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叠加速度分析技术是常规地震资料处理中的重要环节,也是经典的时间域速度建模方法.叠加速度分析技术主要包括速度谱计算和拾取两个步骤.至今为止,多数研究工作通过提高速度谱的分辨率以及抗噪声能力,获得高质量的速度谱从而有利于拾取.本文的目标是将叠加速度分析技术转为一个全自动化的处理流程.从参数估计的角度出发,将叠加速度估计转化为稀疏反演框架下的模型参数估计问题,并通过稀疏反演算法自动反演叠加速度,进而提高叠加速度建模的效率.为实现这一目标,首先给出了正问题的定义,即层状介质中CMP道集的预测模型,利用叠加速度、垂向双程走时(t_0)以及反射子波以及CMP道集时距关系(如双曲时距关系)可以预测CMP道集.接着,速度分析反问题可以描述为已知观测的CMP道集,估计模型参数(叠加速度及t_0时间等).利用模型参数的稀疏性作为约束条件并用L_0范数作为模型稀疏性的度量准则,叠加速度分析可以转化为L_0范数约束下的稀疏反演问题.本文提出了一种基于预测校正思想的匹配追踪算法求解上述反问题,实现了自动叠加速度建模并为后续的高精度速度反演方法提供较好的初始模型.理论和实际资料的测试结果证明了本文方法的有效性. 相似文献
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强随机噪声干扰是导致地震勘探资料低信噪比的主要原因,如何在强随机噪声干扰下获取有效的信息是值得关注的问题.Duffing振子混沌系统是一个非线性的动力学系统,其对强随机噪声具有免疫能力,而对特定的周期性信号具有敏感性.本文提出一种基于Duffing振子混沌系统的速度分析方法.对CMP道集按照时距曲线关系进行移动窗口截取,将所截取的信号构建为待测信号加入Duffing振子混沌系统,通过相图网格分割方法(GPM)判断系统状态的改变,从而在强随机噪声背景下获得高分辨率的速度谱.理论模型和实际资料的处理结果表明,与传统的水平叠加速度分析方法相比,本方法能够在强随机噪声背景下获得更准确的速度分析结果. 相似文献
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传统地震数据稀疏重建方法面临着:(1)叠前共炮点道集或CMP道集反射波为双曲线型同相轴,地震数据重建会损害有效波;(2)地震信号存在噪声和畸变,要求重建方法具有较好的噪声鲁棒性.针对这两个问题,提出一种基于L_1-L_1范数稀疏表示的共偏移距道集地震数据重建方法.该方法利用了共偏移距道集中地震波为水平同相轴,无道间时差,满足空间重建要求,和L_1-L_1范数稀疏表示具有较好的噪声鲁棒性.首先抽取共偏移距道集地震数据,并根据地震采集信息构造复合采样矩阵,然后采用L_1-L_1范数稀疏表示对数据稀疏重建后,再将数据反变换回共炮点道集或CMP道集,能够同时实现地震信号稀疏重建和随机噪声压制.理论模型和实际数据试算结果验证所提方法具有较好重建精度和噪声鲁棒性. 相似文献
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基于非稳态多项式拟合的地震噪声衰减方法研究(英文) 总被引：1，自引：0，他引：1
基于非稳态多项式拟合理论,针对地震数据中同相轴振幅变化这一特征,我们提出了一种地震噪声衰减的新方法。非稳态多项式拟合系数是时变的,通过整形正则化约束多项式拟和系数的光滑性,自适应的估计地震数据的相干分量。基于动校正后的共中心点道集(CMP)中地震信号的相干性,利用非稳态多项式拟合估计有效信号,从而衰减随机噪声。对于线性相干噪声,如地滚波,首先利用径向道变换(RadialTraceTransform,RTT)将地震数据变换到时间一视速度域,在时间—视速度域利用非稳态多项式拟合估计出相干噪声,然后减去相干噪声。该方法可以有效的估计振幅变化的相干分量,不需要相干分量振幅为常量的假设。模拟和实际资料处理结果表明,与传统的稳态多项式拟合和低切滤波相比,该方法可以更为有效的衰减地震噪声,同时保真了地震有效信号。 相似文献
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叠前多级优化联合偏移速度建模 总被引：1，自引：0，他引：1
推导了基于角度域共成像点道集的叠前深度层析速度建模公式,提出了一种叠前多级优化联合偏移速度建模方法.通过基于共散射点(CSP)道集的叠前时间偏移速度分析获取初始速度,利用基于角度域共成像点道集(ADCIGs)的叠前深度层析速度反演进行速度更新建模.实现步骤可以概括为:首先,将叠前地震数据映射为CSP道集,利用CSP道集的叠加速度谱进行速度分析得到均方根速度场;其次,通过Dix公式将均方根速度场转换为层速度场,以此进行层析初始速度建模,基于ADCIGs实现叠前深度层析速度反演,最终得到高精度的叠前偏移速度场.断层模型和实际资料试算结果验证了该方法的正确性和有效性. 相似文献
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本文提出了一种利用叠前CMP道集资料估计介质品质因子的方法,同时提出利用地震道间有效信号的相干性估计层位信息的方法.首先采用具有4个待定系数的函数去逼近震源子波,利用黏弹介质中单程波传播理论推导出地震子波包络峰值处的瞬时频率(EPIF)与不同偏移距处走时的关系;其次利用该关系,外推出该同相轴零偏移距处的EPIF,用小波域包络峰值处瞬时频率法(WEPIF)结合层位信息估计Q值.合成数据的结果表明,EPIFVO法(子波包络峰值瞬时频率随偏移距变化)无边界效应,计算精度相对较高;将该方法用于实际资料算例,结果表明,衰减强弱与储层的吸收有较好的对应关系. 相似文献
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浅层人工地震勘探是当前城市地震活断层探测的主要方法,勘探精度不仅受激发、接收等因素的影响,还与地震数据处理的精度密切相关。速度分析是地震勘探资料处理中的关键环节,它的准确与否对动校正、共深度点叠加、叠后偏移及时深转换等都将产生影响。针对浅层地震资料目的层较浅、叠加次数少和城市背景干扰大等特点,文中对速度分析的参数选取问题进行了研究。首先通过对相邻CDP道集内各接收道炮检距的分析,以及单个和多个CDP道集的对比,提出了用于速度分析的CDP大道集的抽取原则。并通过对不同的CDP大道集、速度扫描间隔、计算时窗长度、动校切除比例等所获得的速度谱的对比分析,对速度谱扫描过程中各参数的选取提出了建议,并对速度分析及时深转换过程中值得注意的问题进行了讨论 相似文献
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叠前地震资料中,高频分量和低频分量随传播距离的衰减特性不同.本文给出了一种在小波域定性估计叠前地震资料衰减参数的方法.该方法利用连续小波变换提取共反射点道集的高、低频分量,以低频分量和高频分量之差定性反映地震波的衰减.通过累加不同偏移距的衰减,提高了估计的稳定性;采用幅度归一化方法,降低了信号幅值对衰减参数估计的影响.将本文提出方法与常用的基于叠后地震资料衰减估计方法用于某油田的地震资料处理,结果表明,本文方法得到的衰减估计结果能够更好地反映油气的空间展布. 相似文献
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针对宽频带高分辨率地震剖面的空间假频问题,本文提出了高密度偏移处理的解决方案。首先对地震空间假频的定义进行了分析,认识到偏移地震剖面与叠加地震剖面中的空间假频是有差异的,偏移地震剖面比叠加地震剖面更易产生空间假频。其次根据地震波动理论,认为野外空间低密度采集的地震信号,包含着地下高密度的地质信息,进而提出地震偏移输出是新的空间采样过程,只要地震叠前时间偏移输出高密度采样,CDP道间距足够小,就可以防止宽频带高分辨率偏移剖面的空间假频。利用二维地震正演模型分析高密度偏移方法的可行性,表明低密度采集的地震数据高密度空间采样叠前偏移处理可以消除地震空间假频噪声。对松辽盆地大庆油田低密度采集的地震资料高密度叠前偏移及提高分辨率处理后,消除了宽频带高分辨率地震的空间假频,宽频带高分辨率地震剖面地震空间分辨率明显提高。 相似文献
