基于星点状方解石胶结与溶解的识别查明砂岩粒间孔隙类型——以雅布赖盆地新河组砂岩为例

目前含油气砂岩中粒间孔隙是原生孔隙还是次生孔隙的认识仍不一致，而对星点状方解石胶结与溶解的识别能够有效地查明粒间孔隙的类型。文章通过铸体薄片细致地观察雅布赖盆地新河组砂岩中的微观现象，以成岩环境演化和成岩序列分析为主线，重视方解石胶结物的赋存状态与物质来源和溶蚀流体来源的配置关系，精细解剖微观现象，从而弄清楚星点状方解石的成因，进而查明砂岩的粒间孔隙类型和储集空间类型。结果表明，粒间孔隙中的星点状方解石是成岩早期浸染状方解石胶结物的溶蚀残余，溶蚀流体为成岩中期的有机酸流体，溶蚀类型为一致性溶解，形成的粒间孔隙为次生孔隙。鉴于此，雅布赖盆地新河组砂岩的储集空间由次生粒间孔隙和次生粒内孔隙（长石、岩屑、方解石胶结物的溶蚀孔隙）组成。 

Identifying intergranular pore types by distinguishing between cementation and dissolution of dotted calcite: A case study of the Xinhe Formation sandstones in the Yabrai Basin, China

There is still no consensus among researchers about whether intergranular pores in oil-bearing sandstone are primary pores or secondary pores. Distinguishing between cementation and dissolution of dotted calcite can effectively identify intergranular pore types. In this paper, taking the diagenetic environment evolution and diagenesis sequence as the thread, we carefully observed the casting slices from the Xinhe Formation sandstones in the Yabrai Basin and finely dissected the microphenomenon by focusing on the calcite cements in its relation between the origins of substance and dissolution fluids and the occurrence mode. The genesis of the dotted calcite was clarified thus, and then the intergranular pore types and reservoir space types in the sandstones were identified. The study results show that the dotted calcite in the intergranular pore is the dissolution residue of the disseminated calcite formed in the early diagenetic stage, and the dissolution type is the consistent dissolution. The dissolution fluid, organic acid fluid formed during the middle diagenetic stage, caused the secondary pores. Therefore, it is concluded that the reservoir space in the Xinhe Formation sandstones in the Yabrai Basin consists of the secondary intergranular pores and the secondary intragranular pores such as dissolution pores of cements of feldspar, lithoclast, lithoclast.