The effects of methane hydrate dissociation at different temperatures on the stability of porous sediments

Song, Yongchen; Zhu, Yiming; Liu, Weiguo; Li, Yanghui; Lu, Yan; Shen, Zhitao

doi:10.1016/j.petrol.2016.05.009

Cited by 69 publications

(33 citation statements)

References 23 publications

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“…Similar linear relationships between shear strength and stiffness versus hydrate saturation were also reported for unfrozen silica sand containing methane hydrate (Masui et al, 2005;Miyazaki et al, 2011). The determined shear strength is largely higher than those reported by W. Liu et al (2013), Song et al (2016), and Li et al (2016). As mentioned in section 1, this is because different methods were used to make the simulated permafrost sediments.…”

Section: Effect Of Gas Hydrate Saturationsupporting

confidence: 77%

Gas Hydrates in Permafrost: Distinctive Effect of Gas Hydrates and Ice on the Geomechanical Properties of Simulated Hydrate‐Bearing Permafrost Sediments

et al. 2019

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The geomechanical stability of the permafrost formations containing gas hydrates in the Arctic is extremely vulnerable to global warming and the drilling of wells for oil and gas exploration purposes. In this work the effect of gas hydrate and ice on the geomechanical properties of sediments was compared by triaxial compression tests for typical sediment conditions: unfrozen hydrate‐free sediments at 0.3 °C, hydrate‐free sediments frozen at −10 °C, unfrozen sediments containing about 22 vol% methane hydrate at 0.3 °C, and hydrate‐bearing sediments frozen at −10 °C. The effect of hydrate saturation on the geomechanical properties of simulated permafrost sediments was also investigated at predefined temperatures and confining pressures. Results show that ice and gas hydrates distinctively influence the shearing characteristics and deformation behavior. The presence of around 22 vol% methane hydrate in the unfrozen sediments led to a shear strength as strong as those of the frozen hydrate‐free specimens with 85 vol% of ice in the pores. The frozen hydrate‐free sediments experienced brittle‐like failure, while the hydrate‐bearing sediments showed large dilatation without rapid failure. Hydrate formation in the sediments resulted in a measurable reduction in the internal friction, while freezing did not. In contrast to ice, gas hydrate plays a dominant role in reinforcement of the simulated permafrost sediments. Finally, a new physical model was developed, based on formation of hydrate networks or frame structures to interpret the observed strengthening in the shear strength and the ductile deformation.

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Section: Effect Of Gas Hydrate Saturationsupporting

confidence: 77%

Gas Hydrates in Permafrost: Distinctive Effect of Gas Hydrates and Ice on the Geomechanical Properties of Simulated Hydrate‐Bearing Permafrost Sediments

et al. 2019

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“…Several experimental studies and field observations have demonstrated the impact of hydrate dissociation in the mechanical properties of MHBS. Hydrate dissociation occurs when the P‐T and salinity conditions of the system are outside the hydrate stability zone.…”

Section: Hydrate‐casm Formulationmentioning

confidence: 99%

A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments

Fuente

Vaunat

Marín‐Moreno

2020

Num Anal Meth Geomechanics

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SUMMARY Recent pore‐scale observations and geomechanical investigations suggest the lack of true cohesion in methane hydrate‐bearing sediments (MHBSs) and propose that their mechanical behavior is governed by kinematic constrictions at pore‐scale. This paper presents a constitutive model for MHBS, which does not rely on physical bonding between hydrate crystals and sediment grains but on the densification effect that pore invasion with hydrate has on the sediment mechanical properties. The Hydrate‐CASM extends the critical state model Clay and Sand Model (CASM) by implementing the subloading surface model and introducing the densification mechanism. The model suggests that the decrease of the sediment available void volume during hydrate formation stiffens its structure and has a similar mechanical effect as the increase of sediment density. In particular, the model attributes stress‐strain changes observed in MHBS to the variations in sediment available void volume with hydrate saturation and its consequent effect on isotropic yield stress and swelling line slope. The model performance is examined against published experimental data from drained triaxial tests performed at different confining stress and with distinct hydrate saturation and morphology. Overall, the simulations capture the influence of hydrate saturation in both the magnitude and trend of the stiffness, shear strength, and volumetric response of synthetic MHBS. The results are validated against those obtained from previous mechanical models for MHBS that examine the same experimental data. The Hydrate‐CASM performs similarly to previous models, but its formulation only requires one hydrate‐related empirical parameter to express changes in the sediment elastic stiffness with hydrate saturation.

