断陷盆地单因素精细取证下的沉积体系综合分析——以歧口凹陷古近系沙三二亚段为例

在对歧口凹陷古近系沙三二亚段的多种单因素沉积学信息——测井相、岩心相、砂分散体系、地震相和地震属性、生物相、矿物岩石学和有机地化与岩石(颜色)、构造、古地貌等分别进行了详细研究的基础上,系统地对多种单因素沉积学信息的空间分布规律和空间配置关系进行了综合分析,总结了沉积学的共性和特殊性规律,使多种单因素沉积学信息起到了相互佐证和互为补充的作用,从而有效地对研究区沉积体系类型、空间配置关系和物源进行了客观的分析和评价。研究认为,歧口凹陷沙三二亚段发育4种主要的沉积体系类型:扇三角洲沉积体系、辫状河三角洲沉积体系、水下扇沉积体系和湖泊沉积体系。其中,在断层活动性强、坡度较陡的地区发育扇三角洲;在坡度较缓的地区发育辫状河三角洲;断控盆地边缘深水区发育近岸水下扇,盆地内部次级断层则控制了远岸水下扇的发育。沉积体系的空间配置受5大主要物源控制:燕山物源、沧县物源、埕宁物源、孔店物源和沙垒田物源。本研究证明,这种"单因素精细取证,多因素综合分析"的方法在拥有丰富勘探资料的断陷盆地沉积体系研究中行之有效。

Comprehensive Analysis of Depositional Systems in Fault Basin Based on the Detailed Study of Individual Factor: A Case Study of the Second Sub-member of the Third Member of the Paleogenic Shahejie Formation in the Qikou Sag

Qikou sag is a typical Paleogenic fault basin in eastern China with an exploration and development history of about half a century and abundant geologic information.First,the multiple factors of the second sub-member of the third member of the Paleogenic Shahejie Formation in the Qikou sag,including logging facies,core facies,sand distributed system,seismic facies and seismic attribution,biofacies,mineralogy and petrology,organic geochemistry,rock color,structure,paleogeomorphology,were studied in detail.Then,the spatial distribution and arrangement of these factors were analyzed systematically to decipher the sedimentology.The consistent sedimentology information enable objective analysis and valuation for the depositional system types,spatial arrangement and provenances.There are four types of depositional systems in the second sub-member of the third member of the Shahejie Formation in the Qikou sag,i.e.,fan delta depositional system,braided delta depositional system,submarine fan depositional system and lacustrine depositional system.Fan delta depositional system developed in the steep area with extensive fault activity;braided delta depositional system developed in the smooth areas ;inshore submarine fan depositional system developed in the fault basin margin and infralittoral submarine fan depositional system was controlled by intrabasinal secondary faults.They were influenced by five main provenances,the Yanshan,Cangxian,Chengning,Kongdian and Shaleitian provenances.It shows that comprehensive analysis of multiple factors with details was effective for the depositional system analysis of fault basins with abundant exploration data.