Warm Pipeline in Permafrost: A Sensitivity Study of the Major Thermal Properties

Pipelines carrying warm contents through permafrost areas present a key challenge to the development of petroleum reserves in the Arctic region. Evaluations have to be made during the pipeline design to avoid signification thaw settlement and large-scale permafrost damage. Current practice in estimating pipeline thaw settlement is primarily based on the assumption of a complete consolidation of the thaw-unstable layer. This often results in an over-conservative estimate and costly over-design. An integrated three-dimensional (3D) finite element (FE) model, developed recently as part of J P Kenny’s in-house simulator tools, has been used successfully to simulate the thermal and mechanical interaction between the pipeline and surrounding permafrost and gives a better estimate of the heat transfer, thaw settlement and pipeline deformation over the pipeline’s service life. Given the lack of experimental data and the complex nature of this problem, the sensitivity study on the major variables, presented in this paper and based on the 3D FE model, offers an in-depth insight into the problem and provides better-based guidelines for proper design of pipelines in permafrost. A number of thermal parameters are studied in this paper and compared based on their impact on the final deformation of the pipeline, so as to identify key parameters in the pipeline-permafrost thaw settlement processes. These parameters include the hydrocarbon content temperature and the convection coefficient, inside the pipe; the thickness and thermal conductivity of the insulation layer, on the pipe exterior; and the initial temperature, soil void ratio and the surface condition of the permafrost/soil, as boundary conditions. Results of current study improve the understanding of the pipeline-permafrost interaction from the heat transfer perspective and provide better guidance to the pipeline design in the permafrost environment.© 2010 ASME