The CFP-based Migration Velocity Model Building

The accuracy of migration velocity modeling affects the result of migration imaging considerably, and the velocity model error makes the imaging result change apparently. The CFP-based migration velocity model building is a new method arose only several years ago. The method has no assumption of small offset or small dip as most other migration velocity analysis methods do, which makes it suitable for model building of complex substructures.The computation of time-reversed focusing operator and the synthesis of CFP gathers are the core techniques of CFP technology. CFP gather is a kind of seismic data with easy interpreting after partially migration for part of diffraction energy has even removed and random noises have been suppressed. According to this method, equal travel-time principle rule, DTS(differential time shift)analysis is principle, and parameter constraint iterative inversioncan modify and update the whole macro velocity model. Migration velocity modeling is set up by using layer-stripping. The CFP-based interval velocity scan method also bases on the equal travel-time principle rule. Firstly we calculate the DTS of each velocity which given in an exact step, then after the DTS analysis we can get the correct velocity model. In this paper we give the introduction of the two methods. The model and real data test has showed the validity of them.