高斯束深度偏移的实现与应用研究

Realization and application of Gaussian beam depth migration

高斯射线束(高斯束)的本质是利用傍轴近似方程在射线中心坐标系中描述波传播。高斯束偏移包括单个高斯束的求解及所有高斯束叠加成像两步骤。单个高斯束分两步求得,即通过运动学射线追踪求取中心射线的路径及走时;通过动力学射线追踪获取中心射线附近的高频能量分布。利用相互独立的高斯束描述波传播,既保持了射线方法的高效性和灵活性,又考虑了波场的动力学特征。高斯束偏移利用相互独立的高斯束叠加成像,解决了射线类方法中的多路径问题,兼具了初至波到达时Kirchhoff积分偏移的灵活性和波动方程偏移的精确性。高斯束偏移方法没有成像倾角限制,并且只需在射线追踪时引进高程管理即可将其应用至起伏地表情况,避免了复杂区的静校正问题,提高了起伏地表地震数据的成像精度。理论数据和实际数据的试验结果证明了该技术的有效性与优越性。

The Gaussian beam is the solution of paraxial approximation equation achieved in ray-centered coordinate.The Gaussian beam depth migration(GBM) contains the single Gaussian beam solution and the imaging stack by all Gaussian beams.The single Gaussian beam is obtained in two steps,including kinematical ray tracing to get ray-path & traveling-time of central ray and dynamic ray tracing to get high-frequency energy near central ray.Wavefield propagation characterization by using independently-individual Gaussian beam preserves the kinematical characteristics while it keeps the dynamic characteristics of wavefield.By utilizing the independently-individual Gaussian beam for imaging stack,GBM can solve the multi-path problem for ray-tracing methods;meanwhile,it is characterized by the flexibility of first-arrival Kirchhoff integral migration and the accuracy of wave equation migration.In addition,GBM isn't restricted by dip,while avoids the static correction problem and improves the imaging accuracy in rugged topography.Theoretical model and actual data proved the effectiveness and advantages of the technique.