气层在纵波和转换波谱分解中的特征

应用拟合追逐分解MPD(Matching pursuit decomposition)法对地震数据进行谱分解能够提供更好的分辨率,在时间分辨率和频率分辨率上到达一致,避免付氏变换方法中时窗大小选择和分析时间点不准确的问题。含气地层对纵波资料产生较大的频率衰减,在储层下方可能见到低频强振幅的低频阴影现象。而转换波资料受气藏影响小,在转换波剖面中不会出现同纵波类似的低频阴影区。因此,综合两种资料在分频剖面上的表现,可以进行含气性异常的预测。对已知气藏的实际多波地震资料,进行MPD分频处理,在不同波场的分频剖面上,分析气层响应特征。     

地震低频伴影的数值模拟与应用

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.     

Numerical simulation of frequency-dependent seismic response and gas reservoir delineation in turbidites: A case study from China

To simulate the frequency-dependent response of turbidite reservoirs in the JZ Area, near the Bohai Sea, China, we apply a diffusive and viscous wave equation (DVWE), which takes into account diffusive and viscous attenuation and velocity dispersion in fluid-bearing poroelastic media. We use a seismic data-driven geological model building approach to produce physical parameter sections, which are then used to numerically synthesize the frequency-dependent seismic response in the DVWE-based simulation. The DVWE-based synthetic section shows the characteristic reflection and geometry of turbidites and delineates the phase delay, instantaneous dominant frequency decrease and magnitude attenuation related to the gas-bearing reservoir. The common frequency sections obtained by instantaneous spectral decomposition of the synthetic section show that a low-frequency shadow (LFS) lies immediately beneath the reservoir. Next, following the implications of the numerical simulation, we then apply LFS and fluid mobility to the data volume. Both hydrocarbon indicators clearly delineate the bright gas reservoir and its spatial distribution. The workflow and methodologies can be expected to be applicable to other frequency-dependent hydrocarbon indicators.     

基于吸收衰减补偿的多分量高斯束逆时偏移

高斯束逆时偏移结合了射线类偏移的高计算效率和波动方程逆时偏移的高精度,能很好地处理焦散点、大倾角成像问题,并且具有面向目标成像的能力.多分量地震资料的偏移技术可以对地下复杂构造进行更准确的成像,由于实际地下介质具有黏滞性,研究黏弹性叠前逆时偏移具有一定的现实意义.本文采用高斯束逆时偏移方法对多分量地震数据进行吸收衰减补偿,首先分别给出纵波和转换波共炮域高斯束叠前逆时偏移方法原理,在此基础上推导补偿吸收衰减的表达式,校正Q引起的振幅衰减和相位畸变,实现基于吸收衰减补偿的多分量高斯束叠前逆时偏移.数值模型的测试结果显示,在考虑地下介质的黏滞性时,本文方法具有更高的成像分辨率.     

基于改进的广义S变换的低频吸收衰减梯度检测

本文利用一种改进的广义S变换对地震波进行时频分解,求取地震波低频段时频谱的吸收衰减梯度,并与利用传统的广义S变换得到的高频段及低频段的吸收衰减梯度进行对比,以期更好地指示油气.理论推导、数值模拟及实际应用结果表明:基于改进的广义S变换的低频吸收衰减梯度可与传统的广义S变换得到的高频吸收衰减梯度相互佐证,更好指示油气.     

转换波Kirchhoff叠前时间偏移的成像优化方案

叠前时间偏移是转换波数据处理流程中的重要技术环节.由于下行P波和上行S波对应着不同类型的传播速度和传播机理,使得转换波偏移的诸多实施环节和实现技巧均有别于常规的纵波偏移.本文就VTI介质转换波Kirchhoff叠前时间偏移实现过程中的几个关键技术环节进行研究分析,并给出了相应的实施方案.首先,依据常速假设推导了简化的转换波时间偏移振幅加权函数,在保证偏移的高效计算的同时,兼顾了成像振幅的准确性;其次,依据直射线近似假设,推导了转换波偏移的最大无假频频率计算公式,确保了算子假频的有效滤除;接下来,设计使用了依据共转换点对称的偏移孔径,保证了偏移孔径的优化选取.此外,本文还提出利用三次卷积插值进行成像网格上参数值的插值运算,以避免传统线性插值算法的非平滑性对偏移剖面中高频信息的不良影响.多个算例的应用效果证明,本文所给出的关键技术环节的实施方案可以有效的提升转换波叠前时间偏移的成像效果.     

