断陷盆地前积地震相及其岩性地层油气藏发育规律——以彰武断陷九佛堂组为例

Foreset facies and its development rule of litho-stratigraphic reservoirs in fault depression basin:Taking Jiufotang Formation of Zhangwu Fault Depression Basin

箕状断陷盆地多发育前积地震相,而前积地震相与岩性地层油气藏密切相关。以彰武断陷三维地震资料精细解释为基础,识别出斜交前积、下超充填前积和小型叠瓦前积3种地震相,并分析其特征及其岩性地层油气藏发育规律:斜交前积,发育在构造平静期(九佛堂3—4砂组),向湖盆推进较远,规模大,代表远岸扇沉积,前积层的中部和上部含油气性好,可以发育有利的岩性地层油气藏;下超充填前积,发育在构造活动期(九佛堂5—7砂组和2砂组),为靠近主干断裂下盘快速充填的近岸扇沉积,扇中—扇根的相变带为潜在的岩性地层油气藏发育区;小型叠瓦前积,发育在较深水地层单元(九佛堂5—6砂组),解释为扇体末端或侧缘沉积,以泥质沉积为主,含油气性差。识别出的前积地震相特征及其含油气规律可以为勘探程度较低的箕状断陷盆地油气勘探提供有价值的参考。

Half graben basin mainly develops foreset facies and it is always related to litho-stratrigraphic reservoir. On the basis of3 D seismic interpretation of Zhangwu Fault Depression Basin, it recognizes three types of foreset seismic facies and analyzes the characteristics and the relation between seismic facies and development rules of litho-stratrigraphic reservoir. Oblique crossing foreset facies mainly develops in tectonic calm period and it indicates infralittoral fan deposition. The middle-upper part of the foreset layer with good oil-gas possibility can develop favorable litho-stratrigraphic reservoir. Downlap filling foreset facies mainly develops in tectonic active period and it indicates nearshore fan deposition. The mid-root fan is the potential area for the development of the litho-stratrigraphic reservoir. Small scale imbricated foreset facies mainly develops in the relative deep water environment and it indicates argillaceous doposition with poor oil-gas possibility. The foreset seismic facies and the related oil-gas possibility can provide good reference for the exploration of half graben basin with low prospecting degree.