RU2818344C1 - Method of extracting oil from oil formation using nanoparticles - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: in the method of extracting oil from an oil formation directly at the well, before pumping into the formation, into a mixing tank are batched fresh or mineralized water and a detergent composition Neominol, which is a water-alcohol solution of a mixture of non-ionic surfactants, and simultaneously, water-insoluble magnesium oxide nanoparticles 5–100 nm in size and with specific surface area of 64.5 m²/g are dosed into the mixing tank using a screw feeder for loose reagents with continuous stirring for at least 30 minutes until they are uniformly distributed. Obtained suspension is pumped into the loading unit of the installation for preparation of solutions from liquid and loose chemical reagents. Then, polyacrylamide is added to the obtained suspension by means of a screw feeder intended for dosing and supply of powdered reagents to obtain a composition for waterflooding at the following ratio of components, wt.%: Neominol 0.1–0.5; said magnesium oxide nanoparticles 0.01–0.07; polyacrylamide 0.3–0.7; said water is the rest. Composition for waterflooding is mixed for 10–15 minutes, then it is pumped into the oil formation through an injection well, oil is extracted from production wells.

EFFECT: increased efficiency of the method of oil extraction from oil formation due to increased surface activity of oil-displacing composition.

1 cl, 1 dwg, 5 tbl, 1 ex

Description

The invention relates to the oil industry, in particular to methods for extracting oil using nanoparticles from a terrigenous oil reservoir and can be used in the development of oil deposits of viscous and super-viscous oil.

There is a known method for processing an underground well having one or more permeable layers (patent RU No. 2693105, IPC E21B 43/22, C09K 8/84, C09K 8/92, B82Y 99/00, publ. 07/01/2019, Bulletin No. 19) comprising providing a treatment fluid containing water and a plurality of water-dispersible nanoparticles present in the treatment fluid at a concentration of about 0.1 to 5.0 wt. %, introducing the specified medium into the underground formation, so that the nanoparticles form one or more aggregates that clog the pores of the formation and block further flow of fluid in the formation. Water-dispersible nanoparticles contain nanocellulose, rod-shaped nanoparticles, nanotubes or halloysite or combinations thereof.

The disadvantage of the invention is the low degree of oil recovery due to the fact that water-dispersible nanoparticles containing nanocellulose primarily affect water-saturated formations, clogging them, and do not affect oil-saturated formations to displace oil.

There is a known method for developing an oil reservoir with heterogeneous permeability (patent RU No. 2725205, MPK E21B 43/22, C09K 8/88, publ. 06/30/2020, Bulletin No. 19), which includes pumping two slugs of an aqueous solution into the injection well: the first slug, containing polyacrylamide with a crosslinker, an aqueous solution containing polyacrylamide with a crosslinker is pumped in as the first rim; a composition of chromium acetate and zinc oxide, wt.%, is used as a crosslinker. %:

polyacrylamide 0.51-0.8 chromium acetate 0.04-0.06 zinc oxide 0.04-0.06 water rest

and a second rim containing a solution of a surfactant surfactant, which additionally contains polyacrylamide, and as a surfactant includes an amphoteric surfactant in the following ratio of components, in wt. %:

polyacrylamide 0.3, amphoteric surfactant 0.3-5.0 water rest.

The disadvantage of this method is the low degree of oil recovery associated with the use of a low-effective amphoteric surfactant, as well as the high consumption of reagents used in two slugs.

The closest is the method of producing hydrocarbon material (patent RU No. 2687412, IPC C09K 8/20, E21B 43/22, C09K 8/60, publ. 05.15.2019, bulletin No. 14), from an underground formation, including the formation of nanoparticles, each of which contains a core containing at least one of the following metals: Mg, Al, Ca, Mn and Zn, and a shell encapsulating the core and containing organic material, combining the nanoparticles with a carrier fluid to obtain a suspension for flooding, pumping the suspension into a subterranean formation containing hydrocarbon material associated with its surfaces to separate it from the surfaces and form an emulsion stabilized by nanoparticles, removing the emulsion from the subterranean formation and modifying at least one of the parameters: temperature, pH value and composition of the emulsion material, after removing the emulsion from a subterranean formation to interact at least a portion of the nanoparticles with the aqueous material to destabilize the emulsion and coalesce the hydrocarbon material. A stabilized emulsion containing a dispersed phase comprising a hydrocarbon material, a continuous phase comprising an aqueous material, and hydrophilic nanoparticles accumulating at an interface between the dispersed phase and the continuous phase, wherein a number of hydrophilic nanoparticles contain a core containing a Mg-Al alloy intended to switching between a first corrosion rate and a second higher corrosion rate as a result of changing at least one property: increasing the temperature of the aqueous material and decreasing the pH value of the aqueous material, and a shell encapsulating the core and containing the polymeric material.

