In this paper we present the results of studies of the Botuobin, Talakh, and Khamakin reservoirs of the Vendian period in the Chayanda hydrocarbon field (Eastern Siberia). Based on an analysis of ...variations in the petrophysical parameters of reservoirs upon an increase in effective pressure from 37 to 57 MPa, i.e., under conditions simulating the development of a field for depletion, changes in the volume and compressibility of the pore space are estimated. In this case, the porosity coefficient decreases by 0.043 abs. %, while the compressibility of the pore space decreases by 0.228 1/GPa. The average volumetric compression strain increases by 0.096%, which means a reduction in the volume of developed reservoirs by almost 0.1% relative to the beginning of development. A deformable formation model developed by Yu.O. Kuzmin based on the geodynamic history of the development of deposits is applied to estimate the magnitude of possible subsidence of the ground surface during development. The maximal values of possible surface subsidence (drawdowns) upon a decrease in reservoir fluid pressure by 5 MPa are estimated to be 0.33 m with allowance for the dynamics of petrophysical parameters and 0.335 m with no allowance for it. The maximal drawdowns are already estimated at 0.60 and 0.65 m upon a decrease in reservoir pressure by 10 MPa and 0.78 and 0.83 m upon a complete depletion of reservoir energy, respectively. The results of the studies show that taking into account the changes in petrophysical characteristics caused by the field development processes alters the estimate of the deformation state of the rock massif and the ground surface above the deposit and, consequently, the estimate of the level of geodynamic risk of oil-and-gas complex objects.
Abstract
Modern information technology makes it easier to control and adequately assess the performance of marine equipment and, specifically, the elements of ship power plants, since they deliver ...efficient technical diagnostic services. The paper proposes the structure and principles of constructing a monitoring and diagnostic system to keep track of elements of ship power plants, enabling to solve current problems facing technical diagnostic systems.
Abstract
The acceleration of internal combustion engines leads to an increase in thermal and mechanical loads on the most critical parts. To ensure the required resource indicators in conditions of ...increased loads, it is necessary to use high-quality lubricants, the requirements for the operational properties of which are also steadily increasing. In order to ensure the necessary physical and chemical characteristics of engine oils, additives are introduced into their composition, but during operation the quality of engine oil decreases, the reasons for this are both the destruction of additives, and the accumulation of dirt particles in the oil and the ingress of fuel and coolant into the oil. The conducted studies are devoted to determining the intensity of engine oil contamination under operating conditions in the Wärtsilä 6L20 engine lubrication system and the effectiveness of the dispersing additives contained in the oil. Samples of Petro Canada and TARO oils brands were used as prototypes at the beginning of the operational period, at the time of average operating time and at the time of oil change. The dispersing ability of the oil was determined by the method of assessing the oil stain. According to the results of the research, it is concluded that when the properties of the oil change as a result of contamination, their dispersing ability remains satisfactory. This result can serve as a justification for extending the service life of engine oil, provided that its properties are monitored during operation.
Abstract
A prerequisite for the long-term and safe operation of marine diesel engines is the high quality of operational materials, which include engine oils and coolants. The required quality of ...operational materials is ensured by the introduction of additives into their composition, which are now increasingly used as nanoparticles. During operation, as a result of the destruction of additives, the operational properties of coolants and engine oils deteriorate. The conducted studies allowed us to evaluate the change in the lubricating ability of engine oils of two brands that are used in marine diesels during operation. As a characteristic of the lubricating ability of the oil, its kinematic viscosity was used. The experimental determination of the kinematic viscosity of engine oil samples having different periods of operation, and the subsequent mathematical processing of the experimental results made it possible to determine the dependencies characterizing the change in the kinematic viscosity of engine oil during its operation. The research results confirm the possibility of scientific justification for extending the use of marine diesel engine oils, which reduces operating costs and increases the environmental safety of marine diesel engines.
This paper presents the results of measurement and calculation within an upgraded Zuber model of critical heat flux (CHF) during nucleate boiling in thin horizontal layers of liquid. The layer height ...was increased in regimes of developed nucleate boiling. The two-phase layer was foam with vapor columns ascending at the corners of a rectangular square lattice. In the calculations, the foam was considered as an isotropic homogeneous system. The model assumes that the diameter of the vapor columns and the critical Helmholtz instability wavelength are independent of the foam density and are determined by the length of the most dangerous Rayleigh--Taylor instability wavelength. The proposed model fits the CHF experimental data for boiling liquid and can explain the CHF decrease in solutions with addition of surfactants that increase foaming.
