Development of mathematical models and optimization of operation modes of the oil heating station of main oil pipelines under conditions of fuzzy initial information

The relevance of the study is substantiated by the fact that when managing the processes of oil transportation through main pipelines, it becomes necessary to determine and select the optimal operating modes of the oil pipeline units, taking into account the fuzziness of some part of the initial information. In this regard, solving the problem of multi-criteria selection of effective operating modes for an oil heating station for a hot oil pipeline system, which is often described in a fuzzy environment, based on the apparatus of fuzzy set theories, is an urgent scientific and practical problem. A method for the synthesis of models in the conditions of fuzzy output parameters of the object has been developed, with the help of which fuzzy models of the investigated oil heating station of the main oil pipeline have been built. Based on the modification and combination of various optimality principles, mathematical formulations of the problem of multi-criteria selection of effective operating modes for an oil heating station in a fuzzy environment are obtained. By modifying and adapting the principles of guaranteed results and equality in a fuzzy environment, a heuristic method has been developed for solving the formulated problem of selecting object's operation modes using the initial fuzzy information. The proposed heuristic method for multi-criteria selection in a fuzzy environment is based on the use of the experience and knowledge of the decision-maker. The proposed approach is implemented in the formulation and solution of the problem of multi-criteria selection of operating modes of the oil heating station in Atyrau of the Uzen-Atyrau-Samara main oil pipeline. As a result of the application of the proposed method, an improvement in the degree of fulfillment of a fuzzy restriction on environmental impact was achieved by 2 %, as well as the optimal values of the operating parameters of the object were improved: the temperature was reduced by 1.85 % (5.67 K), pressure – by 0.04 % (kPa) and fuel consumption – by 2.9 % (0.0002 kg/s). The obtained results have confirmed the effectiveness of the proposed approach to solving the assigned tasks.

Математический алгоритм для обнаружения утечек малой интенсивности

The operating principle of leak detection systems, based on registration of transported medium hydroacoustic fluctuations, appearing due to pipeline loss of containment, consists of identification of hydraulic impulse, originating in case of leakage, using acoustic dynamic pressure measuring sensors - hydrophones. However, during pumping at pipeline stationary operating mode hydrophones also register background noises, which can mask the leakage signal. To separate the useful leakage signal it is important to construct an algorithm that allows lowering the noise component of the signals. Within the scope of experimental research, two pairs of hydrophones were used, which were installed at the functioning main oil pipeline at a distance of 20 km of each other. The distance between the adjacent paired hydrophones was no more than 1 km. Leaks were imitated by draining the product (diesel fuel) in the middle of control section. Authors considered the methods of noisy signals filtration and possible methods of cleared signals processing to determine the leak parameters. Mathematical algorithm that allows minimizing the influence of signal noise by filtration and mutual hydrophone readings compensation was proposed. It is established, that the developed algorithm allows detecting the leakages of low intensity (up to 0.1 % of actual flow) in cases of stationary pipeline operating mode and pumping stop mode. Принцип работы систем обнаружения утечек, основанных на регистрации гидроакустических колебаний транспортируемой среды, возникающих из-за разгерметизации трубопровода, состоит в идентификации гидравлического импульса, возникающего при образовании утечки, с помощью акустических датчиков измерения динамического давления – гидрофонов. Однако гидрофоны в процессе перекачки при стационарном режиме работы трубопровода регистрируют в том числе фоновые шумы, которые могут маскировать сигнал от утечки. Для выделения полезного сигнала утечки актуально построение алгоритма, позволяющего понизить шумовые составляющие сигналов. В рамках экспериментальных исследований использовались две пары гидрофонов, которые устанавливались на действующем магистральном нефтепродуктопроводе на расстоянии 20 км друг от друга. Расстояние между соседними гидрофонами в паре составляло не более 1 км. Утечки имитировались путем выполнения натурных сливов продукта (дизельного топлива) в середине контрольного участка. Авторами рассмотрены методы фильтрации зашумленных сигналов и возможные способы обработки очищенных сигналов с целью определения параметров утечки. Предложен математический алгоритм, позволяющий минимизировать влияние шумовых составляющих сигналов путем фильтрации и взаимной компенсации показаний пар гидрофонов. Установлено, что разработанный алгоритм позволяет обнаруживать утечки малой интенсивности (до 0,1 % от фактического расхода) в условиях стационарного режима работы трубопровода и режима остановленной перекачки.

Evaluation of the geoecological and fire situation in case of the oil spillage on the water surface

The work provides an assessment of the geoecological situation during an oil spill on the water surface. The modeling of the process of oil burning on the water surface is carried out, and also a model for estimating the oil burning time during depressurization of the underwater passage of the main oil pipeline is proposed. The assessment of individual and social risk in case of ignition of an oil spill as a result of depressurization of the underwater crossing of the main oil pipeline is given. The fire risk assessment was carried out under the condition of a guillotine rupture of the underwater pipeline, since, despite the lowest frequency of this type of depressurization, the levels of exposure to damaging factors, due to the largest volume of oil spills, will be maximum and will make the main contribution to the magnitude of the fire risk. When forecasting an emergency, a model of the spread of an oil slick along the water surface of a watercourse was developed, which takes into account the wind speed and the speed of the river flow.