The disadvantage of this method is the low degree of oil recovery, since nanoparticles, each of which contains a core containing at least one of the following metals: Mg, Al, Ca, Mn and Zn, which do not have surface activity, are used to form a nanoparticle-stabilized emulsion. The emulsion is pumped out from the underground formation. Since the viscosity of the emulsion is higher than the viscosity of oil, its transportation and subsequent separation into oil and water requires large energy costs.

The technical objective of the invention is to increase the efficiency of the method for extracting oil from an oil reservoir by increasing the surface activity of the oil-displacing composition by introducing nanoparticle additives into the surfactant and reducing material costs.

The technical problem is solved by a method for extracting oil from an oil reservoir using flooding with nanoparticles, which includes obtaining a flooding composition containing nanoparticles and surfactant surfactants, and injecting it into the oil reservoir.

What is new is that directly at the well, before injection into the formation, fresh or mineralized water and the detergent composition Neominol, which is an aqueous-alcohol solution of a mixture of nonionic surfactants, are dosed into the mixing tank with pumps, and at the same time, insoluble reagents are dosed into the mixing tank using a screw doser for bulk reagents in water, magnesium oxide nanoparticles 5-100 nm in size with a specific surface area of 64.5 m ² /g with continuous stirring for at least 30 minutes until they are evenly distributed, the resulting suspension is pumped into the loading unit of an installation for preparing solutions from liquid and bulk chemicals reagents, then polyacrylamide is added to the resulting suspension using a screw doser designed for dosing and supplying powdered reagents with constant stirring to obtain a composition for flooding with the following ratio of components, wt.%:

Neominol 0.1 - 0.5 These nanoparticles are magnesium oxide 0.01 - 0.07 Polyacrylamide 0.3-0.7 Specified water rest,

the flooding composition is stirred for 10-15 minutes, then pumped into the oil reservoir through an injection well, and oil is extracted from production wells.

To implement the method use:

- detergent composition of the Neominol brand, which is a water-alcohol solution of a mixture of nonionic surfactants according to TU 2458-001-91222887-2011.

- polyacrylamide (PAA) according to TU 2458-024-14023401-2012 with changes. No. 1, 2 or its analogues;

- magnesium oxide (nanoparticles) - MgO (OM) according to TU-6-09-3023-79 or ITS 21-2016 “Production of magnesium oxide, magnesium hydroxide, magnesium chloride Magnesium oxide has a particle size of mainly 5-100 nm, specific surface area 64.5 m ² /g. Nanoparticles are insoluble in water, can have both hydrophobic and hydrophilic properties, and have a positive charge.

To prepare an aqueous solution of surfactants, both fresh and mineralized water are used.

In fig. The dependence of the interfacial tension of surfactant solutions on the concentration of Neominol containing magnesium oxide nanoparticles and without nanoparticles is shown.

The essence of the invention.

Large-scale industrial application of new physical and chemical technologies for increasing oil recovery from oil deposits, increasing the oil recovery factor while intensifying development, will extend the profitable operation of fields at any stage of development and involve in the development of fields with hard-to-recover reserves of extra-viscous oil (SVOC).

During the long-term development of an oil field, the residual oil in the reservoir also undergoes changes: its density and viscosity increase, and its mobility decreases.

The most common type of chemical method for increasing oil recovery in oil displacement processes is the method of polymer flooding in compositions with various chemical reagents. Adding a surfactant to a polymer solution reduces the interfacial tension between formation oil and formation water, reduces capillary forces, increases oil mobility and oil displacement efficiency.

Table 1 shows the values of interfacial tension (σ) of PAA polymer solutions in the presence of Neominol of various concentrations in fresh water and mineralized water (d = 1.120 g/cm ³ ) at the interface with kerosene (d = 0.780 g/cm ³ ). The lower the value of interfacial tension σ at the interface, the easier it is for oil to separate from the rock surface and an increase in oil recovery from the formation.

