基于快速射线束偏移的交互式地震成像

Fast beam migration based interactive seismic imaging

（CGGVeritas公司，美国得克萨斯休斯敦TX 77084）

CGGVeritas, Houston, TX 77084, USA

为了提高偏移速度，使交互式速度建模和速度模型测试成为可能，在对近年来人们提出的快速偏移方法进行成像研究之后提出了快速射线束偏移法。该方法用许多局部相关的同相轴来达到地震记录稀疏表示的目的，提高了偏移效率。同相轴由多路径方式偏移到空间域中，可以使相关噪声和偏移假象得到更有效的压制。快速射线束偏移方法的成像步骤为：①数据分割；②同相轴拾取；③偏移拾取的同相轴得到分偏移像；④〖JP+1〗分偏移像叠加得到总偏移像。以SIGSBEE二维人工数据为例，将快速射线束偏移方法与Kirchhoff成像方法进行了对比，结果表明：采用快速射线束偏移方法能生成质量更高的图像，尤其是盐丘下的构造成像，其速度比Kirchhoff偏移快数十倍。在墨西哥湾实际三维海洋数据成像中（三维面积约210km2），采用快速射线束偏移方法生成的图像和Kirchhoff偏移方法生成的图像质量相仿，但前者比后者的成像速度快两个数量级。

Fast beam migration algorithm has been specifically designed to facilitate very rapid migration turnarounds to allow for interactive velocity model building and validation. Many partial coherent events are used to sparsely represent the seismic traces and improve imaging efficiency. The events are subsequently migrated into spatial domain in a multi-path fashion to suppress the migration artifacts and coherent noises. Four steps in the fast beam migration are described: 1) beam forming; 2) event picking; 3) picked events migration to obtain partial images; and 4) partial image stacking to obtain the final image. Test on the 2D SIGSBEE synthetic dataset demonstrate the superior subsalt imaging capabilities of the algorithm compared to Kirchhoff migrations and resulted in a migration speed of 30 times faster. Images for 3D real data (a 210 km2 dataset from the Mexico Gulf) are similar to those from Kirchhoff migrations but can be produced with a speed of two orders of magnitude higher than by classical imaging schemes.