Pore-scale investigation of permeability evolution during hydrate formation using a pore network model based on X-ray CT

Pore‐Scale 3D Morphological Modeling and Physical Characterization of Hydrate‐Bearing Sediment Based on Computed Tomography

“…For the absolute permeability simulation via PNM, Poiseuille's law and Darcy's law were used as in literature (Dong & Blunt, 2009; Zhang et al, 2020), considering the fluid was incompressible and the fluid density and fluid dynamic viscosity were constant and the relevant velocities were small enough not to produce turbulence. In addition, the flow condition was laminar, and the relation between pressure drop and the flow rate was linear: where g i,j is the conductance of the throat between pore i and pore j , r i,j is the radius of the conducting throat, l i,j is the length of the conducting throat, μ is the viscosity of the flowing fluid, P i and P j are the pressure of pore i and pore j , Q is the total flow, K h is the absolute permeability, L is the length of the network in the flow direction, Δ P is the pressure gradient applied to the boundary (input pressure‐output pressure), and A is the cross‐sectional area of the network.…”

“…Thus, many studies have also been conducted on remolded specimens in the laboratory, and the heat and mass transfer processes have been evaluated widely, which is directly related to NGH exploitation efficiency. Minagawa et al (2008), using proton nuclear magnetic resonance measurement, found that the permeability decreased exponentially with increasing hydrate saturation, and other researchers found a similar phenomenon (Ji et al, 2020;Kang et al, 2016;Zhang et al, 2020). Jin et al (2007) proposed that the X-ray computed tomography (CT) technique could be used to obtain the pore structure and free gas distribution of HBS, where the permeability could be calculated and analyzed.…”

Mechanical behaviors of hydrate-bearing sediment with different cementation spatial distributions at microscales

“…The PNM was used to further study the hydrate spatial distribution influence on the pore space evolution, and the maximal ball method proposed by Dong and Blunt (2009) was used to extract the pore network, and its feasibility has been validated in previous studies ( Wang et al., 2020 ; Zhang et al., 2020a ). The basic principle of PNM is to make the largest inscribed ball in each pore space formed by voxels.…”

“…This phenomenon confirms the result about the pore space radii distribution in the section “The Spatial Distribution Influence of Hydrates on the Pore System”, which is because the imbalance of the hydrate distribution could lead to a significant volume of the large pore space without hydrates. In addition, for the pore space where is no hydrate around, the complexity is not high; thus, the pore and throat would be considered to be larger and fewer during the judgment of PNM ( Zhang et al., 2020a ).…”

Predicting hysteresis loops of the soil water characteristic curve from initial drying

“…It is important to understand that the water stored in soil is usually in an unsaturated state. For unsaturated soils, the SWCC for a drying‐wetting cycle exhibits a hysteresis loop caused by the capillary water by the ink‐bottle effect, ageing phenomena, entrapped air effects, the contact angle difference and capillary condensation (Hillel, 1980; Goh, Rahardjo, & Leong, 2015; Masrouri, Bicalho, & Kawai, 2008; Zhang, Ge, Wang, Zhao, & Song, 2019); the hysteresis caused by the adsorbed water in the soil is related to the temperature, the clay content and the specific surface area of the soil. Consequently, a soil retains more water on the drying curve than that on the wetting curve at a given suction (Figure 1).…”