China offshore basins are located in the convergence area between the Eurasian Plate, the Pacific Plate, and the Philippine Sea Plate, consisting of ten Cenozoic sedimentary basins. Complicated geological processes have... [ view full abstract ]
China offshore basins are located in the convergence area between the Eurasian Plate, the Pacific Plate, and the Philippine Sea Plate, consisting of ten Cenozoic sedimentary basins. Complicated geological processes have resulted in various basin types, topographical forms, filling patterns, and hydrocarbon potentials. The China offshore basins are comprised of continental rift/depression basins (Beibuwan Basin, Bohai Bay Basin, Yinggehai Basin, Taixinan Basin, and Yellow Sea Basin), back-arc basin (East China Sea Shelf Basin), and passive margin basins (Qiongdongnan Basin and Perl River Mouth Basin). Based on 2D/3D seismic data, wire-line well logs, cores, this study aims to (1) reconstruct the tectonic processes that controlled the basin structure and sedimentation of the China offshore basins during the Paleogene and Neogene; (2) characterize the provenance properties, transport systems, and geomorphic features of the various basins; (3) identify the sedimentary facies, depositional systems, and hydrocarbon plays of the China offshore basins. According to the characteristics of mantle convection and crustal stretching, subsidence of the basins can be classified into passive, initiative, and combination thermal subsidence. Most of the China offshore basins were superimposed basins consisting of rifting (Paleocene to Eocene) stage and depression (Oligocene to Miocene) stage which primarily controlled the type of depositional systems, source rocks, and reservoirs. In the rift/depression basins, proximal alluvial-fluvial systems and deep-lake deposits were commonly developed during the rifting stage, which provided hydrocarbon source rocks. Prevalent fluvial-deltaic systems were formed during the depression stage, resulting in sandy successions due to adequate sediment supply and limited accommodation. The thick, widespread sandstone in superimposed rift/depression basins contribute essential reservoirs for hydrocarbon accumulation. In the back-arc basin and passive margin basins, transition zone of non-marine to marine depositional systems including fluvial-dominated deltas, tide-dominated estuaries, and wave-dominated beach-barriers were common due to frequent interaction between river, tide, and wave. Tectonic movements in the Neogene, which is named Neotectonism, mainly adjusted and controlled late hydrocarbon accumulations in the China offshore basins. Due to the distinct characteristics of basin type, structure pattern, sedimentary filling history, and hydrocarbon property, the China offshore basins are subdivided into two belts: Inner Belt of rifting basins with cured oil and Outer Belt of depression basins with natural gas.
Topics: Shelf and shallow water sedimentation , Topics: Lacustrine sedimentation
