Application of Amplitude Ratio Profiles Extracted with Prestack Kirchhoff Integral Migration

The Z component and X component profiles of seismic waves extracted with the prestack Kirchhoff integral migration could approximate to the primary wave （P wave） and converted shear wave （PS wave） profiles under certain conditions. The relative change of their reflection amplitude reflects the formation stress anomaly and subsurface media anisotropy. The principle and method for extracting amplitude ratios were studied and the application of amplitude ratio profiles was also examined when processing and interpreting actual seismic data. The amplitude ratio profile is an effective supplementary means of identifying the stratigraphic boundary and lithology.

Beamlet prestack depth migration and illumination： A test based on the Marmousi model

Beamlet 来源容易让强壮的本地、方向性的人物和罐头完成本地照明和移植。而且，他们比常规迁居方法提供更好的迁居结果。我们介绍让的横梁的基本原则包括窗口的 Fourier 变换和框架理论的 prestack 深度移植。我们基于 Gaussian 功能解释 Gabor-Daubechies (G-D ) 框架。Beamlet 分解在波浪地的本地空格和方向提供信息。我们综合横梁让来源和横梁在使用矩形和 Gaussian 窗口的小浪域让记录然后外推有一个 Fourier 有限差别的操作符的综合数据。我们用标准 Marmousi 模型测试方法。由比较并且分析让并且微笑的方向性的横梁与不同窗户和方向让的单身者的迁居结果，我们证明有 Gaussian 横梁的 prestack 深度迁居的有效性让方法。

Fast least-squares prestack time migration via accelerating the explicit calculation of Hessian matrix with dip-angle Fresnel zone

Amplitude versus offset analysis is a fundamental tool for determining the physical properties of reservoirs but generally hampered by the blurred common image gathers(CIGs).The blurring can be optimally corrected using the blockwise least-squares prestack time migration(BLS-PSTM),where common-offset migrated sections are divided into a series of blocks related to the explicit offsetdependent Hessian matrix and the following inverse filtering is iteratively applied to invert the corresponding reflectivity.However,calculating the Hessian matrix is slow.We present a fast BLS-PSTM via accelerating Hessian calculation with dip-angle Fresnel zone(DFZ).DFZ is closely related to optimal migration aperture,which significantly attenuates migration swings and reduces the computational cost of PSTM.Specifically,our fast BLS-PSTM is implemented as a two-stage process.First,we limit the aperture for any imaging point with an approximated the projected Fresnel zone before calculating the Hessian matrix.Then,we determine whether a seismic trace contributes to the imaging point via DFZ during calculating the Hessian matrix.Numerical tests on synthetic and field data validate the distinct speedup with higher-quality CIGs compared to BLS-PSTM.

Seismic 3D Prestack Time Migration on Parallel Computers

Parallel versions of prestack KirchhofT 3D integral migration algorithm, which is suitable forseismic data processing, are described in this paper. Firstly, the inherent parallel characteristics of seismicdata processing are analyzed. Then some principles in algorithm partition are discussed. Based on these analyses and the system architecture, communication mechanism, this algorithm is divided into four subtasksallocated to four nodes of 990 STAR-l. Then we describe in detail a module-partitioning method-theI / O processing and communication are separated from the computation process, the processes includingI / O processing and communication are allocated to transputer T805 and the other is allocated to processori860. These two processes are synchronized by shared memory and memory-lock mechanism, but the communication betWeen different nodes is implemented through links of transputer. Load balance among fourprocessor modules is performed dynamically. Finally, we discussed the speed--up of the parallel versions ofprestack KirchhofT 3D integral migration algorithm running on four nodes. Some further researches are also melltioned in this paper.

The Offset-Domain Prestack Depth Migration with Optimal Separable Approximation

The offset-domain prestack depth migration with optimal separable approximation, based on the double square root equation, is used to image complex media with large and rapid velocity variations. The method downward continues the source and the receiver wavefields simultaneously. The mixed domain algorithm with forward Fourier and inverse Fourier transform is used to construct the double square root equation wavefield extrapolation operator. This operator separates variables in the wave number domain and variables in the space domain. The phase operation is implemented in the wave number domain, whereas the time delay for lateral velocity variation is corrected in the space domain. The migration algorithm is efficient since the seismic data are not computed shot by shot. The data set test of the Marmousi model indicates that the offset-domain migration provides a satisfied seismic migration section on which complex geologic structures are imaged in media with large and rapid lateral velocity variations.

