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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

Petrophysical parameters inversion for heavy oil reservoir based on a laboratory-calibrated frequency-variant rock-physics model

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Petroleum Science 2023年第6期20卷 3400-3410页

作者： Xu Han Shang-Xu Wang Zheng-Yu-Cheng Zhang Hao-Jie Liu Guo-Hua Wei Gen-Yang Tang CNPC Key Laboratory of Geophysical Prospecting China University of Petroleum(Beijing)Beijing102249China Engineering Research Center of the Ministry of Education for Exploration and Development of Complex Oil and Gas Reservoirs China University of Petroleum(Beijing)Beijing102249China Shengli Oilfield Geophysical Exploration Research Institute SinopecDongying257000ShandongChina

Heavy oil has high density and viscosity, and exhibits viscoelasticity. Gassmann's theory is not suitable for materials saturated with viscoelastic fluids. Directly applying such model leads to unreliable results for seismic inversion of heavy oil reservoir. To describe the viscoelastic behavior of heavy oil, we modeled the elastic properties of heavy oil with varying viscosity and frequency using the Cole-Cole-Maxwell (CCM) model. Then, we used a CCoherent Potential Approximation (CPA) instead of the Gassmann equations to account for the fluid effect, by extending the single-phase fluid condition to two-phase fluid (heavy oil and water) condition, so that partial saturation of heavy oil can be considered. This rock physics model establishes the relationship between the elastic modulus of reservoir rock and viscosity, frequency and saturation. The viscosity of the heavy oil and the elastic moduli and porosity of typical reservoir rock samples were measured in laboratory, which were used for calibration of the rock physics model. The well-calibrated frequency-variant CPA model was applied to the prediction of the P- and S-wave velocities in the seismic frequency range (1–100 Hz) and the inversion of petrophysical parameters for a heavy oil reservoir. The pre-stack inversion results of elastic parameters are improved compared with those results using the CPA model in the sonic logging frequency (∼10 kHz), or conventional rock physics model such as the Xu-Payne model. In addition, the inversion of the porosity of the reservoir was conducted with the simulated annealing method, and the result fits reasonably well with the logging curve and depicts the location of the heavy oil reservoir on the time slice. The application of the laboratory-calibrated CPA model provides better results with the velocity dispersion correction, suggesting the important role of accurate frequency dependent rock physics models in the seismic prediction of heavy oil reservoirs.

关键词： Heavy oil Rock physics velocity dispersion Pre-stack inversion Reservoir prediction

velocity field of wave-induced local fluid flow in double-porosity media

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Science China(Physics,Mechanics & Astronomy) 2014年第6期57卷 1020-1030页

作者： BA Jing ZHANG Lin SUN WeiTao HAO ZhaoBing Geophysical Department Research Institute of Petroleum Exploration and Development School of Geosciences China University of Petroleum (Eastern China) Zhou Pei-Yuan Center for Applied Mathematics Tsinghua University Key Laboratory of Integrative Researches on Geophysics for Petroleum Institute of Geology and GeophysicsChinese Academy of Sciences

Under the excitation of elastic waves,local fluid flow in a complex porous medium is a major cause for wave dispersion and *** the local fluid flow process is simulated with wave propagation equations in the double-porosity medium,two porous skeletons are usually assumed,namely,host and *** them,the volume ratio of inclusion skeletons is *** previous studies have ignored the consideration of local fluid flow velocity field in inclusions,and therefore they can not completely describe the physical process of local flow oscillation and should not be applied to the situation where the fluid kinetic energy in inclusions cannot be *** this paper,we analyze the local fluid flow velocity fields inside and outside the inclusion,rewrite the kinetic energy function and dissipation function based on the double-porosity medium model containing spherical inclusions,and derive the reformulated Biot-Rayleigh(BR)equations of elastic wave propagation based on Hamilton’s *** present simulation examples with different rock and fluid *** between BR equations and reformulated BR equations show that there are significant differences in wave response ***,we compare the reformulated BR equations with the previous theories and experimental data,and the results show that the theoretical results of this paper are correct and effective.

关键词： double-porosity medium elastic wave propagation local fluid flow velocity dispersion Biot-Rayleigh equations petro-physical experiment

Numerical simulation of seismic low-frequency shadows and its application

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Applied Geophysics 2008年第4期5卷 301-306页

作者：贺振华熊晓军边立恩成都理工大学成都610059

Strong low-frequency energy beneath a hydrocarbon reservoir is called a seismic low-frequency shadow and can be used as a hydrocarbon indicator （Tarter et al., 1979） bu the physical mechanism of the observed low-frequency shadow is still unclear. To stud） the mechanism, we performed seismic numerical simulation of geological models with a hydrocarbon-bearing zone using the 2-D diffusive-viscous wave equation which car effectively model the characteristics of velocity dispersion and transform the seismic dat~ centered in a target layer slice within a time window to the time-frequency domain by usinl time-frequency signal analysis and sort the frequency gathers to common frequency cubes. Then, we observe the characteristics of the seismic low-frequency shadow in the common frequency cubes. The numerical simulations reveal that the main mechanism of seismic lowfrequency shadows is attributed to high attenuation of the medium to high seismic frequency components caused by absorption in the hydrocarbon-filled reservoir. Results from a practical example of seismic low-frequency shadows show that it is possible to identify the reservoir by the low-frequency shadow with high S/N seismic data.

关键词： seismic low-frequency shadow numerical simulation diffusive-viscous waveequation velocity dispersion reservoir identification

Experimental study on the multiscale scattering of high-velocity heterogeneous bodies

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Applied Geophysics 2022年第1期19卷 1-10,143页

作者： Qin Zhen-Chao Wei Jian-Xin Di Bang-Rang Wang Di State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing 102249China CNPC Key Laboratory of Geophysical Exploration China University of Petroleum(Beijing)Beijing 102249China.

