The Qingshankou Formation in the Sanzhao sag, the Songliao Basin, holds substantial shale oil resources, but its
accumulation patterns and sweet spot prediction have not been fully understood. Taking the ZY1 Well as an example, this study is focused on the source rock and reservoir characteristics of the shale. We determine the shale oil enrichment patterns and sweet spots distribution by microscopic examination, organic carbon and rock-eval analysis, and rock mineral composition analysis. The results indicate that there are three modes of shale oil accumulation in the study area: shaley, laminar, and interbedded types. In addition, the shaley type shows the greatest shale oil enrichment with good storage capacity, well-developed fissures, grain pores, and organic matter-filled pores. Laminar type has relatively good hydrocarbon generating potential and permeability, while the interbedded shale oil has low oil content due to the low hydrocarbon generating potential and poor storage capacity. Based on the classification of lithofacies and other geological parameters such as oil-bearing potential and reservoir properties of the ZY1 Well, four intervals of sweet spots are predicted. Shaley sweet spots mainly occur in the member 1 of the Qingshankou Formation, while laminated-and interbedded-type sweet spots are primarily found in the members 2 and 3.