ◽  
Damaged Zone ◽  
Divergence Effect ◽  
Zone Velocity ◽  
New Formulation ◽  
Sonic Logging

A new method based on generalized reflection and transmission coefficients is proposed to calculate the synthetic seismograms in radially multilayered media. This method can be used to efficiently simulate full waveform acoustic logs and crosswell seismic profiles in situations where we need to consider borehole effects. The new formulation is tested by comparing our numerical results with previous available work and shows excellent agreement. Because of the use of the normalized Hankel functions and the normalization factors, this new algorithm for computing seismograms is stable numerically even for high‐frequency problems. To show the applicability of this new approach to full waveform sonic logging, we apply it to investigate the effects of complex invaded zones on the geometrical spreading and attenuation estimation for P‐waves. We find that a damaged zone (its velocity is slower than the unperturbed formation velocity) exhibits a convergence effect on the P‐waves, and a flushed zone (velocity is faster than the unperturbed formation velocity) exhibits a divergence effect on the P‐waves.

Migration-based filtering: Applications to geophysical imaging data

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. S219-S228 ◽  
Author(s):  
Jianjian Huo ◽  
Binzhong Zhou ◽  
Qing Zhao ◽  
Iain M. Mason ◽  
Ying Rao
Keyword(s):  
Seismic Profile ◽  
Stoneley Wave ◽  
Imaging Data ◽  
Seismic Profiles ◽  
Coherent Signals ◽  
Vertical Seismic Profiles ◽  
Full Waveform ◽  
Ground Roll ◽  
Geophysical Imaging ◽  
Sonic Logging

Migration is used to collapse “diffractions,” i.e., to focus hyperbolic events that appear in the space-time of a seismic profile — into spots of finite area in the image space. These usually represent scattering objects. However, there are situations in which some of the energy can be focused by migration, and muted without significantly damaging the remaining echoes. Demigration or forward modeling then restores the remaining data, and the removed signals can be rebuilt by subtracting these restored data from the original records. This process can be classified as migration-based filtering. It is demonstrated by synthetic and field data that this filter can be used for suppressing unwanted coherent signals or separating/extracting wavefields of interest: (1) the suppression of ground roll in seismic shot gathers, (2) the suppression of axially guided arrivals in borehole radar profiles, (3) suppressing the direct arrivals to enhance Stoneley-wave reflections in full-waveform sonic logging data, and (4) separating up- and downgoing waves in vertical seismic profiles.

Multifrequency full-waveform sonic logging in the screened interval of a large-diameter production well

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. B243-B257 ◽  
Author(s):  
Majed Almalki ◽  
Brett Harris ◽  
J. Christian Dupuis
Keyword(s):  
Phase Velocity ◽  
Velocity Dispersion ◽  
Large Diameter ◽  
Low Frequency ◽  
Production Well ◽  
Frequency Wave ◽  
Full Waveform ◽  
Phase Velocity Dispersion ◽  
Production Wells ◽  
Sonic Logging

A set of field experiments using multiple transmitter center frequencies was completed to test the application potential of low-frequency full-waveform sonic logging in large-diameter production wells. Wireline logs were acquired in a simple open drillhole and a high-yield large diameter production well completed with wire-wound sand screens at an aquifer storage and recovery site in Perth, Western Australia. Phase-shift transform methods were applied to obtain phase-velocity dispersion images for frequencies of up to 4 kHz. A 3D representation of phase-velocity dispersion was developed to assist in the analysis of possible connections between low-frequency wave propagation modes and the distribution of hydraulic properties. For sandstone intervals in the test well, the highest hydraulic conductivity intervals were typically correlated with the lowest phase velocities. The main characteristics of dispersion images obtained from the sand-screened well were highly comparable with those obtained at the same depth level in a nearby simple drillhole open to the formation. The sand-screened well and the open-hole displayed an expected and substantial difference between dispersion in sand- and clay-dominated intervals. It appears that for clay-dominated formations, the rate of change of phase velocity can be associated to clay content. We demonstrated that with appropriate acquisition and processing, multifrequency full-waveform sonic logging applied in existing large-diameter sand-screened wells can produce valuable results. There are few wireline logging technologies that can be applied in this setting. The techniques that we used would be highly suitable for time-lapse applications in high-volume production wells or for reassessing formation properties behind existing historical production wells.

scholarly journals ACOUSTIC SEISMIC WAVE ATTENUATION IN ROCKS: ESTIMATES INSTABILITIES, FREQUENCY-DEPENDENCE AND INCOHERENCES

