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Date submitted2024-03-20
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Date accepted2024-11-07
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Date published2025-02-27
Analysis of the stress state of rocks transformation near a horizontal well during acid treatment based on numerical simulation
The article presents an overview of the assessment and modelling of the stress state of rocks in the near-wellbore zone of horizontal wells during acid stimulation of the formation for improving the efficiency of oil and gas field development. A numerical finite element model of near-wellbore zone of the reservoir drilled by a horizontal section was compiled using one of oil fields in the Perm Territory as an example. The distribution of physical and mechanical properties of the terrigenous reservoir near the well was determined considering transformation under the action of mud acid for different time periods of its injection. Multivariate numerical simulation was performed and the distribution of horizontal and vertical stresses in near-wellbore zone was determined with regard for different values of pressure drawdown and changes in stress-strain properties depending on the area of mud acid infiltration. It was found that a change in elastic modulus and Poisson's ratio under the influence of acid led to a decrease in stresses in near-wellbore zone. Analysis of the stress distribution field based on the Coulomb – Mohr criterion showed that the minimum safety factor of rock even after the effect of mud acid was 1.5; thus, under the considered conditions of horizontal well modelling, the reservoir rock remained stable, and no zones of rock destruction appeared.
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Date submitted2023-10-31
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Date accepted2024-11-07
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Date published2025-01-24
Specifics of magnetotelluric studies in Antarctica
One of the priority areas of scientific research in Antarctica is the study of its deep structure. Most of the continent is covered with a thick ice sheet, so the main geoscientific data are acquired using geophysical methods, among which magnetotelluric (MT) ones have the greatest penetration depth and insignificant environmental impact. The possibility of acquiring high-quality MT data in the conditions of the sixth continent has long been questioned. The work is aimed at studying the specifics of magnetotelluric survey in Antarctica. The following tasks were set: to summarize the world experience of studying Antarctica using MT sounding methods; to identify factors that negatively affect the high-quality data acquisition; to determine methods for minimizing the influence of these factors. The article analyses geophysical studies conducted by the magnetotelluric sounding method in the Antarctic region from 1964 to the present. The application of the method is complicated by the following: extremely low temperature affects the drop in the batteries capacity, freezing of the non-polarizing electrodes solution, and changes in the strength properties of materials. Electromagnetic noise occurs during strong winds; proximity to the magnetotelluric field source can violate the plane wave principle on which the method is based. The ice sheet covering most of Antarctica does not allow acquiring optimal values of the contact resistance of the electrode grounding; the extended coastline distorts the acquired data. Studies of the influence of factors complicating the MT sounding method in the coastal and central parts of Antarctica made it possible to formulate recommendations for preparing equipment and adapting the work procedure, modifying the processing flow and a set of measures to ensure safety, the implementation of which will both allow safe performance of geophysical investigations and high-quality data acquisition.
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Date submitted2021-01-21
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Date accepted2023-09-20
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Date published2023-12-25
Adaptation of transient well test results
Transient well tests are a tool for monitoring oil recovery processes. Research technologies implemented in pumping wells provide for a preliminary conversion of measured parameters to bottomhole pressure, which leads to errors in determining the filtration parameters. An adaptive interpretation of the results of well tests performed in pumping wells is proposed. Based on the original method of mathematical processing of a large volume of field data for the geological and geophysical conditions of developed pays in oil field, multidimensional models of well flow rates were constructed including the filtration parameters determined during the interpretation of tests. It is proposed to consider the maximum convergence of the flow rate calculated using a multidimensional model and the value obtained during well testing as a sign of reliability of the filtration parameter. It is proposed to use the analysis of the developed multidimensional models to assess the filtration conditions and determine the individual characteristics of oil flow to wells within the pays. For the Bashkirian-Serpukhovian and the Tournaisian-Famennian carbonate deposits, the influence of bottomhole pressure on the well flow rates has been established, which confirms the well-known assumption about possible deformations of carbonate reservoirs in the bottomhole areas and is a sign of physicality of the developed multidimensional models. The advantage of the proposed approach is a possibility of using it to adapt the results of any research technology and interpretation method.