Table 1 - The value of interfacial tension of PAA solutions in the presence of surfactants of various concentrations at the interface with kerosene

PAA polymer concentration,
% wt. Concentration
Surfactant
Neominol,
% wt. Interfacial tension σ, mN/m Dynamic viscosity, mPa⋅s on fresh per mineral. on fresh per mineral. 0.1 0.05 3.75 5.01 5.17 3.81 0.1 2.78 4.29 5.05 3.83 0.3 1.88 3.46 4.15 4.31 0.5 1.9 3.08 4.72 3.88 1.0 1.61 2.17 4.49 4.07 0.3 0.05 6.41 5.79 23.65 11.38 0.1 4.25 4.73 19.16 11.48 0.3 3.34 3.81 23.67 11.31 0.5 3.2 3.25 21.67 11.95 1.0 2.03 2.99 17.71 12.04

Based on the analysis of the data in Table 1, it was found that the most optimal concentration range of the surfactant Neominol in a PAA solution is the range from 0.1% to 0.5%. When the surfactant concentration in the solution decreases from 0.1% to 0.05% (two times), the interfacial tension σ at the interface increases from 2.78 mN/m to 3.75 mN/m in fresh water and from 4. 29 mN/m to 5.01 mN/m - in mineralized water, there is a decrease in the surface activity of the PAA solution containing a surfactant at the interface, which, in turn, reduces the efficiency of oil displacement by the composition from the formation.

When the surfactant concentration in a solution of 0.3% PAA increases from 0.5% to 1%, i.e. twice, the surface activity of the solution at the interface increases (σ decreases by 1.6 times in fresh water from 3.2 mN/m to 2.03 mN/m, and in mineralized water - by 1.09 times, at This results in a disproportionate, unproductive consumption of surfactants, which generally reduces the efficiency of oil displacement from the reservoir.

Since the oil-displacing composition according to the proposed method contains a polymer, the optimal concentrations of this reagent were determined. Table 2 shows the values of the dynamic viscosity of PAA solutions measured on a VISCOMETR RM-100 rotational viscometer in the range of PAA polymer concentrations from 0.1% to 0.9% at temperatures of 20°C and 8°C.

Table 2 Dependence of dynamic viscosity of PAA solutions on polymer concentration

PAA polymer concentration, wt.% Dynamic viscosity of PAA solution at temperature, mPa⋅s 20°C 8°С 0.1 12.87 15.85 0.2 33.62 36.67 0.3 63.50 67.64 0.4 102.2 109.3 0.5 150 158.3 0.6 201.3 209.3 0.7 266.3 285.5 0.8 334.7 346.5 0.9 391.2 419.4

It has been established that the most optimal range of PAA concentration in solution is from 0.3% to 0.7%. When the concentration of polyacrylamide in the solution decreases below 0.3%, the viscosity of the solution decreases below 40 mPa⋅s, which reduces the efficiency of oil displacement from the reservoir, since the ratio of the viscosity of oil and polymer solution increases, which leads to early water breakthrough when oil is displaced into heterogeneous layers.

An increase in the concentration of PAA in the solution above 0.7%, at which the viscosity of the solution becomes above 300 mPa⋅s, leads to problems when pumping the solution into the well, especially if the well has an injectivity below 200 m ³ /day.

The above data show that for more complete extraction of residual oil, it is not enough to displace it only with water or a surfactant with a polymer.

Recently, nanosuspensions, which are water-based suspensions, the dispersed component of which are nanoparticles (NPs), have been used to extract hard-to-recover oil reserves.

The use of nanoparticles improves oil displacement through several mechanisms of action, which include: 1) changing the wettability of the rock, 2) creating disjoining pressure between oil droplets and the rock surface, 3) clogging pore channels, 4) reducing interfacial tension between oil and the injected liquid, 5) inhibition of asphaltene precipitation. In addition, nanoparticles can be used to reduce the viscosity of heavy and viscous oil.

In order to study the effect of nanoparticles on the surface activity of Neominol surfactant solutions, the properties of these solutions were studied in the presence of magnesium oxide (MgO) nanoparticles, which were introduced into surfactant solutions with continuous uniform stirring. The effect of nanoparticles on the surface activity of a Neominol surfactant solution at the interface with a hydrocarbon liquid, which was kerosene, was studied. Measurements of interfacial tension values were carried out using a stalagmometer. The results are presented in Table 3.

