Pore Scale Investigation on Dynamic Permeability Evolution in Hydrate-Bearing Sediments Coupling Media Deformation Effect

As a key parameter determining fluid flow dynamics, it is significant to determine the dynamic permeability evolution during the hydrate phase transition in consideration of media deformation for the safe and efficient development of hydrate-bearing sediments. In this work, a novel methodology of constructing unstructured hydrate-bearing networks with complex morphologies and anisotropy, respectively, in grain-coating and pore-filling hydrate pore habits coupling media deformation was proposed for the first time. After the validation, dynamic permeability evolution regularity considering media deformation was predicted and analyzed. Furthermore, the impact of parameters related to media deformation on the effective pore structure and dynamic permeability evolution was studied in detail. Results indicate that the effective permeability turns smaller, while the decline rate decreases with increasing hydrate saturation due to the difference in the number and compression degree of hydrate-occupied and unoccupied pore elements induced by media deformation. Moreover, the media deformation effect on the effective pore structure intensifies with an increase in the effective stress, a decrease in the elastic modulus, and a reduction in Poisson’s ratio, resulting in a larger decrease in the effective pore-throat radii and reduction in dynamic permeability at the same hydrate saturation. In addition, the number of hydrate-occupied pore bodies and throats grows smaller at the same increment in hydrate saturation as media deformation becomes more pronounced, leading to a slower decline rate and a smaller difference in dynamic permeability with different media deformation parameters.