There are complex heterogeneous entities in the underground medium,and the heterogeneous scale has a substantial impact on wave *** this study,we used a set of 11 samples of glass beads as high-velocity heterogeneous bodies to evaluate the impact of such heterogeneous bodies on the propagation of *** vary the heterogeneous scale by changing the diameter of the glass beads from 0.18 to 11 mm while keeping the same volume proportion(10%)of the beads for the set of 11 *** pulse transmission method was used to record measurements at the ultrasonic frequencies of 0.34,0.61,and 0.84 MHz in the homogeneous *** relationship between P-wave fi eld features and heterogeneity scale,P-wave velocity,and the multiple of the wave number and heterogeneous scale(ka)was observed in the laboratory,which has sparked widespread interest and *** scale affects P-wave propagation,and its wave field changes are *** waveform,amplitude,and velocity of the recorded P-waves correlate with the heterogeneous *** the forward scattering while large-scale heterogeneities,noticeable direct and diff racted waves are observed in the laboratory,which indicates that the infl uence of direct and diff racted waves cannot be ignored for large-scale *** relationship between velocity and ka shows frequency dependence;the reason is that the magnitude of change in velocity caused by wave number is diff erent from that caused by heterogeneous *** to the change in the recorded waveform,amplitude variation,or the relationship between the velocity measured at diff erent frequencies and the heterogeneous scale,the identifi ed turning points of the ray approximation are all around ka=*** ka is less than 1,the velocity changes slowly and gradually approaches the eff ective medium *** ray velocity measured for heterogeneous media with large velocity perturbations in the laboratory is signifi cantly smaller than the

关键词： heterogeneous bodies multiscale scattering velocity dispersion pulse transmission method

Dynamic fluid transport property of hydraulic fractures and its evaluation using acoustic logging

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Petroleum Exploration and Development 2022年第1期49卷 223-232页

作者： LI Huanran TANG Xiaoming LI Shengqing SU Yuanda China University of Petroleum(East China) Qingdao 266580China Key Laboratory of Deep Oil and Gas China University of Petroleum(East China)Qingdao 266580China

The existing acoustic logging methods for evaluating the hydraulic fracturing effectiveness usually use the fracture density to evaluate the fracture volume, and the results often cannot accurately reflect the actual productivity. This paper studies the dynamic fluid flow through hydraulic fractures and its effect on borehole acoustic waves. Firstly, based on the fractal characteristics of fractures observed in hydraulic fracturing experiments, a permeability model of complex fracture network is established. Combining the dynamic fluid flow response of the model with the Biot-Rosenbaum theory that describes the acoustic wave propagation in permeable formations, the influence of hydraulic fractures on the velocity dispersion of borehole Stoneley-wave is then calculated and analyzed, whereby a novel hydraulic fracture fluid transport property evaluation method is proposed. The results show that the Stoneley-wave velocity dispersion characteristics caused by complex fractures can be equivalent to those of the plane fracture model, provided that the average permeability of the complex fracture model is equal to the permeability of the plane fracture. In addition, for fractures under high-permeability(fracture width 10~100 μm, permeability ~100 μm^(2)) and reduced permeability(1~10 μm, ~10 μm^(2), as in fracture closure) conditions, the Stoneley-wave velocity dispersion characteristics are significantly different. The field application shows that this fluid transport property evaluation method is practical to assess the permeability and the connectivity of hydraulic fractures.

关键词： hydraulic fracture dynamic fluid transport property acoustic logging Stoneley-wave velocity dispersion fracture characterization

Viscoelastic characteristics of low-frequency seismic wave attenuation in porous media

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Applied Geophysics 2014年第4期11卷 355-363,508页

作者：凌云韩立国张益明吉林大学地球探测科学与技术学院长春130026 中海石油研究中心北京100027

Mesoscopic fluid flow is the major cause of wave attenuation and velocity dispersion at seismic frequencies in porous rocks. The Johnson model provides solutions for the frequency-dependent quality factor and phase velocity in partially saturated porous media with pore patches of arbitrary shapes. We use the Johnson model to derive approximations for the quality factor Q at the high and low frequency limit, and obtain the approximate equation for Qmin based on geophysical and geometric parameters. A more accurate equation for Qmin is obtained after correcting for the linear errors between the exact and approximate Q values. The complexity of the pore patch shape affects the maximum attenuation of Qmin and the transition frequency ftr; furthermore, the effect on ftr is stronger than that on Qmin. Numerical solutions to Biot’s equation are computationally intensive; thus, we build an equivalent viscoelastic model on the basis of the Zener model, which well approximates the wave attenuation and dispersion in porous rocks in the seismic band.

关键词： Mesoscopic scale johnson model attenuation velocity dispersion zener model

Formation and Evolution of Galaxies: Starlight Synthesis Algorithm

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International Journal of Astronomy and Astrophysics 2022年第1期12卷 68-93页

作者： Nick Barua Swift Xi Inc. Kobe City Japan

This study will see the resurgence of interest in precise velocity dispersion measurements, both for the study of galactic and active nuclei kinematics. As several works suggest, an excellent tactic to measure σ is to use the absorption lines of the calcium triplet, as it is a spectral region relatively free from complications. The discovery of an empirical relationship between the mass of the central black hole (M•) and σ was the leading guide of my detailed study of the calcium triplet region. This search for more accurate methods to calculate the dispersion of velocities, in addition to the careful study of uncertainties. After investing so much time in the development and improvement of the method and its application to so many galaxies, it is time to reap the rewards of this effort, using my results to address a series of questions concerning the physics of galaxies.

关键词： Galaxies Physics Nuclei Kinematics Galactic Nuclei Active Nuclei velocity dispersion