准噶尔盆地南缘山前带构造变速成图

Application of varying velocity mapping technique for mountain front in southern Junggar basin.

准噶尔盆地南缘山前带构造复杂,深部地层横向速度变化剧烈。为了提高构造成图的精度,采用变速成图技术对研究区进行了构造成图。首先将叠后时间偏移域(简称偏移域)的T_0层位数据反偏移(偏移的逆运算)到水平叠加时间域(叠加域);然后利用叠加速度反演方法求取叠加域T_0层位数据网格点所对应的层速度值;最后采用三维射线追踪图形偏移方法将T_0图转换成深度图。对研究区变速成图结果与简单的时-深关系转换结果进行了对比,可以看出变速成图方法有效提高了构造图的精度,在工区的正南边发现一个新的背斜圈闭。

The structures of mountain front in southern Junggar basin are complex and the variation of lateral velocity in deep formation is considerable.In order to improve the accuracy of structure map- ping,varying velocity mapping technique was used to map the structures.Firstly,the T_0 layer data of post-stack time migration domain(abbreviated in migration domain)was de-migrated into common-depth-point-stacking time domain(abbreviated in stacking domain).Then,stacking velocity inversion method was used to obtain the horizontal velocity responding to the grid points of T_0 layer data in stacking domain;finally,3-D ray map-tracing migra- tion method was applied to convert T_0 map into depth map.The varying velocity mapping result was compared to simple time-depth relationship transformation result,showing that the varying veloci ty mapping technique can effectively improve the accuracy of struc- ture maps and an anticlinal trap was discovered in the south of the working area.