Prestack Depth Migration by a Parallel 3D PSPI

Prestack depth migration for seismic reflection data is commonly used tool for imaging complex geological structures such as salt domes, faults, thrust belts, and stratigraphic structures. Phase shift plus interpolation (PSPI) algorithm is a useful tool to directly solve a wave equation and the results have natural properties of the wave equation. Amplitude and phase characteristics, in particular, are better preserved. The PSPI algorithm is widely used in hydrocarbon exploration because of its simplicity, efficiency, and reduced efforts for computation. However, meaningful depth image of 3D subsurface requires parallel computing to handle heavy computing time and great amount of input data. We implemented a parallelized version of 3D PSPI for prestack depth migration using Open-Multi-Processing (Open MP) library. We verified its performance through applications to 3D SEG/EAGE salt model with a small scale Linux cluster. Phase-shift was performed in the vertical and horizontal directions, respectively, and then interpolated at each node. This gave a single image gather according to shot gather. After summation of each single image gather, we got a 3D stacked image in the depth domain. The numerical model example shows good agree- ment with the original geological model.

Internal Multiple Prediction Based on Imaging Profile Prediction and Kirchhoff Demigration

This paper introduces an internal multiple prediction method based on imaging profile prediction and Kirchhoff demigration.First,based on an inputted prestack time migration profile,the method predicts the prestack time migration profile that only includes internal multiples by inverse scattering series method.Second,the method uses velocity-weighted Kirchhoff demigration to create shot gathers that contains only internal multiples.Internal multiple prediction based on the prestack time migration profile effectively reduces the computational cost of multiple predictions,and the internal-multiple shot gathers created by Kirchhoff demigration remarkably reduces the complexity of the practical problem.Internal multiple elimination can be conducted through the combined adaptive multiple subtraction based on event tracing.Synthetic and field data tests show that the method effectively predicts internal multiples and possesses considerable potential in field data processing,particularly in areas where internal multiples develop seriously.

Influences of coarse grid selection on Kirchhoff beam migration

Kirchhoff beam migration is a beam migration method, which focuses on rapid imaging of geological structures. Although this imaging method ignores the amplitude information in the calculation process, it can calculate multi-arrival traveltime. This migration method takes into account both imaging accuracy and computational efficiency. Kirchhoff beam migration employs coarse grid techniques in several key steps such as traveltime calculation, weight function calculation, and imaging calculation. The selection of the coarse mesh size has an important influence on the computational efficiency and imaging accuracy of the migration imaging method. This paper will analyze this influence and illustrate the analysis results by the Marmousi data sets.

深反射地震成像揭示的班公湖-怒江缝合带中段Moho断阶及其大地构造意义

揭示班公湖-怒江(班怒)缝合带Moho(莫霍面)结构对于认识中特提斯洋壳俯冲和南羌塘坳陷成因具有重要地球动力学意义。基于横跨班怒缝合带的深反射地震数据(88°30′E),本文采用了中长波长静校正、噪声压制、优化叠加和叠前深度偏移(PSDM)等地震处理技术,获得了深度域地震反射偏移剖面、层速度场和高分辨率Moho结构。由深度域剖面显示,班怒缝合带Moho位于地表以下65~80 km,呈不连续北向抬升趋势,指示在拉萨地块与南羌塘地块之间存在岩石圈上地幔断阶,最大阶步可达15 km。综合分析缝合带两侧的Moho形态认为,这些断阶受南侧拉萨地体的岩石圈上地幔以19.5°北倾俯冲与北侧南羌塘地块的上地壳抬升驱动,可能与深部存在局部熔融相关。班怒缝合带下的Moho结构表明,随着晚侏罗世—早白垩世中特提斯洋闭合,南羌塘地体由边缘海沉积向前陆盆地转换,形成南羌塘坳陷。