Evaluation of the geoecological and fire situation in case of the oil spillage on the water surface

The work provides an assessment of the geoecological situation during an oil spill on the water surface. The modeling of the process of oil burning on the water surface is carried out, and also a model for estimating the oil burning time during depressurization of the underwater passage of the main oil pipeline is proposed. The assessment of individual and social risk in case of ignition of an oil spill as a result of depressurization of the underwater crossing of the main oil pipeline is given. The fire risk assessment was carried out under the condition of a guillotine rupture of the underwater pipeline, since, despite the lowest frequency of this type of depressurization, the levels of exposure to damaging factors, due to the largest volume of oil spills, will be maximum and will make the main contribution to the magnitude of the fire risk. When forecasting an emergency, a model of the spread of an oil slick along the water surface of a watercourse was developed, which takes into account the wind speed and the speed of the river flow.

Design of an electron beam welding installation based on the existing equipment for connecting pipelines without using a vacuum

The article is aimed at solving the problem of connecting pipelines using electron beam welding. During the presented study, the analysis of the object of study - the main oil pipeline was carried out, during which the main shortcomings in the formed welded joints were identified. The authors also analyzed the methods of forming welded joints, which showed the advantages of electron-beam technology. The means of electron beam welding were selected: a generator, an electron beam gun. The electrical characteristics of the installation have been calculated, which make it possible to formulate the requirements for the purchased equipment. As a result, the authors have designed an installation for electron-beam welding of joints of the main pipeline elements, which makes it possible to form welded seams up to 400 mm deep and 1 mm wide.

Optimization of operating modes of the main oil pipeline according to the criterion of minimum costs for electric energy payment

Рассматривается вопрос о выборе оптимального плана эксплуатации технологического участка магистрального нефтепровода при различных производительностях. В качестве критерия оптимальности принимается минимум суммарных денежных затрат на оплату потребляемой электрической энергии. При изменении планов поставок нефти приходится решать вопрос, является ли новый вводимый режим оптимальным, какова будет величина требуемой дополнительной или неизрасходованной электроэнергии, какие поправки требуется вносить в заявку на электроэнергию. В этой связи определение корректного способа вычисления и сравнения энергопотребления при планировании режимов работы магистрального нефтепровода для разных, изменяющихся планов перекачки является актуальной и важной задачей. Предлагается двухэтапный алгоритм определения оптимального графика работы технологического участка нефтепровода путем решения задачи линейного программирования, сформулированной таким образом, чтобы учесть все особенности расчета стоимости потребленной электрической энергии. Приводится пример расчета с использованием предлагаемого алгоритма. The article considers the issue of choosing the optimal operating schedule for the technological section of the main oil pipeline at various pumping capacities. The optimality criterion is the minimum of total monetary expenses for payment of electric energy consumed for the oil pumping process. It is necessary to decide whether the new regime being introduced is optimal, what amount of additional or unspent electricity will be required, and how much it is needful to adjust the electricity demand when changing oil-pumping plans. In this regard, determining how to correctly calculate and compare energy consumption when planning the operation modes of the main oil pipeline for different, changing pumping plans is an urgent and important task. A two-stage algorithm for determining the optimal operating schedule of the oil pipeline technological section is proposed. The proposed method consists in solving a linear programming problem formulated in a way that takes into account all features of calculating the cost of consumed electrical energy. An illustrative example of calculation using the proposed algorithm is given.

Analysis of the Linear Section Risk Level Including Changes in the Pipe Material Strength Properties during Main Oil Pipeline Operations

Strength properties of the pipe material are random variables and have a statistical straggling that differs for pipe products of different grades. Distribution of these properties significantly effects on the results of calculating the current level of strength reliability and risk of linear sections for the main pipelines. The reliability of such calculations results depends not only on the distribution that obeys the strength properties of the pipe material at the surveyed section, but also on the dispersion limits of these properties. At present, the main pipelines have significant service lives. Due to this, when making assessment of the technical condition, safety, and risk level of linear sections, the issue is raised of how stable the distribution is related to the pipe steel strength properties with an increase of the service life for the main pipeline. The results of studies are presented concerning the actual distribution and limits of dispersion for the strength properties of pipe steel grade 17G1S after a long-term operation of the main pipeline. It is established that the regularities and strength properties dissipation limits for the material of a pipe made of the above steel are changing with time. Based on the results of the study, a practical example is considered related to the assessment of the effect of the identified changes on the probability of failure and the risk level for one of sections at the linear part of the main oil pipeline. The results obtained in the work substantiate the need in considering changes in the distribution of strength properties that arises with an increase in the main pipelines service life. The outlined approach allows to increase the reliability of risk assessment results for the main pipelines having long-term service life.

Research of Application of Anti-Turbulent and Depressor Additives in Pipeline Transport of High Viscosity Oils

The use of anti-turbulent and depressant additives makes it possible to increase the efficiency of oil pipelines transporting high-viscosity oil. In this method, the principle of increasing the efficiency of transportation is based on reducing the hydraulic resistance and increasing the fluidity of oil. The work carried out a theoretical study of the existing types of anti-turbulent and depressant additives. This article presents an experimental study of the effect of the MR 1088 depressant additive on an oil sample from the Usa – Ukhta main oil pipeline.