Abstract: A reservoir with low oil saturation is of complex geologic structures and hydrocarbon accumulation modes. Research of its genesis can help to evaluate reservoir quality and regional exploration situation. In view of such a reservoir in No.1 area in central Junggar basin, the systematic studies of its structure, reservoir rock and hydrocarbon accumulation process are conducted for understanding of its reservoir-forming mechanism, including quantitative and semi-quantitative analyses of the reservoir adjustment, oil-gas re-migration/accumulation, oil/water differentiation sufficiency and the effects of oil/water transition zone height, barrier and interbed of the low permeability reservoir on its oil-water distribution. It is recognized that the reservoir in this area is formed on the premise of oilgas reservoir adjustment and setting conditions of low-amplitude structure and low permeability reservoir rocks with many factors of breakthrough pressure of its barrier and interbed, capillary pressure and oil-gas charging sufficiency, etc.

Key words: Junggar basin, low oil-saturated reservoir, low permeability, abnormal pressure, structure adjustment