Diagenesis and physical property of the Yanchang Formation sandstone reservoirs in southeastern Ordos Basin

The combination of petrology,diagenesis and physical property of the Yanchang Formation sandstone reservoirs in southeastern Ordos Basin has revealed that the Chang-9,Chang-8,Chang-6 and Chang-2 oil reservoirs consist dominantly of feldspathic litharenite,lithic feldspathic sandstone and feldspathic sandstone with poor compositional and textural maturity.The decrease of the porosity by compaction and carbonate cementation resulted in the generation of the low-porosity and low-permeability sandstone reservoirs in the study area.The porosity tends to range between 4% and 8%,and the permeability is generally less than 0.1×10^-3 μm².The Chang-6 oil reservoirs are the best sandstone reservoirs with good porosity and permeability,and the Wang-9 well is believed to be the favourable sedimentary facies zone due to better physical properties of the sandstone reservoirs.