沧东凹陷孔二段页岩纹层结构类型及其对储集性能的影响

Structural Type of Shale Grain Layer in the Cangdong EKⅡand Its Influence on Reservoir Performance

富有机质页岩大多发育有纹层结构,不同的纹层结构对页岩的储集性能有着不同的影响。以沧东凹陷孔二段页岩为研究对象,通过对X射线衍射测试数据、岩心观察、薄片鉴定、氩离子抛光-场发射扫描电镜、AMICS等资料的分析,根据矿物纹层组合关系,总结出3种页岩纹层结构类型,分别为长英质-碳酸盐-黏土型纹层结构、黏土(有机质)-碳酸盐-方沸石型纹层结构、长英质-有机质-黏土(有机质)纹层结构。研究表明,长英质-有机质-黏土(有机质)纹层结构纹层平直且层厚较小,互层现象明显;层理缝与矿物解理缝发育较多且后期被白云石充填,有机孔与粒间孔大量发育,溶蚀孔与晶间孔也少量发育,有机质孔与矿物颗粒间的边缘微裂缝构成了良好的孔-缝联通体系;孔隙度较为均匀的分布在0~6%,孔径介于微孔与宏孔间,孔容最大,储集性能最好。

Most of the organic-rich shales are developed with grain structure,and different grain structures have different effects on the shales’storage performance.By analyzing the X-ray diffraction test data,core observation,thin section identification,argon ion polishing-field emission scanning electron microscopy and AMICS,three types of shale grain structure were summarized based on the mineral grain layer combination relationship,which are long-interstitial-carbonate-clay grain structure,clay(organic matter)-carbonate-equilibrium grain structure,and long-interstitial-organic matter-clay(organic matter)grain structure.These three types are clasticite-carbonate-clay laminae,clay(organic matter)-clay(organic matter)-fonzite laminae,and clasticite-organic matter-clay(organic matter)laminae.The study shows that the clasticite-organic-clay(organic matter)grain layer structure is straight and the layer width is thin,and the interlayer phenomenon is obvious,the laminar joints and mineral decomposition joints are more developed and later filled by dolomite,the organic pores and clasticite pores are developed in large quantities,the dissolution pores and clasticite pores are also developed in small quantities,and the marginal microfractures between organic pores and mineral particles constitute a good pore-joint connection system,the porosity is more uniformly.The pore size is distributed in 0~6%,the pore size is between microporous and macro-porous,the pore capacity is the largest,and the storage performance is the best.