Strategy of velocity model building in prestack depth migration
Ma Yanyan1, Li Guofa1, Zhang Xingyu2, Tian Naxin3, Zhu Wenliang4, Zhai Tongli4
1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China;
2. Nanhai East Petroleum Bureau, CNOOC, Guangzhou, Guangdong 510240, China;
3. Exploration and Production Research Institute, SINOPEC, Beijing 100083, China;
4. Dagang Oilfield Company, Petro China, Tianjin 300280, China
Abstract：Horizon-based tomography and grid-based tomography are two main model building methods for prestack depth migration in real seismic data processing. Using the typical geological model in Qikou Sag and its simulated wave fields, we analyze experimentally the imaging abilities of these two methods. Observations concludes that horizon-based tomography method is relatively robust, nevertheless, only the low frequency components can be inverted. On the other hand, the high frequency components can be inverted by grid-based tomography method. However, it is difficult to converge to the real velocity model. Therefore combined application of the two methods is proposed. First the low-frequency component of velocity model is inverted by horizon-based method, then the high-frequency is inverted by grid-based method. This joint approach is able to improve the reliability of the velocity model, as well as the imaging quality of prestack depth migration.