The research was aimed at deriving an equation for calculating the degree of moisture filling of pore spaces of centrifuged sediments with capillary fringe filtrate. The previously derived analytical ...equation does not take the gas pressure in the centrifuge into account. To take account of the gas pressure, a modification of the equation for calculating the limiting pore diameter determined from the limiting force equilibrium between the fringe capillary forces and the sum of inertial centrifugal forces in combination with forces of gas pressure is proposed. In the example of calculation, cases of formation of a two-layer capillary fringe (with a base layer saturated with the filtrate and an unsaturated fringe layer) and a single-layer capillary fringe were considered. The calculation results showed agreement between the calculated moisture content curves and the experimental data. The obtained data are required for purposeful changes in the parameters of mechanical drying for reducing or increasing the degree of moisture filling of the sediment.
The analysis of the heat transfer investigation results has been carried out at boiling and evaporation in thin horizontal layers of liquid on smooth and structured surfaces. Intensive evaporation of ...thermal plumes at reduced pressure is considered to be the basic mechanism of heat transfer. The thermal plumes could make a significant contribution in heat transfer under conditions of bubble boiling on micro-structured and ribbed surfaces in the areas where vapour bubbles don't emerge.
•Decomposition boundaries of Sr2Mg1−xNixMoO6−δ (SMNMO) at reduction were determined.•Ab initio simulations predict stability of cubic structure at high temperature.•Defect formation enthalpies for ...Sr2Mg1−xNixMoO6−δ are calculated.•New mechanism of SMNMO electrical conductivity in reducing environments was suggested.
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The computational modeling within a density functional theory was applied for simulations of electronic spectra and calculations of structural and energy characteristics of the cubic double perovskite oxides Sr2Mg1−xNixMoO6–δ, where x = 0, 0.5, and 1. The oxygen stoichiometric molybdates are antiferromagnetic semiconductors with an energy gap near 2 eV. The energy-based arguments show that anti-site cation disorder may contribute to the structural stability of the molybdates. It is found that nickel doping is favorable for mitigated chemical expansion. The replacement of magnesium by nickel is accompanied by the contribution of Ni3d states to the valence band while leaving hybrid Mo4d-O2p states in the conduction band virtually unchanged. It is shown that the compounds under study are thermodynamically unstable in heavily reducing conditions which is confirmed by experimental results. The appearance of oxygen deficiency in Sr2Mg1−xNixMoO6–δ results in the formation of oxygen vacancy associated donor states near the bottom of the conduction band and the transition from the intrinsic to degenerate semiconductor. It is suggested that the influence of nickel dopants on the energy and density of the donor states may help to explain variations of the conducting properties with doping level.
Three explicit time integration schemes are compared for solving nonlinear heat conduction problems, local iteration monotone scheme, nonlinear exponential Euler scheme and a scheme based on the ...hyperbolic model of heat conduction, where an artificial second order time derivative term is added to stabilize the computations. The local iteration monotone and exponential Euler schemes are monotone and allow for a sufficiently large time step size. The local iteration monotone scheme is based on a special Chebyshev polynomial approximation, whereas the exponential Euler scheme employs a restarted Krylov subspace procedure. For these two schemes we propose an adaptive time step selection strategy which leads to a significant reduction in computational costs.
The use of mixtures as refrigerants and heat carriers in various power systems has become widespread. The thermophysical properties of mixtures differ from the properties of their components. This ...paper presents the results of a study of the intensity of heat transfer to a non-azeotropic alcohol-water mixture with weight concentration of the volatile component of 20% during forced circulation in a heated smooth circular channel, as well as in a channel with spiral intensifiers with a hydrophobic coating. The experiments were carried out on a closed circulation circuit at a pressure in the storage vessel of 0.04–0.055 MPa. The test section was a stainless steel tube with inner diameter of 7.6 mm and wall thickness of 0.2 mm. The heating was provided due to the electric current passed in the tube wall. The spiral intensifiers had winding pitch of 4 mm; the thickness of the PTFE sleeve was 0.9 mm. The experiments were carried out at mass flux rates of 44–46 kg/m
2
and 316 kg/m
2
. The heat flux density varied in the range
W/m
2
. The use of the spiral intensifiers with the hydrophobic coating during circulation of the non-azeotropic alcohol-water mixture (20%) in the circular channel led to the formation of a significant amount of the vapor-gas phase in the flow at channel wall temperatures below the saturation point of this mixture. The heat transfer coefficient in the channel with the intensifiers grew 2–5 times compared with those in a smooth channel.
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