An experimental device and method for enhanced carbonated water displacement in heavy oil reservoirs using nanofluids

Abstract

The present invention belongs to the technical field of heavy oil reservoir exploitation, and specifically relates to an experimental device and experimental method for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs. The experimental device includes a nanofluid-enhanced carbonized water preparation system, a fluid injection system, a displacement experimental system, an oil and gas measurement system, and a data acquisition and temperature control system. The experimental method includes the following steps: (1) preparing injection fluid; (2) simulating the heavy oil reservoir environment; (3) nanofluid-enhanced carbonized water displacement; (4) systematically evaluating the feasibility of nanofluid-enhanced carbonized water displacement in heavy oil reservoirs; and (5) studying the influence of geological parameters and injection and production parameters on the effect of nanofluid-enhanced carbonized water displacement. The experimental device can observe in real time the microscopic interaction between nanofluid-enhanced carbonized water and heavy oil under high temperature and high pressure reservoir conditions. The experimental method can study the influence of geological and injection and production parameters on the development effect in nanofluid-enhanced carbonized water displacement of heavy oil reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy oil reservoir exploitation, and particularly relates to a heavy oil reservoir nanofluid enhanced carbonated water displacement experimental device and an experimental method. Background Art

[0002] Carbonated water flooding, a new CO2 technology, holds promise for resolving the aforementioned challenges in developing complex reservoirs. During carbonated water flooding, CO2 transfers to the oil phase through mass transfer, causing crude oil to swell and reduce viscosity. Furthermore, carbonated water can alter rock surface wettability and reduce oil-water interfacial tension. However, carbonated water suffers from a low CO2 solubility. To increase CO2 solubility in carbonated water, enhance CO2 mass transfer, and thereby improve oil recovery efficiency, the introduction of nanofluids into carbonated water flooding for heavy oil reservoirs has been proposed. Adding small amounts of nanoparticles and dispersants to carbonated water increases the CO2 solubility in the water, enhancing CO2 mass transfer from the water phase to the heavy oil, thereby improving swelling and viscosity reduction, and enhancing heavy oil fluidity. Nanofluids are uniform, stable suspended colloidal systems composed of nanoparticles (diameters ranging from 1 to 100 nm) dispersed in media such as water, alcohol, and oil. Compared to existing traditional oilfield chemicals, they offer advantages such as environmental friendliness, small size, large surface area, and low cost, and possess significant application potential.

[0003] Although the introduction of nanofluids into the carbonated water flooding process in heavy oil reservoirs has been proposed to increase the amount of CO2 dissolved in the carbonated water, there is currently no experimental method or experimental device suitable for nanofluid-enhanced carbonated water displacement to simulate and observe in real time the microscopic interaction between nanofluid-enhanced carbonated water and heavy oil under high-temperature and high-pressure reservoir conditions, so as to further study the influence of geological and injection-production parameters such as permeability, porosity, nanofluid type, nanofluid concentration, CO2 concentration, salinity or injection rate on development results.

[0004] Chinese patent CN107916915 discloses a carbonized water displacement system and method under high temperature and high pressure, wherein the displacement system includes an injection system, a displacement system, a model system, and a metering system connected in sequence, and the displacement system includes a water displacement system, an oil displacement system, and a carbonized water displacement system connected in parallel between the injection system and the model system. The displacement steps include: establishing the initial oil saturation and irreducible water saturation of the core; performing water displacement on the natural core to obtain the water displacement recovery rate of the core; and performing carbonized water displacement on the natural core to obtain the carbonized water displacement recovery rate of the core after water displacement. The carbonized water is an aqueous solution dissolved in CO2.

[0005] Existing carbonated water displacement experimental models are mainly established based on the comparative evaluation of conventional oil reservoir displacement effects, and do not focus on the characteristics of heavy oil reservoir experimental models. It is also impossible to use the model to observe in real time the microscopic interactions between carbonated water and heavy oil during the displacement process, such as the dissolution and precipitation of CO2, and the mass transfer of CO2.

[0006] However, the experimental device and method for nanofluid enhanced carbonized water flooding in heavy oil reservoirs have not yet been proposed. Summary of the Invention

[0007] The present invention aims to provide an experimental device and method for nanofluid-enhanced carbonated water flooding in heavy oil reservoirs. This device enables real-time observation of the microscopic interaction between nanofluid-enhanced carbonated water and heavy oil in high-temperature and high-pressure reservoirs, while also meeting the requirements of other experiments such as nanofluid flooding, CO2 flooding, and carbonated water flooding. The experimental method is capable of studying the influence of geological and injection-production parameters, such as permeability, porosity, nanofluid type, nanofluid concentration, CO2 concentration, salinity, and injection rate, on the development results of nanofluid-enhanced carbonated water flooding in heavy oil reservoirs.

[0008] The technical solution of the present invention is: a nanofluid enhanced carbonated water displacement experimental device for heavy oil reservoirs, including a nanofluid enhanced carbonated water preparation system, a fluid injection system, a displacement experimental system, an oil and gas measurement system, and a data acquisition and temperature control system.

[0009] The nanofluid-enhanced carbonated water preparation system includes two containers connected in parallel, namely a carbon dioxide container and a nanofluid-enhanced carbonated water container; the bottoms of both containers are connected to a high-precision constant-speed and constant-pressure pump through a control valve and pipeline; the tops of both containers are connected to one end of a back-pressure valve I through a pressure gauge, a control valve and a pipeline, and the other end of the back-pressure valve I is connected to a liquid metering container; the upper part of the liquid metering container is connected to a gas flow meter I.

