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seismic attenuation and Velocity Dispersion to Discriminate Gas Hydrates and Free Gas Zone, Makran Offshore, Pakistan

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International Journal of Geosciences 2016年第8期7卷 1020-1028页

作者： Muhammad Irfan Ehsan Perveiz Khalid Nisar Ahmed Jiachun You Xuewei Liu Tahir Azeem School of Geophysics and Information Technology China University of Geosciences (Beijing) Beijing China Institute of Geology University of the Punjab Lahore Pakistan

Gas hydrates gained a remarkable attention as an unconventional energy resource recently. In order to interpret gas hydrates (part of fluid) and free gas saturated zone accurately, it is essential to implement new technique related to seismic attenuation and velocity dispersion. P wave attenuation and velocity dispersion in porous media made promising imprints for exploration of gas hydrates. The most prominent phenomenon for attenuation and velocity dispersion in porous media is wave induced fluid flow in which wave inhomogeneities are larger than pore size but smaller than wavelength. Numerical simulation technique is applied to analyze frequency dependent velocity dispersion and attenuation in gas hydrates and free gas layer in Makran offshore of Pakistan. Homogeneous and patchy distribution patterns of gas hydrates and free gas within pore spaces of host sediments at lower and higher frequency regime are considered. It is noted that the attenuation and velocity dispersion increase with the increase in gas hydrates saturation. The maximum attenuation is observed at 66% saturation of gas hydrates in the area under investigation. However, in case of water and gas mixture the maximum attenuation and velocity dispersion occur at low gas saturation (~15%). Therefore, based on our numerical simulation, velocity dispersion and attenuation can be used as seismic attributes to differentiate various gas saturations and gas hydrates saturation for Makran offshore area of Pakistan.

关键词： Gas Hydrates seismic attenuation Velocity Dispersion Makran Offshore seismic Attributes

Wigner-Ville distribution and its application in seismic attenuation estimation

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Applied Geophysics 2007年第4期4卷 245-254页

作者：李艳东郑晓东中国石油勘探开发研究院物探技术所北京100083

The attenuation of seismic signals is often characterized in the frequency domain using statistical measures of the power spectrum. However, the conventional Fourier transform-based power spectrum estimation methods suffer from time-frequency resolution problems. Wigner-Ville distribution, which is a member of Cohen class time-frequency distributions, possesses many appealing properties, such as time-frequency marginal distribution, time-frequency localization, etc. Therefore, Wigner-Ville distribution offers a new way for estimating the attenuation of seismic signals. This paper initially gives a brief introduction to Wigner-Ville distribution and the smoothed Wigner-Ville distribution that is effective in reducing the cross-term effect, and then presents a method for seismic attenuation estimation based on the instantaneous energy spectrum of the Wigner-Ville distribution. A real data example from central Tarim Basin in western China is presented to illustrate the effectiveness of the proposed method. The results show that the Wigner-Ville distribution-based seismic attenuation estimation method can effectively detect the difference between reef, shoal and lagoon facies by their attenuation properties, indicating that the estimated seismic attenuation can be used for reef and shoal carbonate reservoir characterization.

关键词： Wigner-Ville distribution time-frequency analysis seismic attenuation reservoir characterization

Physical mechanism of seismic attenuation in a two-phase medium

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Applied Geophysics 2008年第1期5卷 9-17页

作者：李子顺大庆油田勘探开发研究院大庆163712

High-frequency seismic attenuation is conventionally attributed to anelastic absorption. In this paper, I present three studies on high-frequency seismic attenuation and propose that the physical mechanism results from the interference of elastic microscopic multiple scattering waves. First, I propose a new theory on wave propagation in a two-phase medium which is based on the concept that the basic unit for wave propagation is a nano- mass point. As a result of the elasticity variations of pore fluid and rock framework, micro multiple scattering waves would emerge at the wavelength of the seismic waves passing through the two-phase medium and their interference and overlap would generate high- frequency seismic attenuation. Second, I present a study of the frequency response of seismic transmitted waves by modeling thin-layers with thicknesses no larger than pore diameters. Results indicate that high-frequency seismic waves attenuate slightly in a near-surface water zone but decay significantly in a near-surface gas zone. Third, I analyze the seismic attenuation characteristics in near-surface water and gas zones using dual-well shots in the Songliao Basin, and demonstrate that the high-frequency seismic waves attenuate slightly in water zones but in gas zones the 160-1600 Hz propagating waves decay significantly. The seismic attenuation characteristics from field observations coincide with the modeling results. Conclusions drawn from these studies theoretically support seismic attenuation recovery.

关键词： two-phase medium seismic attenuation nanometer wave propagation theory multiple scattering waves.

Performance assessment of genetic programming(GP)and minimax probability machine regression(MPMR)for prediction of seismic ultrasonic attenuation

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Earthquake Science 2013年第2期26卷 147-150页

作者： Manoj Kumar Manav Mittal Pijush Samui National Institute of Rock Mechanics Kolar Gold Fields 563117 Karnataka India School of Mechanical and Building Science VIT University Centre for Disaster Mitigation and Management VIT University

The determination of seismic attenuation （s）（dB/cm） is a challenging task in earthquake science. This article employs genetic programming （GP） and minimax probability machine regression （MPMR） for prediction of s. GP is developed based on genetic algo- rithm. MPMR maximizes the minimum probability of future predictions being within some bound of the true regression function. Porosity （n）（%）, permeability （k）（millidarcy）, grain size （d）（μm）, and clay content （c）（%） have been considered as inputs of GP and MPMR. The output of GP and MPMR is s. The developed GP gives an equation for prediction of s. The results of GP and MPMR have been compared with the artificial neural net- work. This article gives robust models based on GP and MPMR for prediction of s.