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Date submitted2023-07-04
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Date accepted2023-09-20
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Date published2023-10-27
Structure maintenance experience and the need to control the soils thermal regime in permafrost areas
- Authors:
- Anatolii V. Brushkov
- Andrei G. Alekseev
- Svetlana V. Badina
- Dmitrii S. Drozdov
- Vladimir A. Dubrovin
- Oleg V. Zhdaneev
- Mikhail N. Zheleznyak
- Vladimir P. Melnikov
- Sergei N. Okunev
- Aleksei B. Osokin
- Nikolai A. Ostarkov
- Marat R. Sadurtinov
- Dmitrii O. Sergeev
- Roman Yu. Fedorov
- Konstantin N. Frolov
The risks of reducing the stability of buildings and structures are increasing in conditions of climate change and the active development of the territories under the influence of natural and anthropogenic factors. The main causes include: loss of the bearing capacity of frozen soils, various geocryological processes, errors at the stages of design, construction and operation of facilities. Main actual task when conducting research and industrial operations in the cryolithozone is monitoring and, if necessary, managing thermal processes in the permafrost layers interacting with facilities. In this article the obtained positive experience of various technologies applying at various stages of the life cycle of civil and industrial facilities was analyzed. It helps to eliminate or prevent the structure deformation or destruction under the influence of climate change. The methods of permafrost stabilization used in the oil and gas industry in process of industrial infrastructure development of the fields have been studied – freezing (cooling) of foundation soils during construction on heterogeneous foundations. The solution to the problems of minimizing accidents when locating production wells in the permafrost zone of the Yamal Peninsula is considered using the example of an oil and gas condensate field and restoring of the temperature regime of perennial unfrozen soils in areas of valve units of main gas pipelines. An assessment of methods used to maintain the industrial and residential infrastructure within the northern municipalities that ensure the functioning of the fuel and energy complex of the Russian Federation in the Arctic was made. The systems of thermal stabilization in the foundations of buildings and industrial facilities built and operated on permafrost soils allow to fully use the high strength and low deformability of frozen grounds. It ensures the state's long-term plans of the industrial development in the Arctic.
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Date submitted2023-04-29
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Date accepted2023-10-11
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Date published2023-10-27
Pink-violet diamonds from the Lomonosov mine: morphology, spectroscopy, nature of colour
The article presents the results of the first comprehensive study of mineralogical and spectroscopic (IR, PL, EPR) characteristics of diamonds from the Lomonosov mine (Arkhangelskaya pipe) with a unique pink, pink-violet colour. It is shown that all crystals belong to the IaA type, with a total nitrogen content in the range of 500-1500 ppm, with a low degree of aggregation. The colour is heterogeneous, concentrated in narrow twin layers. It is presumably caused by the previously described M2 centres. The colour shade is affected by the content of P1 paramagnetic centres (C-defect). A positive correlation is observed between the colour saturation and the intensity of W7 paramagnetic centres. A convergent model of the formation of pink diamonds is assumed, according to which the determining factors are the ratio and concentration of structural impurities in the diamond, its thermal history, and conditions of plastic deformation, and not the origin of the diamond and the petrochemical properties of its host rocks.
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Date submitted2022-06-27
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Date accepted2023-06-20
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Date published2023-12-25
Analysis of the problems of high-quality drinking water extraction from underground water intakes on Vysotsky Island in the Vyborg district of the Leningrad region
This article presents the results of drilling, experimental filtration work and laboratory studies aimed at assessing the resources and quality of groundwater in the licensed area of Vysotsky Island located in the Leningrad region, in the Gulf of Finland in accordance with the requirements of regulatory documents. Analysis of the results of hydrochemical studies and their comparison with data on water intakes in adjacent areas gives the right to conclude that it is possible to classify a hydrogeological unit as a different type of resource formation than those located in the surrounding areas. Groundwater in this area is confined to an unexplored deep fractured regional high-pressure zone. According to the received data, the explored water intake can be attributed to a unique groundwater deposit, which has an uncharacteristic composition of groundwater in the north of the Leningrad region, which may be due to the mixing of modern sediments and relict waters of the Baltic glacial lake. The stability of groundwater characteristics is confirmed by long-term monitoring.
