The formation and evolution of northeastern ends of the ECSSB, South Sea of Korea, and its significance for petroleum exploration

 The South Sea of Korea has three offshore concession blocks, including a Joint Development Zone(JDZ) that is set up by the license agreement between Korea and Japan. The geological research of the offshore South Sea of Korea is insufficient to define the evolution history and its significance for petroleum accumulation. In this study, evolution of the Xihu Sag within the JDZ area at the South Sea of Korea is tackled based on re-interpretation of the seismic and well data, and are correlated tectonically with that of the ECSSB(East China Sea Shelf Basin). The ECSSB has been initially developed as a back-arc basin over the over-riding Paleo-Pacific plate, and experienced complex tectonic history by successive subduction of the tectonic plates including the Paleo-Pacific (Izanagi) Plate, the Pacific plate, and the Philippine plate since Late Cretaceous in age. The results indicate that the study area can be subdivided into three tectonic domains: Western Slope Belt, Central Uplift Belt, and East Slope Belt. The structural similarity with those of the ECSSB, although the details of structural characteristics are different in different localities, under regional influence of successive subductions of the same tectonic plates, resulting in the conclusion that the area can be assigned into the northeastern ends of the Xihu Sag of the northeastern ECSSB. This might be a common feature of oil–gas accumulation in the eastern ECSSB, and highlights the potential for petroleum exploration at the study area, although further studies on the play concept and complex petroleum system of the area are required.