Impact of Integrated Technologies of Enhanced Oil Recovery on the Changes in the Composition of Heavy Oil

Abstract

This paper deals with the impact of an integrated technology for enhanced oil recovery on the composition of high-viscosity heavy oil produced at the Usinskoye oilfield (Russia, Komi Republic). In order to increase the effectiveness of the thermal-steam stimulation, a surfactant-based composition generating carbon dioxide and an alkaline buffer system is injected into the formation. The analysis of the oil composition is performed via the methods of gradient-displacement liquid adsorption, gas-liquid chromatography, and IR spectroscopy. The results obtained show that two parallel processes are proceeding when pumping an oil-displacing composition. The first process is the additional extraction of residual oil. This process is controlled by an increase in the content of resin-asphaltene substances in oil. The second process is an increase in the coverage of reservoir and the involvement into the development of previously uncovered areas with oil compositionally similar to that at the beginning of development. Using the results of the analysis of the component composition, the individual composition of alkanes, and structural fragments of oil samples in order to control the development of the Usinskoye oilfield, the frontal oil-water boundary advance of the Northern area in the direction of the upper production facility is determined. The obtained patterns of changes in the oil composition after the application of an integrated technology using a surfactant-based composition can be characteristic of other deposits of heavy oil occurring in low-permeability reservoirs

Full text

– 17 –
Journal of Siberian Federal University. Chemist ry 2020 13(1): 17-24
~ ~ ~
DOI: 10.17516/1998-2836-0162
УДК 543.544.43
Impact of Integrated Technologies
of Enhanced Oil Recovery on the Changes
in the Composition of Heavy Oil
Yury V. Savinykh*,
Darya I. Chuykina and Larisa D. Stakhina
Institute of Petroleum Chemistry SB RAS
Tomsk, Russian Federation
Received 15.11.2018, received in revised for m 26.10.2019, accepted 17.01.2020
Abstract. This paper deals with the impact of an integrated technology for enhanced oil recovery
on the composition of high-viscosity heavy oil produced at the Usinskoye oileld (Russia, Komi
Republic). In order to increase the eectiveness of the thermal-steam stimulation, a surfactant-based
composition generating carbon dioxide and an alkaline buer system is injected into the formation.
The analysis of the oil composition is performed via the methods of gradient-displacement liquid
adsorption, gas-liquid chromatography, and IR spectroscopy. The results obtained show that two
parallel processes are proceeding when pumping an oil-displacing composition. The rst process is
the additional extraction of residual oil. This process is controlled by an increase in the content of
resin-asphaltene substances in oil. The second process is an increase in the coverage of reservoir and
the involvement into the development of previously uncovered areas with oil compositionally similar to
that at the beginning of development. Using the results of the analysis of the component composition,
the individual composition of alkanes, and structural fragments of oil samples in order to control the
development of the Usinskoye oileld, the frontal oil-water boundary advance of the Northern area in
the direction of the upper production facility is determined. The obtained patterns of changes in the oil
composition after the application of an integrated technology using a surfactant-based composition can
be characteristic of other deposits of heavy oil occur ring in low-permeability reservoirs.
Keywords: heavy oil, enhanced oil recovery, surfactants, group chemical composition, adsorption
chromatography, gas-liquid chromatography, IR spectroscopy.
Citation: Savinykh Yu.V., Chuykina D.I., Stakhina L.D. Impact of integr ated tech nologies of enhanced oil recovery on t he
changes in the composition of heavy oil, J. Sib. Fed. Univ. Chem., 2020, 13(1), 17-24. DOI: 10.17516/1998-2836-0162
© Siberian Federal University. All rights reserved
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).
* Corresponding author E-mail add ress: yu-sav2007@yandex.ru

