利用全波形反演提高逆时偏移成像的精度

Using full waveform inversion to improve the accuracy of inverse time migration imaging

逆时偏移对速度模型有较强的依赖性,速度模型精度高低决定着偏移效果的好坏,速度模型越准确,偏移效果越好.因此,如何获取高精度的速度模型是实现有效逆时偏移的关键步骤.全波形反演方法利用叠前地震波场的运动学和动力学信息重建地下速度结构能够得到高精度的速度模型.为了验证全波形反演能否提高逆时偏移效果,本论文以OVERTHRUST速度模型为例,在频率域进行全波形反演,并实现了速度模型的更新.逐步缩小了初始速度模型与真实速度模型的残差,提高了速度模型的准确度.然后使用初始OVERTHRUST速度模型以及经过反演的速度模型分别进行逆时偏移,应用结果表明,使用经过全波形反演后的速度模型进行逆时偏移,其成像效果较好.因此,逆时偏移结合全波形反演可以有效的提高成像精度.

Reverse-time migration has strong dependence on speed,The accuracy of velocity model decides the migration effect is good or bad,The more accurate velocity model,migration imaging effect is better. Therefore,how to achieve high precision velocity model is the key step in the reverse-time migration. Full waveform inversion method by using prestack seismic wave field in the kinematic and dynamic information reconstruction underground velocity structure can get high accuracy of velocity model. In order to verify whether the full waveform inversion can apply to reverse-time migration,In the case of OVERTHRUST velocity model,Implementation of the full waveform inversion in frequency domain,and implements the velocity model updating. Gradually narrowed the residual of initial velocity model and the real velocity model,improve the accuracy of the velocity model. Then use the inversion speed model respectively for reverse-time migration,And then use the initial speed of OVERTHRUST model and the inversion velocity model respectively for migration imaging. By comparing the draw, use after full waveform inversion velocity model to get the reverse-time migration precision is higher. Migration imaging of complex structure area more precisely. Therefore,the combination of reverse-time migration and full waveform inversion can effectively improve the imaging accuracy.