Hydrocarbon Generation Characteristics Of Source Rocks With Salt Environments In The Dongpu Depression

The salt environment has an important influence on organic matter occurrence,which is mainly affected by the source,type,preservation and evolution of organic matter,which in turn determines the evolutionary characteristics of organic matter hydrocarbon generation to a certain extent.The sedimentary environment of the Paleogene in the Dongpu Depression changed greatly over the plane,with the saltwater environment in the north,the freshwater environment in the south and the transitional zone in the middle.According to the current exploration results,the organic geochemical characteristics of source rocks are quite different under different environments.The source rocks in the northern part of the saltwater environment have a high organic matter abundance,a good organic matter type,and more than 80% of the proven oil reserves are in the north.Therefore,the study on the hydrocarbon-forming characteristics of source rocks in the Dongpu Depression with different salt environments is of great significance for the evaluation of the remaining resource potential and the clear exploration targets.Firstly,based on a large amount of geochemical data and combined with well drilling,logging,and well logging data,this paper analyzes the geology and geochemical characteristics of source rocks of the Paleogene Es1,Es3 and Es4 of the Dongpu Depression in different salt environments,and finds that the abundance and type of source rock indicators in the Dongpu Depression are significantly superior to freshwater areas,and the high-quality source rocks are mainly distributed around salt rocks.Secondly,the paper studied the hydrocarbon-generating characteristics of source rocks under different sedimentary environments in the Dongpu Depression using a gold-tube pyrolysis experiment,and the results show that the hydrocarbon-generating potentials of the source rocks in different environments are in descending order of saltwater area,brackish water area and freshwater area.Thirdly,through the in-depth analysis of paleoenvironment and paleoproductivity of source rocks with different salt environment,it is found that the formation of source rocks in salt areas is characterized by the humid paleoclimate,high paleoproductivity,the good source of organic matter and preservation conditions.The transitional area is adjacent to the salt area,but it is not a sedimentary center,and the formation of source rocks in transitional area is characterized by the relatively high paleoproductivity,relatively good source of organic matter and preservation conditions.But the formation of source rocks in freshwater areas is characterized by the shallow water,the poor source of organic matter,low paleoproductivity,and relatively poor preservation conditions.Finally,on the basis of comprehensive analysis,the hydrocarbon generation evolution model of source rocks under different salt conditions was established.