关键词： seismic attenuation Geneticprogramming Minimax probability machineregression Artificial neural network Prediction

Stable attenuation-compensated reverse time migration and its application to land seismic data

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Petroleum Science 2023年第5期20卷 2784-2795页

作者： Xin-Ru Mu Qiang Mao Jian-Ping Huang Geosciences Department China University of Petroleum(East China)QingdaoShandong266580China Pilot National Laboratory for Marine Science and Technology(Qingdao) QingdaoShandong266000China

Intrinsic attenuation of the earth causes energy loss and phase distortion in seismic wave *** obtain high-resolution imaging results,these negative effects must be considered during reverse time migration(RTM).We can easily implement attenuation-compensated RTM using the constant Q viscoacoustic wave equation with decoupled amplitude attenuation and phase dispersion ***,the nonphysical amplitude-compensation process will inevitably amplify the high-frequency noise in the wavefield in an exponential form,causing the numerical simulation to become *** is due to the fact that the amplitude of the compensation grows exponentially with *** order to achieve stable attenuation-compensated RTM,we modify the analytic expression of the attenuation compensation extrapolation operator and make it only compensate for amplitude loss within the effective frequency *** on this modified analytic formula,we then derive an explicit time-space domain attenuation compensation extrapolation ***,the implementation procedure of stable attenuation-compensated RTM is *** addition to being simple to implement,the newly proposed attenuation-compensated extrapolation operator is superior to the conventional low-pass filter in suppressing random noise,which will further improve the imaging *** use two synthetic and one land seismic datasets to verify the stability and effectiveness of the proposed attenuationcompensated RTM in improving imaging resolution in viscous media.

关键词： seismic attenuation Reverse time migration Stability strategy Pseudospectral method

Improve Q estimates with spectrum correction based on seismic wavelet estimation

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Applied Geophysics 2010年第3期7卷 217-228,292页

作者：屠宁陆文凯清华大学自动化系

Characterization of seismic attenuation,quantified by Q,is desirable for seismic processing and *** seismic reflection data,the coupling between seismic wavelets and the reflectivity sequences hinders their usage for Q *** the influence of the reflectivity sequences in reflection data is called spectrum correction. In this paper,we propose a spectrum correction method for Q estimation based on wavelet estimation and then design an inverse Q *** method uses higher-order statistics of reflection seismic data for wavelet estimation,the estimated wavelet is then used for spectral *** Q estimation methods are used here,namely the spectral-ratio and centroid frequency shift *** test the characteristics of both Q estimation methods under different parameters through a synthetic data *** and real data examples have shown that reliable Q estimates can be obtained after spectrum correction;moreover, high frequency components are effectively recovered after inverse Q filtering.

关键词： seismic attenuation seismic wavelet quality factor inverse Q filter

Energy Dissipation of P- and S-Waves in Fluid-Saturated Rocks: An Overview Focusing on Hydraulically Connected Fractures

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Journal of Earth Science 2015年第6期26卷 785-790页

作者： J.German Rubino Beatriz Quintal Tobias M.Muller Luis Guarracino Ralf Janicke Holger Steeb Klaus Holliger Applied and Environmental Geophysics Group Institute of Earth Sciences University of Lausanne Energy Flagship Commonwealth Scientific and Industrial Research Organization CONICET Facultad de Ciencias Astronomicasy Geofisicas Universidad Nacional de La Plata Institute of Mechanics University of Bochum

An important characteristic of fractured rocks is their high seismic attenuation, which so far has been mainly attributed to wave-induced fluid flow（WIFF） between the fractures and the embedding matrix. The influence of fracture connectivity on seismic attenuation has, however, recently, only been investigated. Numerical compressibility and shear tests based on Biot＇s quasi-static poro-elastic equations illustrate that an important manifestation of WIFF arises in the presence of fracture connectivity. The corresponding energy loss, which can be significant for both P- and S-waves, is mainly due to fluid flow within the connected fractures and is sensitive to the permeabilities as well as the lengths and intersection angles of the fractures. Correspondingly, this phenomenon contains valuable information on the governing hydraulic properties of fractured rocks and hence should be accounted for whenever realistic seismic models of such media are needed.

关键词： fractured rocks seismic attenuation WIFF fracture connectivity embedding matrix Biot’s theory

An application of matching pursuit time-frequency decomposition method using multi-wavelet dictionaries

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Petroleum Science 2012年第3期9卷 310-316页

作者： Zhao Tianzi Song Wei Library of China University of Petroleum Beijing 102249China CNPC Key Laboratory of Geophysical Exploration China University of PetroleumBeijing 102249China

In the time-frequency analysis of seismic signals, the matching pursuit algorithm is an effective tool for non-stationary signals, and has high time-frequency resolution and a transient structure with local self-adaption. We expand the time-frequency dictionary library with Ricker, Morlet, and mixed phase seismic wavelets, to make the method more suitable for seismic signal time-frequency decomposition. In this paper, we demonstrated the algorithm theory using synthetic seismic data, and tested the method using synthetic data with 25% noise. We compared the matching pursuit results of the time-frequency dictionaries. The results indicated that the dictionary which matched the signal characteristics better would obtain better results, and can reflect the information of seismic data effectively.

关键词： Matching pursuit seismic attenuation wavelet transform Wigner Ville distribution time- frequency dictionary

Crustal Lg attenuation within the North China Craton and its surrounding regions

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Crustal Lg attenuation within the North China Craton and its...