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Accurate simulations of pure-viscoacoustic wave propagation in tilted transversely isotropic media

Petroleum Science 2024年第2期21卷 866-884页

作者： Qiang Mao Jian-Ping Huang Xin-Ru Mu Ji-Dong Yang Yu-Jian Zhang Geosciences Department China University of Petroleum(East China)Qingdao266580ShandongChina Pilot National Laboratory for Marine Science and Technology(Qingdao) Qingdao266207ShandongChina

Forward modeling of seismic wave propagation is crucial for the realization of reverse time migration(RTM) and full waveform inversion(FWI) in attenuating transversely isotropic media. To describe the attenuation and anisotropy properties of subsurface media, the pure-viscoacoustic anisotropic wave equations are established for wavefield simulations, because they can provide clear and stable wavefields. However, due to the use of several approximations in deriving the wave equation and the introduction of a fractional Laplacian approximation in solving the derived equation, the wavefields simulated by the previous pure-viscoacoustic tilted transversely isotropic(TTI) wave equations has low accuracy. To accurately simulate wavefields in media with velocity anisotropy and attenuation anisotropy, we first derive a new pure-viscoacoustic TTI wave equation from the exact complex-valued dispersion formula in viscoelastic vertical transversely isotropic(VTI) media. Then, we present the hybrid finite-difference and low-rank decomposition(HFDLRD) method to accurately solve our proposed pure-viscoacoustic TTI wave equation. Theoretical analysis and numerical examples suggest that our pure-viscoacoustic TTI wave equation has higher accuracy than previous pure-viscoacoustic TTI wave equations in describing q P-wave kinematic and attenuation characteristics. Additionally, the numerical experiment in a simple two-layer model shows that the HFDLRD technique outperforms the hybrid finite-difference and pseudo-spectral(HFDPS) method in terms of accuracy of wavefield modeling.

关键词： Pure-viscoacoustic TTI wave equation Attenuation anisotropy seismic modeling Low-rank decomposition method

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Fractured reservoir modeling by discrete fracture network and seismic modeling in the Tarim Basin,China

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Petroleum Science 2011年第4期8卷 433-445页

作者： Sam Zandong Sun Zhou Xinyuan Yang Haijun Wang Yueying WangDi Liu Zhishui Laboratory for Integration of Geology ＆ Geophysics China University of Petroleum Beijing 102249 China Research Institute of Exploration ＆ Development PetroChina Tarim Oilfield Company Korla 841000 China

Fractured reservoirs are an important target for oil and gas exploration in the Tarim Basin and the prediction of this type of reservoir is challenging.Due to the complicated fracture system in the Tarim Basin,the conventional AVO inversion method based on HTI theory to predict fracture development will result in some errors.Thus,an integrated research concept for fractured reservoir prediction is put forward in this paper.seismic modeling plays a bridging role in this concept,and the establishment of an anisotropic fracture model by Discrete Fracture Network （DFN） is the key part.Because the fracture system in the Tarim Basin shows complex anisotropic characteristics,it is vital to build an effective anisotropic model.Based on geological,well logging and seismic data,an effective anisotropic model of complex fracture systems can be set up with the DFN method.The effective elastic coefficients,and the input data for seismic modeling can be calculated.Then seismic modeling based on this model is performed,and the seismic response characteristics are analyzed.The modeling results can be used in the following AVO inversion for fracture detection.

关键词： Fractured reservoir Discrete Fracture Network (DFN) equivalent medium seismic modeling azimuth-angle gathers

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Optimization of a precise integration method for seismic modeling based on graphic processing unit

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Earthquake Science 2010年第4期23卷 387-393页

作者： Jingyu Li Genyang Tang Tianyue Hu School of Earth and Space Sciences Peking University Beijing 100871 China Department of Earth Sciences Cambridge University Cambridge CB2 3EQ United Kingdom

General purpose graphic processing unit （GPU） calculation technology is gradually widely used in various fields. Its mode of single instruction, multiple threads is capable of seismic numerical simulation which has a huge quantity of data and calculation steps. In this study, we introduce a GPU-based parallel calculation method of a precise integration method （PIM） for seismic forward modeling. Compared with CPU single-core calculation, GPU parallel calculating perfectly keeps the features of PIM, which has small bandwidth, high accuracy and capability of modeling complex substructures, and GPU calculation brings high computational efficiency, which means that high-performing GPU parallel calculation can make seismic forward modeling closer to real seismic records.

