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1.
远震虚震源反射成像方法利用远震初至波在台网之下地表与地下界面间形成的反射波(PPdp震相)波形资料进行台网地区地震反射结构研究.此方法先用台网各台站的平均初至波形求取震源信号,再用该震源信号与各道地震记录作反褶积从而取得反射剖面.本文介绍了远震虚震源反射成像的基本原理和实现步骤,并以三峡地区的观测资料为例,得到三峡库首区上地壳的反射地震剖面.成像剖面中解释出的四川盆地和秭归盆地的底界面位置和形态与地表地质观测和大地构造背景吻合.为验证虚震源成像的能力,本文使用弹性波正演模拟合成地震数据,经过处理实际资料一样的步骤获得虚震源成像结果.正演模拟表明,叠加多个远震的反射地震剖面可以有效地改善成像的信噪比和连续性;虚震源成像需要选择特定的震源频率范围,以减轻高频噪音以及低频造成的成像问题.在研究上地壳结构时,建议在不适合主动源采集和缺乏低频信号的地区尝试远震虚震源方法. 相似文献
2.
《地球物理学进展》2020,(3)
将盲源地震波记录中有用的反射波信号恢复并降低噪声影响,历来是地震勘探数据处理环节中的一个难题.本文利用tesseral软件,通过建立一个典型凹陷模型,对影响盲源地震响应恢复的六个主要因素:自由表面、被动源的震源分布、被动源数目、被动源子波信号的持续时间、震源子波类型和随机噪声的响应特征分别进行研究,研究结果表明,各影响因素对盲源地震响应恢复质量均有一定程度的影响,其中被动源的震源分布情况、能捕获的被动源数目和被动源持续时间这三个因素直接决定了被动源地震响应的恢复质量,能否接收到来自自由地表的多次波,决定了地震响应恢复的可能性.这对实际地震勘探数据处理具有一定的指导意义. 相似文献
3.
近十几年来,井间地震在石油勘探领域发挥着重要作用.然而井间地震波极其复杂,给同相轴拾取、层析成像、偏移成像等工作带来了困难.因此,波场分离成为井间地震数据处理的一项重要内容.目前,不少学者研究了井间上下行波分离,纵横波分离等多种方法,但尚未出现相关文献研究透射波和反射波的分离方法.本文根据井间透射波和反射波在不同道集(共炮点集或共接收点集)中视速度极性的差异,首次提出了一种"透射.反射"波场分离方法.该方法首先在不同道集中利用τ-p变换进行视速度分离,得到反射上行波、反射下行波、透射上行波、透射下行波四个波场,然后选择对应的波场叠加,从而得到透射波和反射波.其中,透射波为井间层析成像提供了相对清晰的初至同相轴,尤其是横渡初至同相轴,以便进行到时提取;所得反射波为井中偏移成像提供了可靠的反射波数据,比人工切除透射波方法更为准确有效.本文通过理论模型试验和实际数据处理,证明了该方法的有效性和实用性.此外,在本文基础上,再进行纵横波分离处理可以得到更多的波场分量,为井间成像提供更有效的数据. 相似文献
4.
被动源面波和体波成像在内蒙古浅覆盖区勘探应用 总被引：1，自引：0，他引：1
地震勘探具有勘探深度和分辨率的优势,在矿产勘探中多被采用.但主动源反射地震具有成本高、在矿区采集困难等难题,限制了其广泛应用.无需主动源激发、利用天然噪声的被动源地震应用于勘探,可成为其低成本替代选项.本文在内蒙古浅覆盖区矿区进行了被动源勘探试验,采用相关计算获得拟炮集记录,并基于频率域信噪比计算,在生成拟炮集前实现了面波和体波甄选,分离了面波和体波.应用面波反演的横波速剖面识别了覆盖层厚度.体波数据经反射波常规处理,获得了成像剖面.经与主动源反射剖面对比,主要结构的反射特征呈现了良好的一致性.本文试验验证了被动源勘探在内蒙浅覆盖区具有良好应用前景,为低成本的面积性勘探实施提供了新的选择. 相似文献
5.
