散射波速度分析方法在南华北盆地破碎地层发育区的应用

针对南华北盆地中、深层断裂发育,地层倾角较大,断块非常破碎,地震波场中反射波、绕射波等多种波发育,目的层速度分析困难,成像精度低等难题,本文在阐明散射波速度分析原理的基础上,介绍了在破碎地层发育区采用散射波速度分析方法,建立叠前时间偏移速度场的方法和应用效果。分析表明,共散射点道集具有明显的优点:①共散射点道集的覆盖次数远远高于CMP道集;②散射波呈双曲线分布,双曲线顶点总是指向真实散射点。这种特点为准确拾取速度提供了条件。对比散射波速度谱和常规速度谱可以看出,散射波速度谱的质量明显优于常规速度谱。实际应用表明,散射波速度分析方法能够高效、客观地建立叠前时间偏移速度模型,改善成像效果。

Application of scattered wave velocity analysss in broken formation zone of the southern part,North China Basin

Seismic imaging in the southern part, North China Basin faces a few difficulties such as complex faults, steep-dipping broken formations, compii-cated wave tields, target inaccurate velocity and poor imaging.To solve these problems, we introduce in this paper a scattered wave velocity analysis method for pre-stack time migration velocity tield based on the scattering principle.We also demonstrate its implementation procedures and application results in a broken formations zone.The analysis shows that common scattered point (CSP) gathers have significant advantages.The fold of CSP gathers is much higher than that of common mid-point (CMP) gathers, as well as the traveltime curve of scattered wave in CSP gathers is hyperbola, whose apex directs real scattered points, which makes t possible to extract accurately the velocity of scattered wave.It is clear that the quality of scattered wave velocity spectrum is much better than that of traditional velocity spectrum.The application results indicate that the scattered wave velocity analysis method could be used to build accurate migration velocity models and improve imaging of steep-dipping broken formations.