Abstract:Good prospect of hydrocarbon exploration and development in Kenjiyak sub-salt Carboniferous, the drilling and study results showed that the Carboniferous hydrocarbon distribution is controlled by structure to a considerable degree. Since the deep depth of Carboniferous targets in the region (deeper than 3500m),especially the rapidly changed velocity in both lateral and vertical direction resulted from significant thickness of overlying Permian salt dome leads to imaging distortion of Carboniferous structures.It makes great difference between the structural map drawn by using former velocity study method and practical drilling depth, inconsistent between the drilled results and structural map and hard to meet the needs of fine structural interpretation.Starting from studying seismic data, the paper analyzed statistically the reflection energy of non-pure rock salt segment in salt dome and velocities of salt dome,yielding statistic relationship between reflection and velocity of non-pure rock salt segment and building up velocity field by “horizon-controlling” velocity-field-built-up method. Using the approach for drawing structural map eliminates the influence of sub-salt on overlying structures,which has good coincidence with following drilling data and provides reliable basic data for next exploration and development.