Differences characteristics and controlling factors of Paleogene high-quality source rocks in Shanan Sag
Shanan Sag is located in the transitional position between Bozhong and Qikou sags with relatively shallow burial depth,and has undergone complex structural evolution.The distribution of oil and gas in the basin and the geochemical characteristics of hydrocarbon source rocks show strong heterogeneity,which has been the difficulty of oil and gas exploration in the Bohai Sea.In this study,the organic geochemistry,organic petrology and inorganic geochemistry are systematically used to analyze the source rock characteristics in four layers from the third member of Shahejie Formation(Es3)to third member of Dongying Formation(Ed3)in the Shanan Sag.The results show that there are significant differences in the organic matter abundance and type of Paleogene source rocks in the Shanan Sag.The middle section of third member of Shahejie Formation(Es3m)and Ed3 source rocks are high-quality,followed by the first(Es1)and second(Es2)members of Shahejie Formation,and the upper section of third member of Shahejie Formation(Es3u)is the worst.The source and organic matter composition of different source rocks shows that the Es3m organic matter mainly comes from freshwater algae,the Ed3 source rock has the highest amount of terrestrial organic matter.Detailed comparative analysis of biomarkers shows that the indicators,such as pristane,phytane,gammacerane,ααα20R regular sterane and 4-methylsterane can be better used to distinguish the different source rocks.During the Es3m and Ed3 sedimentary period,the activities of boundary faults were strong,and the sedimentary water was deep.The hypoxic sedimentary environment with weak to moderate stratification was conducive to the development of high-quality source rocks.Paleoclimate and fault activity control the development and distribution of Paleogene source rock in Shanan Sag,while the formation of high-quality source rock usually requires a higher fault activity rate and lower sand body input.The paleoclimate and fault activity control the development and distribution of Paleogene source rock in the Shanan Sag,while the high-quality source rock usually requires a higher fault activity rate and lower sand input ratio.This study provides a reference for better understanding the high-quality lacustrine source rock development and oil exploration under similar conditions in other continental basins of the world under similar conditions.
万方数据
维普
