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通过铸体薄片、扫描电镜、高压压汞等方法对鄂尔多斯盆地旬邑地区三叠系延长组长9储层成岩作用进行研究,分析成岩作用对储层的影响及孔隙演化,并对储层成岩相进行划分.结果表明:旬邑地区长9储层主要以长石砂岩和岩屑长石砂岩为主.压实作用及胶结作用是造成储层物性变差的主要原因,压实作用造成孔隙度降低约15.5％,胶结作用造成孔隙降低约13.6％.溶蚀作用对储层孔隙改善不明显,仅增加孔隙度约为1.98％.通过分析影响储层物性的主要成岩作用,综合实验测试数据将长9储层划分为4种成岩相:绿泥石膜一粒间孔相、长石溶孔—粒间孔相、碳酸盐致密胶结微孔相及塑性岩屑压实致密相等.其中绿泥石膜—粒间孔相、长石溶孔—粒间孔相为有利的成岩相带,主要分布在砂体中部区域.“,”The diagenesis and its influence on Chang-9 reservoirs in Xunyi area of Ordos Basin is studied by means of thin section,casting film,mercury injection.Pore evolution of Chang-9 reservoirs is analyzed,then diagenetic facies of the reservoirs are identified.The major rock types of the reservoir are mainly feldspar sandstone and lithic arkose sandstone.Compaction and cementation result in loss of the reservoir property.The porosity of the reservoirs decreased by 15.5％ as a result of compaction,then the porosity of the reservoirs decreased by 13.6％ due to cementation.After wads,the improvement of the reservoir pore as a result of dissolution is not obvious,only contributing the increase of porosity by about 1.98％.Base on analysis results,four types of diagenetic facies are identified,namely chlorite filnintergranular pore facies,feldspar solution pore-intergranular pore facies,carbonate cementation facies and soft lithic fragments compaction facies.The chlorite film-intergranular pore facies and feldspar solution pores-intergranular pore facies are the favorable diagenetic facies,which is mainly distributed in the central region of underwater channel sand bodies of delta front.