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1.
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
2.
Prestack depth migration of multicomponent seismic data improves the imaging accuracy of subsurface complex geological structures. An accurate velocity field is critical to accurate imaging. Gaussian beam migration was used to perform multicomponent migration velocity analysis of PP- and PS-waves. First, PP- and PS-wave Gaussian beam prestack depth migration algorithms that operate on common-offset gathers are presented to extract offset-domain common-image gathers of PP- and PS-waves. Second, based on the residual moveout equation, the migration velocity fields of P- and S-waves are updated. Depth matching is used to ensure that the depth of the target layers in the PP- and PS-wave migration profiles are consistent, and high-precision P- and S-wave velocities are obtained. Finally, synthetic and field seismic data suggest that the method can be used effectively in multiwave migration velocity analysis. 相似文献
3.
Angle-domain common-image gathers (ADCIGs) can provide an effective way for migration velocity analysis and amplitude versus angle analysis in oil–gas seismic exploration. On the basis of multi-component Gaussian beam prestack depth migration (GB-PSDM), an alternative method of directly extracting multiwave ADCIGs is presented in this paper. We first introduce multi-component GB-PSDM, where a wavefield separation is proceeded to obtain the separated PP- and PS-wave seismic records before migration imaging for multiwave seismic data. Then, the principle of extracting PP- and PS-ADCIGs using GB-PSDM is presented. The propagation angle can be obtained using the real-value travel time of Gaussian beam in the course of GB-PSDM, which can be used to calculate the incidence and reflection angles. Two kinds of ADCIGs can be extracted for the PS-wave, one of which is P-wave incidence ADCIGs and the other one is S-wave reflection ADCIGs. In this paper, we use the incident angle to plot the ADCIGs for both PP- and PS-waves. Finally, tests of synthetic examples show that the method introduced here is accurate and effective. 相似文献
4.
Bayesian Markov chain Monte Carlo inversion for anisotropy of PP- and PS-wave in weakly anisotropic and heterogeneous media 
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下载免费PDF全文 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. 相似文献
5.
以多分量地震观测为基础,联合纵波和转换横波数据能更有效地估计地下介质的弹性和物性参数,提升地质构造成像与油气储层描述的精度.在海底多分量地震数据处理过程中,观测记录的上-下行波分解和P/S波分离可压制水层鸣震以及P与S波之间的串扰,对偏移成像和纵横波速度建模至关重要.但受海底环境、仪器与观测因素共同影响,许多海底多分量地震资料都无法基于现有的海底波场分离方法与流程取得合理的结果.本文以海底声波场与弹性波场分离基本原理为基础,通过对方法流程的修正,摆脱常规流程对中小偏移距直达波信号的依赖性.借助模拟数据实验讨论了波场分离对海底介质参数、噪声的敏感性.结合东海YQ探区海底多分量地震资料上-下行P/S波分离及其叠前深度偏移处理,验证了本文方法流程的可行性. 相似文献
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基于地震波传播过程中能量衰减的物理机制理论分析,通过梳理已有研究成果,采用正弦函数分频、最小二乘法高阶e指数曲线拟合等技术研发了可实现时间、频率、炮检距和炮域内地震波4D球面扩散与大地吸收衰减补偿方法,解决了常规振幅补偿无法补偿振幅随频率衰减和剩余补偿的问题。实际地震资料处理结果表明,相较于常规振幅补偿方法,该方法可更准确地对球面扩散和大地吸收造成的地震波衰减进行自适应拟合与补偿,较好的恢复中、高频信号成分,提高主频,拓宽频带,有效提高成像分辨率,并较好地保持了振幅的相对关系。 相似文献
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横波速度动校正后的共转换点(CCP)道集内,同时刻的各道横波信号S变换(ST)谱与其叠加道ST谱具有相似关系.因此,可基于这种相似关系设计自适应滤波器来提取多波地震数据中的横波波场.首先对共中心点(CMP)道集应用纵波速度动校正并在各道减去叠加道来去除数据中的纵波波场;然后在CCP道集应用横波速度动校正,将地震道振幅水平调整至叠加道振幅水平并做S变换,以叠加道ST谱为参考对地震道ST谱进行自适应滤波,去除数据中的残余纵波和噪声;最后,将滤波结果的振幅水平恢复至滤波前振幅水平.理论和实际数据试算表明,本文方法可有效提取多波地震数据中的横波波场,为多波多分量横波数据处理提供新思路. 相似文献
