Research of the influence of marine residual fuel composition on sedimentation due to incompatibility

The article shows studies of the problem of active sediment formation during mixing of residual fuels, caused by the manifestation of incompatibility. To preserve the quality and reduce sediment formation during transshipment, storage, and transportation of marine residual fuels, a laboratory method for determining the compatibility and stability of fuels has been developed, which makes it possible to determine the quantitative characteristics of the sediment formation activity. According to the method developed, laboratory studies have been carried out to determine incompatible fuel components and the influence of composition on the sedimentation process. Tests were carried out to determine the quality indicators and the individual group composition of the fuel samples. Based on the results of the studies, the dependences of the influence of normal structure paraffins in the range from 55 to 70 wt. % and asphaltenes in the range from 0.5 to 3.5 wt. % in the fuel composition on the sedimentation activity due to incompatibility were obtained. To obtain a convenient tool that is applicable in practice, a nomogram has been developed on the basis of the dependences obtained experimentally. It was also determined that, after reaching the maximum values of sediment formation with a further increase in the content of n-paraffins, saturation is observed, and the value of the sediment content remains at the same level. Maximum total sediment values have been found to depend on asphaltene content and do not significantly exceed them within 10%. The results of the research presented in this article allow laboratory and calculation to determine the possibility of incompatibility and to preserve the quality of marine residual fuels.publishedVersio

Technique for calculating technological parameters of non-Newtonian liquids injection into oil well during workover

Technique for automated calculation of technological parameters for non-Newtonian liquids injection into a well during workover is presented. At the first stage the algorithm processes initial flow or viscosity curve in order to determine rheological parameters and coefficients included in equations of rheological models of non-Newtonian fluids. At the second stage, based on data from the previous stage, the program calculates well design and pump operation modes, permissible values of liquid flow rate and viscosity, to prevent possible hydraulic fracturing. Based on the results of calculations and dependencies, a decision is made on the necessity of changing the technological parameters of non-Newtonian liquid injection and/or its composition (components content, chemical base) in order to prevent the violation of the technological operation, such as unintentional formation of fractures due to hydraulic fracturing. Fracturing can lead to catastrophic absorptions and, consequently, to increased consumption of technological liquids pumped into the well during workover. Furthermore, there is an increased risk of uncontrolled gas breakthrough through highly conductive channels

Technology for Improving the Efficiency of Fractured Reservoir Development Using Gel-Forming Compositions

Increasing the field development efficiency of fractured reservoirs is a contemporary issue. This paper presents fundamental and exploratory research results in this field using modern high-tech experimental equipment from the “Arctic” Scientific Centre at the Saint Petersburg Mining University. Oil reserves in fractured reservoirs are enormous; however, they are classified as hard-to-recover. The before-mentioned reservoirs require a specific approach when selecting technologies to improve the efficiency of their development. In this paper, as a solution to the problem under discussion, we propose the use of a physicochemical method of developing fractured reservoirs based on the injection of a water shut-off agent to exclude highly permeable water-conducting fractures from the drainage process. This technology makes it possible to effectively include and develop previously undrained reservoir areas by directly controlling their filtration properties with the use of new highly efficient and ecologically safe chemical reagents and process fluids

Technology for Improving the Efficiency of Fractured Reservoir Development Using Gel-Forming Compositions

Increasing the field development efficiency of fractured reservoirs is a contemporary issue. This paper presents fundamental and exploratory research results in this field using modern high-tech experimental equipment from the “Arctic” Scientific Centre at the Saint Petersburg Mining University. Oil reserves in fractured reservoirs are enormous; however, they are classified as hard-to-recover. The before-mentioned reservoirs require a specific approach when selecting technologies to improve the efficiency of their development. In this paper, as a solution to the problem under discussion, we propose the use of a physicochemical method of developing fractured reservoirs based on the injection of a water shut-off agent to exclude highly permeable water-conducting fractures from the drainage process. This technology makes it possible to effectively include and develop previously undrained reservoir areas by directly controlling their filtration properties with the use of new highly efficient and ecologically safe chemical reagents and process fluids

Improving the efficiency of oil well killing at the fields of the Volga-Ural oil and gas province with abnormally low reservoir pressure