时频域油气储层低频阴影检测

为了准确刻画地震信号的局部层次结构,实现高效率的三维地震资料瞬时谱分解,检测油气储层的低频阴影,构造了广义S变换.广义S变换通过引入两个参数,改造S变换的小波函数,使其小波能根据信号处理的具体应用需要而调整.模型信号的仿真发现,广义S变换具有更加优越和灵活可调的时频聚集性能.文中分析了低频阴影的机理,并利用广义S变换对三维实际地震资料进行了瞬时谱分解,它不仅能检测油气储层的低频阴影,而且可以刻画油气储层的岩性边界和空间展布,减小油气储层检测的多解性.     

地震复谱分解技术及其在烃类检测中的应用

谱分解技术在地震解释领域已得到广泛应用,但常用的谱分解方法存在两方面的不足.一是时间分辨率低,难以对薄层进行刻画;二是在烃类检测中多解性强,难以区分流体类型.为了改善该问题,本文提出一种基于地震复谱分解技术的烃类检测方法.复谱分解是指用一个包含多个不同频率Ricker子波的复子波库对地震道进行分解,从而得到时变子波频率和相位信息的过程.借助稀疏反演技术复谱分解可以获得高分辨率的时频能量谱和时频相位谱.本文首先通过拟合算例验证了复谱分解方法刻画薄层的能力以及求取子波频率和相位的准确性.然后利用基于Kelvin-Voigt模型的黏弹波动方程数值模拟对衰减引起子波相位改变的原因进行了分析.最后通过实际资料应用展示了本文方法在储层预测中的高时间分辨率优势,验证了利用子波相位信息识别气藏的有效性.     

基于稀疏约束反演谱分解的频变AVO储层识别方法

时频分析技术是描述和分析非平稳信号的有效工具,如何提高谱分解的时-频分辨率受到了国内外学者的广泛关注.基于稀疏约束反演的谱分解方法(ISD)是近些年提出的一种具有高时-频分辨率的谱分解方法.然而传统ISD方法采用复雷克子波作为母小波函数,很大程度限制了信号分析的分辨率和精度.本文创新性地将传统ISD方法拓展到其他线性变换当中,提高了ISD方法的适用性.利用合成数据测试并对比了传统方法与ISD方法的时频分析结果,研究表明ISD方法不但能提供高分辨率的振幅谱,还能提供可靠的时-频相位谱信息.在此基础上,本文提出将高时-频分辨率的ISD方法与频变AVO(FAVO)反演相结合,得到能指示流体的地震波频散属性.将该方法应用于实际资料,结果表明基于ISD时频方法的FAVO反演结果具有更高的分辨率和准确度,对于储层油气具有更好的指示作用.     

Bayesian Markov chain Monte Carlo inversion for anisotropy of PP- and PS-wave in weakly anisotropic and heterogeneous media

A single set of vertically aligned cracks embedded in a purely isotropic background may be considered as a long-wavelength effective transversely isotropy (HTI) medium with a horizontal symmetry axis. The crack-induced HTI anisotropy can be characterized by the weakly anisotropic parameters introduced by Thomsen. The seismic scattering theory can be utilized for the inversion for the anisotropic parameters in weakly anisotropic and heterogeneous HTI media. Based on the seismic scattering theory, we first derived the linearized PP- and PS-wave reflection coefficients in terms of P- and S-wave impedances, density as well as three anisotropic parameters in HTI media. Then, we proposed a novel Bayesian Markov chain Monte Carlo inversion method of PP- and PS-wave for six elastic and anisotropic parameters directly. Tests on synthetic azimuthal seismic data contaminated by random errors demonstrated that this method appears more accurate, anti-noise and stable owing to the usage of the constrained PS-wave compared with the standards inversion scheme taking only the PP-wave into account.     

