共查询到17条相似文献，搜索用时 328 毫秒
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提出三维Kirchhoff叠前时间偏移角度域共像点道集的改进算法,克服传统角度求取算法局限,可计算相对倾斜地层法线入射角;与Kirchhoff直射线叠前时间偏移求角度算法相比,本文方法考虑射线弯曲效应,包含层速度,角度范围加大,更接近真实入射角;计算走时采取弯曲射线或者适应线性横向变速介质的非对称走时等算法,角度道集在大角度处得到拉平;采用相对保幅的权因子以及覆盖次数校正技术,有利于叠前AVA反演.模型测试结果表明：叠前时间偏移角度道集,相对CMP、CRP所转化角度道集,更准确反应AVA效应;实际三维数据测试表明本文方法可以提供品质优良的角度道集,适用于AVA分析、反演,提高叠前反演分辨率. 相似文献
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针对传统Kirchhoff叠前时间偏移方法的一些不足,以及振幅随入射角、方位角变化(AVA/AVAZ)分析的需要,本文提出一种基于射线理论的三维叠前时间偏移角度域成像方法.它通过横向均匀介质中稳健的射线追踪建立单程波走时和传播角度的数值表,然后在此基础上估算反射波双程走时以及在界面处传播的方位角和入射角,最后基于脉冲响应叠加原理获得三维构造图像和方位\|角度域共成像点道集.与传统方法不同之处在于,上述过程均考虑了地震波在垂向变速介质中的射线弯曲效应和三维传播特征,有利于准确提取随入射角和方位角变化的振幅和时差信息.理论模型合成数据和实际地震资料测试结果展示了方法的优越性与实用性. 相似文献
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本文从单程波方程出发,推导出角度域叠前时间偏移成像幅值计算方法.文章首先在时间域实现了速度梯度引起的幅值透射损失补偿算法;借鉴波动方程偏移的反褶积成像条件,对地震波能量随传播距离的几何扩散进行部分补偿;针对观测系统中炮点覆盖引起的角度域非均匀照明提出了相应的振幅补偿方法.三维水平层状理论模型成像结果表明获得的角道集具有较好的AVA特性. 相似文献
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逆时偏移在提高复杂介质的成像质量方面表现出了优越的性能,但逆时偏移对速度精度的要求比较高.共成像点道集是一种非常重要的叠前深度偏移输出,它除了能为深度偏移处理提供速度信息外,还能够提供振幅和相位等信息,为后续的属性解释提供依据.本文提出一种在逆时偏移成像过程中提取角度域共成像点道集的方法,该方法采用矢量波动方程进行波场传播,并用能流密度矢量(Poynting vector)计算反射角,最后应用互相关成像条件输出角度域共成像点道集.该方法简单易于实现,且几乎不需要额外的计算量和存储量,非常适合于进行逆时偏移速度分析,同时提出的角道集也能用于进行AVA等分析.最后通过模型算例和实际数据检验了方法的有效性和优越性. 相似文献
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共成像点道集(CIG)可用于速度建模、偏移质量控制以及地下属性解释等。对于复杂碳酸盐岩储层,叠前AVO反演技术在储层识别、裂缝预测和流体检测方面的作用日益显著,叠前反演的精度很大程度上依赖于共成像点道集的AVO特性是否符合地下介质的真实地震响应。因此,叠前偏移不仅要实现反射点的准确归位,还必须得到振幅保真的共成像点道集,从而为AVO/AVA反演提供保幅的共成像点道集输入数据。本文在理论上对真振幅Kirchhoff叠前深度偏移和逆时偏移(RTM)抽道集技术的保幅性进行分析:真振幅Kirchhoff偏移抽道集通过改变加权函数实现振幅保持,仅适用于横向速度变化不大的情况;基于双程波动方程的逆时偏移采用互相关成像条件抽取共成像点道集,成像精确且无倾角限制,相对保幅性优于前者,适应任意复杂速度模型。模型和实例测试结果表明:在简单构造区域,真振幅Kirchhoff保幅叠前深度偏移与保幅逆时偏移抽取的共成像点道集都能起到良好的保幅效果;但在复杂构造区,基于逆时偏移抽取的共成像点道集,保留了全部波场的路径与振幅信息,其保幅性与成像精度优于Kirchhoff保幅叠前深度偏移。因此,针对探区的复杂程度差别及勘探精度的不同要求,应选择不同的抽道集方法,保证振幅精度的同时,兼顾生产效率。 相似文献
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角度域成像道集是叠前深度偏移的重要输出结果,它是偏移速度分析、各向异性分析和AVA分析等研究工作的基础.目前存在的角度域成像道集的生成方法受计算效率或角度分辨率的影响,仍然满足不了实际生产的要求.角度域成像道集的生成方法可以大致分为直接法和间接法两大类.在直接方法中,波矢量方向计算和局部平面波分解是两个最重要的内容,它们共同决定角度域成像条件的实现效率和角度域成像道集的质量.为了完善现有的角度域成像道集生成方法,本文提出一种新的波矢量计算方法和局部平面波分解方法.本文先用波动方程任意时刻的柯西条件构造一个只含原波场负频率成分的柯西波场,然后根据柯西波场在时间波数域的振幅谱计算波场的波矢量方向.该方法仅在需要计算波矢量方向的时刻合成柯西波场,不需要增加额外的数据读写操作,是一种高效的波矢量计算方法.本文还以柯西波场为基础提出一种高效的局部平面波分解方法,保证角度域成像条件的实现效率.结合柯西波场和局部平面波分解方法,本文最后给出一种新的角度域成像方法.文中最后的数值实验证明该方法得到的角度域成像道集具有理想的角度分辨率,可以反映地下构造的角度照明情况. 相似文献
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《应用地球物理》2015,(1)
角度域共成像点道集(ADCIGS)是偏移速度分析和振幅随角度变化分析(AVA)的基础数据。传统Kirchhoff叠前深度偏移(KPSDM)按偏移距组织数据,能方便的输出偏移距域共成像点道集(ODCIGS),其高效的角度道集输出是有挑战的。本文提出基于旅行时梯度场的KPSDM角道集输出方法。其核心步骤为:(1)利用任意介质中的动态规划法旅行时计算方法提供炮点和检波点的旅行时场;(2)根据旅行时场的梯度方向计算反射张角;(3)在偏移过程中抽取ADCIGS。由于本文旅行时计算方法没有射线阴影区,也没有对速度光滑性的要求,其角度道集输出在阴影区比传统射线追踪更有优势。基于该角度道集输出方法,本文发展了一种适合大规模三维地震数据的KPSDM及角道集输出的并行实现方案。其基本思想是:(1)按照炮数据来组织输入数据;(2)旅行时场的输入与单炮覆盖范围相联系以节省内存;(3)多炮数据间采用MPI并行处理,单炮深度切片之间采用OpenMp并行处理,可进一步提高内存利用率和并行力度。数值试验结果证明本文角度道集生成方法的优越性和本文实现方案的有效性。 相似文献
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相对保幅的角度域VSP逆时偏移(英文) 总被引：3，自引：1，他引：2
本文介绍了一种改进的角度域VSP逆时偏移方法。对VSP逆时偏移中的逆推公式进行了改进,为方便数值计算出相对保幅的角度域共成像点道集(ADCIGs)。此外VSP记录到的波场信息丰富,包括上行波场、下行波场和直达波场等,本文分析了这些波场的响应特征,发现直达波和下行波在角度域共成像点道集(ADCIGs)上都产生了成像噪音,直达波产生的噪音尤为严重。把该方法用于我国西部地区实际观测的VSP资料,不仅获得相对保幅角度域共成像点道集(ADCIGs),而且压制了成像噪音。通过数值模型试算,实际资料的应用验证了该方法的实用性与有效性,从而为VSP偏移速度分析、VSP AVA/AVO分析和反演等提供可靠的基础资料。 相似文献