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Date submitted2022-06-20
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Date accepted2023-01-10
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Date published2023-08-28
Laboratory, numerical and field assessment of the effectiveness of cyclic geomechanical treatment on a tournaisian carbonate reservoir
Results are discussed for evaluation of effectiveness of the cyclic geomechanical treatment (CGT) on a Tournaisian carbonate reservoir. Analysis of laboratory experiments performed according to a special program to assess permeability changes for Tournaisian samples under cyclic changes in pore pressure is presented. The main conclusion is the positive selectivity of the CGT: an increase in permeability is observed for samples saturated with hydrocarbons (kerosene) with connate water, and maximal effect is related to the tightest samples. For water-saturated samples, the permeability decreases after the CGT. Thus, the CGT improves the drainage conditions for tight oil-saturated intervals. It is also confirmed that the CGT reduces the fracturing pressure in carbonate reservoirs. Using flow simulations on detailed sector models taking into account the results of laboratory experiments, a possible increase in well productivity index after CGT with different amplitudes of pressure variation was estimated. Results of a pilot CGT study on a well operating a Tournaisian carbonate reservoir are presented, including the interpretation of production logging and well testing. The increase in the well productivity index is estimated at 44-49 % for liquid and at 21-26 % for oil, with a more uniform inflow profile after the treatment. The results of the field experiment confirm the conclusions about the mechanisms and features of the CGT obtained from laboratory studies and flow simulations.
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Date submitted2021-05-27
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Date accepted2022-09-06
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Date published2022-11-10
Application of resonance functions in estimating the parameters of interwell zones
It is shown that the use of force resonance leads to the effect of “shaking” the formation, followed by breaking up the film oil and involving it in the further filtration process. For the first time in oilfield geophysics, the concept of passive noise-metering method is justified for monitoring oil and gas deposit development by measuring the quality factor of the contours in the point areas of formation development channels in interwell zones. It is established that determining the depth of modulation for the reactive substitution parameter of the linear FDC chain is crucial not only for determining the parametric excitation in FDC attenuation systems, but also without attenuation in the metrological support for the analysis of petrophysical properties of rock samples from the wells. It is shown that based on the method of complex amplitudes (for formation pressure current, differential flow rates, impedance), different families of resonance curves can be plotted: displacement amplitudes (for differential flow rates on the piezocapacity of the studied formation section), velocities (amplitudes of formation pressure current) and accelerations (amplitudes of differential flow rates on the linear piezoinductivity of the FDC section). The use of predicted permeability and porosity properties of the reservoir with its continuous regulation leads to increased accuracy of isolation in each subsequent sub-cycle of new segment formation in the FDC trajectories, which contributes to a more complete development of productive hydrocarbon deposits and increases the reliability of prediction for development indicators.
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Date submitted2022-04-29
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Date accepted2022-07-21
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Date published2022-11-10
Deep structure, tectonics and geodynamics of the Sea of Okhotsk region and structures of its folded frame
The use of the zonal-block model of the earth's crust for the construction of regional tectonic schemes and sections of the earth's crust based on a complex of geological and geophysical data makes it possible to consider the resulting maps and sections as tectonic models. The main elements of such models are blocks with an ancient continental base and interblock zones formed by complexes of island arcs, an accretionary prism, or oceanic crust. The developed geotectonic model of the Sea of Okhotsk region reflects the features of the deep structure, tectonics, and geodynamics. The Cimmerian Novosibirsk-Chukotka, Verkhoyansk-Kolyma, Kolyma-Omolon, and Amur folded regions and the Alpides of the Koryak-Kamchatka and Sakhalin-Sikhote-Alin folded regions are developed along the northern, western, and southern boundaries of the Sea of Okhotsk megablock with a continental crust type. From the east, the megablock is limited by oceanic basins and island arcs.
