Paleolacustrine environment and development pattern of high-quality source rock of Eocene the hydrocarbon-rich depression of Zhu I depression

High-quality source rocks are the material basis for the formation of oil and gas enrichment. Exploring the development mechanism of high-quality source rocks is of great significance for the selection of potential hydrocarbon-rich depressions. By comprehensively applying geochemical and seismic data, and combining the tectonic evolution and sedimentary background of the depression, the paleolake environment and development model of the high-quality source rocks of the Wenchang Formation in the hydrocarbon-rich depression of the Zhu I Depression were analyzed.

The research shows that the coupling of medium and small-scale sedimentary material input and fault activity controlled the development of deep and semi-deep lakes; a warm and humid climate was a prerequisite for the vigorous growth of aquatic planktonic algae; the input of nutrients such as deep hydrothermal activities, volcanic ash, and granitic sedimentary materials enhanced the initial productivity of the lake basin; and two development models of high-quality source rocks were formed: the "productivity - preservation conditions" co-controlled type and the "preservation conditions" mainly controlled type. Among them, when there is both magmatic activity and terrestrial input of nutrients in the deep and semi-deep lakes, it has a high initial productivity and good preservation conditions, which is the best model for the development of high-quality source rocks.