Geochemical characteristics and accumulation conditions of crude oils in well Ba 1, Tanzhuang Sag, Southern North China Basin

The analysis of the biomarker compositional characteristics of crude oils from the Lower Cretaceous of the Tanzhuang Sag in the Southern North China Basin indicated for the Lower Cretaceous origin,and the reservoir was indigenously generated and accumulated.According to the simulation of burial and thermal evolution histories,there were at least two stages of hydrocarbon charging in the study area.The early stage was the Early Cretaceous and the late stage was from the Late Tertiary to Quaternary.The studies of accumulation conditions revealed that the Lower Cretaceous source rocks in the Tanzhuang Sag had good quality,strong sealing capacity and nice allocation of generation-migration-accumulation;however,the Lower Cretaceous sandstones with low porosity and permeability restricted petroleum exploration.High resolution sequence stratigraphy and sedimentary facies studies were advised to predict favorable sandbodies.