Analysis of ground temperature variation in differential settlement of China-Russia crude oil pipeline: field monitoring and numerical simulation

Abstract

In vast areas of rich frozen soil, the intense heat exchange between the hot oil pipeline and surrounding soil results in the continuous melting of permafrost under the pipeline and the continuous sinking of the pipeline. Moreover, the settlement rate and depth of the pipeline are also different due to the influence of ice content and the thickness of rich frozen soil layer. Therefore, in this paper, based on the field measured data, by adopting the method of numerical simulation, the temperature rise process of the soil around the pipeline under the condition of different subsidence rate and different thickness of rich frozen soil layer is studied. The results show that with the increase of the thickness of the frozen soil layer, the degradation depth of the upper limit of the artificial frozen soil in the lower part of the pipeline increases gradually. Under the same thickness of the frozen soil layer, the influence of the settlement rate of the pipeline on the upper limit of the artificial frozen soil in the lower part of the pipeline mainly concentrates on the initial operation stage of the pipeline; with the increase of the thickness of rich frozen soil layer, the upper limit difference of artificial frozen soil under different settlement rates of pipelines at the same time increases gradually. Of different sedimentation rate and the rich soil layer under the condition of ice -6 m depth of geothermal heating process monitoring, the geothermal heating process can be divided into three stages: melting stage (I), rapid heating stage (II), slow heating stage(III). With the increase of the settling depth, the duration of the phase I and II is significantly reduced, the heating rate is significantly promoted, the duration of phase III is increased significantly and the heating rate is gradually reduced.