对南黄海盆地构造层特征及含油气性的新认识

南黄海是由古、中、新生界叠置而成的一个大型叠合盆地,发育4个特征各异的构造层:构造层Ⅰ(Z-S)、构造层Ⅱ(D-T)、构造层Ⅲ(T3-E)和构造层Ⅳ(N-Q)。构造层Ⅰ在海区广泛分布,主要为一套下古生界的盆地相-台地相沉积建造,最新地震资料推测,其厚度大且稳定,但构造特征不清楚。构造层Ⅱ由上古生界至中生界三叠系组成,是以碎屑岩和灰岩为主的一套海相地层,主要受到印支运动和早燕山运动的强烈影响,南、北部残留地层及结构不同,但以挤压构造样式为主。与陆区比较,南黄海盆地海相构造层Ⅰ和构造层Ⅱ的构造格局相对稳定,变形强度较弱。构造层Ⅲ发育白垩系和古近系,局部存在上三叠统—侏罗系,白垩系和古近系主要赋存在坳陷或凹陷内,隆起或凸起基本缺失,为一套陆相砂泥岩沉积,在北部坳陷分布较广,但厚度变化快,剖面上表现为地堑、半地堑的结构特征,以拉张构造样式为主。构造层Ⅳ(N-Q)为区域沉降的产物。南黄海盆地在形成过程中经历了多次构造运动的改造,不同构造单元具有不同的油气成藏特征和富集规律,北部坳陷发育有古生古储、古生新储、新生古储等油气成藏组合类型,是油气勘探最有利的区域。

A new understanding of the stuctural layers in the South Yellow Sea Basin and their bydrocarbon-bearing characteristics

The South Yellow Sea is a large superimposed basin of the Paleozoic,the Mesozoic and the Cenozoic,which can be divided into four structural layers with different characteristics:Structural layer Ⅰ(Z-S),Structural layer Ⅱ(D-T),Structural layer Ⅲ(T3-E)and Structural layer Ⅳ(N-Q).The layer Ⅰ is composed mainly of a suit of basin and platform faces of the lower Paleozoic by the data from outcrops and wells in the continental area.Based on the latest seismic profiles,it distributes widely and stably in the South Yellow Sea,with quite big thickness,but unclear about its tectonic characteristics.The layer Ⅱ is made up of marine clastic rock and limestone of the upper Paleozoic to the Triassic,with compressive tectonic style predominantly.The residual strata and the structure of the layer,however,are of much variety from the south to the north of the basin,due to the great impact of Indosinian Movement and Yan Shanian Movement in the area.Comparison with its adjacent continent,the tectonic framework of Layer Ⅰ and Ⅱ in the southern Yellow Sea Basin is more stable and the deformational intension is weaker.The Layer Ⅲ includes the Cretaceous and the Paleocene,and the upper Triassic to the Jurassic in some local place.The former,which is a suit of continental sandstone and mudstone,distributes widely in the northern depression,with variable thickness.It is a graben or semi-graben in profile,with extension tectonic style predominantly.The Layer Ⅳ is the result of the regional subsidence.Due to the multi-cycle tectonic movement in the South Yellow Sea Basin,the characteristics of hydrocarbon reservoir and accumulation are different in different structural units.It is suggested that the northern depression would be the most prospective area for hydrocarbon since there are different kinds of hydrocarbon plays,such as old source-old reservoir,old source-young reservoir,and young source-young reservoir.