– 18 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
Влияние комплексных технологий
интенсификации нефтеотдачи
на изменение состава тяжелой нефти
Ю.В. Савиных, Д.И. Чуйкина, Л.Д. Стахина
Институт химии нефти СО РАН
Российская Федерация, Томск
Аннотация. В настоящей работе изучено влияние комплексной технологии для
интенсификации нефтеотдачи на состав добытой тяжелой высоковязкой нефти на Усинском
месторождении (Россия, Республика Коми). Для увеличения эффективности паротеплового
воздействия производилась закачка композиции на основе поверхностно-активных веществ,
генерирующая в пласте углекислый газ и щелочную буферную систему. Для анализа состава
нефти были использованы методы градиентно-вытеснительной жидкостной адсорбционной
и газожидкостной хроматографии, ИК-спектроскопии. Полученные результаты показали,
что при закачке нефтевытесняющей композиции наблюдаются два параллельных процесса.
Первый процесс – доотмыв остаточной нефти. Этот процесс контролируется увеличением
содержания в нефти смолисто-асфальтеновых веществ. Второй процесс – увеличение охвата
пласта и подключение в разработку ранее не задействованных участков с нефтью, сходной
по составу с нефтью в начале разработки. Использование результатов анализа компонентного
состава, индивидуального состава алканов, структурных фрагментов образцов нефти для
контроля разработки Усинского месторождения позволило определить фронт продвижения
контура нефтеносности Северного участка в направлении верхнего объекта. Полученные
закономерности изменения состава нефти после воздействия комплексной технологии
с применением композиции на основе поверхностно-активных веществ могут быть
распространены и на другие месторождения тяжелой нефти, залегающей в низкопроницаемых
коллекторах.
Ключевые слова: тяжелая нефть, повышение нефтеотдачи, поверхностно-активные вещества,
групповой химический состав, адсорбционная хроматография, газожидкостная хроматография,
ИК-спектроскопия.
Цити рован ие: Савины х, Ю.В. Влияние комплексных технологий ин тенсификации нефтеотдачи на изменение состава
тяжелой нефти / Ю.В. Савин ых, Д.И. Чуйкина, Л.Д. Стахи на // Журн. Сиб. федер. ун-та. Хими я, 2020. 13(1). С. 17-24.
DOI: 10.17516/1998-2836-0162
Introduction
Tota l World crude oil reserves are approximately 9-1 trillion barrels, where heavy oil and bitumen
are more than 2/3. Canada and Venezuela each possess approximately 2–3 trillion barrels of eight
trillion barrels of heavy oil and bitumen resources [1, 2]. Russian reserves of heavy high-viscosity oil
are estimated at 44–52 billion barrels. The majority of deposits (71.4%) are located in the Volga-Ural

– 19 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
and West Siberian oil and gas regions. At the same time, 60.4% of the all-Russian reserves of heavy
oils and 70.8% of viscous oils are accounted for the Volga and Ural regions. The deposits of heavy
oil have been found in the republics of Tatarstan, Bashkortostan, Udmurtia, and in Samara and Perm
regions [3]. The ecient development of heavy oil and bitumen resources has an important impact on
global energy supply. Unlike light, low-viscosity oil, these types of crude oil are usually characterized
by high viscosity and density under initial temperature conditions of the reservoir and require a special
approach to their extraction [4]. Since viscous oil is temperature sensitive, it would be most rational
to use thermal processes. The conventional thermal methods for developing oil elds (in their various
modications) are usually clustered into three groups: in-situ combustion, thermal steam treatment of
bottom-hole zones of wells, and injection of steam or hot water as heat carriers into the reservoir (non-
isothermal displacement) [5, 6].
The main methods of long-term and large-scale impact on the oil reservoir are hot water ooding
or steam-stimulation. For this purpose, the hot uid is continuously pumped into the reservoir. The
formation rock and uids around the wells heat up, the temperature rises, the viscosity of a heavy oil
decreases, while its mobility increases. This method is the main one for the extraction of heavy oil and
bitumen resources worldwide [7].
Flooding by gel-forming polymers has proven to be economically and technically successful in
many oil recovery enhancement (EOR) projects, which can often increase oil recovery by 12–15%
[8, 9].
The injection of an oil-displacing composition based on surfactants and an alkaline buer system
has proven itself to be good for increasing the oil recovery coecient and increasing the duration
of the eect of steam stimulation. In the course of oil displacement, surfactants aect the following
interrelated factors: interfacial tension at the oil-water boundary and surface tension at the water-rock
and oil-rock interfaces due to their adsorption at these interfaces. In addition, the eect of surfactants
is manifested in the change in the selective wetting of the rock surface with water and oil, breakdown
and washing o of the oil lm from the rock surface, the stabilization of dispersion of oil in water,
the increase in water ood displacement eciency during stimulated displacement and capillary
imbibitions, and in the increase in relative phase permeability of porous media [10, 11].
The use of various EOR-tech nologies leads not only to an increase in the oil recovery
coecient, but also to a change in the composition of produced oil [12, 13]. In this regard, an in-
depth st udy of the eect of EOR on the composition of produced uids in water-ooded reservoirs
is relevant. In order to identify the patterns in changes of the composition of oil produced after
the use of integ rated EOR-technologies, the oil samples from the Usinskoye oil eld were ta ken
and investigated.
Experimental
Oil samples. The heavy crude oil (8 samples) was sampled from the Usinskoye oil eld (Komi
Republic, Russia) before and after the treatment with a NINKA system (EOR).
EOR compositions. The oil-displacing NINKA composition based on alkaline buer system,
carbamide, and surfactant was developed at the Institute of Petroleum Chemistr y of the SB RAS [14].
SARA analysis. The oil samples were analyzed for the content of the main SARA components
(saturated and aromatic hydrocarbons, resins, and asphaltenes).

