Study On Seismic Velocity Field Building And Varing-Velocity Maping Methods In The Foreland Thrust Belt Of Southern Jungar Basin

There is a better petro geologic condition in southern margin of the Junggar basin in which growing several large anticlinal structures .By more than half a century exploration ,we have discovered several large oil fields. Several years prospect experience show that one of the key factors that make depth structure map is different from time structure map of trap is velocity mapping.In the past directly using seismic velocity field to work that seriously effected by quality of seismic data, complex geological model and other factors and not clear to the variation of the overall velocity in southern margin of the Junggar basin restrict the exploration process.This paper systematically analyses the problems and deficiencies in the methods of velocity field building and varying-velocity mapping which are used to the foreland complex structure .Basing on studying on the characteristic of the geology and velocity data in the south margin of Junggar basin thrust belt ,we improve the existing method of velocity field building and varying-velocity mapping .This paper analyzes the factors which have effect the precision of velocity field building and varying-velocity mapping in the southern margin of Junggar basin thrust belt and search after the technique that fill the mapping precision in foreland structure belt by two aspects which are district velocity field building and local fine varying velocity mapping. For deepening macrocosmic geology cognize to the foreland thrust belt of southern Junggar basin ,this paper builds the velocity field basing on structure modeling and make district Integration layer on seismic and geology ,weeds wrong velocity and controls the precision of velocity field by better drilling velocity .Accordingly ,by using the technique here in before ,we know the macrocosmic form of district structure and provides a groundwork for the work in the future.This paper analyzes the factors which effect the precision of mapping by the seismic velocity of advantaged areas in southern Junggar basin basing on the variation of the overall velocity in southern margin of the Junggar basin .It sums up the methods fill various velocity type areas and searches after ascertaining structures technique for various velocity areas in foreland structure belt .And it preliminary concludes the methods here in after:(1)the method of district velocity field building and local fine varying velocity mapping by dummy well controlling; (2)the varying velocity mapping method in the structure underlay thrust fault; (3)the mapping method in the structure underlay gravel layer; (4)try to use the seismic properties to control velocity .The technique here in before are used in the mapping work of thrust belt in south margin of Junggar basin and makes a good effect. Several wells we propose to drill show well indication of oil and gas so as to expand prospect field.By studying this paper systematically summarized the methods that advance the precision of velocity field building and mapping by district structure and object structure reciprocal action. And the method in this paper provides the groundwork for the future work through no well area or well margin area.