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共聚焦点(CFP)偏移技术是一种基于等时原理,将Kirchhoff积分法的一步偏移分两步聚焦（即激发聚焦和检波聚焦）来完成的叠前地震成像方法.该方法借助于逆时聚集算子和共聚焦点道集来实现叠前偏移成像.基于共聚焦点道集的叠前深度偏移是把基于共炮集的深度偏移的算法引入到CFP技术上来,基于波场延拓的理论来实现偏移成像,该方法首先生成共聚焦点道集,然后基于面炮合成的理论合成聚焦震源,最终通过相关成像来实现叠前偏移成像.该方法选取较少的聚焦点就可以实现对于地下构造的偏移成像,和炮域波动方程偏移相比,其计算效率得到了提高.通过模型试算和实际资料的试处理,验证了该方法在实现叠前深度偏移成像上的正确性和有效性. 相似文献
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当前的三维VSP地震数据偏移成像实现都是在共炮点道集或共检波点道集中逐个道集循环进行的,计算效率相对较低.根据三维VSP观测系统中炮点和检波点布置的特殊性和地震波场满足线性叠加的特性,本文提出了一种三维VSP数据的高效偏移成像方法,即首先通过对三维VSP共接收点道集进行地震数据的广义合成得到一种超道集,然后在共接收点道集的波场深度外推过程中逐步应用多震源波场对超道集进行偏移成像,即利用一次波场深度外推循环完成对所有共检波点道集数据的偏移成像.通过三维VSP模型数据与实际地震数据的偏移成像试验验证了这种高效的超道集偏移成像方法可取得与常规共检波点道集相当的偏移成像效果,还具有极高的计算效率,其计算量与单个共检波点道集的偏移成像计算量相当. 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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《地球物理学进展》2017,(2)
Kirchhoff偏移和逆时偏移(RTM)是目前最广泛应用的两种叠前深度偏移方法.两种方法的基础均为波动方程,理论上没有倾角限制.抽取的共成像点道集(CIG)可用于速度建模、叠前反演以及地下属性解释等.叠前反演的精度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,得到的共成像点道集必须要振幅保真.本文在理论上阐述两种偏移方法的基本原理,并对抽道集技术的保幅性进行对比.Marmousi和Sigsbee2a模型结果表明:在简单构造区,两者的成像效果相当;在复杂构造区,不论在成像精度还是保幅性上逆时偏移都比Kirchhoff偏移优越,特别是高陡倾角断层、岩下构造等复杂构造成像时.然而,在碳酸盐岩储层实际资料处理时发现,由于速度场准确性的限制,两种偏移方法各有优势.因此,在实际应用时,由于无法明确得到地下介质的确切信息,较难对两种偏移方法给出明确的优劣评价. 相似文献
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消除层间多次波是地震勘探资料处理研究领域的难题,尤其对于实际资料的处理,到目前为止还很难找到一种完全有效的方法. 本文给出了仅对一次波成像既波路径偏移方法压制层间多次波方法,在共炮道集和共检波点道集分别计算炮点射线的入射角和检波点射线的出射角,由此计算的角度作为射线追踪的初始角度,计算地震波射线的传播路径. 结合由程函方程计算的走时表,判断偏移范围是反射波还是多次波. 在前期偏移过程压制多次波的理论研究基础上,本文主要研究波路径偏移消除多次波的应用部分. 为了进一步说明效果的有效性,计算了在单炮和共成像点道集压制层间多次波,给出了实际资料的压制多次波的偏移结果. 相似文献
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多聚焦(MF)成像技术综述 总被引：3，自引：2，他引：1
MF(多聚焦)技术是一组以巨模型——独立成像为特征的地震成像方法,在该方法中,大的地震道的叠合道集进行叠加,而每一个叠合道集都横越许多共中心点道集,它用聚焦参数的最优化过程代替了传统偏移方法中的速度模型修正,极大避免了“速度难题”,MF技术可以广泛应用于地震数据处理和反演的各个方面(处理复杂的近地表难题、多次波的等),在解决复杂地质问题时更是有着独到的效果。因此,MF成像技术在地震勘探中将有广阔的应用前景。 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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《地球物理学进展》2015,(5)
在偏移速度分析领域,共成像点道集对偏移速度分析(MVA)而言是非常重要的.目前,用于偏移速度分析的共成像点道集主要有偏移距域共成像点道集(ODCIG)和角度域共成像点道集(ADCIG).由于ODCIG是一种能量聚焦型道集,且在复杂介质条件下存在运动学假象,使其在MVA中的应用受到限制.ADCIG的出现解决了这些问题,它能够适应射线传播的多路径现象,避免假象的产生,波动方程偏移得到的ADCIG被证明是没有假象的道集,也被认为是当前最为合理的道集.论文在CMP域,利用双平方根算子对记录波场进行反向延拓,因为双平方根算子偏移具有倾角假频少、边界处理简单、无需求取震源子波、无需考虑偏移孔径问题以及计算效率高等特点;在频率-波数域将偏移距信息映射到角度域得到ADCIG.ADCIG的提取过程实际是转化了地震数据中的多偏移距信息,本质上,它仍旧是对地震数据中多偏移距信息的体现.最后论文将ADCIG道集应用在SEG/EAGE岩丘模型中,结果表明,不同反射角下的ADCIG可以对地下不同的区域进行成像,且角度域成像具有地震波成像剖面分辨率高,边界干扰较小等特点. 相似文献
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Conventional seismic data processing methods based on post‐stack time migration have been playing an important role in coal exploration for decades. However, post‐stack time migration processing often results in low‐quality images in complex geological environments. In order to obtain high‐quality images, we present a strategy that applies the Kirchhoff prestack time migration (PSTM) method to coal seismic data. In this paper, we describe the implementation of Kirchhoff PSTM to a 3D coal seam. Meanwhile we derive the workflow of 3D Kirchhoff PSTM processing based on coal seismic data. The processing sequence of 3D Kirchhoff PSTM includes two major steps: 1) the estimation of the 3D root‐mean‐square (RMS) velocity field; 2) Kirchhoff prestack time migration processing. During the construction of a 3D velocity model, dip moveout velocity is served as an initial migration velocity field. We combine 3D Kirchhoff PSTM with the continuous adjustment of a 3D RMS velocity field by the criteria of flattened common reflection point gathers. In comparison with post‐stack time migration, the application of 3D Kirchhoff PSTM to coal seismic data produces better images of the coal seam reflections. 相似文献
