三维观测系统对复杂构造叠前成像效果的影响分析

Analysis on influence of 3D geometry on prestack imaging of complex structures

叠前偏移成像效果与观测系统密切相关,明确观测系统参数变化对成像效果的影响对观测系统优化设计至关重要。利用复杂构造区三维物理模拟数据和实际采集的宽方位三维地震数据,进行了观测系统参数的退化处理试验,分析了道密度、观测宽度、线距变化对叠前深度偏移的影响。分析表明:1)观测宽度影响构造成像效果,增加观测宽度利于提高深层构造的断点、断层、断裂下盘成像清晰度和陡倾角同相轴的连续性;2)有效道密度和炮检距分布的均匀性影响偏移噪声的强弱,提高道密度和炮检距的均匀性利于压制偏移噪声,提高剖面信噪比;3)接收线距影响中浅层有效道密度和炮检距分布的均匀性,采用较小的线距获得更高的中浅层有效道密度和更均匀的采样结果,利于保证中浅层成像效果。研究认识可望为复杂构造区观测系统设计提供借鉴。

Prestack migration imaging effect is closely related to the observation system. So that defining the influence of observa？tion system parameter variation on imaging effect is essential to the optimum design of observation system. A observation system pa？rameter degenerate processing test is made by using the 3D physical simulation data in complex structure area and the actual col？lected wide-azimuth 3D seismic data to analyze the influence of trace density, observing width and line interval to prestack depth migration. The analysis result shows that： 1）the observing width has great influence on the imaging. Deepening structures and in？creasing observing width are beneficial to improve the imaging resolution of breaking point, faults and fracture footwall as well as the continuity of the phase axis of steep dip; 2）the effective trace density and the uniformity of offset distribution have great influ？ence on migration noise, and increasing them is beneficial to increase the signal/noise ratio; 3）the receiving line interval influenc？es the shallow layer effective trace density and the uniformity of offset distribution, and further influences shallow layer signal/noise ratio. Using a smaller line interval helps to ensure the shallow layer imaging effect. The study is expected to provide reference for complex structure areas in geometry design.