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Date submitted2022-04-04
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Date accepted2022-05-13
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Date published2022-07-13
Distribution of trace elements controlled by sector and growth zonings in zircon from a miaskite pegmatite of the Vishnegorsky massif, the Southern Urals
Data on the content and distribution of trace and rare-earth elements (SIMS method) in sectors and growth zones of a large zircon crystal from miaskite pegmatites of the Vishnegogorsky massif are presented. The morphology of the zircon crystal is a combination of a dipyramid {111} and prism {010}. It has been established that the growth sector of dipyramid {111} is characterized by almost one order of magnitude higher contents of Y, Nb, REE, Th; higher Th/U and Eu/Eu* values; REE distribution spectra are flatter compared to prism {010} growth sector. A regular decrease in the content of trace and rare-earth elements in the direction from the central zone to the marginal zone of crystal growth was revealed. A smooth regression of zircon crystallization temperature of zircon from 960 °C in the central zone to 740 °C in the marginal zone of the dipyramid sector and 700-650 °C in the prism sector has been revealed, which may be a reflection of thermal evolution of the crystallization process. It is assumed that crystallization of the central zone of zircon occurred at early stages from a relatively trace-еlement-rich melt. The crystallization was completed at lower temperatures, probably, simultaneously with the formation of REE-concentrating minerals, which resulted in natural decrease of content of trace and rare-earth elements in the melt and, consequently, in zircon crystallizing from it.
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Date submitted2021-07-07
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Date accepted2021-10-18
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Date published2021-12-16
Influence of hydraulic compression on porosity and permeability properties of reservoirs
Active development of hard-to-recover oil reserves causes the need for an innovative approach to methods of oil recovery and intensification of its production, based on taking into account the specifics of filtration processes in low-productive reservoirs and complex geological and physical conditions. Pilot works for studying the mechanism of changes in porosity and permeability properties of reservoirs during swabbing of wells are presented. Based on the hydrodynamic investigations performed, the results of the work are analyzed. The method of oil production intensification using hydraulic compression of formation has been developed. It has been shown that when using hydraulic compression technology in the pore space of the formation, the effect of capillary and gravitational forces is strongly reduced. The influence of these forces decreases when significant pressure gradients with changing direction are formed during well swabbing for depression impact on the bottomhole zone of the formation. Hydraulic compression induced an increase in well productivity and flow rate; insights into how how permeability and porosity properties change during well swabbing were clarified. The range of compressive durability (minimum and maximum values) was determined for the Verean deposits of the Melekeskaya Depression and the South Tatar arch. The impact of formation hydraulic compression caused changes in permeability and porosity properties of the reservoir in the bottomhole zone on a qualitative level. Piezo- and hydraulic conductivity increased by 20 %. Experimental work in well 1545 of Keremetyevskoe field showed an increase of piezo- and hydraulic conductivity coefficients, effective formation thickness, change of filtration flows character.
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Date submitted2020-10-26
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Date accepted2021-07-28
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Date published2021-10-21
Investigation of the influence of the geodynamic position of coal-bearing dumps on their endogenous fire hazard
The paper investigates the hypothesis according to which one of the factors influencing the spontaneous combustion of coal-bearing dumps is its geodynamic position, i.e. its location in the geodynamically dangerous zone (GDZ) at the boundary of the Earth crust blocks. This hypothesis is put forward on the basis of scientific ideas about the block structure of the Earth crust and the available statistical data on the location of burning dumps and is studied using computer modeling. A dump located in the area of Eastern Donbass was chosen as the object of research. The simulation results show that the penetration of air into the dump body from the mine through the GDZ, which crosses the mining zone, is possible at an excess pressure of 1000 Pa created by the main ventilation fans. The fire source appearance in the dump body causes an increase in the temperature of the dump mass and becomes a kind of trigger that "turns on" the aerodynamic connection between the dump and the environment, carried out through the GDZ. It is concluded that the establishment of an aerodynamic connection between the mine workings and the dump through the GDZ can be an important factor contributing to the endogenous fire hazard of coal-bearing dumps. The simulation results can be used in the development of projects for monitoring coal-bearing dumps and measures to combat their spontaneous combustion.