复杂山地深度域地震成像处理方法--以龙门山山前带海棠铺复杂构造区为例

山前带复杂构造区蕴藏了丰富的油气资源。地震资料信噪比低和速度建模困难是目前山前带地震数据精确成像面临的主要问题。以龙门山山前带海棠铺地区地震数据为例,开展了叠前深度域地震成像处理方法攻关研究,重点在叠前噪声压制和叠前深度偏移速度建模等两方面开展了研究,具体如下。①加强低频弱信号保护,采用二次信噪分离技术,对噪声记录中有效信号进行二次信噪分离,最大限度保护低频弱信号不受损伤。②优化叠前深度偏移速度建模流程:首先优化传统深度域速度场更新输入道集与偏移输入道集共用一个道集的方式,对驱动速度场更新的输入道集进行五维数据规则化处理以提高其信噪比;然后以地质导向为基础,精细刻画强反射速度缺失界面,联合层析反演并融合深度域近地表速度模型,建立具有地质模型约束的深度域速度场;得到了精确的速度模型后,再修改偏移成像输入道集及偏移方法,将五维数据规则化前的地震道集作为输入道集,将全方位角度域叠前深度偏移作为最终偏移成像方法。将该方法应用于川西北海棠铺地区的地震数据处理,结果表明所提方法大幅提高了研究区的地震成像精度,最终得到的叠前深度偏移成像结果信噪比高,偏移归位合理,为进一步推动该区的深入勘探开发,提供了可供借鉴的深度域地震成像处理经验。

鄂尔多斯盆地南部黄土塬高密度三维地震处理技术与效果

长期以来,地震勘探技术在鄂尔多斯盆地油气勘探中发挥了重要作用(何文渊等,2011)。近年来,中石化在鄂尔多斯盆地南部黄土塬地区逐步开展准高密度、高密度三维地震勘探。黄土塬区地震地质条件异常复杂。一方面,地表覆盖巨厚黄土层,压实作用较弱,结构松散,地震波在传播过程中产生严重的吸收衰减作用和能量屏蔽作用.

复杂地表探区地震勘探的认识及地震数据成像处理的观点

油气地震勘探已经进入了复杂地表、复杂构造、复杂储层和深层目标勘探的阶段,“两宽一高”地震数据采集也已经成为业界的共识。我国西部各油气盆地的山前带/前山带探区已经成为我国油气资源的战略接替区域,并取得了不错的勘探效果。但是,这并不说明我们已经完全解决了“双复杂”探区地震勘探的核心技术问题。首先,界定山前带地震数据成像处理的根本问题在于基于剧变道间时差和低信噪比数据如何建立满足偏移成像要求的速度模型,从勘探地震介质系统的线性性及地震波成像本质是实现地下同一反射点处不同偏移距反射子波的同相位叠加的角度、从道间时差破坏局部线性同相轴线性相位特征的角度、从时间域成像处理与深度域成像处理的分界点在于基于风化层底面之上的速度模型进行静校正后CMP道集中同相轴是否满足双曲时距关系的假设的角度、从当前线性化的层析速度反演仅能估计背景光滑速度的角度、从线性化的偏移成像仅仅依赖于背景光滑速度模型的角度,全面分析了解决山前带地震数据成像处理问题的根本逻辑和方法技术流程,指出以道间时差消除为中心的数据预处理+小平滑基准面+全深度域地震波成像是解决山前带地震数据成像处理问题的正确技术路线。

