3D imaging characteristics of pore and fracture of tight sandstone in Baihetan reservoir area based on μCT technology

Abstract

Microfocus X-ray CT scanning (μCT) is one of the most effective methods for visualization of pore-fracture structure in rock, and its effectiveness in 3d imaging of pore-fracture in tight sandstone should be further explored.Taking the tight sandstone at the dam site of Baihetan Hydropower Station as an example, the pore-fracture 3D imaging characteristics of samples with different scanning accuracy were explored by using ultra-high precision μCT technology and segmentation algorithm, and their influence on obtaining key structural information was analyzed by SEM test.The results show that the combined segmentation method of interactive threshold and Top-hat can extract the pore and fracture information of tight sandstone more accurately. The interactive threshold segmentation method is suitable for the extraction of large pore and fracture, and the Top-hat segmentation method is suitable for the extraction of small pore.Small pores and microcracks are very developed in tight sandstone structure, and there are many isolated pores. Compared with 1.5 μm scanning resolution, 0.62 μm scanning resolution presents a clearer pore network model, but due to the limited testing range at the nanoscale, the key structural information properties may be magnified.Critical microstructure information may be missed when the scanning resolution is greater than 2μm.Therefore, in the study of three-dimensional characteristics of pores and fractures in tight sandstone, high scanning accuracy should be selected and multi-region information acquisition should be carried out to effectively reveal the key microstructure features. This basic work provides a support for further effectively revealing the structural evolution information of tight rocks.

Keywords

• baihetan hydropower station
• pore-fracture
• tight sandstone
• μct technology
• scanning accuracy