Use CT images to assess the scale effect and variations of hydraulic parameters of sandstone samples in western coastal area of Taiwan

• Main Authors: Yun-An Wu, 伍韻安
• Other Authors: Chuen-Fa Ni
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/48k32r

碩士 === 國立中央大學 === 應用地質研究所 === 106 === The technologies of X-ray CT have improved the understanding of geological microstructures, including micro fractures, tortuosity, porosity, permeability, and other important features in rocks. This study aims to quantify the scale effect involved in a relatively homogeneous sandstone rock sample in Kueichulin Formation Yutengping Sandstone (2409 m depth) and Kuanyinshan Sandstone (2531 m depth) in western Taiwan. The variations of sampling volumes are assessed based on 2 μm resolution CT images. The commercial software Avizo is used to do the image processing, which is an important step, including image filtering, binarization and extraction. There are three parts in this study. First, the spatial distribution of porosity and permeability are estimated in the pore scale. The permeability is estimated by the Kozeny-Carman equation. The results show that the average porosity is 24.5% and the average permeability is 5E-14 m², which are one to two order lower than the confining pressure test. Second, in order to do the pore analysis , the best scanning image resolution should be higher than 16 μm. Third, this study analyze the hydraulic diffusivity of sample. The unit volume size is changed into different size. The results show that even when the unit volume size is 100 μm, the hydraulic diffusivity is even different in different size, the scale effect exists.