This paper presents a unique workflow to study the heterogeneity of shale rock samples by the integration of different imaging methodologies. The key components include a proprietary sample preparation procedure, a multiscale imaging protocol, and multi-scale numerical models to upscale the petrophysical properties obtained from 3D microstructures (at high resolution but smaller sample volume) to macro-scale.
Even within a few centimeters, one can observe extremely different shale rock textures due to large variations of porosity, organic content, and mineralogy. The heterogeneous nature of shale calls for core analysis approaches at different scales. In the context of direct visualization of pore/organic/mineral morphology via imaging, different methods for different scales at different resolutions are necessary. For example, whole core sample of shale is typically scanned at mm resolution using digital photography or medical CT (Computed Tomography), while ultrahigh magnification SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy) are used to resolve the nano-porosity commonly seen in shale [1] at nm resolution. The integration of these imaging data becomes an important and challenging problem.
In this paper, we present a systematic approach to integrating the imaging data at different scales for a shale sample. Through a proprietary sample preparation procedure, we are able to acquire high resolution, large field of view 2D SEM images and a 3D uCT volume, which reveal the rock typing of the sample at the plug scale. Specimens [2] from the sample are then extracted for each rock types, and 3D FIB-SEM image volumes are acquired. Algorithms are developed to integrate the data in 2D and 3D at different scales [3], and petrophysical parameters are derived at mm-scale.
URTeC 1579083
