Application of Seismic Forward Modeling Technology in Identification of Stratigraphic Overlap Subtle Traps in Weixi Exploration Area

Weixi exploration area has experienced lacustrine deposits during Liushagang Formation of Eocene and delta deposits during Weizhou Formation of Oligocene. During the deposition of Weizhou Formation, due to the uplift of Weixinan Low Uplift, a depression-uplift pattern of low west and high east was formed near D sub-depression, which provided a favorable place for development of stratigraphic overlap subtle traps. In order to accurately describe stratigraphic overlap subtle traps developed in the lower part of Weizhou Formation, the influence of tuning thickness, velocity and seismic resolution on the identification of stratigraphic overlap points is analyzed by forward modeling technology. The forward simulation analysis shows that only when the formation thickness is greater than the tuning thickness λ/4, the sandstone can form an independent reflection axis; the error between the actual overlap point of the formation and the seismic overlap point is related to the velocity difference between the sandstone and the underlying strata, and the larger the velocity difference, the greater the error; the dominant frequency of seismic data has a certain influence on the error between the seismic reflection pinch out point and the actual pinch out point of the formation, and the higher the dominant frequency, the smaller the error. According to the actual seismic data of Weixi exploration area, a stratigraphic overlap model is designed, and the variation law of pinch out point error and included angle is fitted by forward simulation results, and it is found that there is a power-down function relationship; according to this function relationship, the actual position of overburden pinch out is corrected to improve the prediction accuracy and reduce the exploration risk.