关键词： precise integration method seismic modeling general purpose GPU graphic processing unit

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Amplitude Variation with Offset Responses modeling Study of Walkaway Vertical seismic Profile Data at CO_2 Geological Storage Site,Ketzin,Germany

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Acta Geologica Sinica(English Edition) 2011年第5期85卷 1118-1126页

作者： Sayed Hesammoddin KAZEMEINI Christopher JUHLIN Department of Earth Sciences Uppsala University

An important component of any CO_2 sequestration project is seismic monitoring for tracking changes in subsurface physical properties,such as velocity and density.Different reservoirs have different amplitude variation with offset(AVO) responses,which can define underground conditions. In the present paper we investigate walkaway vertical seismic profile(VSP) AVO response to CO_2 injection at the Ketzin site,the first European onshore CO_2 sequestration pilot study dealing with research on geological storage of CO_2.First,we performed rock physics analysis to evaluate the effect of injected CO_2 on seismic velocity using the Biot-Gassmann equation.On the basis of this model,the seismic response for different CO_2 injection saturation was studied using ray tracing modeling.We then created synthetic walkaway VSP data,which we then processed.In contrast,synthetic seismic traces were created from borehole data.Finally,we found that the amplitude of CO_2 injected sand layer with different gas saturations were increased with the offset when compared with the original brine target layer.This is the typical classⅢAVO anomaly for gas sand layer.The AVO responses matched the synthetic seismic traces very well.Therefore,walkaway VSP AVO response can monitor CO_2 distribution in the Ketzin area.

关键词： CO_2 injection rock physics amplitude variation with offset walkaway vertical seismic profile seismic modeling

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Analytical investigations of seismic responses for reinforced concrete bridge columns subjected to strong near-fault ground motion

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Earthquake Engineering and Engineering Vibration 2007年第3期6卷 237-244页

作者：苏进国宋裕祺张顺益黄昭勋 Dept.of Civil Engineering Taipei University of TechnologyChinese Taipei

Strong near-fault ground motion, usually caused by the fault-rupture and characterized by a pulse-like velocity- wave form, often causes dramatic instantaneous seismic energy （Jadhav and Jangid 2006）. Some reinforced concrete （RC） bridge columns, even those built according to ductile design principles, were damaged in the 1999 Chi-Chi earthquake. Thus, it is very important to evaluate the seismic response of a RC bridge column to improve its seismic design and prevent future damage. Nonlinear time history analysis using step-by-step integration is capable of tracing the dynamic response of a structure during the entire vibration period and is able to accommodate the pulsing wave form. However, the accuracy of the numerical results is very sensitive to the modeling of the nonlinear load-deformation relationship of the structural member. FEMA 273 and ATC-40 provide the modeling parameters for structural nonlinear analyses of RC beams and RC columns. They use three parameters to define the plastic rotation angles and a residual strength ratio to describe the nonlinear load- deformation relationship of an RC member. Structural nonlinear analyses are performed based on these parameters. This method provides a convenient way to obtain the nonlinear seismic responses of RC structures. However, the accuracy of the numerical solutions might be further improved. For this purpose, results from a previous study on modeling of the static pushover analyses for RC bridge columns （Sung et al. 2005） is adopted for the nonlinear time history analysis presented herein to evaluate the structural responses excited by a near-fault ground motion. To ensure the reliability of this approach, the numerical results were compared to experimental results. The results confirm that the proposed approach is valid.