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J.F.B. Bolte 《Geophysical Prospecting》2004,52(6):523-534
The common focal point (CFP) method and the common reflection surface (CRS) stack method are compared. The CRS method is a fast, highly automated procedure that provides high S/N ratio simulation of zero‐offset (ZO) images by combining, per image point, the reflection energy of an arc segment that is tangential to the reflector. It uses smooth parametrized two‐way stacking operators, based on a data‐driven triplet of attributes in 2D (eight parameters in 3D). As a spin‐off, the attributes can be used for several applications, such as the determination of the geometrical spreading factor, multiple prediction, and tomographic inversion into a smooth background velocity model. The CFP method aims at decomposing two‐way seismic reflection data into two full‐aperture one‐way propagation operators. By applying an iterative updating procedure in a half‐migrated domain, it provides non‐smooth focusing operators for prestack imaging using only the energy from one focal point at the reflector. The data‐driven operators inhibit all propagation effects of the overburden. The CFP method provides several spin‐offs, amongst which is the CFP matrix related to one focal point, which displays the reflection amplitudes as measured at the surface for each source–receiver pair. The CFP matrix can be used to determine the specular reflection source–receiver pairs and the Fresnel zone at the surface for reflection in one single focal point. Other spin‐offs are the prediction of internal multiples, the determination of reflectivity effects, velocity‐independent redatuming and tomographic inversion to obtain a velocity–depth model. The CFP method is less fast and less automated than the CRS method. From a pointwise comparison of features it is concluded that one method is not a subset of the other, but that both methods can be regarded as being to some extent complementary. 相似文献
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是否能够正确地建立深度域三维速度模型是三维叠前深度偏移成败的关键 .本文根据Deregowski循环 ,利用叠前深度域地震成像对速度模型变化的敏感性 ,采用偏移迭代逐次逼近最佳成像速度 ,研究开发了一套快捷有效的三维叠前深度偏移深度域速度模型建立技术 .借鉴时间域CDP(共深度点 )道集上常规叠加速度分析的策略 ,在深度域CRP(共反射点 )道集上 ,提出剩余慢度平方谱的概念并建立相应的实现技术 .导出深度域中均方根速度与层速度之间的关系 ;按照串级偏移原理确定偏移循环过程中初始速度、剩余速度及修改后速度之间的关系 ;采用蒙特卡洛非线性优化算法实现从剩余慢度平方谱中自动拾取层速度 ,讨论了其地质速度约束条件和蒙特卡洛非线性优化的收敛准则 ,使得所拾取的层速度模型具有合理的地质意义并获得最佳偏移成像效果 .SEG EAGE理论模型数值试算验证了方法的有效性 ,在海拉尔盆地霍多莫尔工区 ,5 8km2 三维资料的速度模型建立并获得满意的三维叠前深度偏移成像 . 相似文献
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Seismic migration can be formulated in terms of two consecutive downward extrapolation steps: refocusing the receivers and refocusing the sources. Applying only the first focusing step with an estimate of the focusing operators results in a common focal point (CFP) gather for each depth point at a reflecting boundary. The CFP gathers, in combination with the estimates of the focusing operators, can be used in an iterative procedure to obtain the correct operators. However, current 3D seismic data acquisition geometries do not contain the dense spatial sampling required for calculation of full 3D CFP gathers. We report on the construction of full 3D CFP gathers using a non‐full 3D acquisition geometry. The proposed method uses a reflector‐orientated data infill procedure based on the azimuthal redundancy of the reflection data. The results on 3D numerical data in this paper show that full 3D CFP gathers, which are kinematically and dynamically correct for the target event, can be obtained. These gathers can be used for iterative updating of the 3D focusing operators. 相似文献
