渤海湾及沿岸盆地的构造格局

渤海湾及沿岸盆地面积约20万平方公里,包括河北省,山东省北部和西部、辽宁省南部、河南省北部、天津市和北京市等陆地面积约12万7千平方公里,渤海海域面积为7万多平方公里。陆地面积大部被第四纪冲积层所覆盖。渤海最大深度为70米,平均深度为18米。这是一个大型的第三纪断陷-坳陷沉积盆地,是继大庆油田开发之后,在我国东部地区所开发的另一个重要的含油气盆地(图1)。

THE TECTONIC FRAMEWORKS OF BOHAI GULF AND COASTAL BASINS, CHINA

The Bohai Gulf Coastal Basin covers an area of 200,000 sq. km. an important oil and gas province of China It is a polycyclic superimposed basin. Its history of development can be subdi-vided into four stages: 1) Late proterozoic parageosycline Stage(Sinian). 2) Early Palaeozoic cratonic stage (Lower Cambrian-Middle Ordovician). 3) Late Palaeozoic intracratonic coal-bearing sequences stage(Middle Carboniferous-Permian). 4) Mesozoic and Cenozoic taphrogenic rifting and subsidence stages. During the Paleogene rifting stage, three NNE trough systems and three nearly E-W trough systems were initiated as the results of regional extensional stresses. Central rift valleys,low angle gravity faults and a series of wedgeshaped troughs were developed symmetrically surrounding the "Bohai Mantle Plume".The rifting troughs were extended and widened gradually.During the Neogene, a large saucer-shaped sedimentary basin was developed as a thick blanket covering the whole areas either of the Paleogene troughs or the Palaeozoic-Sinian highs. Oil and gas fields are mainly distributed in the Paleogene trough systems controlled by the Rifting Zones.Tertiary structural traps such as Shengli oilfield, Gudao Oilfield and Dagang oilfield are large oil pools.Sinian-Palaeozoic buried-hill traps beneath the Tertiaty unconformity such as Renqiu Oilfield is also a giant Oilfield of the Bohai Gulf Coastal Basin.