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Date submitted2022-05-03
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Date accepted2022-11-22
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Date published2023-02-27
Development of methodology for scenario analysis of investment projects of enterprises of the mineral resource complex
Theoretical and applied aspects of scenario analysis of investment projects of enterprises in the mineral resource sector of the economy are considered, its advantages and disadvantages are analyzed. Taking into account the organizational and economic features of mineral resources management, a number of new modifications of the scenario analysis method, aimed at solving an urgent problem - reducing the information uncertainty in assessing the expected efficiency and risk of investment projects, are proposed. The peculiarity of the proposed new modifications is the use of the interval-probabilistic approach in the implementation of the scenario analysis procedure. This approach is based on a moderately pessimistic system of preferences in obtaining point values of the investment project initial parameters. Fishburn estimates and the hierarchy analysis method were used to reduce subjective uncertainty. The maximum likelihood values in the sense of the maximum a priori probability are used as expected estimates. An additional indicator of risk assessment, which characterizes the probability of the event that the net present value of the project will take a value less than the specified one, is proposed. When analyzing one project, this indicator is more informative than the standard deviation. A statistical hypothesis was tested on the improvement of the validity of investment decisions developed using the modified scenario analysis method compared to the standard method.
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Date submitted2020-05-21
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Date accepted2020-10-05
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Date published2020-11-24
Method of calculating pneumatic compensators for plunger pumps with submersible drive
- Authors:
- Eduard O. Timashev
One of the most promising ways to improve the efficiency of mechanized oil production is a plunger pump with a submersible drive, which allows obtaining harmonic reciprocating movement of the plunger. In the pumping process of well products by plunger pumps, oscillations in the velocity and pressure of the liquid in the lifting pipes occur, which lead to an increase in cyclic variable loads on the plunger, a decrease in the drive life period and the efficiency of the pumping unit. To eliminate the pulsation characteristics of the plunger pump and increase the reliability indicators of the pumping unit (in particular, the overhaul period), pneumatic compensators can be used. A method for calculating the optimal technological parameters of a system of deep pneumatic compensators for plunger pumping units with a submersible drive, based on mathematical modeling of hydrodynamic processes in pipes, has been developed. Calculations of the forming flow velocity and pressure in the lifting pipes of submersible plunger units equipped with pneumatic compensators (PC) have been carried out. Influence of the PC technological parameters on the efficiency of smoothing the oscillations of velocity and pressure in the pipes has been analyzed. Non-linear influence of the charging pressure and PC total volume on the efficiency of their work has been established. Optimal pressure of PC charging, corresponding to the minimum pressure in the tubing during the pumping cycle for the considered section of the tubing, is substantiated. Two ultimate options of PC system placement along the lifting pipes are considered. In the first option, PC are placed sequentially directly at the outlet of the plunger pump, in the second - evenly along the lift. It is shown that the first option provides the minimum amplitude of pressure oscillations at the lower end of the tubing and, accordingly, variable loads on the pump plunger. Nature of the pressure and flow velocity oscillations in the tubing at the wellhead for both options of PC placement has similar values .
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Date submitted2020-01-09
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Date accepted2020-01-20
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Date published2020-02-25
Mechanical Properties of Sandstone using non-Destructive Method
- Authors:
- H. Rajaoalison
- A. Zlotkowski
- G. Rambolamanana
The understanding of physical and mechanical properties of rock is considered as critical in drilling, geo-engineering, and construction applications. As an example, the awareness of these rock parameters contributes to avoid or minimizing instability around the wellbore while drilling. The laboratory experiment of understanding of these parameters can be done in two-different ways: static, where the sample subjects to destruction after the test and dynamic, known as non-destruction method. The non-destructive method using ultrasonic waves under a series of different stress conditions, starting from 7 to 56 MPa with incrementation of 7MPa, has been used in this paper in order to characterize the mechanical properties of dry Zbylutów sandstone at 20 and 80°C. The velocity of primary (P) and secondary (S) waves within these ranges has been recorded in order to understand the behavior of the mechanical properties. The results showed that the Young’s modulus, bulk modulus, shear modulus, and Lame’s constant of Zbylutów sandstone have a positive correlation with good coefficient correlation with the increased stress, while the Poisson’s ratio showed a negative correlation. Besides, the effect of temperature on the rock parameters is approved by the decrease of primary wave velocity in this two-different temperature range. Such results are necessary when preparing the appropriate mud weight for drilling process, which is related to wellbore instability.
