Distribution of Pre-Cenozoic strata and petroleum prospecting directions in China Seas

After 60 years of oil and gas investigation and exploration, the exploration degree of Cenozoic basins and the difficulty of oil and gas discovery in offshore China has increased, and the development of new fields for offshore oil and gas exploration has become an urgent task. Surveys and explorations in recent years have found that characteristics of the residual strata in the Pre-Cenozoic basins in offshore China could be summarized as follows: ① Huge thickness. The thickness of the Pre-Cenozoic varies in the range of 4000～6000 m with a maximum over 9000 m; ② Wide distribution. Pre-Cenozoic Strata are found in five major areas, i.e. the Bohai Sea, the North Yellow Sea, the South Yellow Sea, the East China Sea–the northern South China Sea and the southern South China Sea from north to south; ③ Six sets of strata, which include the Neoproterozoic, the Lower Paleozoic, the Upper Paleozoic, the Lower Mesozoic, the Middle Mesozoic, and the Upper Mesozoic; ④ Two types of stratigraphic architectures, i.e. the type of East China Sea-South China Sea composed only by the Mesozoic, and the type of Bohai-Yellow Sea superimposed by the Neoproterozoic, Paleozoic, and Mesozoic; ⑤ Six sets of source rocks, which include the Lower Cambrian, the Lower Silurian, the Carboniferous, the Permian, the Jurassic, and the Cretaceous source rocks, among which the Lower Cambrian, the Lower Silurian, and the Permian source rocks have the highest organic matter content, and the Jurassic source rocks distribute the most widely; ⑥ Three kinds of reservoirs, namely the porous reservoirs, the fracture-modified reservoirs, and the weathering crust reservoirs. The porous reservoirs mainly consist of dolomite, reef-bank carbonate, and sandstone, and the fracture-modified reservoirs are often associated with large fault zones and/or compressive structural zones, and the weathering crust reservoirs can be further divided into four sub-types: Precambrian metamorphic rocks and magmatic granite, Paleozoic carbonate rocks, Mesozoic volcanic rocks and granite, and Mesozoic clastic rocks. The physical properties and distribution of reservoirs are mainly controlled by tectonics, weathering and leaching process, and burial conditions; ⑦ Six types of plays from the Paleozoic source to the Paleozoic reservoir, from the Paleozoic source to the Mesozoic reservoir, from the Paleozoic source to the Cenozoic reservoir, from the Mesozoic source to the Mesozoic reservoir, from the Mesozoic source to the Cenozoic reservoir, and from the Cenozoic source to the Pre-Cenozoic reservoirs. In conclusion, the Pre-Cenozoic petroleum has great potential and broad prospects in China Seas. Next exploration targets should be focused on the marine Mesozoic-Paleozoic in the South Yellow Sea, the Mesozoic-Cenozoic in the southern East China Sea and the northern South China Sea, and the buried hills in Cenozoic hydrocarbon-rich depressions. The Mesozoic in the North Yellow Sea and the self-generating source to self-storing reservoirs in the Pre-Cenozoic of the Bohai Sea should be paid attention.