致密砂岩储层成因类型分析——以苏北盆地高邮凹陷阜一段为例

Analysis of genetic type of tight sandstone reservoirs:a case study of the first member of Funing Formation in Gaoyou Sag

通过微观薄片图像、CT扫描与流动性分析等手段,以苏北盆地高邮凹陷阜一段致密砂岩为例开展了致密砂岩储层成因类型的分析,认为从形成的主要因素上可以将致密砂岩储层分为原生型与次生型两大类。原生型致密砂岩储层受沉积物自身粒度、分选等因素影响较大,次生型受后期成岩作用改造较强。原生型致密砂岩储层可再细分为细粒型与混杂型,次生型致密砂岩储层可再细分为压实型与胶结型。两种类型的致密砂岩储层虽然物性都较差,但是原生型因为保存了一定的原生孔隙,喉道受到的后期成岩作用影响较少,从而具有较高的孔喉连通性,其蕴含的流体可动性较强。次生型致密砂岩储层可能会有相对较高的孔隙度,但喉道受后期成岩作用影响较大,孔喉连通性较差,其含油饱和度可能会很高,但是流体的可动性较差,后期的产液能力较弱。

By means of microscopic image of thin section,CT scan,liquidity analysis,and so on,taking the first member of Funing Formation in Gaoyou Sag as an example,it was analyzed the genetic type of tight sandstone reservoir.It was believed that the tight sandstone reservoirs can be divided into original and secondary types based on major factors of reservoir formation.The original type reservoir is mainly influenced by the grain size and sorting of the sediments,and the secondary type one is modified strongly by later diagenesis.The original type can be further subdivided into fine grain and hybrid types,and the secondary type can be subdivided into compaction and cementation types.Although the two types of tight sandstone reservoirs are poor in physical properties,the original type has a certain number of primary pores,where its throats are less affected by the later diagenesis.Therefore,the original type reservoir has higher connectivity of pore-throat and fluid mobility.The secondary type of tight sandstone reservoir has relatively higher porosity,but its throats are greatly affected by the later diagenesis.Thus,the connectivity of pore-throat is poor.Even though the oil saturation may be higher,the later production capacity is weak due to poor fluid mobility.