陆架边缘三角洲在层序地层格架中的识别及其意义--以南海白云凹陷为例

doi:10.11743/ogg20110512

摘要/Abstract

摘要：

陆架边缘三角洲具有优质的生、储、盖组合和多种圈闭类型。从成因方面来讲陆架边缘三角洲可分为:物源控制型、海平面控制型和两者混合控制型。在海平面相对静止阶段,河流强大的物源供给不断向陆坡运移,可以使陆架坡折逐渐向远陆方向前进,同时在陆架坡折带及上陆坡形成陆架边缘三角洲沉积;在沉积物供给相对稳定期,海平面下降至陆架坡折附近也可以使大量沉积物穿越广阔的陆架地区达到陆架坡折带甚至上陆坡从而形成陆架边缘三角洲沉积。正是由于以上特征陆架边缘三角洲沉积体系在层序地层格架中具有了一些可识别的依据。例如陆架边缘三角洲通常具有大型斜交S型前积组合反射结构,前积体顶超面与下超面的水平落差可达百米级,远高于陆架内部三角洲前积体的落差;通常形成于层序格架中的低位域;通常在层序格架中形成向陆和向海两个方向的斜坡楔形体等。通过对白云凹陷近期最新钻井资料的分析和长电缆高质量三维地震资料的解释,在白云凹陷珠海组、珠江组均识别出了陆架边缘三角洲沉积体系,并且伴随陆架坡折的迁移形成了独特的沿陆架坡折带分布的深水储层体系,该发现将有助于指导深水油气勘探。

关键词: 深水区, 陆架边缘三角洲, 层序地层学, 白云凹陷, 南海

Abstract:

Shelf margin delta is characterized by high-quality combination of source rocks,reservoirs and caps,and multiple trap types.Based on genetic styles,it can be classified into three types:provenance-dominated type,sea level-dominated type and hybrid type.During the relative quiescence period of sea-level,large amount of sediments are transported to the continental slope by rivers,making the shelf break gradually move seaward.Then shelf margin delta deposits could be formed at the shelf break and continental slope.Moreover,during period with relative stable sediment supply,the lowering of sea level to the shelf break also can transport large amount of sediments crossing broad continental shelf to shelf break,forming shelf margin delta deposits.These characteristics make shelf margin delta system identifiable in sequence stratigraphic framework.For example,shelf margin delta often shows large 'S' progradational reflection structure on seismic profiles,and the thickness between top surface and bottom surface can reaches up to hundreds of meters,much thicker than that within continental shelf.Moreover,the shelf margin delta usually occurs in lowstand system tract and is characterized by landward and seaward slope wedges.Based on integrated analysis of recent well logs and high-resolution 3D seismic data from Baiyun sag,a series of Oligocene-Miocene shelf margin deltas were identified in the Zhuhai Formation and Zhujiang Formation,and some unique deep-water reservoir systems were also recognized in the shelf break.These understandings will be helpful to future deep-water exploration.

Key words: deep-water area, shelf margin delta, sequence stratigraphy, Baiyun Sag, South China Sea

中图分类号:

TE122.1

徐强,王英民,吕明,等. 陆架边缘三角洲在层序地层格架中的识别及其意义--以南海白云凹陷为例[J]. 石油与天然气地质, 2011, 32(5): 733-742. doi: 10.11743/ogg20110512 Xu Qiang,Wang Yingmin,Lü Ming,et al. Identification of the shelf margin delta in sequence stratigraphic frameworks and its significance: a case study of the Baiyun Sag,South China Sea[J]. Oil & Gas Geology, 2011, 32(5): 733-742. doi: 10.11743/ogg20110512

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