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“…Which type is formed preferentially depends on S h and the pore fluid composition with a tendency of pore‐filling GHs to occur under gas‐limited conditions, and grain‐coating GHs being formed in water‐limited sediments (Choi et al, ; Ebinuma et al, ; Priest et al, ). Experimental studies have evaluated effects of varying S h (e.g., Masui et al, ; Santamarina & Ruppel, ), temperatures (Jia et al, ; Song et al, ), pore pressures ( u , Jiang, Zhu, et al, ), and effective stresses ( σ 3 ′, Lee, Francisca, et al, ; Miyazaki, Tenma, et al, ) to identify relevant parameters and initial conditions in the geotechnical analysis of GHBS. In particular with the perspective on sand production issues during natural gas production and potential slope failure of fine‐grained sediments, the effects of fines content (Hyodo et al, ; Jung et al, ; Kajiyama, Hyodo, et al, ; Lee, Santamarina, et al, ; Yun et al, ), lithology and consolidation history (Fujii et al, ; Ito et al, ; Santamarina et al, ; Suzuki et al, ; Yoneda et al, ), and thermo‐hydro‐chemo‐mechanical process coupling (Gupta et al, ; Klar et al, ; Sánchez et al, ; Uchida et al, ) have received attention.…”

Section: Introductionmentioning

confidence: 99%

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

Deusner

Gupta

Xie

et al. 2019

Geochem Geophys Geosyst

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The presence of gas hydrates (GHs) increases the stiffness and strength of marine sediments. In elasto‐plastic constitutive models, it is common to consider GH saturation (Sh) as key internal variable for defining the contribution of GHs to composite soil mechanical behavior. However, the stress‐strain behavior of GH‐bearing sediments (GHBS) also depends on the microscale distribution of GH and on GH‐sediment fabrics. A thorough analysis of GHBS is difficult, because there is no unique relation between Sh and GH morphology. To improve the understanding of stress‐strain behavior of GHBS in terms of established soil models, this study summarizes results from triaxial compression tests with different Sh, pore fluids, effective confining stresses, and strain histories. Our data indicate that the mechanical behavior of GHBS strongly depends on Sh and GH morphology, and also on the strain‐induced alteration of GH‐sediment fabrics. Hardening‐softening characteristics of GHBS are strain rate‐dependent, which suggests that GH‐sediment fabrics dynamically rearrange during plastic yielding events. We hypothesize that rearrangement of GH‐sediment fabrics, through viscous deformation or transient dissociation and reformation of GHs, results in kinematic hardening, suppressed softening, and secondary strength recovery, which could potentially mitigate or counteract large‐strain failure events. For constitutive modeling approaches, we suggest that strain rate‐dependent micromechanical effects from alterations of the GH‐sediment fabrics can be lumped into a nonconstant residual friction parameter. We propose simple empirical evolution functions for the mechanical properties and calibrate the model parameters against the experimental data.

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The effects of methane hydrate dissociation at different temperatures on the stability of porous sediments

Cited by 69 publications

References 23 publications

Gas Hydrates in Permafrost: Distinctive Effect of Gas Hydrates and Ice on the Geomechanical Properties of Simulated Hydrate‐Bearing Permafrost Sediments

Gas Hydrates in Permafrost: Distinctive Effect of Gas Hydrates and Ice on the Geomechanical Properties of Simulated Hydrate‐Bearing Permafrost Sediments

A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

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