Abstract: Sangonghe formation(JIs) in Baobei district of Baolang oilfield, Yanqi basin, is a braided river delta-lacustrine depositional system of shallow gentle slope with coarse grains. It has five microfacies developed, including underwater distributary channel, underwater distributary interchannel, crevasse channel(fan), overband flood deposit and lakeshore swamp deposit. The sand body of underwater distributary channel accounts for over 90 percent of reservoir in study area, which can be classified into flled channel, abandoned channel and progradational channel, based on the .sand body's petrofacies assemblage, scour extent, variation of current energy size. Of which the petrophysics of abandoned channel is the best, the well productivity is the highest too; the flled channel is secondary; progradational channel and crevasse channel(fan) are relatively poor. The study shows that the oil-gas productivity is controlled by types locations and distribution of depositional microfacies in Sangonghe reservoir.

Key words: Yanqi basin, Baobei district, Sangonghe formation, depositional microfacies, oil-gas productivity