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The hazards of amplitude versus offset (AVO) technique mostly applied in seismic explorations for predicting coalbed methane (CBM) content mainly derive from multi-stage amplitude modifications during seismic signal preprocessing. The modifications are undoubtedly necessitated by improving high signal-to-noise ratio (SNR) and high resolution, and achieve high fidelity to some extent; and nevertheless lead to an unfavorable possibility to implement CBM AVO analysis. Similar to sandstone reservoir with gas, AVO analysis preprocessing for CBM reservoir strictly abides by a relative amplitude preserved (RAP) principle and particularly emphasizes on preserving the evanescent class IV AVO anomaly. As for those indispensable dealings with linear noise attenuations, near-surface variety compensations and time/depth spatial imaging, the key technologies adapted to CBM AVO preprocessing should use radial trace (RT) filter, refined surface-consistent amplitude compensation (SCAC), and RAP Kirchhoff prestack time migration (PSTM). The theoretical analysis and one real 3D example in this paper demonstrate that three key technologies compliant to RAP principle in CBM AVO preprocessing can preserve the class IV AVO anomaly and benefit an operation of CBM AVO analysis and an improvement of CBM evaluation. 相似文献
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The technique of amplitude variation with offset or angle (AVO or AVA) can be used to extract fluid and lithology information from prestack seismic data. Based on three-term AVO equations, three elastic parameters can be inverted for by linear AVO inversion. However, many theoretical and numerical studies have demonstrated that by using offset limited data, a three-term AVO inversion may have problems of instability and inaccuracy while inverting for the density term. We have searched for an elastic parameter that contains density information and inverted this parameter in a more stable manner using offset limited data. First, we test the sensitivity of elastic parameters to hydrocarbon reservoirs and select the optimal fluid factor (ρf) that contains density information and has an excellent performance as an inversion parameter used to detect hydrocarbons. Then, we derive approximate PP and PS reflection coefficient equations in terms of the fluid factor. The derived equations allow us to directly estimate the fluid factor of the reservoir. Finally, we apply these equations to synthetic data by employing a joint AVO inversion technique. The results show that the method is stable and unambiguous. 相似文献
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Filters for migrated offset substacks are designed by partial coherence analysis to predict ‘normal’ amplitude variation with offset (AVO) in an anomaly free area. The same prediction filters generate localized prediction errors when applied in an AVO‐anomalous interval. These prediction errors are quantitatively related to the AVO gradient anomalies in a background that is related to the minimum AVO anomaly detectable from the data. The prediction‐error section is thus used