逆时偏移数据体低波数噪声相对保幅衰减技术及应用

逆时偏移成像过程中压制低波数噪声后的叠加剖面仍存在较强能量的低波数噪声,其掩盖了有效反射信号对地质目标细节的精细刻画,因此,相对保幅地恢复有效反射信号是实现逆时偏移技术实际应用的重要保障。为此,将热力学领域中三维扩散滤波方法引入到深度域逆时偏移低波数噪声压制中,并对含低波数噪声的三维逆时偏移成像数据体进行体迭代处理。通过优化迭代次数和扩散系数2个关键参数,实现了低波数噪声和有效反射信号的相对保幅分离,同时采用局部化数据体输入和临时输出存储的优化策略,突破了计算节点内存限制,构建了一种高效的、相对保幅的低波数噪声衰减技术。理论模型和实际地震数据应用结果均表明,该技术处理结果的保真保幅性明显优于国际上常用的拉普拉斯算子去噪方法,且对噪声的敏感性弱,可以在深度域数据体上有效恢复掩盖在低波数噪声能量之下的有效反射信号,实现复杂地质目标的地震精细刻画,且其处理效率能够满足实际生产周期的需求,这可为同类深度域含低波数噪声成像资料的地震精细刻画提供方法和技术参考。

复杂地表窄方位地震数据叠前多维度重构技术应用研究——以准噶尔南缘呼图壁背斜三维为例

叠前数据重构是改善偏前地震数据“规则、均匀、对称”特征,提升叠前偏移成像质量的有效方法。准噶尔盆地南缘地表复杂,障碍较多,地震采集激发和接收的炮、检点位置不规则导致地震面元分布不均匀,叠前偏移成像效果不佳。针对复杂地表非规则采集的窄方位三维数据,在偏前进行了基于傅里叶变换的多维度插值重构技术适应性应用研究。重点开展了窄方位三维叠前地震数据分选和与之对应的叠前数据重构维度选择两方面的研究,运用数据重构关键参数进行试验,建立了复杂地表非规则采集窄方位三维地震数据重构技术流程,大幅改善和提升了中、浅层资料叠前深度偏移成像质量,有效弥补了叠前偏移成像时浅层地震资料覆盖次数低的不足。该技术思路对于类似复杂探区具有较好的借鉴作用和推广价值。

深度域属性分析技术在煤矿小断层识别中的应用研究

现今,叠前深度偏移技术越来越广泛地被应用于煤田地震资料处理中,叠前深度偏移获得的深度域地震数据如何进行资料解释,以获得可靠的地震地质成果,也有待于更加深入研究以及更加广泛地试验。地震属性作为描述地层结构、构造异常的重要特征量,一直以来为地震资料的解释提供了重要的依据。本文主要围绕深度域地震属性分析展开探讨,并通过深度域属性与时间域属性对比分析,认为:①相干体属性、方差体属性、曲率体属性对于较大断层响应敏感,蚂蚁体属性对于小断层响应更加敏感;②基于叠前深度偏移深度域地震数据体对地下构造真实形态的反映,直接对深度域数据体进行属性分析相较于时间域属性分析具有更强的压噪能力,对断层反应更加精准,在构造复杂区域,深度域属性分析的优势更加明显;③深度域多属性融合分析可以降低噪声的干扰,提高信噪比,明显清晰复杂构造区域断层分布,有助于降低小断层漏解释的概率,减低小断层解释平面位置的偏离,有助于提高小断层解释的效率与精度。本次研究以淮南丁集矿某采区13-1煤为例,以巷道揭露资料为依据,验证了叠前深度偏移深度域属性分析的优势与可靠性,为今后的深度域地震资料小构造解释工作提供一定的指导。

新一代高精度地震技术的发展方向——超密度地震技术

地震技术已由常规三维经高精度三维发展到高密度三维,但仍不能满足地表、构造、储层“三复杂”勘探开发目标对地震资料精度的需求。为满足“三复杂”条件下地震成像的需求,依据高密度地震技术及计算机和物探装备的发展趋向,提出了“超密度地震技术”的新思路。通过野外小道距采集实验和小网格正演模拟实验,验证了超密度采集对近地表速度建模与静校正及深层高陡断裂成像的改善。考虑超高密度地震采集的仪器和装备需求及海量数据以及经济可行性,提出了“变道距+插值”的实施策略及相关仪器、存储、计算配套技术,分析认为10×10^(4)道级节点仪、海量数据存储与计算是实现“超密度地震技术”的基础,“小宽高”高密度地震采集技术、“小平滑面”RTM叠前深度偏移技术和压缩感知或五维插值技术是重要的关键技术。未来更高精度的地震技术应是炮道密度大于200×10^(4)道/km^(2)的超密度地震技术,为此,需要加快发展超大规模的节点仪单点采集装备、海量数据存储与计算装备及变道距数据插值技术等,并推进野外地震采集的实践。