高精度频率衰减分析技术及其应用(英文)

本文从含流体孔隙介质中的地震波场的衰减理论出发,对常规的频率衰减分析技术中的"低频阴影"和"频率衰减梯度"分析方法进行了改进,提出了一种高精度的频率衰减分析技术。首先,通过引入三参数小波变换和时频聚焦准则,发展了一种基于自适应三参数小波变换的高精度时频分析方法,其不仅具有很高的时—频分辨率(有利于"低频阴影"分析),而且其频谱只有一个峰,旁瓣比较小(有利于"频率衰减梯度"分析)。其次,采用基于最小二乘法的Nelder-Mead非线性算法对频谱的衰减部分进行拟合计算,可以准确地计算衰减系数,提高了"频率衰减梯度"的计算精度。实际资料的计算结果表明,本文提出的综合"低频阴影"和"频率衰减梯度"方法的频率衰减分析技术能够有效地圈定碳酸盐岩鲕滩储层的发育区域,且两种方法具有很好的一致性,有效地提高了储层预测的可靠性,从而降低了勘探风险。     

A comparative study on hydrocarbon detection using three EMD-based time–frequency analysis methods

Due to strong heterogeneity of marine carbonate reservoir, seismic signals become more complex, thus, it is very difficult for hydrocarbon detection. In hydrocarbon reservoir, there usually exist some changes in seismic wave energy and frequency. In their instantaneous spectrums there often exist such phenomena that show the characteristics of attenuation of high frequency energy and enhancement of low-frequency energy. The three EMD-based time-frequency analysis methods' instantaneous spectra all have certain oil and gas detection capability. In this paper, we introduced the Normalized Hilbert Transform (NHT) and a new method named the HU method for hydrocarbon detection. The model results in the Jingbian Gas Field which is located in the eastern Ordos Basin, China, show that NHT and HU methods can be adopted. They also detect the gas-bearing reservoir efficiently as the HHT method does. The three EMD-based methods, that is, the Hilbert–Huang transformation (HHT) and NHT and HU methods, were respectively applied to analyze the seismic data from the Jingbian Gas Field. Firstly, the seismic signals were decomposed into a finite number of intrinsic mode functions (IMFs) by empirical mode decomposition (EMD) method. The second IMF signal (IMF2) of the original seismic section better indicates the distribution of the reservoir. Information on hydrocarbon-bearing reservoir is mainly in IMF2. Secondly, the HHT, NHT and HU methods were respectively used to obtain different frequency division sections from IMF2. Hydrocarbon detection was realized from the energy distribution of the different frequency division sections with these three EMD-based methods. The practical application results show that the three EMD-based methods can all be employed to hydrocarbon detection. Frequency division section of IMF2 using NHT method was better for the seismic data from the Jingbian Gas Field than when using the HHT method and HU method.     

稀疏时频分解方法的研究与运用（英文）

Gabor变换和S变换是常用的时频分析工具。根据测不准原理,它们的时频分解结果无法在时间域和频率域同时具有很高的分辨率。为了提高非平稳信号时频分解结果的分辨率,本文提出瞬时频率分布函数（IFDF）并利用它表达非平稳信号。当非平稳信号时频成分的分布满足测不准原理对信号可分辨的要求时,瞬时频率分布函数的支集和短时Fourier变换的小波脊支集是同一个集合。利用IFDF的该特征,本文提出一种迭代算法（Sparse-STFT）实现了信号的稀疏时频分解。该算法在每次迭代过程中利用残留信号的短时Fourier变换结果的脊支集更新信号的时频成分,每次迭代得到的时频成分的叠加结果即为最终的稀疏时频分解结果。文中的数值实验证明了Sparse-STFT可以有效地提高非平稳信号时频分解结果的分辨率。最后,本文将该方法应用于地震数据面波的压制中,取得了理想的处理结果。     