岩石圈内部间断面的精细结构隐含了岩石圈形成、增生和改造及破坏等重要的动力学信息.文章发展了地震光照成像新方法以探测岩石圈内部间断面小尺度结构.该方法使用了高频段0.5～4Hz的远震事件地震P波初至及其尾波信号,其对岩石圈间断面的分辨能力达到2km.该方法的基本原理是在台站下方垂直入射透射波响应的自相关等价于震源和地震台站均位于自由地表的反射波响应.透射波响应包括在台站下方穿过间断面到达自由地表的初至P波及其在自由地表和间断面之间反射的多次波.本研究将该方法垂直入射情况进一步拓展到倾斜入射,这提升了该方法的适用性.通过合成理论地震图验证了地震光照成像方法理论的正确性和可行性,探讨了影响成像结果的一些因素,并给出了该方法的数据处理步骤以及成果解释准则.文章利用该方法并结合瞬时频率等结果确定了华北克拉通东部两个固定台站的岩石圈精细结构,发现在两个台站下方岩石圈地幔分别在52和75km的深度存在明显的间断面.西澳大利亚克拉通MBWA固定台站下方,地震光照成像和接收函数揭示的岩石圈结构较为一致,存在明显的岩石圈内部间断面.高频地震光照成像结果可揭示岩石圈精细结构,但其波形更为复杂,建议充分利用层析反演速度和接收函数等已有的地震学信息并作为参考. 相似文献
6.
地震资料含有各种类型多次波,而传统成像方法仅利用地震一次反射波成像,在地震成像前需将多次波去除.然而,多次波携带了丰富的地下结构信息,多次波偏移能够提供除反射波外的额外地下照明.修改传统逆时偏移方法,用包含一次反射波和多次波的原始记录代替震源子波,将SRME方法预测的表面多次波代替一次反射波作为输入数据,可将表面多次波成像.多次波成像的挑战和困难在于大量串扰噪声的产生,针对表面多次波成像中的成像噪声问题,将最小二乘逆时偏移方法与多次波分阶思想结合起来,发展可控阶数的表面多次波反演成像方法,有望初步实现高精度的表面多次波成像.在消除原始记录中的表面多次波后,通过逆散射级数方法预测得到层间多次波,将层间多次波作为逆时偏移方法的输入数据可将其准确归位到地下反射位置.数值实验表明,多次波成像能够有效地为地下提供额外照明,而可控阶表面多次波最小二乘逆时偏移成像方法几乎完全避免成像噪声. 相似文献
7.
与声波被动源数据相比,弹性波被动源数据含有更加丰富的地下地质信息.弹性波被动源数据合成的虚拟炮记录中,同样存在表面相关多次波,影响数据的后续处理以及对地下地质构造的准确判断.对弹性波被动源数据合成的虚拟炮记录进行多次波的预测与匹配相减,将比声波数据更加困难.本文提出弹性波被动源数据一次波估计方法,针对各向同性介质条件下的弹性波被动源数据进行研究,依据声波被动源数据一次波估计方法的研究思路,推导弹性波被动源数据一次波估计方法的理论过程,充分考虑弹性波被动源数据所包含的波场成分,包括纵波、横波以及在传播过程中产生的转换波.在传播过程中,由于能量的损失,略去多次传播的高阶项,进而给出相应的目标函数.利用数据的稀疏性,结合L_1范数约束的最优化问题求解方法,避免对弹性波虚拟炮记录进行多次波的预测与匹配相减,解决多次波影响问题.本文通过合成的弹性波被动源数据,进行一次波估计的测试,并与主动源和合成的虚拟炮记录进行对比,验证本文提出方法的有效性与准确性. 相似文献
8.
复杂地表的单程波动方程地震叠前正演 总被引：4，自引：0，他引：4
作者基于数学检波器和等时叠加原理,实现了复杂地表的单程波动方程地震叠前正演模拟。该方法采用虚拟的数学检波器接收地下的反射地震信号,灵活地将接收点布置在地表的任何地方,从而满足地表起伏的要求。此外,根据等时叠加原理, 该方法采用单程波动方程进行波场延拓和成像,计算简单快速。通过复杂正断层的数值模拟,得到了高信噪比的共炮集地震记录,并采用适用于起伏地形的深度偏移方法对该共炮集地震记录进行了叠前深度偏移,较好地实现了地震波的偏移归位,从而证明了这里提出的起伏地表的单程波动方程地震叠前正演方法是正确和有效的。 相似文献
9.
