Evaluation of Electron Tomography Capabilities for Shale Imaging

Area of Science:

• Materials Science
• Geoscience
• Nanotechnology

Background:

• Electron tomography (ET) offers high resolution for 3D imaging but faces challenges like low signal-to-noise and limited projection angles.
• Shale, a complex nanoporous medium, requires advanced imaging techniques to understand its pore structure for applications like energy storage and fluid transport.

Purpose of the Study:

• To evaluate the capabilities and limitations of electron tomography for reconstructing the 3D pore structure of shale.
• To quantify the impact of reconstruction techniques and acquisition conditions on the accuracy of shale pore characterization.

Main Methods:

• A numerical 3D phantom of Barnett shale with 1.24 nm pixel size was created.
• 2D projection images were numerically generated and reconstructed using common techniques.
• Reconstruction uncertainty was assessed by comparing pore metrics and voxel classification against the phantom.
• Acquisition conditions were varied to quantify artifact effects.

Main Results:

• Reconstruction techniques showed good agreement for large pores but higher variability for nanometer-scale features.
• Limited projection range and reconstruction algorithms were identified as key bottlenecks.
• Accuracy of storage and transport metrics was affected by reconstruction uncertainty.

Conclusions:

• Electron tomography is a valuable tool for characterizing shale nanopores, particularly larger features.
• Improvements in sample preparation (thinning), hardware (holders), and reconstruction algorithms are crucial for accurate imaging of nanoscale features.
• Addressing reconstruction limitations is key to advancing ET applications in complex geological materials.