Diagenesis and reservoir feature of Chang_(4+5) reservoir in Jiyuan-Baoziwan Area,Ordos Basin

The reservoir rock in Chang_(4+5) of Jiyuan-Baoziwan area has been studied on lithology characteristic,diagenesis and petrophysical property with testing methods of casting thin section,X-ray diffraction,scanning electron microscope analysis,etc..It shows that the reservoir rock consists of fine arkose and litharenite lithic feldspar,whose clastic granule appears subangular,compositional maturity is low and textural maturity is medium;the clastic rocks had experienced a series of complex diagenesis as compaction,cementation,pressure solution and dissolution;and the sandstones are of low porosity and low permeability.Based on this,the reservoir is evaluated synthetically,combining with mercury analysis and pore construction analysis.The reservoir is classified into four types,and most of them are type Ⅱand type Ⅲ(medium-inferior).