A microfocus x-ray computed tomography based gas hydrate triaxial testing apparatus

Li, Yanghui; Wu, Peng; Liu, Weiguo; Sun, Xiaofeng; Cui, Zhi Wei; Song, Yongchen

doi:10.1063/1.5095812

Cited by 61 publications

(50 citation statements)

References 48 publications

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“…Figure shows a schematic diagram of the microfocus X‐ray CT‐based gas hydrate triaxial testing apparatus (Li, Wu, Liu, et al, ). Two sizes of specimens (Φ20×40 mm and Φ38×76 mm) could be chosen, and the specimen used in this study was 20 mm in diameter and 40 mm in length for a better CT image resolution.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The different gray values in the CT image reflect the different attenuation coefficients of X‐rays, which are determined directly by the density of each specimen component (Yang et al, ). Since the linear attenuation coefficient of the Xe hydrates is approximately 34 times higher than that of methane hydrates (Li, Wu, Liu, et al, ) and the pressure chamber is 5 mm thick due to safety considerations, it is necessary to increase the voltage of the microfocus X‐ray CT system to ensure X‐ray penetration, but this approach will cause image deterioration in the low‐attenuation part of the X‐rays (such as local regions with a low hydrate saturation or no hydrates) and the periphery of the specimen, which is often called the beam‐hardening effect in X‐ray physics, as shown in Figure a. In this study, hardware optimization was used as a remedy by placing a piece of absorbing material (copper) as a filter between the apparatus and the image intensifier.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Liu

et al. 2020

JGR Solid Earth

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109

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The macromechanical properties (strength, stiffness, stress-strain relationship, etc) of the hydrate-bearing sediment are often correlated with the hydrate cementation failure behavior. In this study, a consolidated drained triaxial shear test with X-ray computed tomography was conducted on a hydrate-bearing sediment with a hydrate saturation of 32.1% under 3 MPa effective confining pressure for revealing the cementation failure behavior. The hydrate occurrences were clearly identified to be cementing, grain-coating, prepatchy cluster and patchy cluster. The cementation failure behavior (morphology), deformation evolution (quantitative statistics), and localized shear deformation at different regions of stress-strain curve were observed and analyzed using computed tomography. In the linearity region, the hydrate-cemented clusters moved as a whole, while small hydrate particles would aggregate to the periphery of the clusters. The noncemented sand particles move disorderly during this process. Localized deformation occurred perfectly exhibit an antisymmetric bifurcation pattern. In the plasticity region, the specimen starts to deform plastically; an internal shear band occurs in the specimen. The hydrates begin to shed from the periphery of the cemented structure, and the grinding effect of hydrates begins to occur between sand particles. However, the shedded hydrates will not enter and fill the neighboring pores but hind the movement of sand particles structurally near the original position. In the yielding region, the hydrate-cemented cluster structure is completely damaged and crushed into small pieces; a shear band with a determined thickness and inclination angle was observed.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Liu

et al. 2020

JGR Solid Earth

Self Cite

109

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“…The three plunger pumps are used to control the confining pressure, the pore pressure, and the axial load with capacities of 16 MPa, respectively. More details about this apparatus can be found in our previous work (Li, Wu et al, 2019). The triaxial pressure chamber is placed at the objective table of the microfocus X‐ray CT system (SMX225CTS‐SV, Shimadzu Co., Japan).…”

Section: Experimental Methodsmentioning

confidence: 99%

Microstructure Evolution of Hydrate‐Bearing Sands During Thermal Dissociation and Ensued Impacts on the Mechanical and Seepage Characteristics

Liu

et al. 2020

JGR Solid Earth

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101

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In this study, a microfocus X‐ray computed tomography‐based triaxial testing apparatus was used to observe and quantify the microstructure evolution of hydrate‐bearing sands during thermal dissociation of hydrate. Three triaxial shear tests with X‐ray computed tomography were conducted to study the influence of hydrate dissociation on the mechanical behavior of hydrate‐bearing sands. The results show that hydrate covering the sand particle surface dissociates first and then at the menisci between sand particles. The secondary hydrate formation mainly occurs on the menisci between sand particles and the surfaces of the hydrate shells where hydrates already exist. Hydrate dissociation could cause fabric changes in hydrate‐bearing sands, resulting in a more isotropic orientation distribution of sand particles. The failure behavior of the hydrate‐free sand specimen is similar to that of the specimen after hydrate dissociation, which shows an obvious drum‐shaped failure pattern with X‐shaped shear bands. However, the hydrate‐bearing sand specimen exhibits a shear band with a determined thickness and inclination angle. Hydrate dissociation could cause a significant loss of supporting cementation, resulting in a decline in the stiffness and failure strength. The failure strength of hydrate‐free sand specimen is slightly higher than that of the specimen after hydrate dissociation; this may due to that the homogeneous orientation frequency distribution can enhance the stability of the force chain between sand particles. The secondary hydrate formation causes sediment deformation resulting in a decrease in absolute permeability due to pore blockage.

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“…[1][2][3][4][5][6][7][8][9][10][11] With advances in computation and imaging technologies, pore scale models are increasingly being used in the oil industry to predict transport properties such as relative permeability and capillary pressure from micro scale rock images. 12 Pore structures of reservoir rocks are complex and their understanding is fundamental to model fluid flow in porous media. Gaining a better understanding of single and multi-phase flow relies largely on quantifying the pore structures from 2D and 3D images, e.g.…”

Section: Introductionmentioning

confidence: 99%

A New Method for Pore Structure Quantification and Pore Network Extraction from SEM Images

Wang

Scott

et al. 2019

Energy Fuels

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The structure of porous media is complex yet fundamental to the understanding of transport processes including single and multi-phase fluid flow. Pore network modelling is a valuable tool for studying these processes in many diverse porous media. This paper presents a new method of discretizing the pore space into connected pore elements which capture the pore geometry and topology. This method discards the difference between pore bodies and throats, instead treats them equally as pore elements which captures the features of pore structure from the widest to the narrowest part of the pore space (pore body to pore throat), honours the topology and does not over-segment the pore space. The method is a higher level discretization of the pore space compared to other traditional methods which construct pore throats explicitly. Pore networks were extracted from three test images using the method and the computed flow properties are compared with finite element simulation in terms of absolute permeability. A reasonable agreement with finite element simulation is achieved, demonstrating the value and functionality of the new pore structure quantification method.

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A microfocus x-ray computed tomography based gas hydrate triaxial testing apparatus

Cited by 61 publications

References 48 publications

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Cementation Failure Behavior of Consolidated Gas Hydrate‐Bearing Sand

Microstructure Evolution of Hydrate‐Bearing Sands During Thermal Dissociation and Ensued Impacts on the Mechanical and Seepage Characteristics

A New Method for Pore Structure Quantification and Pore Network Extraction from SEM Images

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