2025-08-21 ジョンズ・ホプキンス大学(JHU)
＜関連情報＞
- https://hub.jhu.edu/2025/08/21/how-rock-grains-move-and-stress-builds/
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JB031690
X線断層撮影と回折顕微鏡を用いたヌゲット砂岩の結晶学テクスチャ、構造、および応力伝達解析 Crystallographic Texture, Structure, and Stress Transmission in Nugget Sandstone Examined With X-Ray Tomography and Diffraction Microscopy
Ryan C. Hurley, Ye Tian, Mohmad M. Thakur, Jun-Sang Park, Peter Kenesei, Hemant Sharma, Adyota Gupta, Kwangmin Lee
Journal of Geophysical Research: Solid Earth Published: 07 July 2025
DOI:https://doi.org/10.1029/2025JB031690
Abstract
Subsurface processes in sandstones are controlled by porosity, permeability, and deformation mechanisms, all of which are controlled by a complex interplay of crystallographic rock texture, structure, and micromechanics. Texture, structure, and micromechanics have historically been studied using optical and electron microscopy of thin-sections. We employed a new combination of in situ X-ray tomography and ray diffraction microscopy to study crystallographic texture, structure, and grain stresses in 3D. We examined these features in a sample of Nugget sandstone, a sandstone constituting hydrocarbon reservoirs across the American West. Our aims are threefold. First, we demonstrate the utility of X-ray diffraction microscopy probes for revealing texture, structure, and stress transmission in 3D. Second, we apply these techniques to Nugget sandstone and discuss findings in the context of prior work. Third, we study grain stress tensor evolution during mechanical compression to examine whether their heterogeneity and orientation evolution reflect that of inter-particle forces in granular materials. Our results show: (a) larger grains featured higher intra-granular misorientations, possibly from an increased prevalence of cements; (b) pores closed parallel to the loading direction and opened normal to loading; (c) grain stresses featured heterogeneity and orientations similar to inter-particle forces in non-cohesive granular materials; (d) grains featured compressive stresses in the loading direction and tensile stresses orthogonal to the loading direction, the latter resisting sample dilation and grain separation. Our work demonstrates the first known application of multi-modal X-ray tomography and diffraction microscopy to sandstone, providing new 3D insight into the nature of quartz cement and stress evolution.
Key Points
- X-ray diffraction microscopy reveals 3D texture and grain stress evolution in sandstone for the first time
- Diffraction microscopy quantifies grain misorientation and quartz cement prevalence in 3D
- Sandstone exhibits grain stress statistics and orientations reminiscent of force chains in granular materials
Plain Language Summary
The structure and deformation characteristics of sandstones control processes including earthquakes, resource extraction, and CO2 storage. These characteristics have historically been studied with 2D microscopy. Here, we used a unique combination of X-ray measurements to study these quantities in 3D. Focusing on Nugget sandstone, a sandstone constituting formations important for resource extraction and storage in the American West, we make connections between crystal orientations, structure, stress evolution, and failure during uniaxial compression of a small sample. We highlight that compressive stresses in sandstones feature similar characteristics to inter-particle forces in loose granular materials.
