| Up to 58% of the world’s oil and gas basins have salt rock,and the oil reserves are89%of the proven reserves,and the natural gas reserves account for 80%of the global reserves,indicating that the relationship between salt rock and oil and gas is relatively close.As a typical Mesozoic and Cenozoic continental saline lake basin in China,Dongpu Depression has significant differences in salt rock development characteristics and oil and gas occurrence in the north and south.The difference in reserve abundance per unit area between the salt-bearing area in the north and the salt-free area in the south is nearly 20 times.However,as one of the research hotspots in this area,the genetic model of salt rock in the Dongpu Depression is still controversial,and the research on the control effect of salt on the formation process of source rock,its mechanism and model is still incomplete.In view of the above problems,this paper takes the third member of the Paleogene Shahejie Formation,the main source rock series in Dongpu Depression,as the research object,the development and distribution characteristics of salt rock are clarified through petrological,mineralogical and geological data.The variation characteristics of parameters such as Sr/Cu,Mg/Ca,Rb/Sr,B/Ga,Sp,U/Th、V/（V+Ni）,Fe/Mn,etc.,are of great significance to the paleoclimate and paleosalinity of the salt rock development period in Dongpu Depression.Redox conditions and paleo-water depth were studied to clarify the depositional environment of the salt rock development period.The results show that the salinization period of Dongpu Depression was mainly in a dry-hot climate,a reducing deep-water depositional environment,and the water body salinity was high,showing a brackish water environment.Finally,the genetic model of the third member of the Shahejie Formation in the Dongpu Depression is established based on the characteristics of the development and distribution of salt rock and the characteristics of the depositional environment during the development period.The lower sub-member of the third member of Shahejie Formation（Es3）,the middle sub-member of Es3and the upper sub-member of Es3are selected as the research objects respectively,and the source rock’s quality and distribution characteristics of Es3in Dongpu Depression are determined by means of geochemical analysis and geological analysis.Combined with the development characteristics of salt rock,the influence of salt rock on the quality and distribution of source rock in the salt-bearing area in the northern Dongpu Depression is analyzed.The research shows that salt rock has a controlling effect on the abundance of organic matter,the type of organic matter and the degree of thermal evolution.The organic matter abundance and salinity have a normal distribution relationship.The source rock with higher salinity type I and II1kerogen account for a higher proportion of source rock with lower salinity,while the hydrocarbons in the salt rock development interval are higher.The hydrocarbon-generating window of the source rock is obviously enlarged.Finally,the organic matter enrichment model of the third member of the Shahejie Formation in the northern salt-bearing area of Dongpu Depression is established.During the deposition of the third member of Shahejie Formation in Dongpu Depression,the climate was dry and hot,and the water body as a whole showed deep water reduction conditions of brackish water. |