to define a reliability threshold for the identification of AVO anomalies. Coherence analysis also enables quality control of AVO analysis and inversion. For example, predictions that are non‐localized and/or do not show structural conformity may indicate spatial variations in amplitude–offset scaling, seismic wavelet or signal‐to‐noise (S/N) ratio content. Scaling and waveform variations can be identified from inspection of the prediction filters and their frequency responses. S/N ratios can be estimated via multiple coherence analysis. AVO inversion of seismic data is unstable if not constrained. However, the use of a constraint on the estimated parameters has the undesirable effect of introducing biases into the inverted results: an additional bias‐correction step is then needed to retrieve unbiased results. An alternative form of AVO inversion that avoids additional corrections is proposed. This inversion is also fast as it inverts only AVO anomalies. A spectral coherence matching technique is employed to transform a zero‐offset extrapolation or near‐offset substack into P‐wave impedance. The same technique is applied to the prediction‐error section obtained by means of partial coherence, in order to estimate S‐wave velocity to P‐wave velocity (VS/VP) ratios. Both techniques assume that accurate well ties, reliable density measurements and P‐wave and S‐wave velocity logs are available, and that impedance contrasts are not too strong. A full Zoeppritz inversion is required when impedance contrasts that are too high are encountered. An added assumption is made for the inversion to the VS/VP ratio, i.e. the Gassmann fluid‐substitution theory is valid within the reservoir area. One synthetic example and one real North Sea in‐line survey illustrate the application of the two coherence methods. 相似文献
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We introduce a processing technique which minimizes the 'stretching effects' of conventional NMO correction. Unlike conventional NMO, the technique implies constant normal moveout (CNMO) for a finite time interval of a seismic trace. The benefits of the proposed method include preservation of higher frequencies and reduction of spectral distortions at far offsets. The need for severe muting after the correction is reduced, allowing longer spreads for stack, velocity and AVO analysis. The proposed technique has been tested on model and real data. The method may improve the resolution of CMP stack and AVO attribute analysis. The only assumptions for this stretch-free NMO correction are (i) all time samples of a digital reflected wavelet at a particular offset have the same normal moveout, and (ii) reflection records have an interference nature. 相似文献
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提出一种基于Radon 变换和正交多项式变换的多方向正交多项式变换压制多次波方法.抛物Radon变换对不同曲率方向的同相轴叠加,根据速度差异区分一次波和多次波,但Radon反变换会损伤振幅特性,不利于AVO分析.多方向正交多项式变换在Radon变换(某一曲率方向的零阶特性)的基础上,利用正交多项式变换进一步分析同相轴的高阶多项式分布特性,用正交多项式谱表征同相轴AVO特性;根据一次波和多次波速度差异和同相轴能量分布特征实现多次波压制.该方法的优点是仅用一个曲率参数就可描述同相轴剩余时差参数,提高了一次波和多次波的剩余时差分辨率.实验结果表明,该方法可以有效压制多次波并保留一次波AVO特性. 相似文献
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Umberto Spagnolini 《Geophysical Prospecting》1994,42(3):241-259
