SUMMARY

Accurate identification of the locations and orientations of small-scale faults plays an important role in seismic interpretation. We have developed a 3-D migration scheme that can image small-scale faults using diffractions in time. This provides a resolution beyond the classical Rayleigh limit of half a wavelength in detecting faults. The scheme images weak diffractions by building a modified dip-angle gather, which is obtained by replacing the two dip angles dimensions of the conventional 2-D dip-angle gather with tangents of the dip angles. We build the modified 2-D dip-angle gathers by calculating the tangents of dip angles following 3-D prestack time migration (PSTM). In the resulting modified 2-D dip-angle gathers, the Fresnel zone related to the specular reflection exhibits an ellipse. Comparing with the conventional 2-D dip-angle gather, diffraction event related a fault exhibits a straight cylinder shape with phase-reversal across a line related the orientation of the fault. As a result, we can not only mute the Fresnel zones related to reflections, correct phase for edge diffractions and obtain the image of faults, but also detect the orientations of 3-D faults using the modified dip-angle gathers. Like the conventional dip-angle gathers, the modified dip-angle gathers can also be used to image diffractions resulting from other sources. 3-D Field data tests demonstrate the validity of the proposed diffraction imaging scheme.

中文翻译：

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使用具有改进的倾角聚集的衍射对3-D断层成像

概要

准确识别小规模断层的位置和方向在地震解释中起着重要作用。我们已经开发了一种3D迁移方案，该方案可以使用时间衍射来成像小型故障。在检测故障时，这提供了超过经典的瑞利极限（半个波长）的分辨率。该方案通过建立修改后的倾角聚集来成像微弱的衍射，该倾角聚集是通过将常规二维倾角聚集的两个倾角尺寸替换为倾角的切线而获得的。我们通过计算3-D叠前时间偏移（PSTM）之后的倾角切线，来构建修改后的2-D倾角集线。在所得的修改后的二维倾角聚集中，与镜面反射有关的菲涅耳区呈现出椭圆形。与传统的2D倾斜角收集相比，与故障有关的衍射事件表现出笔直的圆柱形状，并且在与故障的方向有关的直线上具有相位反转。结果，我们不仅可以使与反射相关的菲涅耳带静音，校正边缘衍射的相位并获得断层图像，而且还可以使用修改后的倾角波集检测3D断层的方向。像传统的倾角收集器一样，修改后的倾角收集器也可以用于成像其他来源的衍射。3-D现场数据测试证明了所提出的衍射成像方案的有效性。校正边缘衍射的相位并获得断层图像，还可以使用修改后的倾角收集来检测3D断层的方向。像传统的倾角收集器一样，修改后的倾角收集器也可以用于成像其他来源的衍射。3-D现场数据测试证明了所提出的衍射成像方案的有效性。校正边缘衍射的相位并获得断层图像，还可以使用修改后的倾角波集检测3D断层的方向。像传统的倾角收集器一样，修改后的倾角收集器也可以用于成像其他来源的衍射。3-D现场数据测试证明了所提出的衍射成像方案的有效性。