Dynamic in-situ imaging of methane hydrate formation and self-preservation in porous media

Никитин, В. В.; Дугаров, Г. А.; Duchkov, Anton A.; Fokin, Mikhail I.; Drobchik, Arkady N.; Shevchenko, Pavel; Carlo, Francesco De; Mokso, Rajmund

doi:10.1016/j.marpetgeo.2020.104234

Cited by 51 publications

(42 citation statements)

References 55 publications

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“…This result confirmed that the secondary hydrate formation would change the sediment fabric. Significant movement and roatation of sand particles were also observed in previous CT study on hydrate‐bearing sands during formation (Lei, Liu, et al, 2019; Nikitin et al, 2020). In addition, the sediment matrix size and the excess gas/water condition could influence this effect to some extent (Lee et al, 2010).…”

Section: Resultssupporting

confidence: 71%

“…Additionally, XeH requires a much lower equilibrium pressure compared to NGH and thus makes the CT experiment which is conducted in a limited space safer (Chaouachi et al, 2015). In the past decades, NGH has been widely substituted with XeH in studying the microstructural evolution of gas hydrates in sedimentary matrices during hydrate formation and dissociation because of the same morphology between XeH and NGH (Chaouachi et al, 2015; Nikitin et al, 2020; Yang et al, 2016). The experiments were carried out following the procedures mentioned below, which are similar to those used in Hyodo et al (2014): Specimen preparation: First, the water (1.6 g) was well mixed with the dried Fujian sand (18.2 g) to achieve the targeted saturation and density, and the initial water saturation was 28.8%.…”

Section: Experimental Methodsmentioning

confidence: 99%

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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

102

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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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Section: Resultssupporting

confidence: 71%

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

102

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“…For model A, it was found that hydrate first generated at the menisci between sand particles, and this occurrence, so‐called the “cementing” type, has been widely found in many visual experiments (Lei & Seol, 2018; Nikitin et al, 2020) and can greatly enhance the strength and modulus of the sediment (Hyodo et al, 2013). The hydrate then began to encapsulate the sand particle surface, and it connected multiple sand particles.…”

Section: Methodsmentioning

confidence: 97%

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

Sun

et al. 2020

JGR Solid Earth

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Natural gas hydrate is considered to be a promising future energy resource; therefore, obtaining its physical properties is crucial for evaluating gas production efficiency and developing reasonable exploitation strategies. In this study, we present a novel pore-scale 3D morphological modeling algorithm considering various saturation and occurrences (cementing and pore-filling) of hydrate in sediments. To evaluate the performance of the presented algorithm, 14 hydrate-bearing sediment models were constructed based on X-ray computed tomographic images of a consolidated sandy specimen under an effective stress of 3 MPa. Morphologically, the new algorithm generated pore-scale hydrate occurrences coincide with published morphological behaviors of hydrate observed via computed tomography. The tortuosity and fractal dimension of pore spaces of these models were then characterized. The pore networks are also extracted, based on which the evolution of the pore characteristics including the distributions of pore radius, throat radius, throat length, and the coordination number were investigated. Using these generated models, simulations of permeability, thermal conductivity, and electrical conductivity were conducted to evaluate the influences of hydrate saturation and occurrence. These results are validated against published data, demonstrating that this algorithm could be an effective way to construct digital hydrate-bearing sediment models using a single set of computed tomographic images of a hydrate-free specimen. This new method can also be significant for the physical evaluation of natural cores in which hydrate has dissociated during core recovering and transferring.

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“…Note that these CT images were taken over 5 hr after the loading, and this extended scan time allows for hydrate redistribution that could heal hydrate cracks that may initially exist in freshly loaded hydrate. Faster CT scans with brilliant synchrotron sources (Nikitin et al, 2020) immediately after the loading or even during the loading may be required to capture such cracks in hydrate. In fact, hydrate enduring large deformation in Figures 2e′ and 3d′ is porous, which indicates historical development of cracks.…”

Section: Cracks In Hydratementioning

confidence: 99%

Pore‐Scale Investigation Of Methane Hydrate‐Bearing Sediments Under Triaxial Condition

Lei

Seol

2020

Geophysical Research Letters

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Mechanical behavior of hydrate‐bearing sediments is critical for well stability, reservoir deformation, and sea floor settlement during gas production. Current understanding on the mechanism of hydrate strengthening hosting sediments relies on conceptual models based on idealistic pore‐scale assumptions. Yet pore‐scale study is rare and limited to hydrate‐bearing sediments formed with surrogate guest molecules rather than methane. We present for the first time pore‐scale triaxial test results of methane hydrate‐bearing sediments. Besides the traditional stress‐strain relationship, we further explored (1) sand particle crushing and (2) pressure‐temperature dependent strength variations and (3) creep of hydrate‐bearing sediments. Results show that as hydrate enables the sand skeleton to bear additional loads, the potential of sand crushing upon hydrate dissociation also increases. Strength of hydrate‐bearing sediments decreases as pressure‐temperature condition approaches hydrate phase boundary. Hydrate‐bearing sediments creep and heal with time. The new observations suggest additional complications to be considered during gas production.

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Dynamic in-situ imaging of methane hydrate formation and self-preservation in porous media

Cited by 51 publications

References 55 publications

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

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

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

Pore‐Scale Investigation Of Methane Hydrate‐Bearing Sediments Under Triaxial Condition

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