Numerical Simulation Study On Effects Of The Buried Oil Pipeline On Permafrost Temperature

ABSTRACT:Based on the national important project of China-Russia oil pipeline engineering, ANSYS finite element analysis software was used to calculate the temperature field within50years after construction of the pipeline that is related to climatic environment and geological conditions in northeast permafrost areas. The following conclusions can be shown as below:(1) The permafrost along the Mohe-Daqing section of the China-Russia crude oil pipeline, with complex distribution, quite different engineering geological behavior, and poor thermal stability, will be greatly influenced by the oil pipeline.(2) For a certain pipeline, the temperature field distribution of soils around the pipeline varies considerably under different seasonal temperatures; The ground temperature distribution nearby the pipeline is also different from far away.(3) Soils around the pipeline in low temperature permafrost regions are relatively stable, which reach balanced state from the tenth year. Soils in warm permafrost regions are affected significantly, solved by reducing the buried depth of the pipe top part or laying insulation materials.(4) By laying insulation materials can reduce the maximum thawing depth. With a larger thickness of the insulation layer, the disturbances on permafrost will be smaller. The insulation layer thickness of5-8cm is needed in low temperature permafrost regions while in warm permafrost regions the thickness should be larger than8cm or other cooling measures should be taken to protect the permafrost.(5) The maximum thawing depth below the pipe increases with the increase of the buried depth of the pipe top part which affects the temperature field distribution significantly. The overlaying soil thickness of pipe top part can be selected with the range of0.8to1.5m in low temperature permafrost regions, only from the perspective of the temperature field.(6) The average oil temperature has considerable influence on the temperature field distribution. The thawing depth increases with the increase of average oil temperature and the oil temperature should not be too high.