Abstract:Natural gas hydrate (NGH) is considered one of the most promising future energy sources because of its considerable reserves and high energy density, which could meet the growing global energy demand and improve the energy consumption structure. However, NGHs exist in the sediment mainly in the form of cementation or a part of the sediment skeleton, which may be responsible for the stability of native sediments. Therefore, during commercial NGH exploitation, the analysis of the mechanical characteristics of th… Show more
“…In addition, as shown in Figure 8, the permeability of model ST1 is higher than that in model ST08, and that in model ST08 is higher than that in model ST06 which means the larger the particle size, the higher the permeability of the HBS will be. This is because the pores and throats in model ST1 are the largest, while those in model ST06 are the smallest, and the smaller the pores and throats, the greater the resistance for fluid to flow, and the lower the permeability will be [34]. The hydrate saturations' effect on the fractal dimension for three types of models under particle sizes.…”
Nature gas hydrates (NGHs) are regarded as a potential alternative energy source due to their huge reserves and wide distribution. According to the geophysical surveys, the pore-filling hydrates occupy a large proportion of the global hydrate reserves, especially for the marine regions. Therefore, with a novel pore-scale 3D morphological modeling algorithm, this study systematically studied the effect of the particle size on the physical characteristics of the pore-filling hydrate-bearing sediment (HBS). The pore system evaluations and permeability simulations were performed by utilizing pore network modeling (PNM), and the thermal and electrical simulations were conducted by utilizing a finite volume method (FVM). The results show that for the HBS with smaller particle size, the average radius of the pores and throats would also be reduced, and the fractal dimension of the pore system would be increased. In addition, with the increasing hydrate saturation, the fractal dimension of the pore system will increase firstly and then decrease. And these parameter evolutions could impact the physical properties correspondingly; specifically, the decreasing particle size in the HBS would reduce the permeability and electrical conductivity of HBS and enhance the apparent thermal conductivity of HBS.
“…In addition, as shown in Figure 8, the permeability of model ST1 is higher than that in model ST08, and that in model ST08 is higher than that in model ST06 which means the larger the particle size, the higher the permeability of the HBS will be. This is because the pores and throats in model ST1 are the largest, while those in model ST06 are the smallest, and the smaller the pores and throats, the greater the resistance for fluid to flow, and the lower the permeability will be [34]. The hydrate saturations' effect on the fractal dimension for three types of models under particle sizes.…”
Nature gas hydrates (NGHs) are regarded as a potential alternative energy source due to their huge reserves and wide distribution. According to the geophysical surveys, the pore-filling hydrates occupy a large proportion of the global hydrate reserves, especially for the marine regions. Therefore, with a novel pore-scale 3D morphological modeling algorithm, this study systematically studied the effect of the particle size on the physical characteristics of the pore-filling hydrate-bearing sediment (HBS). The pore system evaluations and permeability simulations were performed by utilizing pore network modeling (PNM), and the thermal and electrical simulations were conducted by utilizing a finite volume method (FVM). The results show that for the HBS with smaller particle size, the average radius of the pores and throats would also be reduced, and the fractal dimension of the pore system would be increased. In addition, with the increasing hydrate saturation, the fractal dimension of the pore system will increase firstly and then decrease. And these parameter evolutions could impact the physical properties correspondingly; specifically, the decreasing particle size in the HBS would reduce the permeability and electrical conductivity of HBS and enhance the apparent thermal conductivity of HBS.
“…Figure 2 shows the hydrate spatial distribution influence on the stress-strain relationships for the two specimens, and the deformation processes can also be found in Videos S1 and S2 respectively. Also, terminologically, the axial strain refers to the ratio between the sediment changed length and the corresponding original length, and the deviator stress refers to the difference between the major principal stress and minor principal stress ( Wu et al., 2021 ). Figure 2 The stress-strain relationship of the specimen with different hydrate spatial distributions …”
Dispersed hydrate spatial distribution strengthens the sediment more significantly Dispersed hydrate spatial distribution steepens and thins the shear band Hydrate distribution seems to not affect the pore space evolution during shearing The cementation interfacial area evolution was calculated during shearing
“…Different environmental conditions lead to different pore-scale habits of hydrate in HBPM. The habits of hydrate are commonly grouped into four categories: cementation, particle coating, pore filling, and load bearing [29,[31][32][33].…”
Section: An Extended Three-phase Physicalmentioning
The direct mechanical effects of seepage force on the behavior of hydrate-bearing porous media (HBPM) have commonly been neglected in previous studies. In this work, the physical nature of seepage force in hydrate-bearing porous media under saturated and unsaturated seepage conditions was adequately explained, and then, the direct effects of seepage force on the mechanical behavior of HBPM were quantified. Therefore, the results obtained in this manuscript provide a new insight to evaluate the direct mechanical effects of seepage force.
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