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In areas of complex geology such as the Canadian Foothills, the effects of anisotropy are apparent in seismic data and estimation of anisotropic parameters for use in seismic imaging is not a trivial task. Here we explore the applicability of common‐focus point (CFP)‐based velocity analysis to estimate anisotropic parameters for the variably tilted shale thrust sheet in the Canadian Foothills model. To avoid the inherent velocity‐depth ambiguity, we assume that the elastic properties of thrust‐sheet with respect to transverse isotropy symmetry axis are homogeneous, the reflector below the thrust‐sheet is flat, and that the anisotropy is weak. In our CFP approach to velocity analysis, for a poorly imaged reflection point, a traveltime residual is obtained as the time difference between the focusing operator for an assumed subsurface velocity model and the corresponding CFP response obtained from the reflection data. We assume that this residual is due to unknown values for anisotropy, and we perform an iterative linear inversion to obtain new model parameters that minimize the residuals. Migration of the data using parameters obtained from our inversion results in a correctly positioned and better focused reflector below the thrust sheet. For traveltime computation we use a brute force mapping scheme that takes into account weakly tilted transverse isotropy media. For inversion, the problem is set up as a generalized Newton's equation where traveltime error (differential time shift) is linearly dependent on the parameter updates. The iterative updates of parameters are obtained by a least‐squares solution of Newton's equations. The significance of this work lies in its applicability to areas where transverse isotropy layers are heterogeneous laterally, and where transverse isotropy layers are overlain by complex structures that preclude a moveout curve fitting. 相似文献
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以先进的波动理论为基础的波动方程保幅地震偏移成像是在给出正确位置的同时也给出真实振幅的一种特殊完善.作者从保幅单程波动方程的非稳态相移公式出发,基于反问题求解中常用的摄动理论,利用单平方根算子的渐进展开,从而推导出保幅叠前深度偏移方程的高阶广义屏形式;针对散射波场计算项对于横向变速介质的不稳定性,通过数学近似提出一个有效提高稳定性的策略,应用到波场递归外推过程中,从而得到一种稳定的保幅高阶广义屏叠前深度偏移算子.理论模型试算和实际资料处理表明,该方法不但可以更精确地使散射能量聚焦、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,使AVO响应更加清晰,提高了AVO资料的分析精度. 相似文献
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椭圆展开共反射点(CRP)方法可以获得比常规倾角时差校正(DMO)方法更近似的零偏移距时间剖面和相应CRP速度场.大量研究和实践证实,在非均质性较弱的地区,该方法取得的成果显著.但由于该方法没有考虑速度的横向变化和转换波等情况,当地下介质存在较强非均质性时,该方法不再准确,需要引进反映速度横向变化的双参数(上行波与下行波的平均速度和速度比)进行改进.本文详细推导了引入双参数后的叠加和速度分析算法,并通过数值模型和地震资料处理证实,修正后的算法可以更好地解决地质复杂地区速度建模和叠加成像问题. 相似文献