2017 ◽  
Vol 35 (3) ◽  
Author(s):  
Julián David Peláez ◽  
Luis Alfredo Montes
Keyword(s):  
Frequency Shift ◽  
Seismic Wave ◽  
Wave Attenuation ◽  
Spectral Ratio ◽  
Well Logs ◽  
Well Log ◽  
Seismic Profiles ◽  
Seismic Wave Attenuation ◽  
Transmission Coefficients ◽  
Centroid Frequency

ABSTRACT. Seismic wave attenuation (Q−1) values indicate relevant media properties, such as fluid content and porosity. Q−1 estimates, obtained using both VSP and conventional well log data, did not exhibit comparable trends, nor values. Whereas VSP results represent total attenuation, well log Q−1, which, theoretically, should represent scattering losses, displayed a low percentage correlation with transmission coefficients and other well logs. The influence of processing routines, chosen methodology and input parameters on Q−1-values suggests that ASR (Amplitude Spectral Ratio) and CFS (Centroid Frequency Shift) attenuation estimates should be regarded, in practical terms, as relative quantities instead of absolute ones. Seemingly incoherent negative values are frequent, nonetheless these could hold a physical meaning related to elastic amplification at interfaces. Considering that quality factor (Q) values obtained were more unstable than Q−1-values, it is advisable to report the latter. Keywords: Vertical Seismic Profiles, well logs, transmission coefficients, scattering, amplification.RESUMO. Os valores de atenuação da onda sísmica (Q−1) indicam propriedades relavantes dos meios, tais como conteúdo de fluido e porosidade. As estimativas do Q−1, obtidas usando dados de VSP e dados de poços convencionais, não apresentaram tendências nem valores comparáveis. Enquanto os resultados de VSP representamatenuação total, os resultados dos dados de poços, que teoricamente deveriam representar perdas de dispersão, apresentaramuma baixa correlação percentual com os coeficientes de transmissão e outros dados de poços. A influência das rotinas de processamento, da metodologia escolhida e dos parâmetros de entrada nos valores Q−1 sugere que as estimativas de atenuação ASR (Amplitude Spectral Ratio) e CFS (Centroid Frequency Shift) devem ser, em termos práticos, consideradas como quantidades relativas em vez de absolutas. Valores negativos aparentemente incoerentes são frequentes, no entanto estes poderiam conter um significado físico relacionado `a amplificação elástica nas interfaces. Considerando que os valores do fator de qualidade (Q) obtidos foram mais instáveis do que os valores de Q−1, é aconselhável documentar o último. Palavras-chave: Perfis Sísmicos Verticais, registros de poços, coeficientes de transmissão, dispersão, amplificação.

Quaternion-based anisotropic inversion for flexural waves in horizontal transverse isotropic formations with unmatched sources: A synthetic example

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. A69-A74 ◽  
Author(s):  
Fuqiang Zeng ◽  
Wenzheng Yue ◽  
Chao Li
Keyword(s):  
Structural Information ◽  
Amplitude Ratio ◽  
Flexural Wave ◽  
Data Sets ◽  
Flexural Waves ◽  
P Waves ◽  
Source Type ◽  
Transverse Isotropic ◽  
Sonic Logging ◽  
Incident Waves

The anisotropy of elastic waves has been widely used to obtain structural information on formations in geosciences research. Flexural wave splitting is generally applied to evaluate anisotropy with geophysical inversion methods. Cross-dipole sonic logging has been widely used for anisotropic inversions in horizontal transverse isotropic formations. Traditional methods assume that fast and slow flexural waves are similar in shape and are not dispersive and that the radiation characteristics of the two orthogonal dipole sources are identical. The two above assumptions cannot be satisfied in field conditions. Therefore, the methods used in anisotropy inversion based on these assumptions will lead to inaccurate results. The introduction of the amplitude ratio (AR), the ratio of slow to fast flexural waves, which is not dependent on the source type, can eliminate the wave-shape assumption. Two data sets from orthogonally oriented receivers can be constructed as a quaternion array. Fast and slow flexural waves are the two main incident waves, and other arrivals such as P-waves can be taken as noise. The AR and a quaternion multiple signal classification algorithm are used to demonstrate how to improve the anisotropic inversion and avoid these assumptions. Compared with the traditional method, the new method presents better inversion results for the synthetic example with two different sources. We have determined that the inversion residual from the new objective function can be used to indicate the inversion quality.

