Geochemical Markers For The Formation Condition Of Lacustrine Organic-Rich Shale In Key Areas

The sedimentary facies of continental lacustrine in eastern China change fast and show a strong heterogeneity.In order to describe such heterogeneity in different sedimentary environments efficiently.in this paper,we choose the 4 wells named FY1,L69,BYY2 and Bin1 from Donging sag,Zhanhua sag,the southern of Ordos basin and Qianjiang sag,respectively.The heterogeneity was characterized by the biomarker compounds.The TOC of the source rocks in the above four regions was high,the hydrocarbon generation potential was good,and the organic matter abundance was high,especially the TOC of the Bin1 well is highest.The organic matter type is mainly I-II type,which is in the low-maturing-mature stage in these areas.In order to study the causes of heterogeneity,for the lacustrine shale of different basin types and different sedimentary environments,biomarker compounds and molecular geochemical methods can be used to know that the Eq3 member of the Qianjiang depression formed in the high salinity and strong anoxic.Strongly reduced salt lake sediments and dry climate.Es4 and Es3 members in Jiyang Depression is a brackish water-freshwater sedimentation with reduced reductiveness and stratification of water bodies.The climate gradually changes from dry to warm and humid.Chang 73 member is a wet freshwater deposit.The source of organic matter is mainly low-grade aquatic organisms such as algae,and a certain amount of terrestrial higher plants are mixed.We compared the shale aggregation mechanism of different sediment types know that the conditions of warm and humid climate and reducing oxygen deficiency.is considered to be more suitable for the formation and accumulation of organic matter.The organic matter is mainly aquatic organisms such as algae,and the water salinity changes cause water stratification.It is more conducive to the preservation of organic matter.Although the preservation conditions in southern Ordos basin is not as good as that in other regions,the high organic carbon content may be due to the high productivity of the lake,the sufficient source of organic matter and the better organic matter type.