Abstract
The pore-throat network of rock exerts a vital influence on the permeability and mechanical properties of the rock. Resorting to X-ray micro-CT scanning, the present work investigates the pore-throat structure of marine biogenic carbonate samples from the South China Sea and compares them to terrigenous sedimentary sandstone. With the help of the maximum ball (MB) algorithm, the pore-throat networks inside representative elementary volumes of rock samples are revealed by stick-and-ball diagrams, which enables quantitative analyses afterwards. Higher and more deviant cross sectional porosity was observed for the carbonate samples compared to the sandstone sample, indicating relatively heterogeneous pores in the carbonate. Over 85% of pores in the carbonate samples were classified as mesopores. Irregular triangular cross sections can be inferred for the pores and throats of the carbonate. The type of rock and the porosity seem to have little effect on the shapes of the pores and throats. In the studied carbonate, the average volume of the throat was approximately one order of magnitude smaller than the average volume of a pore. The distribution of throat radius differed significantly between the studied carbonate samples. The average coordination number of the carbonate was measured to be 1.
Highlights
Represented by a lattice of pores connected by throats, the void in rock masses has a fundamental impact on the physical and mechanical properties of the rock
Xie et al [4] tried to quantify the pore morphology of different carbonate samples based on the digital analyses of twodimensional images from thin sections taken under the environmental scanning electron microscope (ESEM)
Du et al [6] applied X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry to study the effect of zinc (Zn) concentration on the pore-size distribution of zinc-contaminated kaolin clay when the clay was stabilized by a cement additive
Summary
Represented by a lattice of pores connected by throats, the void in rock masses has a fundamental impact on the physical and mechanical properties of the rock. To evaluate the reservoir properties of sedimentary rock, a quantitative analysis in terms of the pore morphology is required, which entails the characterization of both the dimensions and shapes of the pores and the connecting throats. Thanks to the development of image processing technologies, scanning electron microscopy and image processing technologies were applied to quantitatively reveal the pore structure of geotechnical materials [2–4]. The present work applies X-ray micro-CT scanning technology to reveal the pore-throat structures of the marine carbonate rocks (sampled from Nansha Islands in the South China Sea, within 400 m from the coral reef surface, numbered from shallow to deep according to the depth of sampling) and the terrigenous sandstone, respectively in order to shed light on the permeability and evolution of sedimentary fabrics for carbonate rocks
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