东濮凹陷古近系沙三段盐岩成因探讨及层序地层学意义

东濮凹陷北部中央隆起带及周边沙三段自下而上发育了三套盐岩层,每套盐岩层由若干个小盐岩韵律组成。盐岩层和油气的运聚有密切的关系。关于东濮凹陷盐岩的成因有很多的解释,笔者在对前人的工作进行细致的研究基础上,通过对盐岩层的地球化学、岩心观察、构造、古气候资料对盐岩的分析,结合各盐岩韵律层的地层对比分析及各盐韵律纵向及横向分布规律,综合分析认为东濮凹陷沙三段盐岩为深水蒸发成盐,盐岩层为最大洪泛面。在此基础上运用层序地层学的观点,将东濮凹陷的古近系的地层划分为两个二级层序和10个三级层序。总结出盐岩的成盐模式和层序地层模式,为沙三段沉积相的研究提供了理论依据,对寻找盐岩有关的隐蔽油气藏具有重要的意义。

Origin of Salt-Rock in Paleogene Shahejie Formation and Its Significance for Sequence Stratigraph in Dongpu Depression

Three sets of salt beds exist in the Sha3 member of the Paleogene Shahejie Formation in the central uplift and its vicinity in the northern Dongpu Depression. Each set of salt bed has a number of salt rhythms of salt rock and mudstone. There is close relationship between deposit of salt beds and migration and accumulation of oil-gas. Different explanations have been presented about the origin of the salt rock. Based on previous studies,through geochemical,structural,palaeoclimatic analysis and core observation as well as stratigraphical correlation of salt beds and their distribution,the paper suggests that the salt rock of the Shahejie Formation was formed by deep-water evaporation salification,and the salt beds represent the MFS. According to sequence stratigraphy,we argue that the Shahejie Formation can be divided into 2 second class sequences and 10 third class sequences in the established models of salification and sequence stratigraphy. All these provide some evidence for further study of sedimentary facies and it is significant for finding oil-gas reservoirs relating to salt rock.