关键词： bridge columns near-fault ground motion seismic modeling

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A scheme to treat the singularity in global seismic wavefield simulation using pseudospectral method with staggered grids

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Earthquake Science 2010年第2期23卷 121-127页

作者： Yanbin Wang Hiroshi Takenaka Department of Geophysics School of Earth and Space Sciences Peking University Beijing 100871 China Department of Earth and Planetary Sciences Kyushu University Hakozaki 6-10-1 Fukuoka 812-8581 Japan

The pseudospectral method has been applied to the simulation of seismic wave propagation in 2-D global Earth model. When a whole Earth model is considered, the center of the Earth is included in the model and then singularity arises at the center of the Earth where r=0 since the 1/r term appears in the wave equations. In this paper, we extended the global seismic wavefield simulation algorithm for regular grid mesh to staggered grid configuration and developed a scheme to solve the numerical problems associated with the above singularity for a 2-D global Earth model defined on staggered grid using pseudospectral method. This scheme uses a coordinate transformation at the center of the model, in which the field variables at the center are calculated in Cartesian coordinates from the values on the grids around the center. It allows wave propagation through the center and hence the wavefield at the center can be stably calculated. Validity and accuracy of the scheme was tested by compared with the discrete wavenumber method. This scheme could also be suitable for other numerical methods or models parameterized in cylindrical or spherical coordinates when singularity arises at the center of the model.

关键词： seismic modeling wave propagation whole Earth pseudospectrai method staggered grid

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A multisymplectic pseudospectral method for seismic modeling

A multisymplectic pseudospectral method for seismic modeling

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中国科学院地质与地球物理研究所2007学术年会

作者： Jing-Bo Chen Institute of Geology and Geophysics,Chinese Academy of Sciences, P.O.Box 9825,Beijing 100029,China

seismic modeling is a foundation of geophysical date processing.A multisymplectic pseudospectral method for seismic modeling is presented in this paper.This method takes the multisymplectic structure of the scalar wave equation into account and possesses discrete multisymplectic conservation laws.Numerical experiments demonstrate the remarkable capability of this new method for long-time simulations.

关键词： seismic modeling Multisymplectic Pseudospectral discretization

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High-Frequency Rayleigh-Wave Method

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Journal of China University of Geosciences 2009年第3期20卷 563-579页

作者： Richard D Miller 徐义贤罗银河陈超刘江平 Julian Ivanov Kansas Geological Survey The University of KansasLawrence KS 66047 USA Institute of Geophysics and Geomatics China University of Geosciences Kansas Geological Survey The University of Kansas

High-frequency （〉2 Hz） Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear （S）-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave （MASW） method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor （Q）, can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model （S-wave velocity or Q） obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeUng high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution.

关键词： Rayleigh wave dispersion high mode mode separation seismic modeling model appraisal.

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modeling the scalar wave equation with Nystrom methods

Modeling the scalar wave equation with Nystrom methods

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中国科学院地质与地球物理研究所2006学术年会

作者： Jing-Bo Chen Chinese Academy of Sciences,Institute of Geology and Geophysics,P.O.Box 9825,Beijing 100029,China.

High-accuracy numerical schemes for modeling of the scalar wave equation based on Nystrom methods are developed in this paper.Space is discretized by using the pseudospectral algorithm.For the time discretization,Nystrom methods are used.Afourth-order symplectic Nystrom method with pseudospectral spatial discretization is presented.This scheme is compared with a commonly used secondorder scheme and a fourth-order nonsymplectic Nystrom method. For a typical time-step size,the second-order scheme exhibits spatial dispersion errors for long-time simulations,while both fourth-order schemes do not suffer from these errors.Numerical comparisons show that the fourth-order symplectic algorithm is more accurate than the fourth-order nonsymplectic one.The capability of the symplectic Nystrom method in approximately preserving the discrete energy for long-time simulations is also demonstrated.

关键词： seismic modeling Nystrom method symplectic

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