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在常规地震资料处理中,实施正常时差校正(NMO)是为了提高共深度点或共中心点叠加剖面上的反射波信号。但有断层出现时,来自断层上下盘的反射的干涉以及断棱的绕射妨碍了断层位置的确定。叠后偏移使绕射图形被破坏,进一步阻碍了绕射中心的正常成像。本文介绍了一种通过集中地震剖面上不连续的绕射点信号振幅,辅助解释绕射棱的新技术。这种技术包括对假定的绕射点施以适当的时差和振幅校正。当炮点—检波点的中点之下存在发生绕射的不连续点时,这个检波点的位置便出现最大的绕射振幅。由于这样的绕射信号的振幅在该检波点两侧衰减很快,因此必须进行适当的振幅校正。绕射信号出现在所有的道上,人们可以利用这些绕射信号叠加,得出一个可能为绕射点位置的叠加道。对所设的位于每个地面点之下的绕射点重复这一过程,产生一个共断点(CFP)叠加剖面,该剖面上的绕射以高振幅为其主要标志。此方法用加噪声和不加噪声的合成记录进行了试验。试验证明这种方法是相当有效的,但它对时差校正所用的速度模型很敏感。因而一般用 NMO 叠加获得的速度模型通过叠加可以使绕射点的位置更为清晰可辨。本文最后介绍了艾伯塔普林斯井以南地区这项技术在野外反射数据集上应用的情况。
In conventional seismic data processing, normal time difference correction (NMO) is implemented to increase reflected wave signals over the co-depth or co-center stacking profiles. However, when a fault occurs, the reflection interference from the fault upper and lower plates and the diffraction of the fractured edge prevent the determination of the fault location. The post-stack offset causes the diffraction pattern to be broken, further hindering the normal imaging of the diffraction center. This paper presents a new technique for aided interpretation of diffraction edges by focusing discontinuous diffraction point signal amplitudes on a seismic section. This technique involves applying the appropriate time difference and amplitude correction to the assumed diffraction points. When there is a discontinuous point where the diffraction takes place below the midpoint of the point-detection point, the maximum diffraction amplitude appears at the position of this detection point. Since the amplitude of such a diffraction signal attenuates rapidly on both sides of the detection point, it is necessary to perform appropriate amplitude correction. The diffraction signal appears on all the tracks, and one can use these diffraction signals to add up to a superimposed track that may be the diffraction point position. This process is repeated for the set of diffraction points located below each ground point, resulting in a common-breakpoint (CFP) superimposed section with diffraction at its major sign of high diffraction. This method was tested with both noisy and noisy synthetic records. Experiments prove that this method is quite effective, but it is very sensitive to the velocity model used for time difference correction. Therefore, the velocity model obtained by the superposition of NMO generally can make the position of the diffraction point clearer by superposition. This article concludes with a description of the use of this technique in the field reflection data set to the south of Alberta Springs.