Taking advantage of the experiment of scanning electron microscopy,the casting thin section,high pressure Hg injection,X-ray diffraction and physical properties,this paper have studied the reservoir essential characteristics,including diagenesis types and intensity,porosity evolution of Shan23 Formation in Su77-Zhao51 well region in the Ordos Basin.The results show that there are mainly two rock types,i.e.quartz sandstone and lithic quartz sandstone,both of which have high compositional maturity and low structural maturity.In addition,the pore type is mainly dissolution pore,while the residual intergranular pore and intercrystalline pore take the second place.After undergoing moderate-strong degree compaction,moderate cementation and strong dissolution,the reservoir is now in the phase B of the middle diagenetic stage,part of which is in the late diagenetic stage.The compaction and cementation result in destroying primary pores,leading to the loss of porosity by 16.94％ and 14.29％,respectively.The intercrystalline pore and dissolution make porosity increase by 0.92％ and 5.64％ so that the reservoir property is improved.The pore space experienced a complex evolutionary process:reduction of primary pore→development of secondary pore→reduction of secondary pore →coexistence of mixture pore.%利用扫描电镜、岩石薄片、高压压汞、X衍射等实验及物性分析资料,对鄂尔多斯盆地苏77、召51区块山23段储层基本特征、成岩作用类型及强度、孔隙演化模式进行研究.结果表明:储层主要岩石类型为成分成熟度较高、结构成熟度较低的石英砂岩和岩屑石英砂岩;孔隙类型以溶孔为主,残余粒间孔和晶间孔含量次之.储层在经历中等-强程度的压实,中等程度的胶结以及强烈的溶蚀作用后,处于中成岩阶段B期,局部处于晚成岩阶段.压实作用和胶结作用导致原生孔隙遭到破坏,孔隙度损失分别为16.94％和14.29％,晶间孔和溶蚀作用分别使孔隙度增加0.92％和5.64％,储层物性得以改善.孔隙空间经历原生孔隙减少→次生孔隙发育→次生孔隙减少→混合孔隙并存的复杂演化过程.
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