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Imaging the PP- and PS-wave for the elastic vector wave reverse-time migration requires separating the P- and S-waves during the wave field extrapolation. The amplitude and phase of the P- and S-waves are distorted when divergence and curl operators are used to separate the P- and S-waves. We present a P- and S-wave amplitude-preserving separation algorithm for the elastic wavefield extrapolation. First, we add the P-wave pressure and P-wave vibration velocity equation to the conventional elastic wave equation to decompose the P- and S-wave vectors. Then, we synthesize the scalar P- and S-wave from the vector Pand S-wave to obtain the scalar P- and S-wave. The amplitude-preserved separated P- and S-waves are imaged based on the vector wave reverse-time migration (RTM). This method ensures that the amplitude and phase of the separated P- and S-wave remain unchanged compared with the divergence and curl operators. In addition, after decomposition, the P-wave pressure and vibration velocity can be used to suppress the interlayer reflection noise and to correct the S-wave polarity. This improves the image quality of P- and S-wave in multicomponent seismic data and the true-amplitude elastic reverse time migration used in prestack inversion. 相似文献
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P-SV转换波处理与传统的P-P波处理有很大的不同,如S波静校正、CCP叠加、P-SV速度分析和偏移等,其中最大的难题就是S波静校正问题.S波速度基本不受潜水面的影响,与纵波静校正没有直接相关性,有时横波静校正量能达到纵波静校正量的十倍,用纵波静校正量乘以比例系数来解决横波静校正问题将导致较大误差.同一接收点X和Z分量存在一定的初至时差,该时差代表了P波和S波在低降速带的走时差,可以利用该时差和近地表纵横波速度比信息去除低降速带对横波的影响,得到准确的静校正量.本文利用多分量初至时差推导了较为精确的横波静校正公式,再结合共检波点叠加求取剩余静校正量的方法,形成了完整的转换波静校正配套方法.利用该方法对苏里格气田二维及三维多波地震资料进行了实际处理,数据处理结果证明了该方法的有效性,该方法尤其适用于其他方法难以奏效的风化层较厚地区的横波静校正量求解,该方法也同时考虑了长波长横波静校正问题. 相似文献
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地震波传播过程中,质点的振动不仅包括三个独立的平移部分,还包括三个独立的旋转部分.本文基于一阶速度-应力弹性波方程,采用分裂完全匹配层(SPML)的吸收边界条件,推导了时间导数二阶精度和空间导数高阶精度的交错网格有限差分格式的弹性波速度与应力各分量计算公式,模拟了各向同性介质中均匀模型和层状模型下的六分量波场,并对二维各向同性层状模型下的三个分量地震记录做高分辨率线性拉东变换得到各自的频散能谱.数值模拟分析结果表明:(1)旋转分量的能量要比平动分量弱的多;(2)在平动分量上,面波能量强,频率低,反射P波能量较强,反射S波能量稍弱;在旋转分量上,反射P波能量很弱,S波能量强;(3)与平动分量相比,旋转分量的频散能谱效果更好,能看到基阶和完整的高阶面波,即旋转分量能反映更多的地下介质信息. 相似文献
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《Journal of Applied Geophysics》2010,72(4):149-156
Characterization of shallow structures was performed by using different approaches analysing both P- and S-wave seismic data with different resolution. The refraction tomography provided P and S velocity models of the first 80 m, while the reflection seismic processing gives a reasonable stacking velocity field until 300 m depth for both P- and S-wave data. So, we estimated the Vp/Vs ratio and an empirical relationship between the two velocities. We characterised the shallow layers using tomographic velocity models and the deeper layers using seismic images with different resolution. The seismic images were obtained by conventional CMP reflection seismic processing and by a novel multi-refractor imaging technique. 相似文献
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多波多分量地震勘探方法在油气田勘探开发中日益受到重视,但在工程和活动断裂探测中过去还没有开展多波多分量地震勘探的先例.本文简要介绍了在北京黄庄—高丽营断裂上开展的三分量浅层地震反射试验数据采集和资料处理方法,以及取得的初步结果.试验结果表明,采用纵波震源或横波震源激发、三分量接收的浅层地震勘探方法,可获得较高信噪比的浅层地震纵波、横波和转换波剖面,特别是水平分量采集的横波和转换波可提供很有意义的地下结构和构造信息.综合利用纵波、横波和转换波剖面特征进行的地质分层和断层解释结果取得了与跨断层的钻孔联合地质剖面结果较好的一致性. 相似文献
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Accurate well ties are essential to practical seismic lithological interpretation. As long as the geology in the vicinity of the reservoir is not unduly complex, the main factors controlling this accuracy are the processing of the seismic data and the construction of the seismic model from well logs. This case study illustrates how seismic data processing to a near-offset stack, quality control of logs and petrophysical modelling improved a well tie at an oil reservoir. We demonstrate the application of a predictive petrophysical