潍北凹陷孔二段沉积特征

Sedimentary characteristics of the second member of the Kongdian Formation in the Weibei depression, Shandong

关键词:  潍北凹陷  孔二段  扇三角洲  近岸水下扇  沉积演化

Key words:  Weibei depression  second member of the Kongdian Formation  fan delta  nearshore submarine fan  sedimentary evolution

摘要:

综合运用岩心、钻井、测井及地震资料,对潍北凹陷古近系孔二段地层特征及沉积演化进行了系统研究。结果表明,潍北凹陷孔二段可以划分为两个中期旋回和9个短期旋回。受到早期古城-潍河口断裂强烈活动的影响,在盆地西北部存在一个沉积沉降中心,地层向南部超覆,由北向南变薄。孔二段主要发育扇三角洲相和湖泊相,古城-潍河口断裂下降盘发育小规模近岸水下扇相。孔二下亚段为盆地初始形成期沉积,湖盆水体较浅,半深湖相仅在古城-潍河口断层下降盘发育,物源供给少且粒度较细;孔二中亚段沉积时期,物源供给充足,南部斜坡带、瓦城断阶带和灶户断鼻带发育大规模的扇三角洲相,扇体前端发育大规模滨浅湖滩坝相;孔二上亚段沉积时期,湖盆水体最深,发育大范围的半湖相沉积,物源供给减少,南部斜坡带、瓦城断阶带和灶户断鼻带继承性发育扇三角洲相,但分布范围变小。扇三角洲前缘水下分流河道砂体、浊积扇及滩坝砂体是孔二段的有利储集砂体。

Abstract:

The present paper gives a detailed description of the stratigraphic characteristics and sedimentary evolution of the second member of the Kongdian Formation in the Weibei depression,Shandong in the light of cores, well logs and seismic data. The second member of the Kongdian Formation in the Weibei depression consists of two medium-term and nine short-term depositional cycles, and is made up of the fan delta facies, nearshore submarine fan facies and lake facies. The study area went through the shallowing-upward and then deepening-upward evolutionary processes, and may serve as good sites with excellent source-reservoir-seal associations favourable for the hydrocarbon accumulation and preservation. The fan delta front subaqueous distributary channel, turbidite fan and beach-bar sandstones are interpreted as favourable reservoir rocks in the study area.