Table 3 - Interfacial tension of 0.1% surfactant solutions containing and without magnesium oxide nanoparticles at the border with kerosene

MgO additive,
% wt. Interfacial tension value of Neominol solutions, mN/m fresh mineralized 0 1.69 2.47 0.01 1.68 (0.6%) 2.14 (13.3%) 0.03 1.38 (18.3%) 2.07 (16.2%)

The interfacial tension of a 0.1% solution of Neominol in fresh water at the interface with kerosene decreased to 18% with an increase in the MgO content in the solution from 0.01% to 0.03% in fresh water and to 16.2% in mineralized water. A small addition of magnesium oxide nanoparticles leads to a reduction in the consumption of expensive surfactants by further reducing the interfacial tension at the interface between two immiscible liquids.

In fig. The dependence of the interfacial tension σ of Neominol solutions of various concentrations, containing and without nanoparticles of magnesium oxide MgO, at the boundary with Ashalcha oil, measured on an optical device (Dataphysics, Germany) using the hanging drop method, is shown. For clarity, the concentration of the surfactant Neominol varied in solutions from 0.1% to 0.4%, the concentration of nanoparticles in surfactant solutions was 0.03%, 0.05%, 0.07%.

Table 4 shows the values of interfacial tension σ, and in parentheses it is indicated how many times the interfacial tension of the surfactant solution decreased when magnesium oxide nanoparticles were introduced into it compared to the control surfactant solution that did not contain nanoparticles.

The interfacial tension of Neominol surfactant solutions containing 0.05% magnesium oxide nanoparticles at the interface with oil decreased most effectively relative to a surfactant solution not containing nanoparticles (by 3.9 times). Other concentrations of magnesium oxide nanoparticles also work, reducing the value of σ to a slightly lesser extent relative to a surfactant solution that does not contain nanoparticles.

Table 4 - Interfacial tension of surfactant solutions at the boundary with oil

Neominol concentration,
% wt. Interfacial tension of surfactant solutions containing MgO nanoparticles at the interface with oil, mN/m 0 0.03 0.05 0.07 0.1 0.99 0.38(2.6) 0.27(3.7) 0.35(2.8) 0.2 0.7 0.29(2.4) 0.23(3.0) 0.24(2.9) 0.3 0.62 0.23(2.7) 0.19(3.3) 0.18(3.4) 0.4 0.51 0.15(3.4) 0.13(3.9) 0.14(3.4)

To increase the recovery of residual oil according to the proposed method, directly at the well, before pumping it into the reservoir into the mixing tank, fresh or mineralized water with a total mineralization of up to 300 g/cm ³ and the Neominol detergent composition, which is an aqueous-alcohol solution of a mixture of nonionic surfactants, are dosed, and at the same time water-insoluble magnesium oxide nanoparticles measuring 5-100 nm with a specific surface area of 64.5 m ² /g are dosed into the mixing container using a screw dispenser for bulk reagents with continuous stirring for at least 30 minutes until they are evenly distributed, the resulting suspension is pumped into the loading unit of the installation for preparing solutions from liquid and bulk chemical reagents, then polyacrylamide is added to the resulting suspension with a screw doser designed for dosing and supplying powdered reagents, with constant stirring to obtain a composition for flooding with the following ratio of components, wt.%: Neominol 0 ,1 - 0.5, the specified nanoparticles are magnesium oxide 0.01 - 0.07, polyacrylamide 0.3-0.7, the specified water is the rest, then pumped into the oil reservoir through an injection well, oil is extracted from production wells.

Preliminary introduction of nanoparticles into the Neominol surfactant solution according to the proposed method, for which magnesium oxide nanoparticles are used, makes it possible to enhance the surface activity of the solution and increase the displacing ability of the resulting suspension - surfactant-polymer composition (by increasing the washing ability, injection of a composition whose surface properties are enhanced by the introduction magnesium oxide nanoparticles).

Filtration experiments to determine the oil displacement coefficient when injecting compositions containing nanoparticles were carried out at temperatures of 8°C and 20°C and are presented in Table 5. A temperature of 8°C is typical for many super-viscous oil deposits, i.e. experiments conducted at this temperature are close to the reservoir conditions of EHV deposits, and at 20°C - to the conditions of terrigenous reservoirs.