– 20 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
The analysis of the group composition of oil was carried out by the method of gradient
displacement liquid adsorption chromatography on silica gel. The samples were analyzed for the
content of saturated (paran-naphthenic) hydrocarbons (SHCs), polycyclo-aromatic hydrocarbons
(PAHCs), neutral resins (NR), sour resins (SR), and asphaltenes (AS). Oil separation was carried out
using a ‘Gradient’ instrument manufactured by Bash NIINP [15]. The withdrawal of the oil fraction
containing a mixture of saturated and aromatic hydrocarbons was carried out by the method of liquid
adsorption chromatography (LAC). Crude oil in an amount of 0.1 g was applied on aluminum oxide
of IV degree activity and then the chromatographic fraction was eluted with 100 ml of hexane. The
chromatographic fraction was evaporated to a volume of 1 ml using a vacuum rotary evaporator. The
concentrate obtained was analysed using a Chromos GC-1000 gas chromatographer equipped with a
25 m long capillary column with an OV-101 phase. Operating mode was as follows: helium was used
as a carrier gas and the temperature of evaporator and interface was 250°C. The column was heated in
the linear mode of temperature programming. The initial temperature Tinit = 80°C was increased at a
rate 10 deg/min up to maximum temperature Tmax =280°C.
IR spectroscopy. The IR spectra were recorded in a thin layer in the range 400-4000 cm-1 us-
ing a Thermo Scientic ‘Nikolet 5700’ FTIR Spectrometer equipped with a Raman module (Thermo
Electron Corporation, USA). The spectroscopic coecient, C, is the ratio of the optical densities (D) of
the characteristic absorption bands in the IR spectral region, which correspond to the respective types
of bonds.
To determine the change in the content of certain groups and bonds in the samples, the optical
density ratios were used [16]:
С1=D1380+72 0/D1610 – the conventional ratio of aliphatic structures to aromatic structures;
С2=D960/D1465 – the conventional ratio of naphthenic structures to aliphatic structures;
C3 =D1610/ D720 – the conventional ratio of aromatic structures to paranic structures;
C4 =D1380/D1465 – the branching coecient which characterizes the conventional content of
СН3- groups;
C5=D1710 / D1465 – the conventional content of С=О groups of carboxylic acids.
Results and discussion
Experience in the development of domestic and foreign oilelds using steam stimulation shows
that the eective implementation of the technology of cyclic steam well treatment requires a careful
consideration of the geological and physical characteristics of the reservoir and a study of scientic
background of the process parameters.
The Usinskoye oileld is located in the Usinsk district of the Komi Republic, 115 km north of the
city of Pechora [17]. Structurally, the Usinsk uplift over all horizons of the sedimentary cover represents
an asymmetric anticlinal fold, which strikes the north-west of north. The Permocarbon deposit of
the Usinsk oileld is a single hydrodynamic system. The three following productive formations or
production facilities are distinguished in the cross-section of the deposit: I – lower production facility
(LPF), II – middle (MPF) and III – upper (UPF). The undersaturated oil in the reservoir is characterized
by a high viscosity of 586-2024 mPa*s and a high density of up to 960 kg/m3. Currently, the Usinskoye
oileld is at the fourth stage of development, which is accompanied by high water cut and low oil
production rates.

