Abstract: Clathrate reservoirs of Class II are modified in order to improve the ability to produce hydrocarbons from them. Specifically a method for improving producibility of subsurface clathrate formation underlain by a mobile aquifer includes drilling a borehole to a depth providing access to the mobile aquifer and injecting a material into the mobile aquifer such that the material passes through pore spaces and forms a barrier underlying the clathrate formation and substantially impeding fluid flow from the mobile aquifer into contact with the clathrate formation.