3D Study of Gas Hydrate Formation and Dissociation in Porous Media and DEM Modeling of Granular Materials

Natural methane gas hydrates availability and ongoing rise in demand for energy, motivated researchers to consider gas hydrates as a potential energy source. Production of methane from hydrate-bearing sediments requires hydrate dissociation for releasing mobile methane gas in sediments prior to gas production operations. Fines may migrate through or clog the pore space of sandy sediments depending on the geometry and topology of the pore space. This dissertation employs unique in situ experiments and techniques to gain a comprehensive understanding of the associated physical processes (such as fines migration, clogging and gas driven fracture) and validation of hydrate dissociation models’ assumptions. 3D synchrotron micro-computed tomography (SMT) was used to acquire 3D direct visualizations of fines clogging, hydrate formation, hydrate dissociation, and gas driven fracture in porous media that help evaluating optimal conditions for the various gas production strategies. The particulate nature of granular materials makes it essential to study the behavior of these distinct particles to gain a fundamental knowledge of the bulk material behavior and characteristics. Fracture of sand particles greatly influences the constitutive relationships and deformation characteristics of natural granular materials. Discrete Element Method (DEM) is a numerical method that has been widely used to model discontinuous materials. High resolution 3D SMT images along with DEM modelling techniques are used in this dissertation to simulate multiscale in-situ experiments reproducing the actual shape of sand particles. Sand particles are modeled as agglomerates of rigid blocks or sub-spheres to study the evolution and distribution of particle fracture, and particle fracture mechanisms. Clumping technique will be used to assess the effect of particle morphology on the macro scale behavior in 1D compression experiments of large-size specimens and study the evolution of force chain and particle kinematics.