Abstract: The tectonic characteristics of HZ25 transfer zone in the Huizhou Sag, Pearl River Mouth Basin, and its controlling effect on hydrocarbon accumulation are discussed in this study. The discussion is based on the latest collected and processed high-quality 3D seismic data and the analysis testing data of three drilled wells. The detailed structural interpretation, coherence slices, and analysis of the displacement-distance relationship show that the HZ25 transfer zone is a synthetic overlapping transfer zone subject to NW-SE tension. This transfer zone connects the headwall of the F₁ fault and the hanging wall of the F₂ fault. Its total interior displacement remained unchanged. The F₃ and F₄ faults were formed in association with the stress of the transfer zone areas, and, finally, the complex paleogeomorphology was formed. It splits the sub-sag and controls the distribution of the reservoir body and the direction of hydrocarbon migration. The transfer zone is the entrance to the uplift drainage basin, provides favorable geological conditions for the growth of an extensive set of coarse-grained sedimented deltas, and for a good reservoir. The fracture system and the delta sandstone, with intensive development relative to their high position, are good places for hydrocarbon migration and accumulation. The transfer zone, coupled with its controlled thick-layer braided delta, forms the stratigraphic-lithological trap. The hydrocarbon breakthrough of HZ25 transfer zone during the Wenchang Group facilitates hydrocarbon exploration in Huizhou Sag of the Lower Paleogene stratum and points to targets for exploration. In addition, a series of transfer zones distributed on the edge of the Huizhou Sag could be good targets for exploration in the future.

Key words: transfer zone, braided delta, stratigraphic-lithological trap, hydrocarbon accumulation, Huizhou Sag