Table 5 shows: change in pressure during injection of the oil-displacing slug; primary - Kvyt(p) and final oil displacement coefficients Kvyt(k) for each experiment, as well as the reduced oil displacement coefficient (PKut.). The reduced oil displacement coefficient, which is equal to the ratio of the final oil displacement coefficient to the injection pressure drop, i.e. Kvyt(k)/ΔР, is used for comparative analysis of the efficiency of oil displacement by various compositions. The higher the given oil displacement coefficient, the higher the efficiency of the oil extraction process.

The results of filtration experiments show that the proposed method for extracting oil from an oil reservoir effectively displaces oil from terrigenous reservoirs of coal deposits at a reservoir temperature of 20°C and from EHV deposits at a reservoir temperature of 8°C.

It is obvious that at a temperature of 20°C the efficiency of oil displacement using the proposed method is much higher than at a temperature of 8°C, since at low temperatures the viscosity of oil is much higher and the filtration resistance it exerts during displacement increases.

Table 5 - Results of filtration experiments on oil displacement from the reservoir model at temperatures of 20°C and 8°C.

No.
experience Researched compositions t of experiment, °C Pressure during composite injection ΔР, MPa Primary Kvyt(p) _. oil water, % Gain ΔKw. oil composition,% Final Kvyt(k). _. oil,% Given. PKvyt. oil,
%/MPa The dynamic viscosity of oil is 160 mPaσ⋅s and the density is 922 kg/m ³ at 20°C. 1 0.3% PAA+ 0.3% Neominol 20 0.84 6.83 16.48 23.31 27.75 2 0.3% PAA+0.1% Neominol+ 0.01% MgO 0.85 6.69 18.0 24.69 29.05 3 0.3% PAA+ 0.3% Neominol+0.02% MgO 0.81 6.83 18.94 25.77 31.82 4 0.3% PAA+ 0.3% Neominol +0.03% MgO 0.78 9.09 25.31 34.4 44.1 The dynamic viscosity of oil is 9900 mPa⋅s and the density is 963 kg/m ³ at t=8°C 5 0.4% PAA+0.4% Neominol 8 1.8 0 19.62 19.62 10.9 6 0.4% PAA + 0.4% Neominol + 0.04% MgO 1.85 0 28.64 28.64 15.48 7 0.7% PAA + 0.5% Neominol + 0.07% MgO 2.7 0 35.08 35.08 13.0 8 (Prototype)
0.3% PAA+ 3.0% BETAPAV 20 2.1 9.98 12.6 22.58 10.7

Even the composition containing minimal concentrations of the reagents included in its composition turned out to be more effective in displacing oil (experiment 2, table 5 with Kvt(k) = 24.69) than the prototype composition with Kvt(k) = 22.58.

The introduction of 0.02% MgO into a 0.3% Neominol solution and its further mixing with 0.3% PAA (experiment 3, table 5) led to an increase in the oil displacement coefficient by 18.94% at 20°C, which is higher than for a composition that does not contain magnesium oxide nanoparticles (experiment 1, table 5), and a prototype (experiment 8, table 5), which includes an amphoteric surfactant - BETAPAV, which does not contain nanoparticles, and the concentration of BETAPAV is 30 times higher than the concentration of AF ₉ -12.

Displacement of oil at 8°C is complicated by the fact that in these experiments a more viscous oil with a viscosity of 9900 mPa⋅s was used. The introduction of 0.04% magnesium oxide nanoparticles into this composition led to an increase in the final oil displacement coefficient by 9.02% (experiment 6, table 5) relative to a composition that did not contain magnesium oxide nanoparticles (experiment 5, table 5). A further increase in the concentration of reagents in the composition (0.7% PAA + 0.5% Neominol + 0.07% MgO, experiment 7, table 5) led to an increase in the oil displacement coefficient relative to the composition not containing nanoparticles (experiment 5, table 5) , by 15.46%. But at the same time, the given PCvt. of oil is lower (13.0 versus 15.48) than the given PCout. oil with a composition of 0.4% PAA + 0.4% Neominol + 0.04% MgO, due to an increase in injection pressure due to an increase in the concentration of PAA polymer in the composition.

