鄂尔多斯盆地富县地区上三叠统长8砂岩储层物性的主要控制因素

研究认为富县地区上三叠统长8期三角洲前缘水下分流河道砂岩储层物性主要受沉积微相、砂岩成分和粒度以及成岩作用的控制。特别指出沉积微相对储层的控制,实际上是沉积(微)相带对砂体类型和物性特征的控制,不同沉积微相的砂岩在储集性能上存在明显的差异。表现为三角洲前缘水下分流河道砂体的孔隙度及渗透率均高于其它沉积微相内砂体的孔隙度和渗透率,而分流间湾的沉积物粒度相对较细,杂基含量高,压实作用强,不利于后期溶蚀流体的流动,储层物性较差。强烈的机械压实、压溶作用、碳酸盐自生矿物的胶结作用使孔隙结构变差,进一步降低砂岩的储集性能;由淡水淋滤及有机物质产生的溶蚀作用,对储层改善具有重要意义。

Major factors controlling reservoir quality of the Upper Triassic Chang 8 sandstones in Fuxian|Ordos Basin

The reservoir quality is strongly influenced by the depositional microfacies,composition and grain size of sandstones,and diagenesis of the Chang 8 subaqueous distribution channel sandbodies of Upper Triassic delta-front facies in Fuxian. Depositional microfacies belts controlled reservoir by sand body types and characteristics of properties. Reservoir performances of sandbodies show significant difference in different depositional microfacies. Porosity and permeability of subaqueous distribution channel sandbodies in delta-front is the highest in related sandbodies,and interdistributary bayisthe worst by small granularity,more matrix,strong mechanical compaction prevented flowing of late dissolution fluid. The strong mechanical compaction,pressure-solution and cementation of authogenetic minerals reduced reservoir performances of sandstones. Dissolutions caused by freshwater leaching and organic acids have significance for improving reservoir.