基于数字岩心的碳酸盐岩复杂孔隙特征研究——以普光气田飞仙关组储层为例

Study on complex pore characteristics of carbonate reservoirs based on digital core:a case study of Feixianguan Formation in Puguang Gas Field

川东北普光气田飞仙关组为一套深层海相碳酸盐岩储层,储集空间类型、组合方式多样,孔隙结构复杂,储层非均质性强,利用常规测井资料难以有效表征其储层的孔隙结构及渗透力。文中应用数字岩心技术精细刻画孔隙结构,即采用全直径岩心CT扫描、微米级X-ray CT扫描、大面积扫描电镜拼图成像技术等,建立纳米—厘米级别的多维度多尺度的岩心数字化表征。对大数据图像特征参数提取和分析,建立了不同类型储层的孔渗关系,将整个储层类型分为三区一带:微裂缝区、粒(晶)间孔主控区、铸模孔区、粒间孔加铸模孔过渡带。研究明确了粒(晶)间孔结构是渗透率的主控因素,更好地明确了该类储层孔隙结构对渗流能力的影响,揭示了礁滩相碳酸盐岩地层的微观渗流特性。

The Feixianguan Formation in the Puguang Gas Field in northeast Sichuan is a set of deep marine carbonate reservoirs with various types and combinations of reservoir space,complex pore structure,and strong reservoir heterogeneity,which makes it difficult to effectively characterize the pore structure and permeability of the reservoirs by using conventional logging data.This paper applies digital core technology to finely characterize the pore structure,using full-diameter core CT scanning,micron-level X-ray CT scanning,and large-area scanning electron microscopy mosaic imaging technology,etc.to establish a multi-dimensional and multi-scale digital representation of the core from nanometer to centimeter level.Through extraction and analysis of big data image feature parameters,the pore-permeability relationship of different types of reservoirs is established,and the entire reservoir is divided into three zones and one belt:microfracture zone,intergranular(intercrystalline)pore dominated zone,moldic pore zone,and a transitional zone between intergranular pores and mold pores.It is clarified that intergranular(intercrystalline)pore structure is the main controlling factor of permeability.The influence of this type of pore structure on reservoir permeability is better understood,and the micro-scale flow characteristics of reef flat facies carbonate reservoirs are revealed.