Numerical Modelling Using Homogenization Techniques of Gas Hydrate Bearing Sediments
Abstract
Natural gas hydrates represent a potential energy resource and a geohazard that it is essential to control. The study of gas hydrate bearing soils (GHBS), which are usually located in ocean floor or in permafrost regions, represents a major interest. The hydrate formation and dissociation processes in porous sediments change their microstructure and their physical properties with it. Several multi-physical models have already been applied to GHBS but a reliable mechanical constitutive model is difficult to develop due to the complexity and the instability of these soils.
Based on these observations, we concentrated our analysis on the mechanical behavior before integrating it into a finite element (FE) code. First, the relation between the elastic moduli of the soil and its gas hydrate volume fraction has been determined through an analytical homogenization calculation. However, in the literature GHBS showed an inelastic macro-mechanical behavior, which is strongly related to the different physical and morphological characteristics of both the soil matrix and the gas hydrates inclusions. This led us to apply a numerical periodic homogenization method based on Fast Fourier Transforms (FFT). This method allows the use of elastoplastic laws and complex geometries to define the microstructural components of material. The results obtained with this technique can thus be used to determine a macroscopic constitutive behavior adapted to the type of mixed hydrate-sediments that we want to simulate. The previous developments have then been incorporated into a FE code. Hydraulic couplings via fluid pressures and classical fluid flow models have been used, as well as kinetics and thermodynamics models. The mechanical behavior can be defined either through analytical homogenization or multi-scale calculations. The FFT-based calculation is carried out at the microstructural level for each FE integration point.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMOS34A..05A
- Keywords:
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- 3004 Gas and hydrate systems;
- MARINE GEOLOGY AND GEOPHYSICS