鄂尔多斯盆地陇东地区长4+5油层组致密砂岩储层成岩作用及成岩相

运用铸体薄片鉴定、扫描电镜、X-衍射及高压压汞等测试方法，系统分析了鄂尔多斯盆地陇东地区长4+5油层组砂岩储层的成岩作用特征及其对储层物性的影响，进而对储层成岩相特征及有利成岩相的分布进行了研究。结果表明：研究区长4+5储层成岩阶段总体处于中成岩阶段A-B期，压实作用与碳酸盐胶结作用造成原始孔隙的大量损失，使储集层物性变差；早期绿泥石薄膜的发育有利于原生孔隙的保存；溶蚀作用使物性得到明显改善。根据成岩作用对物性的影响，划分出绿泥石薄膜-粒间孔相、高岭石胶结-长石溶蚀相、伊利石胶结-长石溶蚀相、碳酸盐胶结相、硅质-伊利石胶结相等5种成岩相带，优质储集层与成岩相密切相关，绿泥石薄膜-粒间孔成岩相的砂体物性、含油性最好，是研究区长4+5储集层石油最富集的成岩相带。

Diagenesis and diagenetic facies of the Chang 4+5 tight sandstone reservoirs in Longdong area,Ordos Basin

Based on thin sections,SEM,X-ray diffraction,mercury injection,this paper analyzed the diagenesis and its impact on Chang4+5(the 4^th and 5^th Member of the Yanchang Fm)oil layers in Longdong area,Ordos Basin.Based on the analysis results,we studied the characteristics of diagenetic facies and the distribution of favorable facies.The Chang4+5 oil layers is at the mid-diagenetic A-B stage,and the early compaction and carbonate cementation resulted in loss of great numbers of primary pores,resulting in poor reservoir quality.However,the early chlorite thin film was favorable for the protection of primary pores and dissolution improved reservoir quality.According to the impact of the diagenesis on reservoir quality,five types of diagenetic facies were identified,namely chlorite thin film-residual intergranular pore facies,kaolinite cementation-feldspar dissolution facies,illite cementation-feldspar dissolution facies,carbonate cementation facies and siliceous-illite cementation facies.High quality reservoirs are closely related to the diagenetic facies,and the chlorite thin film-residual intergranular pore diagenetic facies is the best in reservoir physical property and petroliferous property,thus is the most favorable diagenetic facies for oil enrichment in this area.