– 21 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
Investigation of the oils sampled from various production facilities of the Usinskoye oileld:
lower (LPF), middle (MPF) and upper (UPF) revealed features and signicant dierences in their
composition [18]. The main dierences are observed in the content of paranic, naphthenic, and
aromatic hydrocarbons. These data were used to dierentiate oil-bearing facilities and to monitor the
development of the Usinskoye eld after application of the methods of enhanced oil recovery.
In 2017, in the Northern area of the Usinskoye oileld, a cyclic steam treatment of the formation
(CST) was performed, followed by the injection of the NINKA oil-displacing composition. The
introduction of oil-displacing composition into the reservoir was carried out through production wells,
which provided a signicant increase in oil production.
The results of the changes in composition of the oil samples taken from the Northern area of the
Usinskoye oileld after application of the integrated production technology are shown in Table 1.
The area under consideration is located in the attic zone of the reser voir, where all three
facilities (upper, middle and lower) were penetrated, which explains the dierences in the
composition of the oil produced. A comparison of the group composition of oil samples extracted
after application of the integrated method in 2018 with earlier samples (2017) taken from the
same wells has showed a dierence in the composition of oils. After injection of the composition
the content of paran-naphthenic (saturated) hydrocarbons (SHCs) in the oil samples increased
by 7-15%. Paran-naphthenic hydrocarbons were represented by alkanes and saturated cyclic
str uctures. The total content of aromatic and polycycloaromat ic hydrocarbons (PAHCs) has
insignicantly changed. The main amount of resins (7-23%) are sour (SR), while the content
of neutral resins (NR) does not exceed 5% rel. After injection of the NINKA composition, a
decrease in the content of resin-asphaltene substances (RAS) by 2-14% was observed. The R AS
is the total content of neutral and sour resins and asphaltenes (As) (Table 1). Gas chromatography
was used to analyze the hexane fractions (saturated hydrocarbons) of oil separated by LAC
(Fig. 1).
The data obtained for the group composition of the oils indicate that after the composition was
injected into the wells, the zones of the reservoir previously water unushed were included into the
Table 1. Group composition of the oil samples taken from the Norther n area of the Usinskoye oileld
Well No. Date of
sampling
Content, wt%
SHCs PA HCs NR SR As RAS
81X X 12 . 2 017 60 16 3 7 14 24
81X X 04. 2018 67 12 2 8 10 20
60XX 04. 2 017 43 19 423 11 38
60XX 04 .2018 58 18 213 924
XX62 1 2.2017 50 23 517 527
XX62 0 4.2 018 57 18 213 10 25
XX68 04 . 2017 52 13 215 17 34
XX68 04 .2018 66 9 1 13 11 25
SHCs – saturated (paran-naphthenic) hydrocarbons; PAHCs – polycycloaromatic hydrocarbons; NR – neutral
resins; SR – Sour Resins; As – asphaltenes; RAS – resin-asphaltene substances (sum of NR, SR, As)