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在克希霍夫叠前时间偏移处理中,地震波走时的计算方法是决定大偏移距地震资料成像品质的重要因素.在常规的三维转换波各向异性叠前时间偏移公式中,走时的计算是基于等效单层各向异性介质的非双曲线方法.用这种方法处理的成像道集,在偏移/深度比超过一定阈值后,成像道集中的反射同相轴将出现过偏现象,这种偏移不平的同相轴将影响偏移叠加的最佳响应,使得偏移成像波组呈低频化特征,最终降低三维转换波偏移成像质量.我们采用层状介质的走时计算方法代替常规算法,并且利用了常规方法的转换波各向异性偏移速度模型.基于层状介质的算法能够提高大偏移距转换波走时计算精度,克服中浅地层大偏移距远道成像道集中反射同相轴逐渐上翘的问题.两个地区的三维转换波资料处理结果证实,基于层状各向异性介质的转换波克希霍夫叠前时间偏移方法,明显改善了反射成像剖面的连续性和分辨率,提高成像剖面构造的可解释性. 相似文献
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Investigating a time‐shift extended imaging condition in a Kirchhoff pre‐stack depth migration algorithm 
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下载免费PDF全文 Gareth Shane O'Brien Sean Joseph Delaney Michael Igoe John Doherty Andrew Colhoun 《Geophysical Prospecting》2018,66(4):688-706
Extracting true amplitude versus angle common image gathers is one of the key objectives in seismic processing and imaging. This is achievable to different degrees using different migration techniques (e.g., Kirchhoff, wavefield extrapolation, and reverse time migration techniques) and is a common tool in exploration, but the costs can vary depending on the selected migration algorithm and the desired accuracy. Here, we investigate the possibility of combining the local‐shift imaging condition, specifically the time‐shift extended imaging condition, for angle gathers with a Kirchhoff migration. The aims are not to replace the more accurate full‐wavefield migration but to offer a cheaper alternative where ray‐based methods are applicable and to use Kirchhoff time‐lag common image gathers to help bridge the gap between the traditional offset common image gathers and reverse time migration angle gathers; finally, given the higher level of summation inside the extended imaging migration, we wish to understand the impact on the amplitude versus angle response. The implementation of the time‐shift imaging condition along with the computational cost is discussed, and results of four different datasets are presented. The four example datasets, two synthetic, one land acquisition, and a marine dataset, have been migrated using a Kirchhoff offset method, a Kirchhoff time‐shift method, and, for comparison, a reverse time migration algorithm. The results show that the time‐shift imaging condition at zero time lag is equivalent to the full offset stack as expected. The output gathers are cleaner and more consistent in the time‐lag‐derived angle gathers, but the conversion from time lag to angle can be considered a post‐processing step. The main difference arises in the amplitude versus offset/angle distribution where the responses are different and dramatically so for the land data. The results from the synthetics and real data show that a Kirchhoff migration with an extended imaging condition is capable of generating subsurface angle gathers. The same disadvantages with a ray‐based approach will apply using the extended imaging condition relative to a wave equation angle gather solution. Nevertheless, using this approach allows one to explore the relationship between the velocity model and focusing of the reflected energy, to use the Radon transformation to remove noise and multiples, and to generate consistent products from a ray‐based migration and a full‐wave equation migration, which can then be interchanged depending on the process under study. 相似文献
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Pre-stack Kirchhoff depth migration local space-shift imaging condition: synthetic and data examples
