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针对宽频带高分辨率地震剖面的空间假频问题,本文提出了高密度偏移处理的解决方案。首先对地震空间假频的定义进行了分析,认识到偏移地震剖面与叠加地震剖面中的空间假频是有差异的,偏移地震剖面比叠加地震剖面更易产生空间假频。其次根据地震波动理论,认为野外空间低密度采集的地震信号,包含着地下高密度的地质信息,进而提出地震偏移输出是新的空间采样过程,只要地震叠前时间偏移输出高密度采样,CDP道间距足够小,就可以防止宽频带高分辨率偏移剖面的空间假频。利用二维地震正演模型分析高密度偏移方法的可行性,表明低密度采集的地震数据高密度空间采样叠前偏移处理可以消除地震空间假频噪声。对松辽盆地大庆油田低密度采集的地震资料高密度叠前偏移及提高分辨率处理后,消除了宽频带高分辨率地震的空间假频,宽频带高分辨率地震剖面地震空间分辨率明显提高。
Aiming at the problem of spatial aliasing in broadband high-resolution seismic sections, a solution to high-density offset processing is proposed in this paper. Firstly, the definition of seismic aliasing in seismic space is analyzed. It is recognized that there is a difference between the spatial aliasing in offset seismic profile and superimposed seismic profile. Offset seismic profile is more likely to generate spatial aliasing than superimposed seismic profile. Secondly, according to the seismic wave theory, it is considered that the seismic signal collected in the low-density field contains the high-density underground geological information, and then the seismic offset output is a new spatial sampling process. As long as the seismic prestack time migration outputs high-density sampling, CDP track spacing is small enough to prevent the spatial aliasing of broadband high-resolution offset profiles. The feasibility of using high-density offset method to analyze two-dimensional seismic forward model shows that low-density seismic data collected in high-density spatial sampling pre-stack migration can eliminate the aliasing noise in seismic space. After high-density prestack migration and resolution enhancement of seismic data acquired at low density in the Daqing Oilfield, Songliao Basin, the spatial aliasing of high-resolution wide-band high-resolution earthquakes was eliminated. The spatial resolution of high-resolution broadband seismic data was obviously improve.