A Model for the Elastic Modulus of Hydrate-Bearing Sediments

Abstract

A model for the elastic modulus of hydrate-bearing sediment (HBS) is presented considering the variation of the hydrate saturation and hydrate occurrence mode. The model is based on the classical series and parallel modes, introducing a parameter of statistical force transfer paths among particles in HBS. Macro-triaxial compression tests and micro X-ray computed tomography (CT) observations of HBS in the gas-saturated formation mode were conducted. The applicability of the model was checked through the comparison between tests and theoretical results.

Mechanical properties of gas hydrate-bearing sediments during hydrate dissociation

“…In nature, GHBS consists of four components, i.e., soil/rock skeleton, GH, water, and gas [7]. Triaxial compression tests were conducted when GH formed in pores of the specimen under a non-dissociation condition, simulating the mechanical behavior before GH exploitation [8][9][10][11][12][13][14][15]. The results indicated that: different GHBS preparation methods such as gas saturated method and water saturated method lead to obvious differences in the mechanical behavior; the GH existence mode in the pores of sediments varies with the increase of GH saturation, leading to the transition of the deformation from shear shrinkage to shear dilatancy.…”

State‐of‐the‐art brief review on sanding problem of offshore natural gas hydrates sediments

“…In the lab experiments, it has been found that the increasing hydrate saturation alters the formation deformation from the shear shrinkage to shear dilatancy. [45][46][47] It is because that the little presence of hydrate cannot affect the formation strength. 41 The low hydrate concentration in the sediment means that the soil is the major content in the rock skeleton, which makes the sand particles and the cementation between particles bear the most shear stress.…”

“…The common triaxial tests in the lab conditions use the NGH samples in the static nondissociation conditions. [46][47][48][49] Not just the static hydrate can affect the mechanical behavior, the dynamic change of NGH cannot be ignored. The dynamic change of NGH can help to develop natural gas resources but can cause the sand production problem, like the two sides of the coin.…”

“…89 Mohr-Coulomb and Drucker-Prager criteria have been used to evaluate the NGH sediment strength with better applicability. 46,47 According to the calculation results, it has been verified that the calculation result of Drucker-Prager is not as accurate as that of the Mohr-Coulomb yield criterion. 90,91 The comparison between the Tresca yield criterion and Mises yield criterion shows that the Tresca yield criterion obtains a larger calculation result than that of Mises yield criterion.…”

A hypoplastic model for gas hydrate‐bearing sandy sediments

“…Several models have been proposed to formulate the stress‐strain relationship of GHBS . The elastic modulus of gas hydrate‐bearing coarse sand is formulated by series and parallel model, and the shear strength of tetrahydrofuran hydrate‐bearing clay is analyzed on the basis of the Mohr‐Coulomb and Drucker‐Prager criterion . The Duncan‐Chang model is applied to simulate the nonlinear elastic behavior of GHBS .…”