Reservoir characteristics and main controlling factors of Chang 4+5 and Chang 6 reservoirs in Wangwazi area of Ordos Basin

The rock type of Chang 4+5 and Chang 6 reservoirs of Wangwazi area is mainly of lithic feldspar sandstone and the pore type is mainly of intergranular pore,secondarily of feldspar dissolved pore.The reservoirs are generally expressed as medium-low porosity and ultra-low permeability,in which the physical properties of Chang(4+5)2 reservoirs are relatively good,followed by Chang 61 and Chang 62,and the porosity and permeability distribution is characterized by single peak value.The reservoirs are greatly affected by diagenesis,compaction is the main factor of reservoir variation,followed by cementation.Dissolution is the main factor to improve reservoir property,the development of chlorite plays a positive role in the preservation of porosity and reservoir permeability,and the development of Kaolinite is an important factor to improve the development of secondary porosity.