1. Institute of Exploration and Development, PetroChina Jilin Oilfield Company, Songyuan 138000, Jilin, China;
2. The First Production Plant, Daqing Oilfield Co. Ltd, Daqing 163111, Heilongjiang, China

To understand the oil and gas potential of the under-explored Sankeyushu fault depression of Tong-hua Basin, the characteristics of source rock, reservoir, caprock and their assemblage in the Lower Cretaceous of the study area were systematically evaluated. It shows that the Sankeyushu fault depression contains thick dark mudstones with strong hydrocarbon generating capacity in two sets of lacustrine successions of the Lower Cretaceous Yingzuilazi and Linzitou formations, and is a "small and fertile" hydrocarbon-rich fault depression with great explo-ration potential. The fault depression is not only with thick and mature source rocks, but also overlapping fan delta front sand bodies. In addition, the early faults in the fault depression are less active, and the source rocks and res-ervoirs are closely interbedded, forming a favorable "self-generating and self-storing" source-reservoir-caprock as-semblage, which is favorable for the formation of fault-lithologic traps, volcanic barrier traps and tight fractured li-thologic traps. Among them, Tongdi 2-Tongdi 4-Tongdi 18 well area in the central-south part of Sankeyushu fault depression is a favorable exploration zone. Industrial gas flow was obtained from the well Tongdi 17 geng, which preliminarily confirmed the exploration potential of Sankeyushu fault depression.