Geothermal Aspects for Designing a Water Ballasted Bottom Founded Gas Plant for the Mackenzie River Delta

The gas plant for the proposed Niglintgak Anchor Field is expected to be assembled on a barge, towed to the Mackenzie River Delta and ballasted down onto the bottom of an excavation advanced into the side of a river channel. In order to place the barge onto the excavation, ballast tanks inside the barge will be filled with water pumped from the river. The gap between the barge and side slopes of the excavation will then be backfilled with excavated materials. The ballast water inside the unheated barge may convey thermal impact to the existing permafrost below the barge. During 2006 to 2008, field tests were initiated to investigate the water freezing progression and growth of hydrostatic pressure in the test tank as well as the dynamics of permafrost temperature under the tank. Based on results of the field tests, 3-dimensional geothermal analyses for the gas plant barge were carried out to predict the development and seasonal melt of ice within the ballast tanks and assess permafrost conditions under the barge over the operational life of the structure. Various scenarios of the ballast water freezing were considered.