Abstract: The tight oil reservoir characteristics and densification causes of Jurassic Badaowan Formation in Mosuowan-mobei area of Junggar basin were studied by using integrated analysis of cores, thin section identification, scan election microscope and well logging data. The results show that reservoir has a low and ultra-low porosity and permeability in general, is a typical deep tight sandstone reservoir. Reservoir sand body is mainly delta front subaqueous distributary channel fine and middle-fine sandstone, maturity is low, with high debris content, high content of plastic lithic and low content of cement, that is, "two high and one low". It can be divided into three porosity evolution zones in vertical which taking 4 100 m and 4 500 m as the boundary, they are reducing-primary, stable-mixing, and increasing-secondary pore. The pore size is mainly middle-small, and the pore throat is middle-fine pore-fine throat with poor sorting, connectivity, percolation ability and structure are relatively poor. Tight sand reservoir is controlled by relative stability of sedimentary environment, main component of reservoir rock, burial depth and cements occurrence state, and so on, which constitute the background, internal and external densification. The densification reservoir of Badaowan Formation formed mainly due to relatively stable deposition environment, low compositional maturity, high debris and plastic debris content, deeply buried reservoir make pressolution largely reducing pore space, and different types of cements in four states filling pore throat.

Key words: Junggar basin, Mosuowan-Mobei area, Badaowan Formation, deep tight oil reservoir, densification causes