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Date submitted2020-09-09
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Date accepted2021-03-29
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Date published2021-09-20
Developing features of the near-bottomhole zones in productive formations at fields with high gas saturation of formation oil
The article studies the formation features of the bottomhole zones in productive formations during operation of production wells in the north of the Perm Territory. Their distinctive feature is the high gas saturation of formation oil. The most widely used parameter in Russian and world practice – the skin factor was used as a criterion characterizing the state of the bottomhole zone. Analysis of scientific publications has shown that one of the main problems of applying the skin factor to assess the state of bottomhole zones is the ambiguity of interpretations of its physical meaning and the impossibility of identifying the prevailing factors that form its value. The paper proposes an approach to identifying such factors in the conditions of the fields under consideration, based on multivariate correlation-regression analysis. Choice of this tool is due to the complexity of the processes occurring in the “formation – bottomhole zone – well” system. When describing complex multifactorial processes, the chosen method demonstrates a high degree of reliability. For a large number of wells in the region, significant material was collected and summarized, including the results of determining the skin factor (1102 values) during hydrodynamic investigations, as well as data on the values of various geological and technological indicators, which can probably be statistically related to the value of the skin factor. A series of multidimensional mathematical models has been built; the skin factor was used as a predicted parameter, and data on the values of geological and technological indicators were used as independent indicators. Analysis of the constructed models is a key stage of this study. Set of parameters included in the multidimensional models, sequence of their inclusion and contribution to the total value of the achieved determination coefficient as the main indicator for the performance of the constructed models were studied. It has been established that the main factor influencing the state of the bottomhole zone is oil degassing. Significant differences in the formation features of the skin factor in the terrigenous and carbonate sediments at the fields under consideration have been determined.
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Date submitted2021-01-28
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Date accepted2021-04-21
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Date published2021-06-24
Unusual metasomatites (phyolithites) in the Kolvitskiy gabbro-anorthosite rock mass: composition and structural position
Complex mineralogical, geochemical, and geological-structural characteristics of a rare collection stone of violet color, phyolithite, in the southwestern part of the Kola Peninsula. This is a metasomatic rock formed under the conditions of brittle deformations on gabbro-anorthosites of the Paleoproterozoic Kolvitskiy rock mass. As a result of potassium metasomatosis, the plagioclase of the initial rocks was replaced by a fine-grained mica aggregate of muscovite-phengite composition with inclusions of Va-aluminoseladonite (up to 20-30 microns). Ba-aluminoseladonite contains 6.6-10.5 % by weight of BaO. Manganese is the only chromophore that accumulates in the rock during metasomatosis. It is manganese that provides the purple-violet color of pseudomorphs of mica according to anorthite. The phyolithites is depleted by REE and has a positive Eu-anomaly. The phyolithites are confined to the areas of fracturing of the north-eastern strike, located in the zone of dynamic influence of the north-western closure of the Onega-Kandalaksha rift of the Riphean age. Other formations (injection conglomerates and lamproites) are also associated with the formation of this structure, which owe their origin to an intense fluid flow.
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Date submitted2020-08-20
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Date accepted2021-04-01
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Date published2021-06-24
Features of the mineral and chemical composition of the Northwest manganese ore occurrence in the Highveld region, South Africa
- Authors:
- Aleksandr N. Evdokimov
- Benedict L. Pharoe
The Northwest manganese ore mineralisation is located at a relative distance from traditionally known manganese mining areas in a new manganese-bearing region (Highveld) in the Northwest Province, Republic of South Africa. The ore occurrence was studied on farms: Buchansvale 61 IQ, Weltevreden 517 JQ, Rhenosterhoek 343 JP and Kafferskraal 306 JP. The data obtained from studying the geology of the area pointed out to interests regarding the development criterias for search of similar ore mineralisations in the northwest region of South Africa. The ore occurs predominantly in the form of powdered manganese wad, manganese nodules and crusts, confined to the karstic structures of the upper section of the dolomites. X-ray powder diffraction (XRD), Scanning electron microscopy with energy dispersive link (SEM-EDS) and X-ray fluorescence were utilized to unveil the mineral and chemical composition of the ore samples. The present study therefore presents the results on both chemical and mineral composition of manganese ores, and their depth and longitudinal distribution. Karstic areas causing an increased local thickness of the ore body were identified. The geochemical and microspcopic study of the ores indicates their supergene nature. The main ore minerals includes cryptomelane, lithiophorite, purolusite, hollandite and romanechite associated with impurity components of Ba, Ce, Co, La, Cr, Zn and V.
