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    基于散射波干涉叠加法的PS波叠前时间偏移

    PS-wave prestack time migration using scattered-wave interference stacking

    • 摘要: 可控震源三分量采集技术凭借施工便捷的优势在沙漠区得到广泛应用,但该技术采集到的地震记录存在有效信号能量弱、信噪比低以及“黑三角”现象严重发育等缺陷,极大地制约了转换波的成像与反演工作。为此,提出了面向低信噪比PS波的散射波干涉叠加叠前时间偏移方法。该方法依据炮点—检波点—成像点之间的时距关系,建立输入地震道振幅样点到目标成像道集样点的映射关系,并结合PS散射波走时构建干涉叠加地震道,实现相位一致能量的相干增强与噪声压制,并进一步从理论上评估了初始速度模型对PS波干涉道集的影响机理。模拟数据与实际数据的验证结果表明,该方法对初始速度依赖性较低,能在低信噪比条件下输出稳定且高质量的PS波成像道集,显著提升了PS波偏移成像的精度,为沙漠区弹性波勘探提供了技术支撑。

       

      Abstract: Three-component vibroseis acquisition has been widely used in desert regions due to its operational convenience; however, the resulting records suffer from weak effective signal energy, low signal-to-noise ratio (SNR), and pronounced “black triangle” artifacts, which severely hinder the imaging and inversion of PS waves. To address this issue, an interferometric stacking prestack time migration method specifically designed for low-SNR PS-wave data is proposed. Based on the time–distance relationship among the source, receiver, and imaging point, a mapping relationship is established between amplitude samples in the input seismic traces and those in the target PS-wave common-image gathers. Incorporating PS scattered-wave traveltime, an interferometrically stacked seismic trace is constructed to enhance phase-consistent energy while suppressing noise. Furthermore, the influence of the initial velocity model on the interferometric PS-wave gathers is analyzed theoretically. Tests on synthetic and field data demonstrate that the proposed method has low dependence on the initial velocity model, delivers high-quality PS-wave common-image gathers under low-SNR conditions, and significantly improves PS-wave migration accuracy, thereby providing effective support for elastic wave exploration in desert regions.

       

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