Thermal evolution characteristics of Paleogene source rocks and their main controlling factors in northern part of Dongpu depression

Based on the soluble organic matters,biomarkers and vitrinite reflectances,this paper analyzed comprehensively thermal evolution characteristics of Paleogene source rocks and their main controlling factors in different subsags within the northern part of Dongpu depression.The results show that Paleogene source rocks of both Qianliyuan and Haitongji sags have developed into high and over-mature stages,while Paleogene source rocks of Puwei subsag only belong to the mature stage.Compared with Haitongji sag,Qianliyuan sag and Puwei subsag have wider range of hydrocarbon generation in the?longitudinal direction,shallower threshold depth for hydrocarbon generation,and deeper threshold depth for high maturity.Sha-3 member is the major source rock in all subsags,the main stage of hydrocarbon generation is Dongying period,and there existed secondary hydrocarbon generation since Minghuazhen period.The?main factor controlling Paleogene source rocks' thermal evolution differences among different subsags is formation temperature,followed by abnormal high pressure,and the type of organic matter has no obvious effect.