CALCULATION OF REGULATED HEAT EXCHANGE OF GROUND PIPELINE IN BUNCH IN SELF-DIPPING MODE WITH FOLDED SURFACE

Abstract

In the areas of permafrost in Russia, an extensive infrastructure of pipeline transportation facilities has been created. The largest pipeline projects are Eastern Siberia - Pacific Ocean 1, 2 (ESPO), Vankor - Purpe, Zapolyarye - Purpe, Yamal - Europe, Kuyumba - Tayshet and Power of Siberia. The main and auxiliary facilities of the pipeline system use permafrost soil as bases and are designed to operate in certain temperature conditions. The rise in the temperature of frozen soils and the decrease in their carrying capacity pose a serious threat to roads, oil and gas pipelines, reservoirs, sites of oil and gas facilities, buildings and structures. In the zones of permafrost, the soils are extremely different in composition, moisture content and stability in conditions of thawing and freezing. If the pipeline functions as a cold device, there is a drop in soil heaving due to the occurrence of asymmetric ice formations appearing on the pipe with time. If the pipeline functions as a hot device, the soil may begin to melt, resulting in uneven draft. Limit conditions also arise at the interface between different soils. These non-uniform movements result in horizontal, vertical and transverse stresses, longitudinal stresses and torsional stresses on the pipeline. The speed and degree of such movements are determined by the thermal calculation, but their consequences are not evaluated in the regulations. It is not clear from SP 25.13330.2012 what sizes of halos or what sediment values are dangerous for pipelines operating in certain conditions in permafrost. Based on the practice of operating pipelines, it was observed that a pipeline laid on the ground has a lower accident rate. On this basis, this article substantiates the applicability of the onshore laying of the pipeline in permafrost, taking into account its self-dipping. The problem of heat transfer of the onshore pipeline in the bunch is solved, taking into account its self-dipping from the frozen surface. The values of sediment and pipeline buckling, the position of the axis of the pipeline when a stable mark is reached are determined. The paper takes into account transfer modes, in which the value of the thawing halo during the entire period of operation remains within acceptable limits to prevent the progression of the melting of the frozen soil mass. The article presents an algorithm for solving complex problems of defining safe thawing halos, taking into account phase transitions, ground subsidence, pipeline subsidence, and the effect of the seasons change on heat transfer during the pipeline operation period, knowledge of which is necessary to assess the performance of the pipeline. The practical value of this work lies in the fact that the obtained calculations can be used in the design of oil pipelines on frozen soils, taking into account the requirements of environmental safety.