Актуальность исследования обусловлена недостаточной технологической эффективностью применяемых на месторождениях Волго-Уральской нефтегазоносной провинции составов глушения для подземного ремонта скважин. Вязкость растворов на забое скважины не является достаточной и пропускает фильтрат жидкости глушения сквозь пласт, что приводит к поглощению технологической жидкости и кольматации призабойной зоны пласта. Недостаточные показатели критического напряжения сдвига также влияют на эффективность операций глушения, поскольку малые значения напряжения сдвига говорят об излишней подвижности технологической жидкости в стволе скважины. Цель: сравнить свойства разработанного полимерного состава глушения со свойствами уже применяемого состава с аналогичным принципом действия, а также сравнить свойства разработанного нефтяного геля со свойствами инвертно-эмульсионного раствора, применяемого на месторождениях. Сделать вывод о полученных данных для новых композиций в сравнении со старыми. Методы: имитация пластовых процессов, помещение существующих составов глушения в установки, создающие пластовые условия, и дальнейшее измерение их свойств. Проведение аналогичных операций с новыми составами для проверки сходимости результатов. Анализ полученных данных, сравнение свойств различных составов между собой. Объекты: жидкости глушения скважин, применяемые на месторождениях Волго-уральской нефтегазоносной провинции, а также разработанные полимерные составы и жидкости на углеводородной основе. Результаты. Получены сравнительные характеристики основных свойств блокирующих составов, такие как: скорость коррозии, эффективная вязкость, комплексная вязкость, статическое напряжение сдвига, предельное напряжение сдвига, а также время деструкции. Полученные результаты позволяют рекомендовать разработанные составы для применения на месторождениях Волго-Уральской нефтегазоносной провинции.The relevance of the research is caused by the insufficient technological efficiency of the killing compositions used in the fields of the Volga-Ural oil and gas province for underground workover of wells. The solutions' viscosity at the bottom of the well is not sufficient and passes the killing fluid filtrate through reservoir, which leads to the absorption of the process fluid and clogging of the bottomhole formation zone. Insufficient values of critical shear stress also affect the efficiency of killing operations. Low values of shear stress indicate excessive mobility of the process fluid in the wellbore. The main aim of the research is to compare the properties of the developed polymer killing composition with the properties of the already used composition with a similar mode of action, as well as compare the properties of the developed oil gel with the properties of invert emulsion solution used in the fields. Another aim is making a conclusion about the data obtained for new compositions in comparison with the old ones. Objects: well killing fluids used in the fields of the Volga-Ural oil and gas province, as well as developed polymer compositions and hydrocarbon-based fluids. Methods: imitation of reservoir processes, placement of existing killing compounds in installations that create reservoir conditions and further measurement of their properties; carrying out similar operations with new compositions to check the convergence of the results; analysis of the data obtained, comparison of the properties of various compositions with each other. Results. The authors have obtained the comparative characteristics of the main properties of blocking compositions, such as: corrosion rate, effective viscosity, complex viscosity, static shear stress, ultimate shear stress, and degradation time. The results obtained allow us to recommend the developed compositions for use in the fields of the Volga-Ural oil and gas province

Well Killing Technology before Workover Operation in Complicated Conditions

Well killing is an important technological stage before conducting workover operation, one of the tasks of which is to preserve and restore the natural filtration characteristics of the bottomhole formation zone (BFZ). Special attention should be paid to the choice of well killing technologies and development of wells in complicated conditions, which include abnormally low reservoir pressure, high oil-gas ratio and carbonate reservoir type. To preserve the filtration characteristics of the productive formation and prevent fluid losses in producing wells during well killing operation, blocking compositions are used. At the same time, an informed choice of the most effective well killing technologies is required. Consequently, there is a need to conduct laboratory physicochemical and coreflood experiments simulating geological, physical, and technological conditions of field development, as similar as possible to actual reservoir conditions. The article presents the results of experimental studies on the development well killing technologies of producing wells during workover operation in various geological, physical, and technological conditions of oil field development. Physicochemical and coreflood laboratory experiments were carried out with the simulation of the processes of well killing and development of wells in reservoir conditions with the use of modern high-technology equipment in the Enhanced Oil Recovery Laboratory of the Department of Development and Operation of Oil and Gas Fields at St. Petersburg Mining University. As a result of the experimental studies, new compositions of well killing and stimulation fluids were developed, which ensure to prevent fluid loss, gas breakthrough, as well as the preservation, restoration and improvement of the filtration characteristics of the BFZ in the conditions of terrigenous and carbonate reservoirs at different stages of oil field development. It is determined that the developed process fluids, which include surfactants (YALAN-E2 and NG-1), have a hydrophobic effect on the porous medium of reservoir rocks, which ultimately contributes to the preservation, restoration and improvement of the filtration characteristics of the BFZ. The value of the presented research results is relevant for practice and confirmed by the fact that, as a result of field tests of the technology for blocking the BFZ with the composition of inverse water–oil emulsion during well killing before workover operation, an improvement in the efficiency of wells operation was obtained in the form of an increase in their oil production rate by an average of 5–10 m3/day, reducing the time required for the well to start operating up to 1–3 days and reducing the water cut of formation fluid by 20–30%

Well Killing Technology before Workover Operation in Complicated Conditions

Well killing is an important technological stage before conducting workover operation, one of the tasks of which is to preserve and restore the natural filtration characteristics of the bottomhole formation zone (BFZ). Special attention should be paid to the choice of well killing technologies and development of wells in complicated conditions, which include abnormally low reservoir pressure, high oil-gas ratio and carbonate reservoir type. To preserve the filtration characteristics of the productive formation and prevent fluid losses in producing wells during well killing operation, blocking compositions are used. At the same time, an informed choice of the most effective well killing technologies is required. Consequently, there is a need to conduct laboratory physicochemical and coreflood experiments simulating geological, physical, and technological conditions of field development, as similar as possible to actual reservoir conditions. The article presents the results of experimental studies on the development well killing technologies of producing wells during workover operation in various geological, physical, and technological conditions of oil field development. Physicochemical and coreflood laboratory experiments were carried out with the simulation of the processes of well killing and development of wells in reservoir conditions with the use of modern high-technology equipment in the Enhanced Oil Recovery Laboratory of the Department of Development and Operation of Oil and Gas Fields at St. Petersburg Mining University. As a result of the experimental studies, new compositions of well killing and stimulation fluids were developed, which ensure to prevent fluid loss, gas breakthrough, as well as the preservation, restoration and improvement of the filtration characteristics of the BFZ in the conditions of terrigenous and carbonate reservoirs at different stages of oil field development. It is determined that the developed process fluids, which include surfactants (YALAN-E2 and NG-1), have a hydrophobic effect on the porous medium of reservoir rocks, which ultimately contributes to the preservation, restoration and improvement of the filtration characteristics of the BFZ. The value of the presented research results is relevant for practice and confirmed by the fact that, as a result of field tests of the technology for blocking the BFZ with the composition of inverse water–oil emulsion during well killing before workover operation, an improvement in the efficiency of wells operation was obtained in the form of an increase in their oil production rate by an average of 5–10 m3/day, reducing the time required for the well to start operating up to 1–3 days and reducing the water cut of formation fluid by 20–30%