Minimization of seismic residuals does not guarantee uniqueness of the model, and this implies ambiguities in the inversion. Amplitude vs. offset (AVO) inversion does not lead to a unique solution of single elastic interface parameters unless converted and S-wave or critical angle reflections are available. Given the ambiguity of AVO inversion, this paper discusses the interaction between AVO and velocity estimation. The number of independent parameters necessary to describe an isolated reflection with AVO behaviour and residual velocity error is determined. Statistical analysis allows the establishment of an approximate equivalence of the effects of AVO and slight velocity variations; this equivalence cannot be solved without geological a priori information (kinematic equivalence). The data are then decomposed into compound events (i.e. sequences of N interfaces that follow each other at a fixed time lag). The decomposition is obtained by extrapolating the results of the analysis from narrowband to wideband data. Compound events decomposition demonstrates that AVO inversion is ambiguous, not only in the physical parameter space (P- and S-wave velocities, and density) but also kinematically. As an example of compound event decomposition, a medium is derived. This medium is geologically implausible but is kinematically equivalent. 相似文献
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2D multiscale non-linear velocity inversion 总被引：2，自引：0，他引：2
An efficient and robust non-linear inversion method for velocity optimization combining a global random search followed by a simplex technique is presented. The background velocity field is estimated at different spatial scales by analysing image gathers after iterative prestack depth migrations. First, the global random search is used to determine the main features/trends of the velocity model (large-scale component). Then, the simplex technique improves the resolution of the velocity field by estimating smaller-scale features. A measure of the quality of the velocity model (objective function) is based on flattening offset events in depth-migrated image gathers. To help constrain the solution, the algorithm can incorporate a priori information about the model and a smoothness condition. This 2D velocity estimation offers the benefit of being semi-automatic (requiring minimal human intervention) as well as providing a global and objective solution (which is a useful approach to an interpretation-derived velocity-estimation technique). The method is applied to a real data set where AVO analysis is carried out after prestack depth migration, as structural effects are non-negligible. It is demonstrated that the method can successfully estimate a laterally inhomogeneous velocity model at a computational cost modest compared with an interpretation-based iterative prestack depth velocity-analysis technique. 相似文献
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地震波传播算子的计算效率和精度是制约三维叠前深度偏移的关键因素. 广义屏传播算子(GSP, Generalized Screen Propagator)是一种在双域中实现的广角单程波传播算子. 这一方法略去了在非均匀体之间发生的交混回响,但它可以正确处理包括聚焦、衍射、折射和干涉在内的各种多次前向散射现象. 通过背景速度下的相移和扰动速度下的陡倾角校正,广义屏算子能够适应地层速度的强烈横向变化. 这种算子可以直接应用于炮集叠前偏移,通过将广义屏算子作用于双平方根方程,还可以获得一种高效率、高精度的炮检距域叠前深度偏移方法,用于二维共炮检距道集和三维共方位角道集的深度域成像. 本文首先简述了炮检距域广义屏传播算子的理论,进而讨论了共照射角成像(CAI, Common Angle Imaging)条件,由此给出各个不同照射角(炮检距射线参数)下的成像结果,进而得到共照射角像集. 由于照射角和炮检距的对应关系,共照射角像集又为偏移速度分析和AVO(振幅随炮检距变化)分析等提供了有力工具. 相似文献
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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. 相似文献