Astronomical time scale of a Middle Eocene lacustrine sequence from the Dongpu Sag, Bohai Bay Basin, Eastern China

2021 ◽  
pp. 104747
Author(s):  
Dong Guo ◽  
Zhijun Jin
Keyword(s):  
Time Scale ◽  
Middle Eocene ◽  
Eastern China ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
Astronomical Time

Sedimentary deformation features as evidence for paleoseismic events in the middle Eocene in the Dongying Depression of the southern Bohai Bay Basin, eastern China

2020 ◽  
Vol 57 (8) ◽  
pp. 954-970
Author(s):  
Zhongshuai Hou ◽  
Shiyue Chen ◽  
Shun Zhang ◽  
Huaiyu Yang
Keyword(s):  
Middle Eocene ◽  
Eastern China ◽  
Active Faults ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
The North ◽  
Dongying Depression ◽  
Gravity Flows ◽  
Tectonically Active ◽  
Deformation Features

Cores from the middle Eocene sediments of the Dongying Depression of the southern Bohai Bay Basin in east China yield various kinds of sedimentary deformation structures. They include microfolds, load casts, flame structures, ball-and-pillow structures, load-cast ripples, pinch-and-swell structures, boudinage structures, sand dikes, microfaults, and cataclastic breccias. Gravity flows, including turbidites and debris flows, also occur in the study area. The deformation layers can be divided into plastic deformation and brittle deformation types. These develop in a succession composed mainly of dark finely laminated and massive mudstone interbedded with thin sandstones and carbonate rocks that accumulated in a low-energy semi-deep to deep lacustrine environment in a tectonically active setting. Considering the facies attributes in the study area, intrinsically possible trigger mechanisms such as rapid sediment loading and storm currents are absent. Thus, the sedimentary deformation features should be induced by seismic activity, and the same with the gravity flows. These seismites are interpreted to have originated from earthquakes with magnitudes exceeding M 5.6. Basin-controlling faults in the north border of Dongying Depression give rise to the occurrence of seismites. The increasing occurrence frequency of seismites from Es4u to Es3l corresponds with the increase in the activity velocity of the basin-controlling faults. Compared with the seismites developed in other fault depressions in the Bohai Bay Basin, seismites developed in the Dongying Depression are relatively smaller scale and are dominated by microfault layers, relatively more cohesive sediments, and greater distance between seismites and active faults results in the occurrence of these features.

scholarly journals Reservoir Characteristics of Buried-hill Draping Zone in L Oilfield, Offshore China

2021 ◽  
Vol 10 (2) ◽  
pp. 33
Author(s):  
Yujuan Liu ◽  
Qianping Zhang ◽  
Bin Zheng ◽  
Jing Zhang ◽  
Zhaozhao Qu
Keyword(s):  
Seismic Data ◽  
Eastern China ◽  
Seismic Facies ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
Sedimentary Characteristics ◽  
Reservoir Characteristics ◽  
Production Practices ◽  
Buried Hill ◽  
Different Parts

The reservoir in different parts of buried-hill draping zone is often quite different, so it is of great significance to clarify the reservoir characteristics for exploration and development. Based on core, well logging, seismic data and production data, reservoir characteristics of oil layer Ⅱ in the lower second member of Dongying Formation of L oilfield, Bohai Bay Basin, offshore eastern China are systematically studied. Analyses of seismic facies, well-seismic combination, paleogeomorphology, and sedimentary characteristics are carried out. Sediment source supply, lake level and buried hill basement geomorphology all contribute to reservoir quality. The research suggests that the different parts of buried-hill draping zone can be divided into four types. Reservoir thickness and physical properties vary. The area where the provenance direction is consistent with the ancient valley direction is a favorable location for the development of high-quality reservoirs. Under the guidance of the results, oilfield production practices in L oilfield offshore China are successful. Knowledge gained from study of L oilfield has application to the development of other similar fields.

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