Reservoir damage: the impact of skin effect on gas hydrate production potential

In the numerical model of a hydrate reservoir, the estimated gas production rate showed a gradual increase under constant pressure, whereas both field trials and laboratory tests exhibited a slight decrease. This discrepancy can be addressed by introducing a dynamically evolving skin in the hydrate reservoir. This study numerically investigates the impact of near-wellbore skin effects on NGH production performance. The damage degree of near-wellbore region was assessed using the skin factor, and the effects of both positive and negative skins were analyzed in terms of their influence on fluid flow, gas and water production rates, and reservoir behavior. Positive skin, caused by fines migration, reservoir consolidation or sand control failure, severely impedes gas production, with observed reductions of up to 59 %. In contrast, negative skin, induced by stimulation, moderately improves production, though the extent of improvement is constrained by the challenge of achieving significant negative skin factors. Sensitivity analyses reveal that skin permeability and thickness critically influence gas production. When skin permeability is lower than that of the formation, flow resistance increases sharply, while thicker skin zones further restrict pressure propagation and hydrate dissociation. Conversely, for negative skin scenarios, increased permeability enhances flow, but further improvements become marginal beyond certain thickness thresholds. History matching of stratified hydrate model against to field production date demonstrates that a dynamic evolution of skin is essential for accurate prediction of field gas production. Pressure and temperature recovery, along with a decrease in gas production rate, serve as important indicators of skin formation. These findings emphasize the necessity of incorporating skin effects into numerical models. Continuous monitoring of well parameters is vital for early detection of skin formation and for implementing timely interventions to maintain efficient and sustainable NGH production.