Explicitly Coupled Thermal Flow Mechanical Formulation for Gas-Hydrate Sediments

Klar, Assaf; Uchida, Shun; Soga, Kenichi; Yamamoto, Koji

doi:10.2118/162859-pa

Cited by 70 publications

(51 citation statements)

References 1 publication

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“…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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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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“…This class of deformation, which is caused by changes in stress states, whether volume contraction or expansion, can be assessed based on the material stiffness. Many of reservoir-scale geomechanics simulators, including those presented by the Lawrence Berkeley National Laboratory (LBNL) group [40][41][42], by the Korea Advanced Institute of Science and Technology (KAIST) group [39,43], and by the Cambridge University group [44][45][46], adopt elastoplasticity to model sediment deformation behaviors. Thereby, one of the elastic moduli (typically Young's modulus or bulk Energies 2016, 9, 775 15 of 23 modulus), Poisson's ratio ν, and strength parameters (cohesion and friction angle, if Mohr-Coulomb yield criterion used) for material yielding are typically used as input parameters for describing elasto-plastic behavior.…”

Section: Stress-and Strain-dependent Young's Modulusmentioning

confidence: 99%

“…Therefore, it is presumed that the presence of hydrate causes increases in the air-entry value and the residual water saturation. To date, few reservoir-scale simulation studies have considered the effect of hydrate saturation on relative permeability; Klar et al [45,46] and Konno et al [58] incorporated the effect of hydrate saturation on the relative permeability of water and gas phases, as shown in Table 5. Therefore, the semi-empirical parameters describing sediment pore structures, such as relative permeability index N i , van Genuchten parameters a, b and c, and irreducible water and gas saturation, can be estimated using the water retention curve that was experimentally obtained for hydrate-free sediments.…”

Section: Relative Permeabilitymentioning

confidence: 99%

“…Accordingly, Young's modulus of hydrate-bearing sediments is assumed based on linear interpolation between the values at two different hydrate saturations-typically, one for hydrate-free sediment and the other for a certain hydrate saturation (e.g., [40][41][42][43][44][45][46]62]). On the other hand, a logarithmic increase of the secant Young's modulus of hydrate-bearing sediments has been also observed with increasing hydrate saturation by Yoneda et al [25].…”

Section: Geomechanical Propertiesmentioning

confidence: 99%

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Geomechanical, Hydraulic and Thermal Characteristics of Deep Oceanic Sandy Sediments Recovered during the Second Ulleung Basin Gas Hydrate Expedition

et al. 2016

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This study investigates the geomechanical, hydraulic and thermal characteristics of natural sandy sediments collected during the Ulleung Basin gas hydrate expedition 2, East Sea, offshore Korea. The studied sediment formation is considered as a potential target reservoir for natural gas production. The sediments contained silt, clay and sand fractions of 21%, 1.3% and 77.7%, respectively, as well as diatomaceous minerals with internal pores. The peak friction angle and critical state (or residual state) friction angle under drained conditions were~26 • and~22 • , respectively. There was minimal or no apparent cohesion intercept. Stress-and strain-dependent elastic moduli, such as tangential modulus and secant modulus, were identified. The sediment stiffness increased with increasing confining stress, but degraded with increasing strain regime. Variations in water permeability with water saturation were obtained by fitting experimental matric suction-water saturation data to the Maulem-van Genuchen model. A significant reduction in thermal conductivity (from~1.4-1.6 to~0.5-0.7 W·m −1 ·K −1 ) was observed when water saturation decreased from 100% to~10%-20%. In addition, the electrical resistance increased quasi-linearly with decreasing water saturation. The geomechanical, hydraulic and thermal properties of the hydrate-free sediments reported herein can be used as the baseline when predicting properties and behavior of the sediments containing hydrates, and when the hydrates dissociate during gas production. The variations in thermal and hydraulic properties with changing water and gas saturation can be used to assess gas production rates from hydrate-bearing deposits. In addition, while depressurization of hydrate-bearing sediments inevitably causes deformation of sediments under drained conditions, the obtained strength and stiffness properties and stress-strain responses of the sedimentary formation under drained loading conditions can be effectively used to assess sediment responses to depressurization to ensure safe gas production operations in this potential target reservoir.

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“…However, hydrate reservoirs in deep water are generally low-strength formations, which make the wellbore collapse to be a commonly occurred issue during hydrate production process [9][10][11][12]. In addition, hydrate dissociation during hydrate production operation is another contributor to both the complex accidents within the borehole (i.e., borehole instability and casing damage, etc.)…”

Section: Introductionmentioning

confidence: 99%

Investigation method of borehole collapse with the multi-field coupled model during drilling in clayey silt hydrate reservoirs

Cheng

Wang

et al. 2018

Frattura Ed Integrità Strutturale

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ABSTRACT. The global reserves of natural gas hydrates are extremely abundant, but hydrate reservoirs are usually clayey silt hydrate reservoirs with low strength, and borehole collapse is a key issue during the drilling operation. In the present work, both the investigation method and the finite element model that used for investigating borehole collapse in hydratebearing sediment are developed, and the superiority of the investigation method developed herein is also analyzed. The results show that changes in temperature and/or pore pressure do not necessarily lead to the hydrate dissociation. Hydrate dissociation occurs only when both temperature and pore pressure satisfy the conditions of hydrate dissociation. Moreover, the applicability of the investigation method developed herein is verified by comparing the equivalent plastic strains obtained by the coupled model developed in this paper and the simplified model respectively. In addition, the simplified model overestimates the extent of the wellbore collapse for the drilling operation in hydrate-bearing sediments. All these results demonstrate that both the investigation method and the finite element model can be used for borehole stability simulation in hydrate-bearing sediments. KEYWORDS.Hydrate-bearing sediments; Hydrate dissociation; Wellbore instability; Borehole collapse; Finite element analysis.Citation: Li, Q. C., Cheng, Y. F., Li, Q., Wang, F. L., Wei, J., Ding, J. P., Zhang, H. W., Song, B. J., Zhang, C., Yan, C. L., Investigation method of borehole collapse with the multi-field coupled model during drilling in clayey silt hydrate reservoirs, Frattura ed Integrità Strutturale, 45 (2018) 86-99.

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Explicitly Coupled Thermal Flow Mechanical Formulation for Gas-Hydrate Sediments

Cited by 70 publications

References 1 publication

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

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

Geomechanical, Hydraulic and Thermal Characteristics of Deep Oceanic Sandy Sediments Recovered during the Second Ulleung Basin Gas Hydrate Expedition

Investigation method of borehole collapse with the multi-field coupled model during drilling in clayey silt hydrate reservoirs

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