基于局部倾斜叠加的快速射线束叠前时间偏移

宽方位高密度地震勘探可以有效的提高地震资料的空间分辨率和裂缝预测的精度,但地震道数的增加也大幅度提升了地震数据的处理成本.为提高海量地震数据偏移处理的计算效率,本文发展了一种快速射线束叠前时间偏移方法.该方法首先根据给定的射线束中心间隔将炮记录划分为一系列数据子集,然后利用倾斜叠加将数据子集分解为不同方向的平面波,最后根据射线束中心到地下成像点的双程走时和射线参数拾取相应的平面波振幅累加到成像点上.同Kirchhoff叠前时间偏移相比,本文方法不但保持了一致的成像精度,且由于仅需在稀疏的射线束中心位置进行成像累加运算,计算效率得到了大幅度的提升.文中所给出的模型和实际资料的测试结果验证了本文方法的正确性和有效性.

Fast prestack beam time migration based on local slant stacking

Wide azimuth, high density seismic acquisition is an effective technique to enhance horizontal and vertical resolutions of seismic images. However, the densely-sampled seismic data inevitably increases the computational cost of seismic processing. To improve the computational efficiency of seismic imaging process, we develop a fast prestack beam time migration method which can be generalized as three main steps. First, we divide an input shot gather into a series of super-gathers using a pre-defined beam center spacing. Then, we use local slant stack to decompose each super-gather into local plane waves. Finally, we calculate the two-way traveltimes and ray parameters associated with beam centers and then use them to accumulate the amplitudes of the decomposed local plane waves to imaging points. Since the imaging process is repeated with sparsely-sampled beam centers instead of densely-sampled receivers, the proposed beam time migration significantly can not only reduce the computational cost, but also produce images comparable to Kirchhoff time migration. Tests on synthetic and real seismic data demonstrate the correctness and effectiveness of the proposed method.