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In this case study we consider the seismic processing of a challenging land data set from the Arabian Peninsula. It suffers from rough top‐surface topography, a strongly varying weathering layer, and complex near‐surface geology. We aim at establishing a new seismic imaging workflow, well‐suited to these specific problems of land data processing. This workflow is based on the common‐reflection‐surface stack for topography, a generalized high‐density velocity analysis and stacking process. It is applied in a non‐interactive manner and provides an entire set of physically interpretable stacking parameters that include and complement the conventional stacking velocity. The implementation introduced combines two different approaches to topography handling to minimize the computational effort: after initial values of the stacking parameters are determined for a smoothly curved floating datum using conventional elevation statics, the final stack and also the related residual static correction are applied to the original prestack data, considering the true source and receiver elevations without the assumption of nearly vertical rays. Finally, we extrapolate all results to a chosen planar reference level using the stacking parameters. This redatuming procedure removes the influence of the rough measurement surface and provides standardized input for interpretation, tomographic velocity model determination, and post‐stack depth migration. The methodology of the residual static correction employed and the details of its application to this data example are discussed in a separate paper in this issue. In view of the complex near‐surface conditions, the imaging workflow that is conducted, i.e. stack – residual static correction – redatuming – tomographic inversion – prestack and post‐stack depth migration, leads to a significant improvement in resolution, signal‐to‐noise ratio and reflector continuity. 相似文献
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Amplitude versus offset information is a key feature to seismic reservoir characterization. Therefore amplitude preserving migration was developed to obtain this information from seismic reflection data. For complex 3-D media, however, this process is computationally expensive. In this paper we present an efficient traveltime based strategy for amplitude preserving migration of the Kirchhoff type. Its foundations are the generation of traveltime tables using a wavefront-oriented ray-tracing technique, and a generalized moveout relation for 3-D heterogeneous media. All required quantities for the amplitude preserving migration are computed from coarsely gridded traveltime tables. The migration includes the interpolation from the coarsely gridded input traveltimes onto the fine migration grid, the computation of amplitude preserving weight functions, and, optionally, the evaluation of an optimized migration aperture. Since ray tracing is employed for the traveltime computation the input velocity model needs to be smooth, i.e. velocity variations of spatial dimensions below the wavelength of the considered reflection signals are removed. Numerical examples on simple generic models validate the technique and an application to the Marmousi model demonstrates its potential to complex media. The major advantage of the traveltime based strategy consists of its computational efficiency by maintaining sufficient accuracy. Considerable savings in storage space (105 and more for 3-D data with respect to no interpolation at all) can be achieved. The computational time for the stack can be substantially reduced (up to 90% in 3-D) with the optimized migration aperture since only those traces are stacked which really contribute to the image point under consideration. 相似文献