Abstract: The central inversion zone of the Liaoxi Depression is the enrichment area of high quality light crude oil in the Liaodong Bay exploration area. However, the genetic types, source and accumulation of crude oil have not been systematically studied. Based on the analysis and comparison of the biomarkers, three sets of effective source rocks of the Shahejie Formation were distinguished. The first, third and fourth members of the Shahejie Formation, are obviously different in the source of organic matter and sedimentary environment. It is confirmed that plankton is the main component of organic matter in the three sets of source rocks. The first member of the Shahejie Formation (E2s1) has the highest plankton content and the least terrestrial organic matter input. The content of dinoflagellate in the fourth member of the Shahejie Formation (E2s4) was significantly higher than that in the first and third members of the Shahejie Formation (E2s1, E2s3). Both E2s3 and E2s4 source rocks were deposited in the freshwater and weakly alkaline reducing environment, and the E2s1 source rock was deposited in the brackish to saline alkaline strongly reducing environment. The crude oil found in the central inversion zone can be divided into three source-related types through hierarchical cluster analysis(HCA). The oil-source correlation results show that the type Ⅰ crude oil is the mixed oil originated from the E2s3 and E2s1 source rocks, which is mainly distributed in the middle block and the middle area of the east block on the central inversion zone. The type Ⅱ crude oil is originated from the E2s4 source rocks, which is distributed in the southern area of the east block on the central inversion zone. The type Ⅲ crude oil is the mixed oil originated from the E2s3 and E2s4 source rocks, which is mainly distributed in the west block and the northern area of the east block on the central inversion zone. On this basis,

the main controlling factors of hydrocarbon accumulation in the central inversion zone of the Liaoxi sag were analyzed. Oil and gas
reservoirs on the central inversion zone are controlled by multiple factors, including the distribution of effective source rocks and the math of fault and sand bodies.

Key words: HCA, biomarker, Shahejie Formation, triaromatic steroids, oil-source correlation, Liaoxi Depression