Thaw‐Subsidence Effects on Offshore Pipelines

Abstract

This paper reviews permafrost conditions from the deeper water conditions offshore through the shallower water near‐shore area to the onshore colder permafrost conditions. Depending on the initial depth to the permafrost surface, some deepening of the thaw line beneath the pipe will result from operating the pipeline at temperatures much above the permafrost melting point. Some preliminary geothermal predictions indicate incremental thaw depths of 0–10 m because of pipe operation, depending on the initial depth to the permafrost table. Uniform thaw subsidence poses less of a concern than differential settlement, which might induce curvatures and strains in the buried line. Differential thaw subsidence resulting from thawing of a buried permafrost zone was modeled using a simple finite element program and a thermal strain analogy to represent the thaw contraction of a buried permafrost layer. The pipe was treated as a