南海深水多次波成像 总被引：1，自引：0，他引：1
南海海域水深可达5 km,是我国未来油气勘探最有前景的区域.南海海域地震资料含有各种类型多次波,在地震成像前需将多次波去除.然而与传统的一次反射波偏移比较,多次波携带更多的地下结构信息,多次波偏移可提供更好的地下成像.本文提出了一种修改传统逆时偏移的方法,利用多次波进行成像.该方法用包含一次波和多次波的记录代替震源子波,用预测多次波代替一次反射波作为输入数据.在逆时偏移处理流程中,将地表多次波记录沿时间延拓到各个深度层,通过互相关成像条件将包含一次波和多次波的地震记录沿时间延拓到相同深度层.将多次波偏移结果与一次波偏移结果的差应用目标函数进行匹配,弥补一次波偏移的不足.对Sigsbee2B数据做数值测试的结果表明与传统一次反射波偏移相比,该方法可以得到范围更大、均衡性更好的地下照明度.将该方法应用到南海深水实际资料成像,获得了南海深水地震资料多次波成像剖面.偏移结果表明,多次波成像可以弥补反射波照明的不足,由此说明多次波偏移是未来的一个重要研究方向. 相似文献
10.
利用地震波正向传播方程对属于波形线性反演问题近似求解方法的地震数据偏移成像进行重新推导,得到了适合散射地震数据的散射偏移成像方法和适合反射地震数据的反射偏移成像方法.以地震波传播的散射理论为出发点,首先根据描述一次散射波正向传播的线性方程研究建立散射地震数据的偏移成像方法理论;利用高频近似对产生散射波场的地下速度扰动函数的空间变化进行近似,推导出地下反射率函数,再由散射波传播方程推导出基于反射率函数的反射波传播方程,然后根据描述一次反射波正向传播的线性方程研究建立反射地震数据的偏移成像方法理论.本文指出和修正了Claerbout偏移成像方法中的不足,提出的地震数据偏移成像方法是对当前偏移成像方法理论的完善,使反射地震数据偏移成像具有了更坚实的数学物理理论基础,得到的偏移成像结果相位正确、位置准确、分辨率提高. 相似文献
11.
Passive seismic has recently attracted a great deal of attention because non‐artificial source is used in subsurface imaging. The utilization of passive source is low cost compared with artificial‐source exploration. In general, constructing virtual shot gathers by using cross‐correlation is a preliminary step in passive seismic data processing, which provides the basis for applying conventional seismic processing methods. However, the subsurface structure is not uniformly illuminated by passive sources, which leads to that the ray path of passive seismic does not fit the hyperbolic hypothesis. Thereby, travel time is incorrect in the virtual shot gathers. Besides, the cross‐correlation results are contaminated by incoherent noise since the passive sources are always natural. Such noise is kinematically similar to seismic events and challenging to be attenuated, which will inevitably reduce the accuracy in the subsequent process. Although primary estimation for transient‐source seismic data has already been proposed, it is not feasible to noise‐source seismic data due to the incoherent noise. To overcome the above problems, we proposed to combine focal transform and local similarity into a highly integrated operator and then added it into the closed‐loop surface‐related multiple elimination based on the 3D L1‐norm sparse inversion framework. Results proved that the method was capable of reliably estimating noise‐free primaries and correcting travel time at far offsets for a foresaid virtual shot gathers in a simultaneous closed‐loop inversion manner. 相似文献
12.
We apply interferometric theory to solve a three‐dimensional seismic residual statics problem to improve reflection imaging. The approach calculates the static solutions without picking the first arrivals from the shot or receiver gathers. The static correction accuracy can be significantly improved by utilising stacked virtual refraction gathers in the calculations. Shots and receivers may be placed at any position in a three‐dimensional seismic land survey. Therefore, it is difficult to determine stationary shots and receivers to form the virtual refraction traces that have identical arrival times, as in a two‐dimensional scenario. To overcome this problem, we use a three‐dimensional super‐virtual interferometry method for residual static calculations. The virtual refraction for a stationary shot/receiver pair is obtained via an integral along the receiver/shot lines, which does not require knowledge of the stationary locations. We pick the maximum energy times on the interferometric stacks and solve a set of linear equations to derive reliable residual static solutions. We further apply the approach to both synthetic and real data. 相似文献
13.
