Abstract: The Cretaceous reservoir in Junggar basin is on the whole characterized by low component maturity, low cement con-tent, high textural maturity and developed clay film in lithology. The rock types are dominated by feldspathic litharenite and lithic sandstone with point contact relations among grains, film-pore cementation. Relative high content of feldspar and commonly exist-ing analcite cements are another features different from Jurassic reservoir. In diagenesis, most part is week, primarily in early phase of diagenetic A-B; residual primary intergranular pores are the most important type of Cretaceous system; while secondary dissolution porosity is mostly developed in glutenite of Tugulu group bottom; and the coarser the lithology, the better the pore configuration. In exception of Kayindike area, the quality of Cretaceous reservoir is generally high. The high quality reservoir is due to low content of plasticlast and fillers. The low paleo-geothermal gradient, weak diagenesis and late deep buried pattern are favorable for preservation of porosity. The sandstone diagenetic compaction is the main reason for loss of reservoir porosity, the sand partical size is an important factor affecting reservoir quality. In addition, it is sedimentary environment that results in the difference of rock types; solution is major factor of incremental porosity in Cretaceous conglomerate and glutenite; developed clay film is major reason for forming low resistivity of Cretaceous oil zones.

Key words: Junggar basin, Cretaceous, reservoir rock, feature, orig