Abstract: Taking Upper Jurassic-Cretaceous strata in Songliao basin as a research target, the relationship between the accommodation space changes and oil-gas reservoir in lacustrine basin is studied by way of comprehensive explanation of geochemical, drilling and core data. During the deposition of the first member of Qingshankou formation and the first-second members of Nen-jiang formation, tremendous growth of the accommodation space resulted in wide distribution of source rocks with high organic carbon content and good organic matter type. The accommodation space change caused by periodically tectonic and climatic changes controlled the characteristics of source-reservoir-caprock assemblage, and formed some types of different assemblages with source bed in ancient formations and reservoir bed in recent formations as well as source bed in recent formations and reservoir bed in ancient formations. Also, the accommodation space changes controlled the evolution of sequences and the distribution of system tracts, in which base fan and slope fan of lowstand system tracts are the most favorable for the oil and gas accumulations.

Key words: continental facies, source-reservior-caprock assemblage, sequence, sequence stratigraphy