Study on miscible diagenesis and its impact on reservoir property in Youquanzi oilfield

This paper studies the diagenesis and reservoir properties of the Youshashan formation in Youquanzi region by using data of X-ray diffraction,ordinary thin section,casting thin section,scanning electron microscopy and cathode-ray.The result shows that the reservoirs in this area mainly contain siltstone(pelitic siltstone),grain limestone and marl.Compaction and cementation are the main reasons for reservoir porosity loss,especially carbonate cementation,followed by clay cementation;the presence of chlorite cement inhibits further cementation and is helpful to the preservation of intergranular pores;while the reservoir properties are greatly improved by the denudation during fold turn-back period and the dissolution of calcite and salt rock.The reservoir is in the late stage of early diagenesis,with dissolution porosity as the main pore type.