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Date submitted2020-11-11
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Date accepted2021-03-02
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Date published2021-04-26
Oil and gas content of the understudied part in the northwest of the Timan-Pechora oil and gas province according to the results of basin modeling
Comprehensive interpretation of the results for regional seismic operations and reinterpretation of archived seismic data, their correlation with the drilling data of more than 30 deep wells, including Severo-Novoborsk parametric well, made it possible to clarify the structural maps and thickness maps of all seismic facies structures developed in the territory and water area in the junction of the north of Izhma-Pechora depression and Malozemelsko-Kolguevsk monocline of Timan-Pechora oil and gas province. Data obtained were used at basin modeling in TemisFlow software in order to reconstruct the conditions of submersion and transformation of organic substance in potential oil and gas bearing formations. Modeling made it possible to get an idea of the time and conditions for the formation of large zones of possible hydrocarbons accumulation, to establish space-time connections with possible sources of generation, to identify the directions of migration and on the basis of comparison with periods of intense generation, both from directly located within the operation area and outside them (taking into account possible migration), to identify zones of paleoaccumulation of oil and gas. Work performed made it possible to outline promising oil and gas accumulation zones and identify target objects for further exploration within the site with an ambiguous forecast and lack of industrial oil and gas potential.
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Date submitted2020-07-02
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Date accepted2021-02-16
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Date published2021-04-26
Development of viscoelastic systems and technologies for isolating water-bearing horizons with abnormal formation pressures during oil and gas wells drilling
Article provides a brief overview of the complications arising during the construction of oil and gas wells in conditions of abnormally high and abnormally low formation pressures. Technological properties of the solutions used to eliminate emergency situations when drilling wells in the intervals of catastrophic absorption and influx of formation fluid have been investigated. A technology for isolating water influx in intervals of excess formation pressure has been developed. The technology is based on the use of a special device that provides control of the hydrodynamic pressure in the annular space of the well. An experiment was carried out to determine the injection time of a viscoelastic system depending on its rheology, rock properties and technological parameters of the isolation process. A mathematical model based on the use of a special device is presented. The model allows determining the penetration depth of a viscoelastic system to block water-bearing horizons to prevent interformation crossflows and water breakthrough into production wells.
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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 submitted2020-05-05
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Date accepted2020-10-05
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Date published2020-11-24
Assessment of the Influence of Water Saturation and Capillary Pressure Gradients on Size Formation of Two-Phase Filtration Zone in Compressed Low-Permeable Reservoir
The paper examines the influence of capillary pressure and water saturation ratio gradients on the size of the two-phase filtration zone during flooding of a low-permeable reservoir. Variations of water saturation ratio s in the zone of two-phase filtration are associated with the pressure variation of water injected into the reservoir; moreover the law of variation of water saturation ratio s ( r , t ) must correspond to the variation of injection pressure, i.e. it must be described by the same functions, as the functions of water pressure variation, but be subject to its own boundary conditions. The paper considers five options of s ( r , t ) dependency on time and coordinates. In order to estimate the influence of formation and fluid compressibility, the authors examine Rapoport – Lis model for incompressible media with a violated lower limit for Darcy’s law application and a time-dependent radius of oil displacement by water. When the lower limit for Darcy’s law application is violated, the radius of the displacement front depends on the value of capillary pressure gradient and the assignment of s function. It is shown that displacement front radii contain coefficients that carry information about physical properties of the reservoir and the displacement fluid. A comparison of two-phase filtration radii for incompressible and compressible reservoirs is performed. The influence of capillary pressure gradient and functional dependencies of water saturation ratio on oil displacement in low-permeable reservoirs is assessed. It is identified that capillary pressure gradient has practically no effect on the size of the two-phase filtration zone and the share of water in the arbitrary point of the formation, whereas the variation of water saturation ratio and reservoir compressibility exert a significant influence thereupon.
