多尺度CT成像技术识别超低渗透砂岩储层纳米级孔喉

以鄂尔多斯盆地X地区长6储层为研究对象,利用多尺度CT成像技术、聚焦离子束扫描电镜技术,结合Avizo软件的强大数据处理和数值模拟功能,对研究区目的层岩石样品进行不同尺度孔喉分维数重构,建立三维超低渗透砂岩储层纳米级孔隙结构模型.研究表明,微米尺度下,超低渗透砂岩储层孔喉形态呈点状、球状和条带状及管状.储集空间类型以溶蚀微孔为主且多孤立分布,局部孔隙为片状,连通性较差.纳米尺度下,超低渗透砂岩储层孔喉系统整体较发育,孔喉形态呈球状、短管状.远离裂隙处多为孤立状,连通性较差,仅具有储集能力.微裂缝、粒间缝发育部位多为短管状,有一定连通性,相当于喉道.微观非均质性较强,岩样整体较致密,局部相互连通,溶蚀孔及裂隙对储集能力、渗滤能力具有控制作用.数值计算求得目的层A、Y、C三个样品的孔隙度分别为6.95%、5.55%、4.44%,渗透率分别为0.828×10^-3μm²、0.115×10^-3μm²、0.00065×10^-3μm².聚焦离子束扫描电镜与多尺度CT成像...

Identification of ultra-low permeability sandstone reservoir nano pore-throat by multi-scale CT imaging technique

By the multi-scale CT imaging technique,Focused Ion Beam Scanning Electron Microscopy(FIB-SEM),data processing and numerical simulation module of Avizo software,we reconstructed fractal dimensions of the Chang 6 reservoir in the X area of Ordos Basin rock samples in the study area at different scales.In addition,established a three-dimensional nanoscale porethroat model for ultra-low permeability sandstone reservoirs.The research show that at the micron scale,the pore-throat morphology of the ultra-low permeability sandstone reservoir is point-like,spherical,striped,and tubular.The reservoir space is dominated by dissolution pores,with many pores and isolated distribution,while the local pores are patchy and the connectivity is poor.At the nanometer scale,the ultra-low permeability sandstone reservoir is relatively dense,the pore throat system is more developed,the pore throat shape is spherical,short tube,local interconnection.Far away from the fissure,the pore throat is mostly isolated,and the connectivity is poor.It has only the storage function;the micro cracks and the pores near the seams are mostly short tubular and the connectivity is enhanced.The dissolution holes and microcracks at the nanoscale have a controlling effect on porosity and permeability parameters.By numerical calculation,the porosity of three samples,A,Y,C is 6.95%,5.55%and 4.44%,respectively.The permeability is 0.828×10^-3μm^2,0.115×10^-3μm^2,0.00065×10^-3μm^2,respectively.Focused ion beam scanning electron microscopy and multi-scale CT imaging technique can quantitatively characterize the micro-and nanoscale pore structure of ultra-low permeability sandstone reservoirs.