深反射地震剖面法为了获取深部结构特征常常采取大的偏移距采集数据.目前公开发表的相关资料中,鲜有利用深反射地震炮集数据获取近地表的结构特征.为此,本文通过正演测试了相关数据处理流程,即利用有限差分正演了起伏地表模型的大偏移距地震单炮弹性波场特征,通过共检波点域面波信号F-K频谱叠加构建新方法,从深反射地震数据集中提取了高品质的多阶面波频散曲线,再利用多阶面波联合反演获得了近地表的结构特征.在前述正演流程基础上,利用跨越班公湖—怒江缝合带的SinoProbe深反射地震剖面中的实际炮集数据,求取了基阶和一阶瑞利波频散曲线,联合反演后得到近地表横波速度结构.该结果与初至波走时反演获取的纵波速度结构具有较好的一致性,且在近地表的浅层分辨率较纵波速度结构特征更高,而更与已有地质认识相吻合.本文提供的相关数据处理流程表明利用深反射地震炮集数据,也能够获取近地表浅层的横波速度结构. 相似文献
14.
Retrieving virtual reflection responses at drill‐bit positions using seismic interferometry with drill‐bit noise 
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下载免费PDF全文 In the field of seismic interferometry, researchers have retrieved surface waves and body waves by cross‐correlating recordings of uncorrelated noise sources to extract useful subsurface information. The retrieved wavefields in most applications are between receivers. When the positions of the noise sources are known, inter‐source interferometry can be applied to retrieve the wavefields between sources, thus turning sources into virtual receivers. Previous applications of this form of interferometry assume impulsive point sources or transient sources with similar signatures. We investigate the requirements of applying inter‐source seismic interferometry using non‐transient noise sources with known positions to retrieve reflection responses at those positions and show the results using synthetic drilling noise as source. We show that, if pilot signals (estimates of the drill‐bit signals) are not available, it is required that the drill‐bit signals are the same and that the phases of the virtual reflections at drill‐bit positions can be retrieved by deconvolution interferometry or by cross‐coherence interferometry. Further, for this case, classic interferometry by cross‐correlation can be used if the source power spectrum can be estimated. If pilot signals are available, virtual reflection responses can be obtained by first using standard seismic‐while‐drilling processing techniques such as pilot cross‐correlation and pilot deconvolution to remove the drill‐bit signatures in the data and then applying cross‐correlation interferometry. Therefore, provided that pilot signals are reliable, drill‐bit data can be redatumed from surface to borehole depths using this inter‐source interferometry approach without any velocity information of the medium, and we show that a well‐positioned image below the borehole can be obtained using interferometrically redatumed reflection responses with just a simple velocity model. We discuss some of the practical hurdles that restrict the application of the proposed method offshore. 相似文献
15.
Time‐lapse seismic surveying has become an accepted tool for reservoir monitoring applications, thus placing a high premium on data repeatability. One factor affecting data repeatability is the influence of the rough sea‐surface on the ghost reflection and the resulting seismic wavelets of the sources and receivers. During data analysis, the sea‐surface is normally assumed to be stationary and, indeed, to be flat. The non‐flatness of the sea‐surface introduces amplitude and phase perturbations to the source and receiver responses and these can affect the time‐lapse image. We simulated the influence of rough sea‐surfaces on seismic data acquisition. For a typical seismic line with a 48‐fold stack, a 2‐m significant‐wave‐height sea introduces RMS errors of about 5–10% into the stacked data. This level of error is probably not important for structural imaging but could be significant for time‐lapse surveying when the expected difference anomaly is small. The errors are distributed differently for sources and receivers because of the different ways they are towed. Furthermore, the source wavelet is determined by the sea shape at the moment the shot is fired, whereas the receiver wavelet is time‐varying because the sea moves significantly during the seismic record. 相似文献
16.
