Study On Seismic Velocity Field Building And Varing-Velocity Maping Methods In Kuche Depression

The important parts in seismic interpretation work are the velocity field building and varying-velocity mapping. The thesis analyzes the problems and shortages of the ancient and present methods, which are used in velocity field building and varying-velocity mapping for the complex piedmont region.In the complex piedmont region, it is facing with many problems in mapping due to the seismic datum's quality and the theoretic restriction of the conventional velocity field building and varying-velocity mapping. On the basis of researching the characteristics of the geological and velocity data in Kuche in Tarim Basin, the thesis analyzes the factors that affect the accuracy of velocity field building and varying-velocity mapping in this area, and explores some methods of velocity analysis applied to the complex piedmont region. These technologies are three types of analysis methods of interval velocity rule, the method of improving the precision of velocity field in complex area, viz. building field by interval velocity filling method based on structure modeling, and the method of reducing varying-velocity mapping's error, viz. calculate accurately by the CMP datum plane's altitude when the result of surface-layer survey is used.It is obligatory to enhance integrative analysis with various existing velocity-data for acquiring exact cognition and forecast of layer's velocity in area where there are low the seismic datum's quality. In Kuche Depression,there are three sorts of method about layer-velocity's rule. It is the first method to analyze rule of the velocity who been computed by good quality stack-velocity when to build velocity fields using layer-control method. The second method is contrasting of linking well's VSP(or Sonic) velocity curve in area being adequate wells. The last method is making velocity's rule map by using various velocity datum. It help to hold rule of layer velocity filed in area. At the same time, it is basis of constructing velocity field in complex region.In low quality stack-velocity datum area, the stack velocity isn't used in building velocity field because it is imaging velocity for acquiring good seismic image and isn't agree to layer actual velocity. We search after to establish velocity field by interval velocity packing means for improving precision of velocity field in the area. The means is building velocity field by basis of considering fault complex structural modeling and confirming complex region layer's velocity referring to aforementioned analytic velocity rule.Surface is another affect factor working low accurate of mapping in the complex piedmont region. Because CMP is used in velocity analysis of seismic datum processing and building velocity filed of seismic datum interpretation, it is a surface in time. It must transform to depth. We explore a new methods using fruit of investigate to regional surface layer to calculate CMP's value in depth. It reduce CMP's affect to mapping's accurate.Application of these techniques in Kuche's velocity analysis and building velocity filed and vary-velocity mapping, structural map's accurate been improved and reflect exact complex structural form. They achieve good benefit of oil exploration by drilling.