The Research For P-SV Converted-wave Static Correction

P-SV converted-wave static correction is the world's recognized difficult in land P-SV converted-wave seismic exploration. With the improvement of the exploration , P-SV converted wave exploration is increasing. P-SV converted-wave seismic data SNR is low, the P-SV converted-wave static correction become he most important one of the key technologies in the P-SV converted-wave seismic processing. One hand ,P-SV converted-wave static correction has become a measure of P-SV converted-wave seismic data processing technology, on the other hand, it has become the bottlenecks of data processing.P-SV converted-wave static correction is made up by the shot point P wave of static correction and the reciver point SV wave of static correction. As SV wave spread faster than the P-wave, and liquid have no impact to SV wave, causing static correction of SV wave is big than the P-wave correction 2-10 times. And the wave propagation paths is skewness, making P wave of static correction algorithm can not be directly applied to the converted-wave static correction processing. SNR in the converted wave record is low, near to the first break time wave,P wave refraction, converted wave refraction, and other information mixed up together, all this to make the first break time of converted waves are not easily distinguishable,and difficult to pick up. It has caused refraction static correction algorithm can not be used in the converted wave static correction applications.Experts have provide two way to resolve the problem of static correction .The first is correlation in CRP stack trace to static correction, The second is the delay time difference algorithm. Both the application of the algorithm has achieved some success, but there are problem, such as the range of application, and so on. In this paper, author devised some practical algorithm based on the results of previous studies, through serious study on the converted wave.Based on the analysis of the converted wave propagation, the focus is the P wave refraction and the converted wave refraction time-distance curve equation in the converted-wave records. Through these equations author got an important result: P-P-P refraction and P-P-SV refraction in parallel under certain conditions. Based on this characteristic, the author define the First Time Break of the converted wave, and put forward to the first break time of converted wave Some criterion. Under the guidance of these guidelines, achieved a further result : automatic identification the first break time of the converted wave by the energy stack algorithm. On the basis of this paper to achieve the algorithm that byτ-p transformation automatically pick up the first break time of P-SV converted wave.The way of correlation in CRP stack trace to static correction is detected in the paper. Through theoretical model and the formula analysis,it has best effect at flat reflector. For the accuracy of the algorithm and application conditions, author improved new way to put forward a more practical algorithm. On the initial static correction of the calculation used optimization algorithm, effective overcome the calculation in the low SNR Record. According to the P-wave data structure correcting the results, which makes the algorithm may be applied to the complex structure of reflection. Actual data calculation results show that the improved algorithm is better than the old one.The delay time difference algorithm is proposed in recent years for the complex structure of the converted wave static correction, in some areas the application has shown the good results. However, the algorithm in the calculation of the difference of the first break time of P-wave and the converted wave , the correlation algorithm is fail when the noise is many or the first break time wave energy is weak, and so on, are often difficult to get accurate results. The author resolve the problem by using the time difference of the first break time wave stack sections. The algorithm also makes a much more precision.Automatically pick up the first break time of P-SV wave and using the first break time to fitting line ,we have got the static correction, in the actual data processing achieved good results. Before using this algorithm, the shot static correction is resolved. By using the first break time of CSP to fitting line instead of using the first break time of COP. The use of the algorithm in Sulige, Sichuan, Tarim, Daqing and Shengli Oilfield have got satisfactory results.