An Analytical Model for the Permeability in Hydrate-Bearing Sediments Considering the Dynamic Evolution of Hydrate Saturation and Pore Morphology

Hydrate-saturation-dependent permeability in sediments is largely affected by the pore morphology of hydrate. Hydrate pore morphology evolves from a single pore habit, which depends on its formation conditions, toward a sophisticated hybrid habit with increased hydrate saturation. Resulted permeability reduction curves in hydrate-bearing sediments are diverse and lack universal models. By using a two-parameter logistic function to link microscale hydrate pore habit evolution with macroscale permeability variations, this study establishes a pore-morphology-weighted permeability model that well captures the permeability evolution in hydrate-bearing sediments at various conditions. The universality of this model is validated and the values of the two parameters in the model are calibrated using published laboratory and pressure core data. This newly proposed model offers a mechanistic understanding of the permeability in hydrate-bearing sediments and an elegant expression that can be implemented in reservoir simulators for field-scale gas production estimation.