Abstract: The oil-gas exploration of subsalt structure in Kuqa depression indicates that the structural styles appear to be seriously distorted in time section for being influenced by the structural styles and velocity structures of overlying strata, resulting in partly big differentiation from real configuration. This paper analyzes the key factors affecting the distorted degree of subsalt structure by forward modeling, classifies the distorted subsalt structure into two types of distorted ones, one is affected by wave diffraction, the other is by wave reflection, based on dynamic feature of seismic wave propagation, and introduces two concepts: the subsalt structure's horizontal level line (L sh ) and the average velocity change trend line (v av ), which can be used to distinguish the true or false and distorted degree of subsalts in time section. It is concluded that the prestack migration and time-depth conversion method can be applied to effective correction of such a distorted phenomenon and prediction of the migration direction and distance of highs, hence providing more reliable traps and well locations for petroleum exploration.

Key words: Tarim basin, Kuqa depression, subsalt structure, time section, prestack migration, time-depth conversion, correction