Extracting accurate common image angle gathers from pre-stack depth migrations is important in the generation of any incremental uplift to the amplitude versus angle attributes and seismic inversions that can lead to significant impacts in exploration and development success. The commonly used Kirchhoff migration outputs surface common offset image gathers that require a transformation to angle gathers for amplitude versus angle analysis. The accuracy of this transformation is one of the factors that determine the robustness of the amplitude versus angle measurements. Here, we investigate the possibility of implementing an extended imaging condition, focusing on the space-lag condition, for generating subsurface reflection angle gathers within a Kirchhoff migration. The objective is to determine if exploiting the spatial local shift imaging condition can provide any increase in angle gather fidelity relative to the common offset image gathers. The same restrictions with a ray-based approach will apply using the extended imaging condition as both the offset and extended imaging condition method use travel times derived from solutions to an Eikonal equation. The aims are to offer an alternative ray-based method to generate subsurface angle gathers and to understand the impact on the amplitude versus angle response. To this end, the implementation of the space-shift imaging condition is discussed and results of three different data sets are presented. A layered three-dimensional model and a complex two-dimensional model are used to assess the space shift image gathers output from such a migration scheme and to evaluate the seismic attributes relative to the traditional surface offset common image gathers. The synthetic results show that the extended imaging condition clearly provides an uplift in the measured amplitude versus angle over the surface offset migration. The noise profile post-migration is also improved for the space-lag migration due to the double summation inside the migration. Finally, we show an example of a space-lag gather from deep marine data and compare the resultant angle gathers with those generated from an offset migration and a time-shift imaging condition Kirchhoff migration. The comparison of the real data with a well log shows that the space-lag result is a better match to the well compared to the time-lag extended imaging condition and the common offset Kirchhoff migration. Overall, the results from the synthetics and real data show that a Kirchhoff migration with an extended imaging condition is capable of generating subsurface angle gathers with an incremental improvement in amplitude versus angle fidelity and lower noise but comes at a higher computational cost. 相似文献
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试图运用波场动力学途径,旨在增强观测系统分析评估,本文提出基于单程波方程的角度域照明分析方法.本文方法不仅可用于观测系统设计,对叠前成像资料的考量、叠前振幅补偿和AVA（Amplitude Versus Angle,振幅随角度变化）反演也必具重要的意义.文中通过目的层邻域单个绕射点的正、反传波场分析,给出地下目标的水平和倾斜界面随角度变化的成像照明强度.单程波方法可用于模拟地震波在复杂速度构造下的传播,并得到较准确的幅值和多次到达的波场,用以对绕射点正、反传分析时可在照明分析中简明地利用幅值信息和多次到达的波场.本文方法可显现复杂盖层下目标的照明情况.本文中也对照明能量随传播距离的几何扩散进行补偿,突显了角度域的照明均匀度和范围,从而使得所分析的结果可直接应用于AVA的分析及补偿.针对照明分析的特点,文中建议可用一种快速的单程波波场延拓策略——频率速度相关变步长波场深度延拓.数值实验结果表明了本文方法是可行且有效的. 相似文献
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本文提出了一种基于双平方根算子的共炮检距道集波动方程保幅叠前深度偏移方法,将振幅误差补偿作为偏移的一部分与“运动学偏移”一起在偏移过程中实现.其基本内容包括：(1)从保幅的单平方根算子方程出发,推导出由双平方根算子定义的保幅单程波方程;(2)根据地震波摄动理论把速度场分裂为层内常速背景和变速扰动,分别在频率－波数域和频率－空间域求得波场深度延拓的偏移时移量及振幅校正系数,从而得到最终的DSR保幅波场延拓算子;(3)在高频假设条件下,把DSR保幅波场延拓公式中的积分运算进行稳相近似,得到保幅波场延拓的相移公式.理论分析和模型数值试验表明,该方法不但可以使散射能量聚焦、归位,提高成像精度;而且可以输出正确反映地下反射系数的振幅信息,为后续的地震属性分析（如AVO/AVA）提供更真实的地震信息. 相似文献
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Directional‐oriented wavefield imaging: a new wave‐based subsurface illumination imaging condition for reverse time migration 下载免费PDF全文