– 22 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
development. These reservoir zones contained the oil similar in its composition to the initial one
produced without EOR application. These data make it possible to appreciate the cont ributions of
residual oil and that of bypassed oil from the not water-ooded pillars to the well production. The
most noticeable dierences in the molecular mass distribution (MMD) of n-alkanes are observed
for oil samples from wells No. 60XX and No. 81XX. These dierences in the composition are due
to the fact that dierent operational facilities objects are under development. The oil of the lower
production facility (well No. 81XX) is characterized by the almost complete absence of n-alkanes
and the presence of a high ‘naphthenic’ hump (Fig. 1 c), while the oils from the upper and middle
production facilities (well No. 60XX) contain high concentrations of paranic hydrocarbons (Fig. 1 a)
[18]. The chromatograms of hexane fractions isolated from the initial oil samples showed that crude
oil from the well No. 60XX was also produced predominantly from the upper and middle facilities,
while the crude oil from the well No. 81XX was extracted from the lower facility. Figure 1 shows
no signicant changes in the MMD of n-alkanes for the same well after injection of the composition
(Fig. 1 a, b, c, d). This indicates that the production facility for each well has not changed after
injection of the composition.
To characterize the oils, the spectral coecients C1-C5 were calculated from the data of IR
spectrometry (Table 2).
Based on the data, it was found that all samples belong to the naphthenic-aromatic type of
oils (C3 = 1.43-1.55). A low degree of aliphaticity (C1 = 3.14-3.51) suggests a low content of alkane
structures. Small dierences were established for the C1 coecient characterizing the content of paran
Fig. 1. Chromatograms of saturated hydrocarbon fraction of oil samples from the Northern area of the Usinskoye
oileld: a – well No. 60XX (12.2017); b − well No. 60XX (04.2018); c – well No. 81XX (11.2017); d – well
No. 81XX (04.2018)
(NR) does not exceed 5% rel. After injection of the NINKA composition, a decrease in the content
of resin-asphaltene substances (RAS) by 2-14%% was observed. The RAS is the total content of
neutral and sour resins and asphaltenes (As) (Table 1). Gas chromatography was used to analyze the
hexane fractions (saturated hydrocarbons) of oil separated by LAC (Fig. 1).
Fig. 1. Chromatograms of saturated hydrocarbon fraction of oil samples from the Northern
area of the Usinskoye oilfield: a – well No. 60XX (12.2017); b − well No. 60XX (04.2018); c –
well No. 81XX (11.2017); d – well No. 81XX (04.2018)
The data obtained for the group composition of the oils indicate that after the composition was
injected into the wells, the zones of the reservoir previously water unflushed were included into the
development. These reservoir zones contained the oil similar in its composition to the initial one
produced without EOR application. These data make it possible to appreciate the contributions of
residual oil and that of bypassed oil from the not water-flooded pillars to the well production. The
most noticeable differences in the molecular mass distribution (MMD) of n-alkanes are observed
for oil samples from wells No. 60XX and No. 81XX. These differences in the composition are due
to the fact that different operational facilities objects are under development. The oil of the lower
production facility (well No. 81XX) is characterized by the almost complete absence of n-alkanes

– 23 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
structures, which is due to the oil extraction from dierent production facilities. This is conrmed by
data obtained by gradient displacement chromatographic analysis.
The optical densities D of the band in the region of 1710 cm–1 are in the range 0.04–0.06, which
is typical for the presence of aliphatic oxygen-containing NINKA compounds. Coecient C5 is
0.6–0.7, which suggests the oxidized type of oil samples. The results of IR spectrometry showed that
no signicant changes were observed in the ratio of naphthenic, aromatic, and oxygen-containing
fragments and structures for both initial oil samples and those taken after application of the integrated
EOR-technology.
Conclusions
Based on the study of the dynamics of changes in the composition of oil produced after the
application of integrated EOR-technologies, the eectiveness of methods of oil recovery enhancement
has been shown. The use of the NINKA composition in conjunction with the PCO in the Northern
area of the Usinskoye oileld has showed that new low-permeability interlayers were involved in
the development when using the integrated EOR-technology. This is due to a number of processes,
including counterow capillary percolation and a decrease in surface tension at the rock-oil boundar y
under the inuence of the NINKA composition containing a surfactant and an alkaline buer system.
Acknowledgements
The work was performed within the framework of the Program of Fundamental Scientic Research
of the State Academies of Sciences (Project V.46.2.3 No. 0370-2019-0002).
References
1. Dusseault M.B. Comparing Venezuelan and Canadian heavy oil and tar sands. Paper 2001-061
presented at the Petroleum Society’s Canadian International Petroleum Conference. Calgary, Alberta,
Canada, June 12–14; 2001.
2. Meyer R.F., Attanasi E.D., Freeman P.A. Heavy oil and natural bitumen resources in geological
basins of the world. Open File-Report 2007-1084, U.S. Geological Survey; 36 p.
Table 2. Spectral coecients of oil samples from the Northern area of the Usinskoye oileld
Well No. Date of
sampling
Spectral coecients
С1 С2 С3 С4 С5
81X X 12 . 2 017 3.34 0.07 1.55 0.57 0.06
81X X 04. 2018 3.30 0.08 1.54 0.58 0.06
60XX 04. 2 017 3.31 0.09 1.43 0.60 0.07
60XX 04 .2018 3.51 0.07 1.54 0.58 0.06
XX62 1 2.2017 3.27 0.08 1. 53 0.59 0.07
XX62 0 4.2 018 3.4 4 0.07 1.55 0.58 0.06
XX68 04 . 2017 3.39 0.08 1.49 0.58 0.06
XX68 04 .2018 3.14 0.09 1.45 0.60 0.07
С1 = D1380 +720/D1610; С2 = D975/D1465; С3 = D1610/D720; С4 = D1380/D1465; С5 = D1710/D1465

