江汉盆地潜江凹陷盐间页岩油储层不同岩相微观储集特征——以古近系潜江组三段4亚段10韵律为例

Microscopic reservoir characteristics of different lithofacies from inter-salt shale oil reservoir in Qianjiang Sag,Jianghan Basin:a case study of Paleogene Eq34-10 rhythm

通过岩石薄片鉴定、扫描电镜、压汞—液氮吸附联合测定及微米CT三维重构等实验手段,对江汉盆地潜江凹陷潜江组页岩油储层的矿物组成、岩相组合、孔缝类型、孔隙结构及孔隙发育规律进行研究。盐间古近系潜江组三段4亚段10韵律页岩油储层主要岩相有纹层状泥质白云岩相、纹层状云(灰)质泥岩相和钙芒硝充填纹层状云质泥岩相;储集空间主要包括层间缝、晶间孔、晶间溶孔等。盐间页岩油储层孔隙的发育主要受岩性、岩相控制,钙芒硝充填纹层状云质泥岩相—纹层状云(灰)质泥岩相—纹层状泥质白云岩相孔隙发育程度依次增强。纹层状泥质白云岩相孔隙中宏孔最为发育,孔隙连通性最优,含油性最佳,为盐间页岩油储层中的优势岩相,是盐间页岩油最有利的勘探目标。

The mineral composition,lithofacies association,pore-fracture type,pore structure and pore development control of the Qianjiang Formation shale oil reservoir in the Qianjiang Sag of the Jianghan Basin were studied using thin section petrography,scanning electron microscopy,mercury injection-liquid nitrogen adsorption and 3 D reconstruction of micro-CT.The main lithofacies of Eq34-10 rhythm(the tenth rhythm in the fourth submember of the third member of the Qiangjiang Formation)are laminated argillaceous dolomite,laminated dolomitic(calcareous)mudstone and mirabilite filled laminated dolomitic mudstone.The main reservoir porosity includes interlayer fractures,intergranular pores and intergranular solution pores.The pore development of inter-salt shale oil reservoir is mainly controlled by lithology and lithofacies,and the pore development degree of mirabilite filled laminated dolomitic mudstone,laminated dolomitic(calcareous)mudstone and laminated argillaceous dolomite increase accordingly.Macro-pores are the most developed porosity in the laminated argillaceous dolomite facies,with the best pore connectivity and oil-bearing properties,and is the dominant lithofacies in the inter-salt shale oil reservoir and the most favorable exploration target.