Near Surface Statics Based On Double Focus Method

Facing creasingly complex near-surface acquisition conditions, static has become a vital technique problem to settle in seismic data process. It was used to utilize time shift static to eliminate complex near-surface effects, but this method is restricted by near-surface consistence condition and greatly depends on velocity. Time shift static hardly meet the request of high precision process when counter with complex surface acquisition conditions. This paper introduce a kind of new static method developed recently—near surface static based on double focus method, its theory base is common focus point technology, it depends completely on data-driven, makes use of synthesis operators to describe near-surface effects. Based on equal travel time principle, we can update these operators. Using the updated operators, we can correct rugged surface to a sub-weather plane surface, thus the effects of rugged surface and complex near-surface are eliminated.In the progress of using the double focus method to realize static, the key technique is attain correct synthesis operator, which desired sufficient acknowledgment with the near-surface configuration. The paper use middle result of CFP technology—CFP gather and DTS gather, and analyzes near-surface configuration by means of parameter constraint iterative inversion integrated with perturbation methods. Equal travel time principle and DTS analysis are the basis of correct synthesis operator calculation. Before updating the operators, we analyze the effects of wrong synthesis operator on synthesized CFP gather and shape of DTS, thus we can see the necessity of the updating operator. And we also have to consider operator's amplitude, the paper introduces an new approximative calculation of operator amplitude to get desired operator's amplitude, which is also improves differentiate of synthesis operator and CFP gather, thus improves collection precision of DTS. In addition, the paper also use steady phase principle to obtain high quality CFP gather.In this paper we give the introduction of above methods, the model tests showed their validity. The processing results of model and real data proved that near-surface static based on double focus method is prior to the conventional time shift static. And the prospect of this technique is very good.