model in the preparation and integration of the logs before building the seismic model and we quantify our improvements in well-tie accuracy. The data for the study consisted of seismic field data from a 3D sail line through a well in a North Sea oilfield and a suite of standard logs at the well. A swathe of fully processed 3D data through the well was available for comparison. The well tie in the shallow section from first-pass seismic data processing and a routinely edited sonic log was excellent. The tie in a deeper interval containing the reservoir was less satisfactory: the phase errors within the bandwidth of the seismic wavelet were of the order of 20°, which we consider too large for subsequent transformation of the data to seismic impedance. Reprocessing the seismic data and revision of the well-log model reduced these phase errors to less than 10° and improved the consistency of the deep and shallow well ties. The reprocessing included densely picked iterative velocity analysis, prestack migration, beam-forming multiple attenuation, stacking the near-offset traces and demigration and remigration of the near-offset data. The petrophysical model was used to monitor and, where necessary, replace the P-wave sonic log with predictions consistent with other logs and to correct the sonic log for mud-filtrate invasion in the hydrocarbon-bearing sand. This editing and correction of the P-wave transit times improved the normal-incidence well tie significantly. The recordings from a monopole source severely underestimated the S-wave transit times in soft shale formations, including the reservoir seal, where the S-wave velocity was lower than the P-wave velocity in the drilling mud. The petrophysical model predicted an S-wave log that matched the valid recordings and interpolated between them. The subsequent seismic modelling from the predicted S-wave log produced a class II AVO anomaly seen on the CDP gathers around the well. 相似文献
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在地震勘探资料处理中,子波的零相位化有助于提高地震资料的分辨率、改善叠加剖面的质量.常规的相位校正方法是利用测井合成记录对井旁地震记录进行相位估计,然后对整条剖面进行常相位校正,该方法没有考虑地震子波相位的非稳态性（相位随时间和空间变化）.虽然通过局部相似度方法利用最大方差模准则或包络最大相似度准则可以估计出随时间和空间变化的相位属性,但是由于零相位判别准则本身具有一定的局限性,因此精度有限.针对这一问题,本文在局部地震属性和局部平面波模型下,提出了一种井约束的非稳态相位校正方法,该方法不仅考虑了子波相位的非稳态性,而且充分利用了测井合成地震记录进行相位校正精度高的优点.理论模型和实际资料处理表明,本文方法可以有效实现信号的零相位化,有利于改善叠加效果,提高资料的分辨率. 相似文献
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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. 相似文献
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南黄海海相地层的地震波场特征和层位标定一直是困扰地震勘探的重要问题.为了近距离、高精度和高分辨率地观测井周围构造特征和岩石性质引起的波场变化,为地震资料的采集、处理与解释提供地震波衰减规律、速度与层位标定等信息,对大陆架科学钻探CSDP-2井实施了近零偏移距垂直地震剖面（VSP）观测.针对海相地层顶部强反射界面地震波穿透难的问题,采用了大容量气枪震源并设计了气枪阵列组合方式,提高了激发地震波的能量,获得了强反射界面之下清晰的PP、PS下行波和上行波信号.采用了三分量偏振合成、组合滤波和波场分离等处理方法,对VSP观测数据进行处理,获得了海相三叠系—志留系的精细的纵波、横波速度结构和地层吸收因子等物性数据,建立了钻井地层、测井、VSP上行波和多道地震剖面对应关系,实现了不同尺度的地质和地球物理属性资料的有效衔接,标定了钻井地质剖面上各深度地质体的地震反射特性,厘定了过井地震剖面上反射同相轴的地质属性.此次观测取得的纵波、横波速度信息,成为建立南黄海海相地层速度模型主要的资料来源,也是地震资料的岩性反演处理不可缺少的信息. 相似文献
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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. 相似文献
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Introduction It has been known that each soil type responds differently when it is subjected to ground mo-tion from earthquakes. So, the study of local site effects on seismic ground motions is one of the most important goals of earthquake engineering. It is practical importance to develop methods for assessing the nature and potential of sediment amplification, especially when choosing the location and design of critical and essential facilities. At present, however, the method by which site … 相似文献