The Cenozoic basin offshore the Bohai Sea underwent a multicycle-rifting during its evolutionary process, which resulted in the multiple unconformities in the strata. The tectonic activities shown by these unconformit...The Cenozoic basin offshore the Bohai Sea underwent a multicycle-rifting during its evolutionary process, which resulted in the multiple unconformities in the strata. The tectonic activities shown by these unconformities have different manifestations and influences on the basin evolution. The authors systematically analyze the tectonic evolution characteristics of the sags off-shore the Bohai Sea with a large set of hydrocarbon exploration data. The analysis reveals that two phases of tectonic activities during the late depositional stage of the third member of Shahejie Formation (about 38 Ma) and the late depositional stage of Dongying Formation (about 24 Ma) reflect the significant changes in the basin's features and structural framework before and after these tectonic activities. As a result, the two phases of tectonic activities are recognized as important turning points (i.e., tectonic transitions) of Cenozoic basin evolution. The regional dynamic backgrounds of the two phases of tectonic transitions are also discussed. It is suggested that the early tectonic transition occurred at about 38 Ma under such regional dynamic back- ground that a huge kinematics adjustment happened between Eurasian Plate and its neighboring plates, i.e., Pacific Plate and Indian Plate. Meanwhile, the Tan-Lu Fault's slip reversed from left lateral to right lateral. The late tectonic transition occurred in late Paleogene (about 24 Ma) and reflected the Himalayan orogeny's influence on the Chinese continent and even the Asian continent; at the same time, the stress field produced by the escape tectonics was related to the Himalayan orogeny, superposed on the pre-existing stress field, and then enhanced the right lateral slip activity of the Tan-Lu Fault.展开更多
According to the characteristics of sedimentary microfacies, unique vertical depositional sequences and well logging response, the authors propose that a shallow water delta was widely developed in the Neogene of the ...According to the characteristics of sedimentary microfacies, unique vertical depositional sequences and well logging response, the authors propose that a shallow water delta was widely developed in the Neogene of the Laibei area, Bohai Bay Basin of northern China. Based on seismic minimum amplitude slices, well logging data, test analytical data and so forth, detailed research on the evolution of the shallow water delta of the Neogene Lower Member of Minghuazhen Formation was conducted. The results indicate that the third-order sequence base level controls sandbody types. During a period of low base level, a distribu- tary channel sandbody of shallow water deltaic plain was developed. With base level rising, the sandbody type gradually changed into a subaqueous distributary channel sandbody and a sheet sand can be found as well. The fourth-order sequence base level controls mediumshort term evolution of the sandbody. Within a sequence, due to the rising and falling of base level, the sandbody assemblages are identified as an upward-coarsening type, an upwardfining and a compound type respectively. Regionally, from the Laibei Low Uplift to the Huang- hekou Sag, the shallow water delta evoluted from a dendritic shape, to a cuspate shape and finally to a sheet shape.展开更多
基金supported by the Important National Science & Technology Specific Project (Grant No. 2011ZX05023)
文摘The Cenozoic basin offshore the Bohai Sea underwent a multicycle-rifting during its evolutionary process, which resulted in the multiple unconformities in the strata. The tectonic activities shown by these unconformities have different manifestations and influences on the basin evolution. The authors systematically analyze the tectonic evolution characteristics of the sags off-shore the Bohai Sea with a large set of hydrocarbon exploration data. The analysis reveals that two phases of tectonic activities during the late depositional stage of the third member of Shahejie Formation (about 38 Ma) and the late depositional stage of Dongying Formation (about 24 Ma) reflect the significant changes in the basin's features and structural framework before and after these tectonic activities. As a result, the two phases of tectonic activities are recognized as important turning points (i.e., tectonic transitions) of Cenozoic basin evolution. The regional dynamic backgrounds of the two phases of tectonic transitions are also discussed. It is suggested that the early tectonic transition occurred at about 38 Ma under such regional dynamic back- ground that a huge kinematics adjustment happened between Eurasian Plate and its neighboring plates, i.e., Pacific Plate and Indian Plate. Meanwhile, the Tan-Lu Fault's slip reversed from left lateral to right lateral. The late tectonic transition occurred in late Paleogene (about 24 Ma) and reflected the Himalayan orogeny's influence on the Chinese continent and even the Asian continent; at the same time, the stress field produced by the escape tectonics was related to the Himalayan orogeny, superposed on the pre-existing stress field, and then enhanced the right lateral slip activity of the Tan-Lu Fault.
基金the National Science and Technology Major Project (Exploration Technologies for Offshore Hidden Oil/Gas) (Project No.: 2011ZX05023-00205) for financial support
文摘According to the characteristics of sedimentary microfacies, unique vertical depositional sequences and well logging response, the authors propose that a shallow water delta was widely developed in the Neogene of the Laibei area, Bohai Bay Basin of northern China. Based on seismic minimum amplitude slices, well logging data, test analytical data and so forth, detailed research on the evolution of the shallow water delta of the Neogene Lower Member of Minghuazhen Formation was conducted. The results indicate that the third-order sequence base level controls sandbody types. During a period of low base level, a distribu- tary channel sandbody of shallow water deltaic plain was developed. With base level rising, the sandbody type gradually changed into a subaqueous distributary channel sandbody and a sheet sand can be found as well. The fourth-order sequence base level controls mediumshort term evolution of the sandbody. Within a sequence, due to the rising and falling of base level, the sandbody assemblages are identified as an upward-coarsening type, an upwardfining and a compound type respectively. Regionally, from the Laibei Low Uplift to the Huang- hekou Sag, the shallow water delta evoluted from a dendritic shape, to a cuspate shape and finally to a sheet shape.
