Seismic Wave Attenuation
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Seismic Wave Attenuation
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Author : M. N. Toksöz
language : en
Publisher:
Release Date : 1981
Seismic Wave Attenuation written by M. N. Toksöz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1981 with Science categories.
"We have undertaken the editing of this volume to help the broad-range research effort gain a better understanding of attenuation and its applications to seismic exploration problems... We have emphasized the material most relevant to exploration geophysics. As a result, most of the papers compiled here deal with sedimentary rocks, the effects of fluids, and the pressure ranges encountered in shalow crustal layers."--Preface.
Seismic Wave Attenuation In Unconsolidated Sediments
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Author : Mohammed Badri
language : en
Publisher:
Release Date : 1985
Seismic Wave Attenuation In Unconsolidated Sediments written by Mohammed Badri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1985 with categories.
Seismic And Petro Physical Studies On Seismic Wave Attenuation
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Author : Wasiu Raji
language : en
Publisher:
Release Date : 2012
Seismic And Petro Physical Studies On Seismic Wave Attenuation written by Wasiu Raji and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Anelasticity and inhomogeneity in the Earth decreases the energy and modifies the frequency of seismic waves as they travel through the Earth. This phenomenon is known as seismic attenuation. The associated physical process leads to amplitude diminution, waveform distortion and phase delay. The level of attenuation a wave experiences depends on the degree of anelasticity and the scale of inhomgeneity in the rocks it passes through. Therefore, attenuation is sensitive to the presence of fluids, degree of saturation, porosity, fault, pressure, and the mineral content of the rocks. The work presented in this thesis covers attenuation measurements in seismic data; estimation of P- and S-wave attenuation in recorded well logs; attenuation analysis for pore fluid determination; and attenuation compensation in seismic data. Where applicable, a set of 3D seismic data or well logs recorded in the Gullfaks field, North Sea, Norway, is used to test the methods developed in the thesis. A new method for determining attenuation in reflection seismic data is presented. The inversion process comprises two key stages: computation of centroid frequency for the seismic signal corresponding to the top and base of the layer being investigated, using variable window length and fast Fourier transform; and estimation of the difference in centroid frequency and traveltime for the paired seismic signals. The use of a shape factor in the mathematical model allows several wavelet shapes to be used to represent a real seismic signal. When applied to synthetic data, results show that the method can provide reliable estimates of attenuation using any of the wavelet shapes commonly assumed for a real seismic signal. Tested against two published methods of quality factor (Q) measurement, the new method shows less sensitivity to interference from noise and change of frequency bandwidth. The method is also applied to seismic data recorded in the Gullfaks field. The trace length is divided into four intervals: AB, BC, CD, and DE. The mean attenuation (1/Q_m) calculated in intervals AB, BC, CD, and DE are 0.0196, 0.0573, 0.0389, and 0.0220, respectively. Results of attenuation measurements using the new method and the classical spectral ratio method (Bath 1974, Spencer et al, 1982) are in close agreement, and they show that interval BC and AB have the highest and lowest value of attenuation, respectively. One of the applications of Q measured in seismic records is its usage for attenuation compensation. To compensate for the effects of attenuation in recorded seismograms, I propose a Q-compensation algorithm using a recursive inverse Q-filtering scheme. The time varying inverse Q-filter has a Fourier integral representation in which the directions of the up-going and down-going waves are reversed. To overcome the instability problem of conventional inverse Q-filters, wave numbers are replaced with slownesses, and the compensation scheme is applied in a layer-by-layer recursive manner. When tested with synthetic and field seismograms, results show that the algorithm is appropriate for correcting energy dissipation and waveform distortion caused by attenuation. In comparison with the original seismograms, the Q-compensated seismograms show higher frequencies and amplitudes, and better resolved images of subsurface reflectors. Compressional and shear wave inverse quality factors (Q_P (-1) and Q_S (-1)) are estimated in the rocks penetrated by well A-10 of the Gullfaks field. The results indicate that the P-wave inverse quality factor is generally higher in hydrocarbon-saturated rocks than in brine-saturated rocks, but the S-wave inverse quality factor does not show a dependence on fluid content. The range of the ratio of Q_P (-1) to Q_S (-1) measured in gas, water and oil-saturated sands are 0.56 - 0.78, 0.39 - 0.55, and 0.35 - 0.41, respectively. A cross analysis of the ratio of P-wave to S-wave inverse quality factors, (Q_P (-1))/(Q_S (-1) ), with the ratio of P-wave to S-wave velocities, V_P/V_S , clearly distinguishes gas sand from water sand, and water sand from oil sand. Gas sand is characterised by the highest (Q_P (-1))/(Q_S (-1) ) and the lowest V_P/V_S ; oil sand is characterised by the lowest (Q_P (-1))/(Q_S (-1) ) and the highest V_P/V_S ; and water sand is characterized by the V_P/V_S and (Q_P (-1))/(Q_S (-1) ) values between those of the gas and oil sands. The signatures of the bulk modulus, Lame's first parameter, and the compressional modulus (a hybrid of bulk and shear modulus) show sensitivities to both the pore fluid and rock mineral matrix. These moduli provided a preliminary identification for rock intervals saturated with different fluids. Finally, the possibility of using attenuation measured in seismic data to monitor saturation in hydrocarbon reservoirs is studied using synthetic time-lapse seismograms, and a theoretical rock physics forward modelling approach. The theory of modulus-frequency-dispersion is applied to compute a theoretical curve that describes the dynamic effects of saturation on attenuation. The attenuation measured in synthetic time-lapse seismograms is input to the theoretical curve to invert the saturation that gave rise to the attenuation. Findings from the study show that attenuation measured in recorded seismograms can be used to monitor reservoir saturation, if a relationship between seismogram-derived attenuation and saturation is known. The study also shows that attenuation depends on other material properties of rocks. For the case studied, at a saturation of 0.7, a 10% reduction in porosity caused a 5.9% rise in attenuation, while a 10% reduction in the bulk modulus of the saturating fluids caused an 11% reduction in attenuation.