The complex geological conditions in doubly complex areas tend to result in difficult surface survey operations and poor target layer imaging in the subsurface which has a great impact on seismic data quality. In this paper, we propose an optimal crooked line survey method for decreasing the surface survey operational difficulties and improving the sub-layer event continuity. The method concentrates on the surface shooting conditions, first, selecting the proper shot positions based on the specific surface topographic features to reduce the shot difficulties and then optimizing the receiver positioning to meet the prerequisite that the subsurface reflection points remain in a straight line. Using this method cannot only lower the shooting difficulty of rough surface condition areas but also overcome the subsurface reflection point bending problem appearing in the traditional crooked line survey method. On the other hand, we use local infill shooting rather than conventional overall infill shooting to improve sublayer event continuity and uniformity with lower survey operation cost. A model has been calculated and processed with the proposed optimal crooked line survey and local infill shooting design method workflow and the results show that this new method can work for seismic surveys in double complex areas. 相似文献
17.
Progress in the imaging of the mantle and core is partially limited by the sparse distribution of natural sources; the earthquake hypocenters are mainly along the active lithospheric plate boundaries. This problem can be approached with seismic interferometry. In recent years, there has been considerable progress in the development of seismic interferometric techniques. The term seismic interferometry refers to the principle of generating new seismic responses by cross‐correlating seismic observations at different receiver locations. The application of interferometric techniques on a global scale could create sources at locations where no earthquakes occur. In this way, yet unknown responses would become available for the application of travel‐time tomography and surface‐wave dispersion studies. The retrieval of a dense‐enough sampling of source gathers would largely benefit the application of reflection imaging. We derive new elastodynamic representation integrals for global‐scale seismic interferometry. The relations are different from other seismic interferometry relations for transient sources, in the sense that they are suited for a rotating closed system like the Earth. We use a correlation of an observed response with a response to which free‐surface multiple elimination has been applied to account for the closed system. Despite the fact that the rotation of the Earth breaks source‐receiver reciprocity, the seismic interferometry relations are shown to be valid. The Coriolis force is included without the need to evaluate an extra term. We synthesize global‐scale earthquake responses and use them to illustrate the acoustic versions of the new interferometric relations. When the sampling of real source locations is dense enough, then both the responses with and without free‐surface multiples are retrieved. When we do not take into account the responses from the sources in the direct neighborhood of the seismic interferometry‐constructed source location, the response with free‐surface multiples can still be retrieved. Even when only responses from sources at a certain range of epicentral distances are available, some events in the Green's function between two receiver locations can still be retrieved. The retrieved responses are not perfect, but the artefacts can largely be ascribed to numerical errors. The reconstruction of internal events – the response as if there was a source and a receiver on (major) contrasts within the model – could possibly be of use for imaging. With modelling it is possible to discover in which region of the correlation panel stationary phases occur that contribute to the retrieval of events. This knowledge opens up a new way of filtering out undesired events and of discovering whether specific events could be retrieved with a given source‐receiver configuration. 相似文献
18.
基于反射波动方程,本文提出了一种估计地下反射率分布的地震数据最小二乘偏移方法.高频近似下,非齐次的一次反射波动方程的源项是由反射率与入射波场的时间一阶导数相互作用产生的.根据反射波动方程,利用线性最小二乘反演方法由地震反射数据重建出地下产生反射波的反射源,再结合波场正演计算出的地下入射波场,得到地下反射率分布的估计.在地下反射源的线性最小二乘反演重建中,我们采用迭代求解方法,并以地震波的检波器单向地下照明强度作为最小二乘优化问题中Hessian矩阵的近似. 相似文献
19.
现有的微震记录直接成像方法是将微震记录既当作入射记录,也当作散射记录,从而实现偏移成像.但此方法并不能突出透射波所携带的来自震源下方的深层散射波信息.本文在假设已知微震位置与子波的前提下,提出了对微震下方构造进行逆时偏移的成像方法.该方法类似于常规的逆时偏移,只是震源位置在地下.这使得在成像时,地下更深部的入射波场相比震源在地表时会更为精确,因此能够获得更加准确的成像结果.该方法会给成像结果带来一种尾波高频干扰：地下的震源发出的上行波与上方介质作用后,所产生的多级散射波会干扰反传波场.对此,在成像过程中,对入射场和散射场都进行左右行波分离,以压制该噪声.而在子波信息未知,无法重构入射场时,使用了激发时间成像条件,也能够实现同等效果的偏移成像,且不会出现尾波高频干扰.利用数值实验验证了本文方法的有效性. 相似文献