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Date submitted2018-05-06
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Date accepted2018-07-17
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Date published2018-10-24
Obtaining intermetallic compounds in Al–Ti–Zn system
- Authors:
- V. V. Kaminskii
- S. Y. Petrovich
- V. A. Lipin
Binary intermetallic compounds – titanium aluminides (TiAl, Ti 3 Al) – when added to the alloys, significantly increase their strength and special properties. The most promising direction to produce intermetallic compounds are mechanochemical technologies, including mechanical alloy building. Mechanical alloying makes it possible to introduce much smaller particles into the metal matrix than can be achieved using standard powder metallurgy technologies. In addition to mechanical synthesis, aluminum-based intermetallic compounds were produced by self-propagating high-temperature synthesis (SHS) of solid chemical compounds. The synthesis was carried out according to a multistage scheme: preparation of titanium and aluminum powder, mixing; synthesis of the Al 3 Ti intermetallic compound by the SHS method in vacuum followed by mechanical activation of stoichiometric charges. The aim of the research was to study the dynamics of the development of nanodispersed phases in the process of synthesis during mechanical alloying. The power absorbed by the unit mass of the material for different processing times of the charge was calculated. When the level of the specific power (dose) of mechanical treatment was 3.5 kJ/g, the maximum content of intermetallic compound in the resulting material was achieved. Based on calculations and the data obtained during X-ray phase analysis, the dependence of the change in the content of ternary intermetallic compounds in the final product on the absorbed power was determined. As a result of the studies using raster electron microscopy and X-ray analysis, it was found that mechanical alloying of nanostructured intermetallic compounds Ti 4 ZnAl 11 and Ti 25 Zn 9 Al 66 with the size of nanodisperse phases less than 12 nm in the Al–Ti–Zn system, the weight ratio of proportion of the latter reaches 74 %.
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Date submitted2018-05-04
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Date accepted2018-07-23
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Date published2018-10-24
Analysis of possible enhancementof properties of VK15 material used for drilling tools
- Authors:
- Yu. A. Kurganova
- K. S. Panina
- P. S. Beshenkov
Traditionally, when drilling hard and abrasive rocks, it is recommended to use a tungsten-cobalt hard alloy VK15. The analysis of information on the possibility of improving the potential of the material has demonstrated the existence of mechanisms that provide structural transformations that enhance its strength, hardness and toughness. The use of such technology instead of traditional methods will lead to an increase in the operating efficiency and durability of the tool. During the work, experimental samples of alloy VK15 were obtained by sintering in four different modes. Then their properties were analyzed. The results of the metallographic study carried out on the «Carl Zeiss» microscope made it possible to estimate the distribution of tungsten carbide grains in cobalt bon and show the grinding of the carbide phase. Thus, with traditional sintering, the amount of tungsten carbide grains with an average size of less than 1 μm in diameter from the entire size range reaches 19.5 %, while after additional heat treatment with a holding time of 1280 °C, the value was 41.5 %; 900 °C – 59.1 %; 600 °С – 54.5 %. The maximum improvement results were the following: hardness by 18 %, a coercive force by 49 %, and crack resistance by 11 % of the traditional alloy, there were achieved at 900-1280 °C. A hypothesis has been put forward on the formation of additional structural elements not detected by the methods of optical metallography. Studies of the topology and structure of the samples on an atomic force microscope confirmed the presence of nanoscale inclusions from 20 to 40 nm (presumably tungsten carbide) in a cobalt bond.For VK15, comparative studies of properties and analysis of the microstructure of experimental samples obtained by the traditional sintering and modified technology have shown that the sintering mode at 900 °C is a priority.
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Date submitted2015-10-18
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Date accepted2015-12-01
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Date published2016-08-22
Effect of surface geometry and insolation on temperature profile of green roof in Saint-Petersburg environment
- Authors:
- S. A. Ignatev
- D. S. Kessel
The paper addresses an issue of creating an environment favorable for the life in megacities by planting vegetation on the rooftops. It also provides information about rooftop greening practices adopted in other countries. The issues of ‘green roof’ building in climatic conditions of Saint Petersburg and roof vegetation impact on the urban ecosystem are examined. Vegetation composition quality- and quantity-wise has been proposed for the roof under research and a 3D model of this roof reflecting its geometric properties has been developed. A structure of roof covering and substrate qualitative composition is presented. An effect of rooftop geometry on the substrate temperature is explored. The annual substrate temperature and moisture content in different parts of the roof have been analyzed. Results of thermal imaging monitoring and insolation modelling for different parts of green roof surface are presented.
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Date submitted2010-07-16
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Date accepted2010-09-06
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Date published2011-03-21
The aboveground oil pipeline temperature regimes calculation
- Authors:
- S. Yu. Trapeznikov
The theoretical and experimental investigations of the highviscosity oil transportation temperature regimes to improve the pipeline efficiency are caused by the insufficient knowledge of its heat transfer process. The dependencies for the hydraulic resistance coefficient and the dimensionless heat transfer coefficient of Nusselt are proposed.