Abstract: With further exploration of major structural traps in southern Songliao basin, the prospecting target has gradually focused on the non-structural reservoirs dominated by litho-stratigraphic traps. However, the complex and hidden nature of this type of reservoirs in geologic condition and distribution pattern cause them to be difficult to understand or recognize, adding the difficulty for their explorations. The great potentials for exploration of litho-stratigraphic reservoirs do not appear until new methods and technologies have been applied and in-depth understandings have been gained. In recent two or three years, big discoveries have been made in Jilin oilfield, in which 80 percent of reserves are found in some areas of thin sand-shale interbedding of its delta front There still exist petroleum potentials amounting to 6×10⁸ t for exploration in this area, especially in southern Songliao basin where the litho-stratigraphic traps will be more important domains and deserve extra attention. Hence, geologically speaking, this study on the hydrocarbon accumulation of lithostratigraphic reservoirs in Songliao basin is of vital significance to exploration of the southern Songliao basin.

Key words: Songliao basin, south, litho-stratigraphic reservoir, depositional system, oil-gas assemblage