The paper discusses the issues and peculiarities of wax deposition in non-isothermal main pipelines for ‘hot’ pumping of oil, characterized by an increased content of paraffins - positive fluid loss temperatures, risks of congelation and intensification of wax deposition. Problems of pumping waxy oils are solved by thermochemical methods aimed at eliminating the risks of blocking the section at low ambient temperatures and long downtime of the linear part for the period of regular scheduled and emergency repair work. If the issue of determining the permissible safe shutdown time and start-up modes has been given a fairly large number of scientific works both in domestic and foreign literature, then the tasks of optimizing the operating costs associated with determining the required frequency of pigging, dosages of chemical reagents, today, remain unresolved and require rational solutions that are necessary and sufficient in order to maintain energy efficiency and system reliability. At the same time, the issues of ecology, especially for Arctic oil and gas regions, dictate new more stringent requirements for the special pumping methods, developed decades ago.
This article presents the results of the performed analysis of the influence of various factors on the efficiency of hot oil pumping, substantiates the shortcomings of the equipment and chemical reagents used, caused by an insufficient level of preheating of oil due to a number of technological limitations adopted decades ago. The results of experimental studies of the dependence of the intensity of wax deposition on the temperature gradient in the near-wall zone are presented, confirming the advantages of low-temperature pipeline transportation of preliminarily heat-treated oil in comparison with a preheating scheme characterized by shock dosages of chemical reagents, on the one hand, partially solving the problem of extending the permissible safe shutdown time, and with the other, leading to the intensification of wax depositions on the inner surface of the walls of a non-insulated oil pipeline.
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