首都圈地区远震基底PS波分裂研究

远震PS波的一个重要优势是其携带台站下方介质的各向异性信息.本文基于首都圈数字地震台网2002-2003年记录的高精度远震波形资料,从基底PS转换波入手,采用三分量PS波分裂偏振分析方法,获取各个台站下方来自基底的PS波分裂参数,包括快波偏振方向和快、慢波的时间延迟等,分析台站下方浅部地壳介质的各向异性特征.几个台站的研究结果显示,该方法保持了原始波场的信息,可以用来分析PS波分裂特征;短周期台站记录的远震来自基底的PS波具有干扰少、信噪比高的特点,存在分裂现象,各台站快慢波时差超出我们的预期值,平均在0.1~0.2 s左右.此研究可与横波分裂相对比,对于认识地壳各向异性及其内部的应力状态,分析其构造及地震活动现象有较大的意义.     

Numerical modeling of PP- and PS-wave azimuthal anisotropy in HTI media

This study focuses on the factors that may affect the feasibility of performing elliptical anisotropy analysis on azimuthal PP- and PS-wave data in HTI media, with the aim of using the modeling results as guidance in real seismic data application. Our results reveal that there is an offset limitation for both PP- and PS-waves in elliptical anisotropy fitting, and that PS-waves show a wider applicable offset range and larger observable azimuthal anisotropy than PP-waves. The major axis of the elliptical fit to the amplitudes of the R-component is perpendicular to the fracture strike, which is opposite to that in PP-wave analysis. The azimuthal interval travel time of PS-waves shows a nearly elliptical distribution and the major axis of the fit ellipse is perpendicular to the fracture strike, which is same as that in PP-wave analysis. For data within the applicable offset range, the anisotropic magnitude obtained from amplitude and travel time attributes of PP- and PS-waves exhibits a dependence on fracture density, and the major to minor axis ratio of the fit ellipse may be used to infer the relative distribution of fracture densities.     

谱图重排的谱分解理论及其在储层探测中的应用

谱分解理论是把单道地震记录分解为连续的时频谱平面,是地震资料处理和解释的重要技术之一.由于谱分解方法的多解性,所以同一道地震记录因为分解方法不同,得到的时频谱是不一样的.短时傅里叶变换,小波变换,S变换和匹配追踪算法都是对信号开窗分析,这些方法都受到不确定性原理的限制.Wigner-Ville变换避开了不确定性原理的限制,但是交叉项的存在限制了本方法的使用.本文利用谱图重排的时频分析方法(RSPWV)对合成的单道地震记录和实际的地震资料进行了分析.与短时傅里叶变换和匹配追踪算法的比较得出:此方法具有较高的时频分辨率,能够很好地识别气层.     

Analyzing seismic imagery in the time–amplitude and time–frequency domains to determine fluid nature and migration pathways: A case study from the Queen Charlotte Basin,offshore British Columbia

Combining time–amplitude and time–frequency information from seismic reflection data sets of different resolutions allows the analysis of anomalous reflections from very-shallow to great subsurface depths. Thus, it can enhance the imaging of subsurface features which have a frequency-dependent reflectivity such as gas. Analysing seismic data of different resolution in the time–amplitude and time–frequency domains is a powerful method to determine hydrocarbon migration pathways from deep reservoirs to the seafloor. This interpretation method has been applied to the formerly-glaciated offshore Queen Charlotte Basin hosting several seafloor pockmarks and mounds associated with the leakage of underlying hydrocarbon reservoirs. Low-frequency shadows observed in the time–frequency domain provide evidence of different resolutions that several anomalous reflection amplitudes may be attributed to the occurrence of gas. The seismic imagery shows that gas uses a fault to migrate from deep reservoirs included in Upper Mesozoic strata towards secondary reservoirs located along the fault plane into Neogene layers. Once gas reaches a porous cut-and-fill succession, migration changes from structurally- to stratigraphically-controlled before gas leaks through unconsolidated Quaternary sediments forming the shallow subsurface to eventually seep at the seafloor where pockmarks and carbonate mounds are formed.     