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Date submitted2019-11-20
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Date accepted2020-01-20
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Date published2020-10-08
Effect of shear stress on the wall of technological pipelines at a gas condensate field on the intensity of carbon dioxide corrosion
The object of the study is a section of the gas and gas condensate collection system, consisting of an angle throttle installed on a xmas tree and a well piping located after the angle throttle. The aim of the study is to assess the impact of the flow velocity and wall shear stress (WSS) on the carbon dioxide corrosion rate in the area of interest and to come up with substantiated recommendations for the rational operation of the angle throttle in order to reduce the corrosion intensity. In the course of solving this problem, a technique was developed and subsequently applied to assess the influence of various factors on the rate of carbon dioxide corrosion. The technique is based on a sequence of different modeling methods: modeling the phase states of the extracted product, three-dimensional (solid) modeling of the investigated section, hydrodynamic flow modeling of the extracted product using the finite volume method, etc. The developed technique has broad possibilities for visualization of the obtained results, which allow identifying the sections most susceptible to the effects of carbon dioxide corrosion. The article shows that the average flow velocity and its local values are not the factors by which it is possible to predict the occurrence of carbon dioxide corrosion in the pipeline section after the angle throttle. The paper proves that WSS has prevailing effect on the corrosion intensity in the section after the angle choke. The zones of corrosion localization predicted according to the technique are compared with the real picture of corrosion propagation on the inner surface of the pipe, as a result of which recommendations for the rational operation of the angle throttle are formed.
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Date submitted2019-11-04
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Date accepted2020-01-12
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Date published2020-10-08
PDC cutter pressure on plastic-brittle rock in the process of its destruction
- Authors:
- Oleg B. Trushkin
- Hamzja I. Akchurin
Presently, there are no methods for calculating the parameters of the drilling practices with rock-cutting tools equipped with polycrystalline diamond composite (PDC cutters). To create such a method requires the studying their work. The article presents the results of bench studies of the PDC cutters in the process of a rock sample breakdown when reproducing the actual layout of the cutters on the working surface of the bit. An important parameter of PDC cutters operation, which is necessary for the bit load analysis, is the pressure of the cutters on the rock during its breakdown. The total pressure of a cutter on the rock can be broken into two mutually perpendicular components: the forcing pressure and the cutting pressure. It is proposed to evaluate the PDC cutters loading at breakage of rocks of different hardness using relative values of forcing and cutting pressures, which are calculated relative to the yield strength of the rock by the die. It is established that the variability of the average relative pressures of forcing and cutting is significantly influenced by drifting per bit turnover and the radius of the cutter on the bit. The dependences of the maximum relative pressures of PDC cutters at the plastic-brittle rock breakdown on the drifting per bit turnover and the radius of the cutter location on the bit are obtained. It has been established that when drifting up to 0.4 mm per turn, the main mechanism of breakdown is cutting, and with the increase of the breakdown depth, the process of forcing becomes decisive.
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Date submitted2019-09-25
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Date accepted2019-12-20
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Date published2020-04-24
Study of the well near-bottomhole zone permeability during treatment by process fluids
- Authors:
- Evgenii A. Rogov
In the process of drilling-in productive horizons, several irreversible physical and chemical processes take place in the near-wellbore zone of the formation: stress state of the rocks changes, penetration of the filtrate and solid phase, as well as drilling mud into the reservoir, and swelling of clay particles of intergranular cementing material are observed. As a result, permeability of productive horizon is significantly reduced and, consequently, potential inflow of oil or gas from formation is excluded. An equally serious problem exists during well servicing and workover, when the use of irrational fluids of well killing causes negative consequences associated with deterioration of reservoir properties of formations in the wells being repaired. Article presents the results of the experiments on permeability of clayed porous samples after exposure to various compositions of liquids. In order to increase permeability of near-borehole zone of the formation and increase productivity of wells completed by drilling, and after well servicing and workover, a composition of the process fluid containing a 15 % aqueous solution of oxyethylene diphosphonic acid (OEDA) with addition of a surfactant is proposed.
