Abstract: Biyang sag is a small half-graben basin full of oil and gas of Cenozoic. With its formation controlled by Tanghe-Liyuan fault of N-W strike and Liyuan-Biyang fault of N-E strike, Biyang sag is a fan-shaped and halfgraben-like basin which is deep in southeastern part and shallow in northwestern part. It is found that a huge thickness of Hetaoyuan formation of Paleogene with good hydrocarbon-generating conditions is laterally contacted to the old metamorphic complex on the faulting arctic region in the southeastern margin of Biyang sag, which allows to forming basement reservoirs. This paper presents the sag's sequence stratigraphy, sedimentary system, marginal faulting style, source rock condition and oil shows investigation in the southern margin as well as basement lithology and reservoir quality. The petroleum accumulation models of basement reservoir on this arctic region are then development. The advantageous targets for petroleum exploration are given.

Key words: basement rock, source rock, petroleum accumulation model, basement hydrocarbon reservoir