Abstract: The basic characteristics of oil-gas reservoir are presented, the deposition, reservoir-cap rock assemblage and hydrocarbon accumulation stages are analyzed and the process of hydrocarbon accumulation is dynamically recovered in Niujuanhu oilfield. It is shown that it is in good assemblage and its crude oil originates from lacustrine source rocks of Lucaogou formation of Upper Permian, dominated by low-mature oil. The Xishanyao formation of Lower Jurassic is characterized by fan delta, fluvial and lacustrine deposits with sandstone and glutenite, etc. and primary intergranular pore and intergranular dissolved pore, belonging to porous-type reservoir of low porosity and low permeability. Lucaogou formation is characterized by coastal lake, hemi-deep lake, volcanic eruption and fluvial deposits with pore, fissure and cavity, being fracture-pore-type reservoir. Its crude oil originates from both source and reservoir in itself, and its hydrocarbon accumulation occurs in several stages and durative and starts from Late Triassic, but the main stages are Late-Jurassic to Cretaceous. Jurassic reservoir is principally formed at Late Cretaceous. Himalayan movement period is significant to the preservation of different horizons of reservoirs in this basin.

Key words: Santanghu basin, source-reservoir-cap rocks assemblage, source rock, hydrocarbon accumulation stage