下载免费PDF全文 The key objective of an imaging algorithm is to produce accurate and high‐resolution images of the subsurface geology. However, significant wavefield distortions occur due to wave propagation through complex structures and irregular acquisition geometries causing uneven wavefield illumination at the target. Therefore, conventional imaging conditions are unable to correctly compensate for variable illumination effects. We propose a generalised wave‐based imaging condition, which incorporates a weighting function based on energy illumination at each subsurface reflection and azimuth angles. Our proposed imaging kernel, named as the directional‐oriented wavefield imaging, compensates for illumination effects produced by possible surface obstructions during acquisition, sparse geometries employed in the field, and complex velocity models. An integral part of the directional‐oriented wavefield imaging condition is a methodology for applying down‐going/up‐going wavefield decomposition to both source and receiver extrapolated wavefields. This type of wavefield decomposition eliminates low‐frequency artefacts and scattering noise caused by the two‐way wave equation and can facilitate the robust estimation for energy fluxes of wavefields required for the seismic illumination analysis. Then, based on the estimation of the respective wavefield propagation vectors and associated directions, we evaluate the illumination energy for each subsurface location as a function of image depth point and subsurface azimuth and reflection angles. Thus, the final directional‐oriented wavefield imaging kernel is a cross‐correlation of the decomposed source and receiver wavefields weighted by the illuminated energy estimated at each depth location. The application of the directional‐oriented wavefield imaging condition can be employed during the generation of both depth‐stacked images and azimuth–reflection angle‐domain common image gathers. Numerical examples using synthetic and real data demonstrate that the new imaging condition can properly image complex wave paths and produce high‐fidelity depth sections. 相似文献
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Moshe Reshef 《Geophysical Prospecting》2014,62(6):1453-1467
We present an innovative approach for seismic image enhancement using multi‐parameter angle‐domain characterization of common image gathers. A special subsurface angle‐domain imaging system is used to generate the multi‐parameter common image gathers in a summation‐free image space. The imaged data associated with each common image gathers depth point contain direction‐dependent opening‐angle image contributions from all the available incident and scattered wave‐pairs at this point. Each direction‐dependent opening‐angle data can be differently weighted according to its coherency measure. Once the optimal migration velocity is used, it is assumed that in the actual specular direction, the coherency measure (semblance) along reflection events, from all available opening angles and opening azimuths, is larger than that along non‐specular directions. The computed direction‐dependent semblance attribute is designed to operate as an imaging filter which enhances specular migration contributions and suppresses all others in the final migration image. The ability to analyse the structural properties of the image points by the multi‐parameter common image gather allows us to better handle cases of complicated wave propagation and to improve the image quality at poorly illuminated regions or near complex structures. The proposed method and some of its practical benefits are demonstrated through detailed analysis of synthetic and real data examples. 相似文献