采用多点地质统计法重构页岩的数字岩心

由于实验设备获得的页岩岩样大多是微米或毫米尺度,如果要获得更大尺度和范围内的孔隙结构,必须通过对其特征的三维重构才能实现。为此,提出了基于纳米精度的体数据与多点地质统计方法的页岩三维数字岩心重构方法。以页岩纳米CT数据为训练图像,使用数据模板提取其中的结构特征,通过多点地质统计方法将结构特征重构到数字岩心中;形成了以变差函数曲线、孔隙直径分布和孔隙连通性来判别重构岩心与真实页岩结构相似度的判别方法 ;基于格子玻尔兹曼方法验证了相似度评价方法。结果表明:(1)变差函数可以检验重构岩心与真实岩心的空间相似性,孔隙直径分布和孔隙连通性可以检验流动特征的相似性;(2)当变差函数曲线、孔隙直径分布和孔隙连通性相似时,重构岩心与真实岩心的渗透率相近,表明所提出的重构方法与结构相似度评价方法是有效的;(3)由于强非均质性,不同位置的重构页岩岩心渗透率差异可超过100倍。该研究成果对构建三维大尺寸强非均质性页岩数字岩心、认识页岩孔隙结构、分析流动规律具有指导作用。

Reconstruction of digital shale cores using multi-point geostatistics

The shale samples obtained from experimental apparatus are mostly in the scale of micron or nanometer. To investigate the pore structures in a larger scale and range, therefore, it is necessary to perform 3D structural reconstruction. In this paper, a 3D reconstructionmethod of digital shale cores based on nano-precision volume data and multi-point geostatistics was developed. In this model, the nano-CT data of shale is taken as the training images, and the structural characteristics are extracted by using the data template and then reconstructed in the digital cores by means of multi-point geostatisitcs. The structural similarity between the reconstructed cores and the real shale was discriminated based on variogram, pore diameter distribution and pore connectivity. And this similarity evaluation method was verified by means of the Lattice Boltzmann method. It is indicated that variogram can be used to reconstruct the spatial similaritybetween the reconstructed cores and the real cores, and pore diameter distribution and pore connectivity can be used to verify the flowing characteristics; that when variogram, pore diameter distribution and pore connectivity are similar, the permeability of reconstructedcores is close to that of real cores, demonstrating the validity of the reconstruction method and the similarity evaluation method; and that due to strong heterogeneity, the permeability of reconstructed shale cores at different positions may be different by 100 times. These research results can be used as reference for reconstructing 3D large-scale digital shale cores with strong heterogeneity, understanding the pore structures of shale and analyzing the flowing laws.