An increase in the concentrations of the components of the injected composition (experiment 7, table 5) led to an increase in the final oil displacement efficiency to 35.08% and a decrease in the reduced oil displacement efficiency to 13.0%. Despite the higher PCv. in experiment 6, this composition turned out to be less profitable due to the increase in filtration resistance when pumping the composition, which is another confirmation that the concentrations of the components of the composition when implementing the proposed extraction method should not exceed, respectively: surfactant - 0.5% wt., nanoparticles magnesium oxide - 0.07% wt., PAA polymer - 0.7% wt.

An example of a specific implementation.

The proposed method is carried out using standard (existing) oilfield equipment that provides transportation, preparation (mixing) and injection of aqueous solutions into the well: a complex for preparing solutions from liquid and bulk chemical reagents KUDR-8 or analogues; pumping units type ANTs-320 according to TU 26-02-30-75 or analogues.

Well 1 develops an oil reservoir 6 m thick, with a porosity of 20%. Well injectivity is 350 m ³ /day. at a pressure on the water pipeline of 8.0 MPa.

The method is implemented through injection wells. An aqueous solution is prepared directly at the well before injection into the formation by mixing the components using the KUDR-8 installation.

Water and surfactant Neominol are dosed into the container for liquid reagents by pumps at a flow rate that provides the required concentrations of the components in the working solution.

Simultaneously with the dosage of the surfactant Neominol, magnesium oxide is dosed into the mixing container using a screw doser for bulk reagents with constant stirring for at least 30 minutes.

After this, the resulting suspension is pumped into the loading unit of the KUDR installation, equipped with a screw dispenser designed for dosing and supplying powdered reagents. From the hopper, PAA is supplied by a screw dispenser at a flow rate that provides the required concentrations into the jet apparatus, with constant stirring. The composition is mixed for 10-15 minutes and pumped into the well.

Prepare a solution in water with a density of 1100 kg/m ³ of the following composition: a) surfactant Neominol with a concentration in the composition of 0.3 wt.%. b) magnesium oxide with a concentration in the composition of 0.03% wt. After mixing these reagents, PAA polymer powder is introduced with a concentration in the composition of 0.3 wt.%, water - the rest (corresponds to experiment 4, table 5).

The consumption of reagents per 1 m ³ of water is surfactant Neominol - 3.3 kg, OM - 0.33 kg, PAA - 3.3 kg.

A composition with a volume of 300 m ³ is pumped in, after which the well switches to normal operation. A month later, the average flow rate from the surrounding production wells increased from 8.5 tons/day to 11.5 tons/day. The increase in the average daily flow rate was 3 tons/day.

The results obtained show that there was an increase in oil recovery using the proposed method as a result of injection of a composition of an aqueous solution of the surfactant Neominol, which additionally contains magnesium oxide nanoparticles and a polymer.

In this case, the displacing ability of the composition increases and its washing ability increases due to the injection of the surfactant Neominol, the surface properties of which are enhanced by the introduction of magnesium oxide nanoparticles, which leads to a decrease in the concentration of the surfactant and helps reduce material costs.

Claims (3)

A method for extracting oil from an oil reservoir using flooding with nanoparticles, including obtaining a composition for flooding containing nanoparticles and surfactant surfactants, and pumping it into the oil reservoir, characterized in that directly at the well, before injection into the reservoir, the mixing tank is dosed with pumps. fresh or mineralized water and the cleaning composition Neominol, which is an aqueous-alcohol solution of a mixture of nonionic surfactants, and at the same time, water-insoluble magnesium oxide nanoparticles measuring 5-100 nm with a specific surface area of 64.5 are dosed into the mixing container using a screw dispenser for bulk reagents m ² /g with continuous stirring for at least 30 minutes until they are evenly distributed, the resulting suspension is pumped into the loading unit of the installation for preparing solutions from liquid and bulk chemical reagents, then into the resulting suspension with a screw doser designed for dosing and supplying powdered reagents, with constant stirring, polyacrylamide is added to obtain a composition for flooding at the following ratio of components, wt.%: Neominol 0.1-0.5 indicated magnesium oxide nanoparticles 0.01-0.07 polyacrylamide 0.3-0.7 specified water rest, the flooding composition is stirred for 10-15 minutes, then pumped into the oil reservoir through an injection well, and oil is extracted from production wells.