College of Earth Sciences, Jilin University, Changchun 130061, China

The sandstone diagenesis and its reservoir significance of Lower Cretaceous in North Yellow Sea Basin are studied by the analysis of the thin sections of sandstone and variation of porosity and permeability. The research shows that the reservoir sandstones are mainly composed of feldspar sandstone, feldspar quartz sandstone and lithic quartz sandstone. The sandstone reservoirs are in the late stage of the A-sub-period to early stage of B-sub-period in the middle diagenesis stage. The main types of diagenesis in studied area are compaction, pressure dissolution, cementation, metasomatism, alteration, dissolution and recrystallization. The main types of porosity are intergranular pores, intracellular pores, interstitial pores and secondary cracks. Feldspar sandstone is the main reservoir. Compaction, pressure dissolution, cementation and recrystallization decrease the porosity of sandstone and reduce the physical properties of the reservoir and play a destructive effect. Metasomatism, alteration and dissolution increase sand porosity, improve the physical properties of the reservoir, and play a constructive role. The porosity and permeability of the coring section decrease with depth and are abnormally high at depths of 3 000~3 020 m and 3 140~3 250 m,which are the secondary pore development zone.