Reservoir Characteristics and Evaluation of Chang 4+5 Oil Memberof Majiashan area,Jiyuan Oilfield,Ordos Basin

The reservoir rock of the Chang 4+5 oil member in Majiashan area,Jiyuan Oilfield has been studied on lithology characteristic,diagenesis and petrophysical property using casting thin section,X-ray diffraction,scanning electron microscope analysis and so on.It shows that the reservoir rock consists of silty and fine-grained arkose,and has low compositional maturity and medium textural maturity.The clastic rocks experienced a series of complex diagenesis as compaction,cementation,pressure solution and dissolution.The sandstones are low porosity and low permeability.Based on the research of mercury analysis and pore construction analysis,the reservoir is evaluated synthetically.The reservoir is classified into three types,and at present type Ⅰand Ⅱ are good reservoirs for production.