The Study On The Sedimentary System The Permian Shiqianfeng Formation In The Eastern Ordos Basin

The ordos basin is a large superimposed basin rich in oil and gas in China.The signals of oil and gas were discovered in several groups of the basin after years of exploration.However,the Shiqianfeng formation,which is located in the fluvial-arid lacustrine environment,is commonly thought not to be capable of hydrocarbon generation due to the lack of source rocks.As a result,the sedimentary characteristics,sedimentary facies,sequence stratigraphic frameworks as well as sedimentary systems and models in the sequence stratigraphic frameworks of the Permian Shiqianfeng formation located in the eastern margin of the basin are lacking.Therefore,a complete set of methods and systems have not yet been formed.In order to build Shiqianfeng formation sequence stratigraphic frameworks and analyze sedimentary systems in the frameworks,the sedimentary depositional model of the sedimentary prototype is established,laying a solid foundation for the further exploration of regional oil and gas as well as the improvement of the production of oil and gas in the basin.In order to solve the existing problems,this paper employs geological theory as a guidance and uses the mixture of field geological work and indoor comprehensive research,with a combination of macroscopic observation and microscopic research to study the depositional system,which provides important basic reference for the oil and gas exploration in the eastern margin of Ordos basin.The main achievements and cognition are as follows:(1)Researches of Shi qianfeng formation regards the sedimentary marks as a main basis of sedimentary facies division,mainly including petrology marks,sedimentary tectonic marks and paleontologic evidence.All kinds of sedimentary symbols have obvious characteristics in targeted area.(2)In the eastern ordos basin outcrop area Shiqianfeng formation of observation and description can be found area mainly includes 10 kinds of rock and 6 kinds of rock phase combination.(3)Shiqianfeng formation of delta sedimentary facies sedimentary types are mainly of delta front subfacies,the main development in two segment,three segment,four segment and five segment of formation,lake sedimentary facies mainly development in one segment of formation.(4)3 types of short-term cyclic patterns can be identified in the Shiqianfeng formation of the research area,including the retrogradational superpositional patterns,progradational superpositional patterns and retrogradational-progradational superpositional patterns.The Shiqianfeng formation in the research area mainly developed progradational and retrogradational-progradational superpositional patterns,and the retrogradational-progradational superpositional pattern is the most common type.(5)The study area of Shiqianfeng formation in the research area can be divided into 1 long-term,4 middle term and 9 short-term cyclic sequences,which correspond well with the groups,segments and sub-segments in litho-stratigraphic units division.(6)The sequence stratigraphic framework of the Shiqianfeng formation is established according to the determination of Jushui River-Liulin chengjiazhuang –Pingliang Erdaogou Profile and the division principle of sequence stratigraphy.(7)The sedimentary system of the Shiqianfeng Formation in the study area shows a typical continental sedimentary model,namely,the delta front-shallow lake sedimentary model.