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Date submitted2019-07-17
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Date accepted2019-09-04
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Date published2019-12-24
On flood protection measures for potash mines
- Authors:
- A. A. Baryakh
- E. A. Gubanova
Development of water-soluble ore deposits is associated with the necessity to preserve water blocking strata (WBS), which separate aquifers from the mine gob. One indicator of the rate of man-induced load on WBS layers is subsidence of the earth surface, which defines the character of shift trough formation of the earth surface. The greatest threat of WBS discontinuity is posed by the areas located at the edges of a shift trough. From the perspective of Upper Kama deposit of potassium and magnesium salts, by means of mathematical modelling methods authors demonstrated that in the capacity of threat indicators of WBS hole destruction it is possible to use the following parameters of a shift trough: edge length scaled to the depth of mining operations and maximum subsidence of the earth surface. Critical combination of these factors is responsible for the discontinuity at the edges of water blocking strata. These parameters of a shift trough can easily be controlled by instrumental procedures and can be included in the basics of a general monitoring system of WBS state at potash mines. In order to protect the mine from the inrush of fresh water, it is necessary to form softening zones at the edges of mined-out areas near permanent or temporary borders of mining operations. Authors review different options of softening zone formation. Numerical tests have demonstrated that the most efficient way to protect water blocking strata is the formation of softening zones by means of backfilling the stopes of the workable seam or its exclusion from mining operations.
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Date submitted2019-02-26
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Date accepted2019-05-22
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Date published2019-08-23
Systemic Diagnostics of the Arctic Industry Development Strategy
The article analyzes organizational and economic problems of the industry in the Arctic and discloses methods and tools for researching these problems. An attempt to use the method of system diagnostics is made, which has established itself as a basis for determining the development strategy of industry in the Arctic zone of the Russian Federation (AZRF). This method allows to explore the mechanism of natural resources development in the Arctic, such as hydrocarbons and marine biological resources; as well as the organization of logistics and transport corridors for trade of goods produced in the North and in the central regions of Russia. The role, significance and content of the strategy as an essential element of the system for managing natural wealth development in the Arctic in the context of its growing importance in development of global transport corridor are revealed. Importance of a systematic approach to the development of industry in the Arctic is substantiated, it will ensure development of all investors interested in this region; will allow the state, large corporations, small and medium-sized businesses to work together for the long term. The proposed method for system diagnostics of strategizing the development of industrial potential in the AZRF can be used in the implementation of «Development Strategy for the Arctic Region» as part of roadmap realization for the Arctic region.
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Date submitted2019-03-13
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Date accepted2019-05-07
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Date published2019-08-23
Modern Mathematical Forecast Methods of Maintenance and Support Conditions for Mining Tunnel
- Authors:
- S. A. Ignatyev
- A. E. Sudarikov
- A. Zh. Imashev
The research focuses on mathematical methods of mining pressure forecast to develop rational support patterns for mining tunnels and to ensure safety of mining operations. The purpose of research is to develop the methodology of applying advanced calculation methods and software solutions based on neural networks to reduce dispersion of factors influencing stability of mining tunnels, as well as to define rational parameters of mining tunnel support. The authors review the algorithm of geomechanical process examination, which is divided into several stages. First of all, it is proposed to use cluster analysis to examine location conditions of man-made outcrops, which allows to divide all the diversity of existing conditions for mining tunnel construction. Cluster analysis first allows to reduce the dispersion of factors that influence the stability of mining tunnels in various clusters, and then to determine rational parameters of tunnel support in each cluster. After the problem of cluster analysis is solved, it is proposed to use software programs that allow to study geomechanical processes in each cluster. At this stage, both standard methods (normative techniques, numerical modelling, analogies use, etc.) and the most advanced methods – neural networks – can be applied. Described algorithm of solving geomechanical problems, which utilizes advanced numerical methods and a software package based on neural networks, ensures an individual approach to estimation of mining pressure under varying conditions of man-made outcrop location in the rock mass.