Research and application of spectral inversion technique in frequency domain to improve resolution of converted PS-wave

Multi-wave exploration is an effective means for improving precision in the exploration and development of complex oil and gas reservoirs that are dense and have low permeability. However, converted wave data is characterized by a low signal-to-noise ratio and low resolution, because the conventional deconvolution technology is easily affected by the frequency range limits, and there is limited scope for improving its resolution. The spectral inversion techniques is used to identify λ/8 thin layers and its breakthrough regarding band range limits has greatly improved the seismic resolution. The difficulty associated with this technology is how to use the stable inversion algorithm to obtain a high-precision reflection coefficient, and then to use this reflection coefficient to reconstruct broadband data for processing. In this paper, we focus on how to improve the vertical resolution of the converted PS-wave for multi-wave data processing. Based on previous research, we propose a least squares inversion algorithm with a total variation constraint, in which we uses the total variance as a priori information to solve under-determined problems, thereby improving the accuracy and stability of the inversion. Here, we simulate the Gaussian fitting amplitude spectrum to obtain broadband wavelet data, which we then process to obtain a higher resolution converted wave. We successfully apply the proposed inversion technology in the processing of high-resolution data from the Penglai region to obtain higher resolution converted wave data, which we then verify in a theoretical test. Improving the resolution of converted PS-wave data will provide more accurate data for subsequent velocity inversion and the extraction of reservoir reflection information.     

基于精确Zoeppritz方程的非线性AVO三参数反演

常规AVO三参数反演通常存在密度反演不准确的问题,而密度参数对常规油气藏中的流体识别、流体饱和度计算、孔隙度计算以及非常规油气藏中TOC含量计算、裂缝预测等都至关重要,因此对于研究如何利用大偏移距振幅信息和富含密度信息的PS波地震资料来提高密度反演结果的稳定性和精度显得尤为重要.研究基于贝叶斯反演理论框架,引入三变量Cauchy分布先验约束,利用精确Zoeppritz方程构建了AVO三参数联合反演的目标函数,对目标函数进行Taylor二阶非线性简化,得到模型参数的迭代更新公式,实现了大偏移距地震振幅信息的利用和PP波、PS波联合反演.合成数据和实际地震数据的方法测试结果表明,新方法不仅可以直接反演纵波速度、横波速度和密度,而且还具有很高的精度,尤其是密度反演结果.基于合成数据的PP波、PS波单独反演结果与PP波和PS波联合反演结果对比显示,联合反演稳定性更好,精度更高,抗噪能力更强,验证了该方法的可行性和有效性.与基于Aki-Richards近似公式的反演结果对比表明,该反演方法具有更高的反演精度和更好的抗噪性.     

空间局部加权回归自适应TFPF

时频峰值滤波(TFPF)算法是一种非常有效的去噪方法.但是传统的TFPF采用的单一窗长,并且仅沿时间方向进行滤波,忽略了信号的空间信息,并且TFPF近似等效成一个时不变的低通滤波器,不能追踪快速变化的信号.针对这些问题,引入空间局部加权回归自适应TFPF(SLWR-ATFPF).鉴于随机噪声在各个位置的方向随机性,以及有效信号在各个位置的方向确定性,首先利用空间局部加权回归(SLWR),对含噪信号进行空间加权,从而使加权之后的信号包含空间信息.然后,再引入凸集和Viterbi的思想,对空间加权之后的信号进行自适应滤波.从而,完成时空域二维自适应滤波.将SLWR-ATFPF应用于合成记录和实际的共炮点记录,实验结果表明,改进的方法与原算法相比,能够在压制低信噪比(SNR)随机噪声的同时更好地保留有效信号.