Variance-based determination of dominant model parameters for sand migration in homogeneous gas hydrate-bearing reservoir

Abstract

Sand migration in gas hydrate-bearing reservoir poses a serious problem for a successful long-term gas production. Because gas production is achieved through hydrate dissociation, often driven by depressurization, the process of sand migration involves highly coupled multiphysics behavior. For example, hydrate dissociation causes sediment deformation and may increase the potential of sand migration but hydrate dissociation can also increase permeability, which may lower hydraulic gradient at a given flow rate, leading to reduction in sand migration. Other factors include that sand inflow (or outflow) would cause the increase (or decrease) in pore pressure due to void volume change and thus may halt (or accelerate) hydrate dissociation. An analytical thermo-hydro-mechanical sand migration model to incorporate these interacting features requires a number of parameters and it is important to quantify the significance of each parameter to this complex process of sand migration in gas hydrate-bearing reservoir. This study, therefore, conducts a series of sand migration analyses in field-scale homogeneous gas hydrate-bearing reservoir subjected to depressurization and presents the relative importance of each parameter to the volume of produced sand from a production zone. It is found that the volume of produced sand is mostly dominated by the parameter converting shearing deformation to sand detachment potential and by the parameter increasing critical hydraulic gradient for sand detachment with hydrate saturation.