基于射线理论点扩散函数的成像域最小二乘偏移

Image domain least-squares migration based on ray-based point spread function

最小二乘偏移能够消除非规则地震采集、带限子波等因素对偏移结果造成的不良影响,提高成像分辨率和振幅保真度,但高昂的计算成本严重制约了其实用性和应用前景.本文基于射线理论格林函数和地震波走时一阶近似,提出了一种快速的点扩散函数计算方法,不但可以大幅降低点扩散函数的计算成本,还能够适应任意的空间采样以保证点扩散函数的插值精度.以此为基础,本文进一步发展了成像域最小二乘偏移方法,能够高效、灵活地实现地下反射率的迭代更新,并最终获得分辨率更高、照明更加均衡的反演成像结果.文中给出的模型和实际数据的测试结果验证了上述方法的正确性和有效性.

Least-squares migration is able to eliminate the adverse effects of irregular seismic acquisition, band-limited source wavelet and other factors on seismic migration, and improve imaging resolution and illumination. However, the huge computational cost significantly hinders the application of this method. In this paper, we present a fast point spread function calculation method based on ray-based Green′s function and first-order traveltime approximation, which not only can reduce the computational cost but also can adapt arbitrarily spatial sampling to ensure interpolation accuracy. Then, we develop an imaging domain least-squares migration method to produce subsurface reflectivity with higher resolution and amplitude fidelity. The synthetic and the real data tests verify the correctness and effectiveness of the proposed method.