Recent laboratory and field data suggest that hydrates form very porous pipeline plugs which transmit pressure freely, while hydrates act as significant flow obstructions. The blocked flow causes an ocean pipeline to rapidly equilibrate to the ocean temperature at 4 degrees C, When the hydrate plug is dissociated through total depressurization of the pipeline, the hydrate plug will be converted to an ice plug which significantly dissociates longer than the hydrate. This work formulates the first dissociation model in rectilinear coordinates. It indicates that there may be an optimum pipeline pressure for the most rapid dissociation of all solid phases resulting from hydrate pipeline blockages. Surprisingly, the high ice thermal diffusivity provides the highest heat flux when some ice is present. (C) 1998 Elsevier Science B.V. All rights reserved.