Zarubezhneft

In the work, an ultrafine-grained (UFG) state was formed in a low-carbon steel by equal-channel angular pressing (ECAP) (8 passes, 200 °С), demonstrating high mechanical properties (yield strength is 1021 MPa, tensile strength is 1072 MPa, ductility is 10.7 %) along with satisfactory corrosion resistance (0.345 mm/year). To explain the reasons for improvement of strength properties and changes in corrosion properties, UFG steel microstructure was analysed using electron microscopy and X-ray scattering methods. Specifically, electron microscopy methods revealed structural refinement of ECAP-processed steel, resulting in the formation of equiaxed grains averaged ~240 nm in size. Modified Williamson–Hall and Warren–Averbach X-ray procedures were applied to find the patterns of changes in coherent scattering domains size, density ρ and fraction fs of screw-type dislocations, effective outer cut-off radius Re of dislocations and some other parameters of low-carbon steel depending on a number of ECAP passes (degree of deformation). X-ray diffraction analysis and small-angle X-ray scattering methods were used to determine evolution trends of mass fraction, size and morphology of various precipitates depending on the number of ECAP passes. Based on the obtained data, a model of microstructure transformation during UFG state formation in steel was proposed. Furthermore, strengthening mechanisms of both coarse-grained and UFG steels were discussed. It was found that in initial state, steel strength was primarily ensured by grain-boundary strengthening and precipitation of small Ме23С6 and Ме3С2 precipitates. It was shown that during UFG structure formation, steel strength increases due to grain-boundary strengthening and dislocation density increase. The contribution of precipitates in the UFG state to the strengthening decreases and this is due to their growth during ECAP processing. It was found that an increase in corrosion rate of UFG steel results from a decrease in ferrite grain size, an increase in grain-boundary dislocations density and a cellular structure formation.

The crystal chemical characteristics and causes of their variations in the weakly and strongly modified by epigenetic processes dolomites of the Middle Riphean Avzyan Formation in the Bashkir meganticlinorium have been determined. The studies were accomplished by the X-ray diffraction, X-ray fluorescence, and SEM/EDS analysis methods. The Avzyan dolomites are marked by increased parameters of the crystal lattice (aav = 4.8105 Å, cav = 16.0211 Å) and reduced values of the substructural reflection (Kav = 0.66) in comparison with stoichiometric dolomites. The average content of elements is as follows: Fe(II) 4545 ppm, Mn 423 ppm, and Sr 124 ppm. Increase in parameters of the crystal lattice of the Avzyan dolomites shows direct correlation with increase in the contents of Fe and Mn, whereas values of the substructural reflection have an inverse correlation. Rocks of all studied sections include two generations of dolomite and calcite. The calcite–dolomite veinlets were formed at 260–530°C and 0.3–2.3 kbar. In dolomites of different subformations, the average value of parameters of the crystal lattice a and c decreases from the early (Kataskin subformation) to the late Avzyan (Tyul’men subformation). In the same direction, average values of the coefficient K of the dolomite structure ordering increase. Dolomites of different stratigraphic levels of the Avzyan Formation underwent intense epigenetic transformations caused by the impact of medium- and high-temperature Fe- and Mn-containing fluids on rocks. Change in the crystal chemical characteristics of the Avzyan dolomites is associated not so much with the process of regional metamorphism, as with the activity of postmagmatic (sections near the Veselovka Settlement and on the Tyul’men River) and catagenetic (sections near the Islambaevo Settlement and on the Bol’shoi Avzyan River) of fluids, which percolated along the fracture zones.

Гидравлические расчеты являются частью разнообразного инженерного программного обеспечения во многих областях, включая нефтегазодобычу. Повышение эффективности их численной реализации важно для решения практических обратных задач восстановления неизвестных параметров многих процессов. Целью данной работы является снижение алгоритмической сложности расчета изменяющегося во времени перепада давления при движении смеси в трубе при известных параметрах смеси. Рассматриваются задачи расчета изменения гидростатического давления и потери давления на трение для заданной зависимости удельных потерь давления на трение от расхода. Показано, как за счет правильного выбора переменных можно свести расчет потерь давления на трение к алгоритму линейной сложности, а расчет гидростатического давления — к алгоритму линейно-логарифмической сложности от размерности входных данных. Hydraulic calculations play an important role in a variety of engineering software in many areas, including oil and gas production. Increasing the efficiency of their numerical implementations is important for solving practical inverse problems of recovering unknown parameters of many processes. The purpose of this work is to reduce the algorithmic the complexity of calculating the time-varying pressure drop of slurry on its way through the tubing, given the slurry and the tubing parameters. Hydrostatic pressure and frictional pressure loss are being calculated as functions of specific friction pressure losses, tubing geometry and slurry pumping schedule. The correct choice of variables, introduced in this paper, allows to reduce the algorithmic complexity of the friction pressure loss to linear while hydrostatic pressure to linear-logarithmic complexity on the input data dimensions.

Due diligence in the field of VAT in the age of digitization. Purpose: The purpose of this chapter is to present the possibilities of using IT tools and databases by a taxpayer exercising due diligence. The most important circumstances that will be taken into account by tax officials in the assessment of entrepreneurs’ activities in VAT settlements are presented in the document Methodology for assessing due diligence by buyers of goods in domestic transactions, which is why this document is presented in this chapter. Selected IT tools and databases are also discussed useful in verifying contractors and transactions. Design/methodology/approach: To achieve the purpose, the documents published by the Ministry of Finance was used. In addition, information available on the Internet about search engines and databases was used. Information obtained during various meetings and trainings with taxpayers was also used. Findings: Based on the analysis, it can be concluded that the taxpayer can verify the contractor and partly the transaction using publicly available databases and IT tools. For a taxpayer who wants to exercise due diligence, it is useful to know the Methodology and know about the available sources of information and how to use them.

The paper considers the issues of the development of Bobrikovsko-Radaevsky and Tula formations among the Arlansky and Yugomashevsky oilfields, which are classic examples of the development of terrigenous reservoir. The analysis of the operational parameters was carried out for horizontal wells that were drilled into the terrigenous part of the Lower Carboniferous formations. There is a problem of premature flooding of the wells, which has low specific production rate of recoverable reserves. The displacement characteristics are similar to the typical displacement characteristics for a reservoir with an active aquifer based on analogy analysis. According to the results of the calculations performed, it was revealed that the time to achieve critical water cut is affected by the volume of oil equal to the volume of the half-cylinder figure with a radius equal to the distance between the wellbore tracing and the position of the oil-water contact, as well as the fluid rate. Achieving ater cut for wells with active bottom waters is a natural process of formation development within the downhole zone volume. The influence of downhole pressure on displacement characteristics for wells from different groups was studied. Wells were grouped according to the liquid rate, and it was shown that the displacement characteristics are improving for a group of wells with increasing liquid rate. Keywords: terrigenous reservoir; oil; oilfield; horizontal well; water cut; fluid flow rate; forced extraction; bottom water; displacement characteristics.

The results of three-dimensional poroelastic modeling of the junction area of multilateral boreholes for wellbore stability estimation of the fishbone are presented. The situations with the main wellbore orientation along with the minimum and the maximum horizontal stresses in sandstone with character and reduced strength were considered. The ranges of permissible depression on the reservoir are determined for the fishbone in production mode. When it is planned to conduct the sidetrack in the sandstone with reduced strength, the safe mud pressure exceeding the pore pressure was defined. It was shown that in the case of the formation of a mud cake on the wellbore walls, the pressure drop could be reduced by 40% with junction area stability preserving.