Abstract: There are several anomalies in seismic fuzzy zones at the junction region of the Yinggehai Basin and the Qiongdongnan Basin in the northern South China Sea.There are many types of fuzzy bodies in the peripheral zones. Diapirs, submarine pockmarks and oil and gas seepage systems are developed in the western Yinggehai Basin. Volcanic activity was frequent in the northern Hainan uplift. Buried hill groups and volcanoes are developed in the eastern Qiongdongnan Basin. The exploration degree in this area is low, and the sealing conditions are scarce as the result of being near the provenance. Aiming at the problem that the geological types of the fuzzy zones are not clearly assigned in this area, the seismic response characteristics of the fuzzy zones are summarized. Combined with the formation mechanism and evolution law of various geological anomaly bodies, analogy analysis of seismic facies of the anomaly bodies in the peripheral zones was conducted, and the three-dimensional visualization characterization of the anomaly bodies was carried out. The study shows that these fuzzy zones have the characteristics of small scale, no magma capsule and shallow root, etc. Combined with the analysis of drilling data, these fuzzy zones are characterized as gas chimneys. The gas chimneys in this area are distributed in groups and zones, and are still active during the Late Quaternary, with active oil and gas migration, thus they are favorable oil and gas enrichment zones. The research results show that this area has a better exploration prospect, and the targets with good trap conditions can be used as the breakthrough direction for next exploration.

Key words: gas chimney, diapir, volcano, seismic facies analogy, junction region of Yinggehai-Qiongdongnan Basins, oil and gas seepage