Vertical open fractures and shear‐wave velocities derived from VSPs, full waveform acoustic logs, and televiewer data

Geophysics ◽  
1993 ◽  
Vol 58 (6) ◽  
pp. 818-834 ◽  
Author(s):  
Frédéric Lefeuvre ◽  
Roger Turpening ◽  
Carol Caravana ◽  
Andrea Born ◽  
Laurence Nicoletis
Keyword(s):  
Shear Wave ◽  
Azimuthal Anisotropy ◽  
Stoneley Wave ◽  
Correlation Technique ◽  
Seismic Profiles ◽  
Vertical Seismic Profiles ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Full Waveform ◽  
Zero Offset

Fracture or stress‐related shear‐wave birefringence (or azimuthal anisotropy) from vertical seismic profiles (VSPs) is commonly observed today, but no attempt is made to fit the observations with observed in‐situ fractures and velocities. With data from a hard rock (limestones, dolomites, and anhydrites) region of Michigan, fast and slow shear‐wave velocities have been derived from a nine‐component zero offset VSP and compared to shear‐wave velocities from two full waveform acoustic logs. To represent the shear‐wave birefringence that affects the shear wave’s vertical propagation, a propagator matrix technique is used allowing a local measurement independent of the overburden layers. The picked times obtained by using a correlation technique have been corrected in the birefringent regions before we compute the fast and slow velocities. Although there are some differences between the three velocity sets, there is a good fit between the velocities from the shear‐wave VSP and those from the two logs. We suspect the formations showing birefringence to be vertically fractured. To support this, we examine the behavior of the Stoneley wave on the full waveform acoustic logs in the formations. In addition, we analyze the borehole televiewer data from a nearby well. There is a good fit between the fractures seen from the VSP data and those seen from the borehole.

Multipole logging in a formation with stress‐relief‐induced anisotropy

Geophysics ◽  
1994 ◽  
Vol 59 (12) ◽  
pp. 1806-1812 ◽  
Author(s):  
Lasse Renlie
Keyword(s):  
Fundamental Mode ◽  
Transverse Isotropy ◽  
Stress Relief ◽  
P Wave ◽  
Spectral Behavior ◽  
Full Waveform ◽  
Damaged Zone ◽  
Isotropic Elasticity ◽  
Full Waveforms ◽  
Tangential Directions

The stress relief associated with the drilling of a borehole may induce a mechanically damaged zone with radial transverse isotropy (RTI), where the properties in the radial direction differ from those in the axial and tangential directions. The effect of such a zone on multipole acoustic full‐waveform logging is investigated using a numerical model based on the frequency‐axial‐wavenumber method. Calculations of the spectral behavior show that the fundamental mode associated with the multipole source behaves the same way in an RTI zone as it does in a damaged zone with isotropic properties. In a slow virgin formation, calculations of full waveforms show that the presence of a damaged zone with RTI is more difficult to detect than a damaged zone with isotropic elasticity because the refracted P‐wave encounters an isotropic zone but not an RTI zone. The results indicate that a damaged zone with RTI, which is a precursor to destructive events such as borehole instability and sand production, can be detected only by analyzing the spectral behavior of the fundamental mode.

The deep roots of the western Pyrenees revealed by full waveform inversion of teleseismic P waves

Geology ◽  
2016 ◽  
Vol 44 (6) ◽  
pp. 475-478 ◽  
Author(s):  
Yi Wang ◽  
Sébastien Chevrot ◽  
Vadim Monteiller ◽  
Dimitri Komatitsch ◽  
Frédéric Mouthereau ◽  
...  
Keyword(s):  
Waveform Inversion ◽  
Full Waveform Inversion ◽  
Deep Roots ◽  
P Waves ◽  
Full Waveform ◽  
Western Pyrenees

scholarly journals Reflection and transmission of P-waves at a very rough interface between two isotropic elastic solids

2021 ◽  
Author(s):  
Pham Chi Vinh ◽  
Do Xuan Tung ◽  
Nguyen Thi Kieu
Keyword(s):  
Incident Wave ◽  
Elastic Layer ◽  
Incident Angle ◽  
P Wave ◽  
Rough Interface ◽  
Elastic Solids ◽  
P Waves ◽  
Reflection And Transmission ◽  
Reflected Waves ◽  
Transmission Coefficients

This paper deals with the reflection and transmission of P-waves at a very rough interface between two isotropic elastic solids. The interface is assumed to oscillate between two straight lines. By mean of homogenization, this problem is reduced to the reflection and transmission of P-waves through an inhomogeneous orthotropic elastic layer. It is shown that a P incident wave always creates two reflected waves (one P wave and one SV wave), however, there may exist two, one or no transmitted waves. Expressions in closed-form of the reflection and transmission coefficient have been derived using the transfer matrix of an orthotropic elastic layer. Some numerical examples are carried out to examine the reflection and transmission of P-waves at a very rough interface of tooth-comb type, tooth-saw type and sin type. It is found numerically that the reflection and transmission coefficients depend strongly on the incident angle, the incident wave frequency, the roughness and the type of interfaces.

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