– 24 –
Journal of Siberian Federal University. Chemistry 2020 13(1): 17-24
3. Makarevich V.N., Iskritskaya N.I., Bogoslovsky S.A. Resource potential of heavy oil deposits
in the European part of the Russian Federation. Petroleum Geology. Theoretical and Applied Studies.
2012. Vol. 7(3), P. 1-16. (In Russ.)
4. Iskritskaya N.I., Makarevich V.N., Shchepochkina A.A. Main trends in the development of
hard-to-extract oil reserves of the Russian Federation. Oil and gas geology 2015. No. 4, P. 62–66. (In
Ru s s .)
5. Antoniadi D.G. Scientic foundationsis for the development of oil deposits by thermal methods.
Moscow: Nedra, 1995. 314 p. (In Russ.)
6. Wu Z., Liu H. Investigation of hot-water ooding after steam injection to improve oil recovery
in thin heavy-oil reservoir. Journal of Petroleum Exploration and Production Technology 2019. Vol.
9(2), P. 1547 – 1554.
7. Burkova A.A. Cyclic steam treatment of the bottom-hole formation zone. Bulatov Scientic
Conference 2018. Vol. 2-1, P. 98-104. (In Russ.)
8. Wei B., Romero-Zerón L., Rodrigue D. Oil displacement mechanisms of viscoelastic polymers
in enhanced oil recovery (EOR): a review. Journal of Petroleum Exploration and Production
Technology 2014. Vol. 4(2), P. 113–121.
9. Wei B., Laiming Lu, et al. From Phase Behavior to Understand the Dominant Mechanism of
Alkali-Surfactant-Polymer Flooding in Enhancement of Heavy Oil Recovery. Journal of Surfactants
and Detergents 2 017. Vol. 20(2), P. 355–366.
10. Sreela Pal, M. Mushtaq et al. Review of surfactant-assisted chemical enhanced oil recovery
for carbonate reservoirs: challenges and future perspectives. Petroleum Science 2018. Vol. 15(1), P.
77-102.
11. Fusheng Zhang, Jian Ouyang et. all. Enhanced oil recovery from heavy oil reservoirs utilizing
a displacement agent. Chemistry and Technology of Fuels and Oils 2012. Vol. 48(3), P. 202–207.
(In Russ.)
12. Savinykh Yu.V., Chuykina D.I. Change in the composition of high viscosity oil upon contact
with surfactants. Oil & Gas Journal Russia 2017. No. 3, P. 84-87. (In Russ.)
13. Chuikina D., Russkikh I.V., Stakhina L.D., Serebrennikova O.V. Investigation of the
Composition of High-Viscosity and Heavy Oils in the Course of EOR-Process Simulation. Journal of
Siberian Federal University. Chemistry 2017. Vol. 2(10), P. 206-215. (In Russ.)
14. Altunina L.K., Kuvshinov V.A., Kuvshinov I.V. Surfactant systems for eective thermal-
steam reser voir stimulation. Oil &Gas Journal Russia 2010. No. 6, P. 68-75. (In Russ.)
15. Sokolova V.I., Kolbin M.A. Liquid chromatography of petroleum products. Moscow:
Chemistry, 1984. P. 41-51. (In Russ.)
16. Pentin Yu.A., Vilkov L.V. Physical Methods in Chemistry. Moscow: Mir Publishing House,
2003, 683 p. (In Russ.)
17. Chuykina D.I., Serebrennikova O.V., Stakhina L.D., Altunina L.K. Features of the geological
structure of the Usinskoye deposit and composition of extracted oil. Exposition Oil & Gas 2018. No. 1,
P. 18-21 (electronic journal http://runeft.ru/archive/2017/1_2018.htm). (In Russ.)
18. Chuikina D.I., Kozlov V.V., Stakhina L.D., Savinykh Y.V. Study of the Composition of Heavy
Oil during the Simulation of Oil Displacement in Porous Media. Journal of Siberian Federal University.
Chemistry 2018. Vol. 3(11), P. 323-332. (In Russ.)