Thermal-steam stimulation (TSS) is considered as the most effective among all up-to-date methods for heavy oil production. However problem consists in lower coverage by steam injection and decreased TSS efficiency at later stage of the development. Paper presents the results of solving this problem by combining thermal-steam and physicochemical stimulations and using "cold" technologies involving thermotropic gel-forming and oil-displacing systems: gels increase reservoir coverage, whereas oil-displacing systems increase oil displacement. In 2008-2013 172 wells were treated on the Permian-Carboniferous reservoir of high-viscosity oil in Usinsk oilfield using IPC SB RAS technologies. As a result the increase in oil production rate ranged of 3-24 ton/d per one well and incremental oil production amounted to 980 tons per one well treatment. It is promising to use integrated technologies alternating injection of steam, gel-forming and oil-displacing systems. They are commercially produced in Russia and China. In 2014 to improve TSS efficiency pilot tests of new technologies were successfully carried out: using gelled system based on surfactants with controlled viscosity to increase simultaneously reservoir coverage and oil-displacement factor; using polymer gel-forming system – for selective water shutoff in production wells. TSS is effective, but expensive method. It is promising to use "cold" technologies. To enhance oil recovery from high-viscosity reservoirs at 20-40 °С we propose to use gels and sols based on low temperature inorganic gel-forming system and oil-displacing alkaline and acid systems based on surfactants, inorganic buffer solution and polyol with controlled viscosity, from tens to hundreds mPa·s, and low freezing point, -20÷-60 °С. In 2014 pilot tests of new "cold" technologies were carried out in Usinsk oilfield. Alkaline system was injected into 5 and acid system into 10 low productivity production wells. After injections oil production rate increased by 5-15 ton/d, fluid flow rate increased by 15-25 m3/d. The technologies were recommended for commercial application.

The results of laboratory and field tests of physicochemical technologies for enhanced oil recovery are presented for oil fields developed by flooding and thermal-steam stimulation. These technologies can be used in extreme climatic conditions of the Arctic. A promising concept has been developed using reservoir energy or that of the injected heat carrier to generate oil-displacing fluid, gels and sols in situ. Physicochemical bases for EOR have been developed involving chemical intelligent systems: gel-forming and oil-displacing systems based on surfactants self-regulating a complex of properties, optimal for oil displacement, in a reservoir for a long time. Pilot tests of EOR technologies were successfully carried out in oil fields of Russia, China, Vietnam, Oman and Germany using gel-forming systems and surfactant compositions developed at IPC SB RAS. Such systems are commercially produced in Russia and China. The results of pilot tests and commercial application of the technologies for enhanced oil recovery and water shutoff are presented for oil fields with difficult-to-recover reserves including deposits of high-viscosity oils. For effective development of difficult-to-recover oil reserves and further increase in oil production it seems promising large-scale use of advanced complex technologies for enhanced oil recovery combining basic reservoir treatment by water or steam injections with physicochemical methods increasing reservoir sweep and oil-displacement factor at simultaneous intensification of the development. The achieved scientific and technical level of the works enables to create new EOR technologies for hydrocarbon deposits located in the Arctic shelf of Russia, in the Urals and Siberia, as well as reagents adaptable to works in the extreme climatic conditions.

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Physicochemical aspects of enhanced oil recovery (EOR) from heavy high-viscosity deposits, developed in natural mode and combined with thermal methods, using systems based on surface-active substances (surfactants), coordinating solvents and complex compounds are considered, which chemically evolve in situ to acquire colloidal-chemical properties that are optimal for oil displacement. Thermobaric reservoir conditions, interactions with reservoir rock and fluids are the factors causing the chemical evolution of the systems. To enhance oil recovery and intensify the development of high-viscosity deposits, acid oil-displacing systems of prolonged action based on surfactants, inorganic acid adduct and polyatomic alcohol have been created. As a result of experimental studies of acid-base equilibrium in the systems with donor-acceptor interactions – polybasic inorganic acid and polyol, the influence of electrolytes, non-electrolytes and surfactants, the optimal compositions of the systems were selected, as well as concentration ranges of the components in the acid systems. When the initially acid system interacts with the carbonate reservoir to release CO2, the oil viscosity decreases 1.2-2.7 times, the pH of the system rises and this system evolves chemically turning into an alkaline oil-displacing system. As a result it provides effective oil displacement and prolonged reservoir stimulation. The system is compatible with saline reservoir waters, has a low freezing point (minus 20 ÷ minus 60 oC), low interfacial tension at the oil boundary and is applicable in a wide temperature range, from 10 to 200 oC. In 2014-2018 field tests of EOR technologies were successfully carried out to intensify oil production in the test areas of the Permian-Carboniferous deposit of high-viscosity oil in the Usinsk oil field, developed in natural mode and combined with thermal-steam stimulation, using the acid oil-displacing system based on surfactants, coordinating solvents and complex compounds. The pilot tests proved high efficiency of EOR technologies, as far as the oil production rate significantly increased, water cut decreased to intensify the development. The EOR technologies are environmentally safe and technologically effective. Commercial use of the EOR is promising for high-viscosity oil deposits.

To enhance the oil recovery of high-viscosity oil deposits in the temperature range of 20-210 °C, the multifunctional composition based on surfactants, aluminum and ammonium salts, an adduct of inorganic acid, carbamide and polyol with an adjustable viscosity and high oil-displacing ability was created. The composition has a low interfacial tension, a high buffer capacity in a wide pH range, 2.5-10 units pH, a delayed reaction with carbonate rocks, prevents the precipitation of insoluble reaction products, increases the permeability of reservoirs. The composition is both oil-displacing and flow-diverting, provides an enhance in the oil recovery factor (ORF) due to the increase in the oil displacement and formation sweep by water or steam flooding. Practical recommendations are given on the application of the composition at the Permian-Carboniferous deposits of the Usinsk oilfield.