Abstract:

Based on the sequence stratigraphy theory, this study analyzed the main structural sedimentary cycles and key sequence boundary features of Paleogene in the beach area in Liaohe depression, and four secondaryorder sequences and eleven thirdorder sequences were defined. The results reveal that the sequence development features of Paleogene in the study area are mainly controlled by tectonic movement, tectonic intensity and sedimentation cycles. The secondaryorder sequence boundary can be considered as the transition interface of the structural configuration and sedimentary environment, controlling the sedimentary system and types of sedimentary facies. The thirdorder sequence boundary can be considered as the transition interface of the sequence superposition pattern and sedimentary environment, controlling the features and evolution of system tract within the sequence. The distribution of sand bodies was affected by the paleogeomorphic model and slope scale. The development of sand bodies was vertically controlled by depositional cycles and system tracts. The study on the reservoircap assemblage indicates that the secondaryorder sequence and the maximum regional flooding surface affect the reservoir forming configuration, and the thirdorder sequence and system tract control the vertical distribution of oil and gas.

Key words: depression, sequence characteristic, slope break type, distribution of sand bodies, distribution of oil and gas reservoir