地震海洋学新进展

多尺度动力过程是当前海洋学研究的重点。地震海洋学能在数百km的剖面上获得分辨率为10 m的高质量数据,基于该数据能够解析涡旋边缘的亚中尺度动力现象(如北冰洋地震剖面研究发现的漂亮旋臂)和内孤立波的振幅垂向结构,并能够进行内孤立波波形变化与混合参数分布叠合分析等,本文对这些方面获得的新认识和新进展进行了综述。同时,共偏移距剖面叠前偏移方法充分利用多道地震的多次覆盖特点,获得随时间变化的一系列地震图像,为地震海洋学在海洋内部结构的时空演变研究方面增添了利器。因此,地震海洋学提供的新的时空视角必将在海洋多尺度动力过程研究中起到重要作用。

Reverse-Time Prestack Depth Migration of GPR Data from Topography for Amplitude Reconstruction in Complex Environments

With increased computational power, reverse-time prestack depth migration（RT-PSDM） has become a preferred imaging tool in seismic exploration, yet its use has remained relatively limited in ground-penetrating radar（GPR） applications. Complex topography alters the wavefield kinematics making for a challenging imaging problem. Model simulations show that topographic variation can substantially distort reflection amplitudes due to irregular wavefield spreading, attenuation anomalies due to irregular path lengths, and focusing and defocusing effects at the surface. The effects are magnified when the topographic variations are on the same order as the depth of investigation––a situation that is often encountered in GPR investigations. Here, I use a full wave-equation RT-PSDM algorithm to image GPR data in the presence of large topographic variability relative to the depth of investigation. The source and receiver wavefields are propagated directly from the topographic surface and this approach inherently corrects for irregular kinematics, spreading and attenuation. The results show that when GPR data are acquired in areas of extreme topography, RT-PSDM can accurately reconstruct reflector geometry as well as reflection amplitude.

点扩散函数深度域反演

当前地震勘探领域缺乏深度域反演的有效方法,无法直接利用深度偏移后的地震数据进行储层预测。为解决这一问题,本研究采用基于点扩散函数的深度域反演方法对深度域地震数据进行反演,该方法借鉴光学领域的点扩散函数的概念,在偏移速度场中加入均匀分布的点散射体,然后使用波动方程有限差分的方法进行正演模拟,在此基础上进行叠前声波波动方程逆时偏移,得到点扩散函数。并且本研究依据最小二乘理论推导了点扩散函数深度域声波阻抗反演的公式,最后使用该反演方法在Marmousi模型和实际的地震资料上进行了测试。反演测试结果表明:该深度域反演方法反演结果精度高,稳定性好。

活动断层地震勘探中的高精度偏移与反偏移技术

为了进一步发展活动断层空间位置和精细结构探查技术,解决在活动断层探测地震数据处理过程中,缺少一种通过数学手段对地震成像结果进行可靠性评价的问题,开展了将‘反偏移’这一地震波偏移成像的逆运算引入活动断层探测地震数据处理的研究。分析了偏移与反偏移的关系,提出了以叠前深度域逆时偏移和波动方程反偏移为核心的主动源地震勘探数据高精度处理流程。选择了生长断层、花状构造等有代表性的复杂断裂构造实际探测数据进行处理。处理结果表明,利用本文提出的以波动方程逆时偏移和反偏移为核心的地震数据处理流程,能够有效提高活动断层地震成像剖面的可靠性和精确度。通过本次研究可以认为将偏移和反偏移这一对严格对应的地震数据处理算子引入活动断层探测领域,有助于推动活动断层探测精确度和分辨力的提升。尤其是在开展钻孔联合地质剖面探测或科学钻探研究时,应用本文方法进行地震勘探数据高精度成像处理,利用多种数学手段相互检验,能够有效确保断层上断点定位准确,节约钻探成本。