In
    recent years, further exploration practice in Sanhu area of Qaidam Basin
    discovers that not all the seismic anomalies are caused by gas in reservoirs.
    After deeply analysis, the seismic anomalies can be divided into three groups
    according to the genesis. The first type is caused by surface low-velocity zone
    (non-gas). The second type is caused by the high-abundance gas. The third type
    is caused by the above two facts. Seismic forward modeling and repeated
    experiments show that common offset profile analysis technique can effectively
    identify the seismic anomalies caused by surface low-velocity zone. After
    identifying this type of seismic anomalies, by jointly applying seismic
    tomography static correction and pre-stack depth migration, the seismic
    anomalies can be eliminated.