鄂尔多斯盆地东南部二叠系山2—盒8段致密砂岩储层特征及主控因素

利用铸体薄片、岩心物性、扫描电镜、恒速压汞等分析测试资料，对鄂尔多斯盆地东南部二叠系山2—盒8段致密砂岩储集层的微观孔喉特征进行了定性、定量评价，并分析了砂岩储层致密化的主要成因。研究结果表明：①鄂尔多斯盆地东南部二叠系山2—盒8段砂岩储层主要以石英砂岩、岩屑石英砂岩、岩屑砂岩为主，孔隙类型主要为残余粒间孔、（颗粒、胶结物）溶孔、自生黏土矿物晶间孔和少量微裂缝。②研究区不同渗透率级别砂岩孔隙半径相差不大，而喉道半径差异明显；随着渗透率增大，致密砂岩喉道半径分布范围变宽，粗喉道所占比例增大，表明渗透率主要受控于相对含量较低的大喉道数量。③研究区砂岩孔隙结构的非均质性受沉积微相控制，三角洲前缘水下分流河道砂体的物性最好，远沙坝、三角洲前缘席状砂等物性较差。④成岩作用是研究区目的层段储集层微观孔隙结构复杂化的主控因素，长期持续的埋藏压实作用造成了颗粒接触紧密，部分在压溶作用下转变为线状—凹凸接触，致使孔喉大量减少；而多期石英次生加大、不同类型的黏土矿物和碳酸盐胶结物充填堵塞孔喉，进一步加剧了渗透率的降低和储集层的致密化。

Characteristics and main controlling factors of tight sandstone reservoirs of Permian Shan 2 to He 8 members in southeastern Ordos Basin

Based on the analysis and test data of casting thin section， core physical properties， scanning electron microscope，constant-rate mercury intrusion， the micro pore and throat characteristics of tight sandstone reservoirs of Permian Shan 2 to He 8 members in southeastern Ordos Basin were quantitatively and quantitatively evaluated， and the main reasons for the densification of sandstone reservoirs were analyzed. The results show that： （1）The sandstone reservoirs of Permian Shan 2 to He 8 members in southeastern Ordos Basin are mainly composed of quartz sandstone，lithic quartz sandstone and lithic sandstone. The reservoir pores mainly include residual intergranular pores，（particles， cements），dissolved pores， authigenic clay-mineral intercrystalline pores and a small number of microcracks.（2）The pore radius of sandstone with different permeability has little difference， but the throat radius is obviously different. With the increase of permeability， the distribution range of the throat radius becomes wider，and the proportion of the large throat increases， indicating that the permeability is mainly controlled by a relatively small number of large throats.（3）The heterogeneity of the pore structure of the sandstone in the study area is controlled by sedimentary microfacies. The underwater distributary channel sand bodies of delta front have the best physical properties， while distal bar and delta front sheet sand have poor physical properties.（4）Diagenesis is the main controlling factor for the complexity of the microscopic pore structure of the reservoirs in the study area. Long-term continuous burial and compaction resulted in close contact of particles， and part of them were transformed into linear-concave-convex contact under pressure solution，resulting in a large reduction of pore throats. Multi-phase quartz secondary enlargement，and the filling of pores with different types of clay minerals and carbonate cements，further aggravated the decrease in permeability and the densification of the reservoir.