Scattering And Attenuations Of Seismic Waves Part I
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Author : AKI
language : en
Publisher: Birkhäuser
Release Date : 2013-12-18
Scattering And Attenuations Of Seismic Waves Part I written by AKI and has been published by Birkhäuser this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-12-18 with Science categories.
Reprint from Pure and Applied Geophysics (PAGEOPH), Volume 128 (1988), No. 1/2
Seismological Attenuation Without Q
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Author : Igor B. Morozov
language : en
Publisher: Trafford Publishing
Release Date : 2010-11
Seismological Attenuation Without Q written by Igor B. Morozov and has been published by Trafford Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-11 with Science categories.
Seismological Attenuation without Q represents a comprehensive and critical review of the present approach to describing the seismic-wave attenuation within the Earth. Starting from first physical principles, author Igor B. Morozov shows that the existing model of attenuation based on the concept of quality factor, or Q, is inadequate and represents only a phenomenological model. In most cases, Q should not be interpreted as a physical property of the Earth's medium. This text offers an alternate view developed using the concept of attenuation coefficient and illustrated using many theoretical and data examples. The new approach leads to significant advances in understanding the physics of Earth's anelasticity, measurement, and modeling attenuation of seismic waves. A systematic and hitherto unseen pattern of attenuation coefficients is recognized within a broad range of wave types and frequencies, which leads us to a general and clear picture of the attenuation structure of the Earth. At the same time, Morozov also elucidates a number of unsolved problems, such as numerical modeling and inversion for seismic attenuation and understanding its relation to the structure and the physical state of the deep Earth. Most notably, Seismological Attenuation without Q shows that the attenuation problem is significantly more complex than presented in the Q-based, visco-elastic model.
Scattering And Attenuation Of Seismic Waves Part Ii
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Author : WU
language : en
Publisher: Birkhäuser
Release Date : 2013-11-21
Scattering And Attenuation Of Seismic Waves Part Ii written by WU and has been published by Birkhäuser this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-11-21 with Science categories.
Reprint from Pure and Applied Geophysics (PAGEOPH), Volume 131 (1989), No. 4
Seismic Wave Attenuation In Eastern North America
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Author : I. N. Gupta
language : en
Publisher:
Release Date : 1989
Seismic Wave Attenuation In Eastern North America written by I. N. Gupta and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with Earth movements categories.
Seismic Wave Attenuation
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Author : Stanford University. Department of Geophysics
language : en
Publisher:
Release Date :
Seismic Wave Attenuation written by Stanford University. Department of Geophysics and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
Seismic Wave Propagation And Scattering In The Heterogenous Earth
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Author : Haruo Sato
language : en
Publisher: Springer Science & Business Media
Release Date : 2008-12-17
Seismic Wave Propagation And Scattering In The Heterogenous Earth written by Haruo Sato and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008-12-17 with Science categories.
Seismic waves – generated both by natural earthquakes and by man-made sources – have produced an enormous amount of information about the Earth's interior. In classical seismology, the Earth is modeled as a sequence of uniform horizontal layers (or sperical shells) having different elastic properties and one determines these properties from travel times and dispersion of seismic waves. The Earth, however, is not made of horizontally uniform layers, and classic seismic methods can take large-scale inhomogeneities into account. Smaller-scale irregularities, on the other hand, require other methods. Observations of continuous wave trains that follow classic direct S waves, known as coda waves, have shown that there are heterogeneities of random size scattered randomly throughout the layers of the classic seismic model. This book focuses on recent developments in the area of seismic wave propagation and scattering through the randomly heterogeneous structure of the Earth, with emphasis on the lithosphere. The presentation combines information from many sources to present a coherent introduction to the theory of scattering in acoustic and elastic materials and includes analyses of observations using the theoretical methods developed.
Seismic Wave Attenuation Characteristics From Pulse Experiments
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Author : Francis Collins
language : en
Publisher:
Release Date : 1956
Seismic Wave Attenuation Characteristics From Pulse Experiments written by Francis Collins and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1956 with Elasticity categories.