Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

Abstract

[1] The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably < 40% of pore space) appear to be determined by stress-dependent soil stiffness and strength. At high hydrate concentrations (>50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

Examination of Hydrate Formation Methods: Trying to Create Representative Samples

“…This indicates debonding of hydrate from the mineral grains. The resulting stiffness of the sample, however, was still higher than the moist sand sample it was formed from, which is also consistent with the behavior of a sample containing hydrate occupying the pore bodies [Yun et al, 2007].…”

Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluation of Technology and Potential

“…Masui et al (2005) conducted some pioneering geomechanical studies using hydrate-impregnated Toyoura sand, developed stress and strain relationships, and defined the relationship between S H and various geomechanical properties (e.g., modulus of elasticity, Poisson's ratio, internal friction angle, etc.). Investigations of geomechanical properties of sediments containing tetrahydrofuran hydrate have been conducted at Georgia Tech (Lee et al, 2007;Yun et al, 2007). Current investigations of the geomechanical strength of methane HBS are being performed at Lawrence Berkeley National Laboratory in a specially designed apparatus that permits the concurrent analysis of coupled geomechanical, geophysical and flow processes, and x-ray CT scans (Figure 19.…”

Numerical simulations for analyzing deformation characteristics of hydrate-bearing sediments during depressurization

“…A vast variety of triaxial shear tests have been performed on HBS to understand the stress-strain behavior under different hydrate saturations (Yun et al, 2007;Miyazaki et al, 2011;Zhang et al, 2012;Ghiassian and Grozic, 2013;Hyodo et al, 2013;Hyodo et al, 2014;Li et al, 2016). Based on these experimental data, various constitutive models of HBS have been proposed and improved (Pinkert and Grozic, 2014;Lin et al, 2015;Pinkert et al, 2015;Sun et al, 2015;Shen et al, 2016;Uchida et al, 2016).…”