The Study Of Static Correction In The Western With Complex Surface Condition

The factual surface and structure are very complex in the western of China , static correction is the choke in seismic imaging. This problem is becoming the chiefly task with the development of seismic exploration in Loess Plateau Tableland, desert and Mountainland. Research on static correction in the western with complex surface conditionhas been done and some progress has been achieved in this article.Firstly, near surface velocity modeling is the vital problem in static correction in the western with complex surface condition. In the western the model built with small refraction and micro-well logging data directly can not satisfy seismic exploration requirements. The effect of refraction wave static correction is limited by the condition that there are no stable refracting layers, the adaptability of tomography static correction is better but is limited by the factual observation data. So this article researched on the method of near surface modeling with tomography inversion constrained by the factual data using Kriging method, by which the near-surface modeling precision is improved, The model precision has been improved with this method, so the near surface model can be built more exactly in complex surface area.Secondly, a method of non-surface-consistency static correction is necessary. Now most of static correction methods used widely in production are based on the assumption of surface consistency that the velocity of near surface in lower-velocity region is assumed far lowered than that of the down layer, seismic wave is spreading vertically in the region, seismic wave of different types is spreading along the same path in the region, that means the time-delays of seismic wave are same on the same shot point or same receiver point. But in the complex western, acute topography undulation, sharp lateral and longitudinal velocity variations in low velocity regions result in the time-delays of seismic wave arriving at different receiver are complex, the actual near-surface structure is very different from that based on the assumption of surface consistency. So big deviations were produced between the actual static correction and based on the surface consistency. We called the deviation as non-surface-consistency static correction. The reason brings this deviation has been researched in this article, a method of non-surface-consistency static correction has been put forward to deduce the deviation.Thirdly, some methods of department and reconstruction of static correction value have been researched as auxiliary technology, and obvious effect has been achieved.Fourthly, this article also covers some preliminary research on long wavelength static corrections that has been confusing geophysicists for a long time, and put forward a spatial fixed arrangement method for long wavelength static correction, The problems in long wavelength static correction are solved by inactively picking the static correction boundary, good effect with this method has been achieved. The research on datum plane static correction based on wave field continuation also has been covered, its feasibility has been proved by model experiment in this article.