The research on hydrocarbon generation and expulsion characteristics of main source rocks in the Dongying Sag of the Jiyang Depression and their depositional environmental impacts

Lacustrine faulted basins are important areas for oil and gas exploration, where the hydrocarbon generation and expulsion characteristics of source rocks are influenced by various factors such as depositional environment, tectonic evolution, and organic matter abundance, exhibiting significant heterogeneity that poses challenges to resource evaluation. Taking the Dongying Sag in the Jiyang Depression as the study area, this research systematically analyzed the hydrocarbon generation and expulsion characteristics of three major source rock intervals (upper Es4, lower Es3, and middle Es3) and their controlling factors. The results indicate that source rocks in the lake basin center and shallow lacustrine environments are characterized by high organic matter abundance and strong hydrocarbon generation potential. In contrast, those in shallow shoals and delta front environments have lower hydrocarbon generation efficiency. The hydrocarbon generation and expulsion capacity of source rocks are closely related to the degree of organic matter enrichment, with micro-pore structures and depositional facies playing significant roles in expulsion efficiency. Among the source rock intervals, the upper Es4 layer contributes the most to resource potential and exhibits the highest hydrocarbon generation and expulsion potential. This study reveals the hydrocarbon generation and expulsion characteristics of source rocks under different depositional environments and their key controlling factors, providing theoretical support for oil and gas exploration in the Dongying Sag of the Jiyang Depression and offering valuable insights for evaluating source rocks in similar lacustrine faulted basins.