Keywords: 
• diagenesis /
• lapidofacies /
• pore texture /
• Zhenbei area /
• Ordos Basin

Abstract: Based on the data analysis of casting lamella, scan electron microscope and X-ray diffractions etc, the diagenesis include compaction, cementation, dissolution and fracturing, which belong to the “A” late diagenesis on Chang 3 reservoirs in Zhenbei area of oilfield in Ordos Basin. The compaction and cementation destroy the primary-texture of pore intensively, dissolution and fracturing change the pore structure effectively. The Chang 3 reservoirs in Zhenbei area develop dissolution facies, compaction facies, cementation facies and antigenic chlorite cementation residual pores facies, which impact the pore character of reservoirs. The sandstone develops secondary-pore facies and residual pores facies that have the better pore texture. The sandstone porosity and permeability are better; the pelitic impurity compaction facies and carbonate cementation facies develop in sandstone that have the lesser pore, so that the sandstone porosity and permeability are very poor in this area.