Diagenetic characteristics and its effect on reservoir of the lower porosity and permeability Sandstones of the 8th member of Shihezi in Yanqi 2 borefild

The data of cast slice, thin sections, scanning electron microscopy and X-diffraction were applied to analyze the petrology, diagenesis, diagenetic stage division and its effect on the reservoir of Yanqi 2 borefild in Ordos Basin. The results show that, the rock types are quartz sandstone, lithic quartz sandstone in the study area of He 8 reservoir. These sandstones have already been in stage A of the later diagenetic stage, a small amount has been in stage B of the later diagenetic stage. They experienced compaction, cementation, metasomatism, dissolution and fracturing. Among them, compaction and cementation are the main destructive diagenesis; dissolution and fracturing are major constructive diagenesis.