Quantitative analysis of statistical properties of organic-rich mudstone using large field-of-view SEM images

Abstract

This paper presents a quantitative and statistical analysis of large field-of-view (FOV) scanning electron microscope (SEM) images of organic-rich shale samples. The samples are from the Upper Devonian Duvernay Formation at the onset of the condensate hydrocarbon window. Our data set contains 12 mosaic SEM images which were each obtained by stitching 100+ high-resolution SEM images. The goal was to establish a basis for deriving meaningful statistical properties of the pore space that can be used for characterization and possibly up-scaling purposes.The results show that pores smaller than ≈ 100 nm in diameter are the predominant type in the studied Duvernay shale samples in terms of the number of pores. However, chord length distribution analysis shows that decompression/desiccation cracks can heavily skew statistical properties such as the first moment of the distribution. Two characteristic length scales were computed by using the two-point correlation function to show the disparity of scales in the same sample imaged at different resolutions. Our analysis indicate that there is a scale dependency on the computed properties of the pore space, and statistical convergence cannot be claimed without having a multi-scale approach for characterization.