Effect of Fluid Saturation on Gas Recovery from Class-3 Hydrate Accumulations Using Depressurization: A Case Study of the Yuan-an Ridge Site in Southwestern Offshore Taiwan

This study focused on the effect of initial hydrate saturation on gas recovery from a depressurized Class-3 hydrate accumulation via a simulation study of the Yuan-An Ridge hydrate deposit located in southwestern offshore Taiwan. Our simulation results showed that the recovery factors for a 20-year operation time in the case of a 70% pressure decline were 0.37, 0.47, 0.49, 0.51, and 0.13 for initial hydrate saturations of 30%, 40%, 50%, 60%, and 70%, respectively. The depressurization is not suitable for hydrate deposits with a high hydrate saturation over 70% except when the formation permeability is higher than 2 Darcy.