[0010] The introduction of the back pressure valve I, the liquid metering container and the gas flow meter I can measure the CO2 solubility in the configured nanofluid enhanced carbonated water, thereby quantitatively verifying the accuracy of the nanofluid enhanced carbonated water preparation.

[0011] The fluid injection system consists of three containers connected in parallel: a formation oil container, a formation water container, and the nanofluid-enhanced carbonated water container from the nanofluid-enhanced carbonated water preparation system. The bottoms of the formation oil and formation water containers are connected to a high-precision constant-speed and constant-pressure pump via control valves and pipelines. The tops of the formation oil, formation water, and nanofluid-enhanced carbonated water containers are connected to one end of the displacement model in the displacement experiment system via pressure gauges, control valves, and pipelines. This is used to inject nanofluid-enhanced carbonated water, formation oil, and formation water into the displacement model.

[0012] The displacement experimental system consists of a displacement model, the other end of which is connected to a vacuum pump via a control valve and pipeline. The displacement model is connected in series with a high-temperature, high-pressure observation window and back-pressure valve II, which is connected to a back-pressure control pump and a pressure gauge. A high-definition camera is located above the high-temperature, high-pressure observation window, and a light source is located below it. These cameras are used to observe and record the microscopic interactions between the nanofluid-enhanced carbonated water and the heavy oil during the displacement process. A vacuum pump, located between the displacement model and the high-temperature, high-pressure observation window, maintains a vacuum throughout the experimental setup. The high-temperature, high-pressure observation window can withstand temperatures and pressures exceeding 50°C and 10 MPa, simulating the conditions of heavy oil reservoirs.

[0013] The oil and gas measurement system includes a gas-liquid separator connected to a back-pressure valve II. The upper part of the gas-liquid separator is connected to a gas flow meter II for measuring the gas production during the nanofluid-enhanced carbonized water displacement process. The bottom of the gas-liquid separator is connected to a liquid collection container, which is placed on an electronic balance for measuring the liquid production quality during the nanofluid-enhanced carbonized water displacement process.

[0014] The data acquisition and temperature control system includes a computer connected to the displacement model's pressure sensor to measure pressure changes within the displacement model during nanofluid-enhanced carbonated water displacement. The computer is also connected to the displacement model's temperature controller and the heating plate and insulation jacket surrounding the displacement model. These controls control the temperature of the heated displacement model and simulates the temperature of the heavy oil reservoir.

[0015] Furthermore, the displacement model of the experimental device for nanofluid-enhanced carbonated water displacement in heavy oil reservoirs has an inner diameter of 25-50 mm and a length of 100-1000 mm. This size range, determined through extensive simulation experiments and theoretical calculations, is optimized to better reflect the oil, gas, and water seepage processes at the scale of heavy oil reservoirs.

[0016] Furthermore, the high-definition camera of the heavy oil reservoir nanofluid enhanced carbonated water displacement experimental device has a pixel greater than 12 million and a frame rate greater than 30 frames per second; and the light source is a white light source.

[0017] Furthermore, the displacement model of the nanofluid-enhanced carbonated water displacement experimental device for heavy oil reservoirs is equipped with pressure measuring points at the beginning, middle, and end. This allows for accurate detection of pressure changes at different locations within the displacement model during the experiment, preventing the failure to detect certain areas of the displacement model due to a lack of pressure measuring points.

[0018] Furthermore, the visual range of the high-temperature and high-pressure observation window of the nanofluid-enhanced carbonated water displacement experimental device for heavy oil reservoirs is between 50 and 200 mm in length, 5 and 30 mm in width, and 1 and 5 mm in thickness. This thickness can ensure that the nanofluid-enhanced carbonated water and heavy oil can flow in the high-temperature and high-pressure visual window, and can also enable the light source and high-definition camera to cooperate to obtain clear images.

[0019] An experimental method for nanofluid-enhanced carbonated water displacement in heavy oil reservoirs using the above-mentioned experimental device comprises the following steps:

[0020] (1) Preparation of injection fluids: Preparation of formation oil, formation water, and nanofluid-enhanced carbonated water;

[0021] Preparation of formation oil: Based on the dissolved gas-oil ratio and gas compressibility factor of the reservoir heavy oil, formation oil is prepared at the reservoir pressure and temperature to simulate the heavy oil in the actual reservoir. The prepared formation oil is then introduced from the sample preparation container into the formation oil container. The viscosity of the formation oil under formation conditions is greater than 5000 mPa·s.

[0022] Preparation of nanofluid-enhanced carbonated water:

[0023] a. Add a soluble metal salt, a dispersant, and nanoparticles to distilled water and stir until the soluble metal salt and dispersant are completely dissolved and the nanoparticles are uniformly dispersed to prepare a nanofluid; disperse the nanofluid using an ultrasonic disperser; the ultrasonic disperser has an output power of 100-1000W and an operating frequency of 20-25kHz;

[0024] b. Set the volume to V N The nanofluid is introduced into the nanofluid enhanced carbonated water container to discharge the air in the container;

[0025] c. According to the experimental pressure P and experimental temperature T Based on the Duan model, the amount of CO2 dissolved in a pure soluble metal salt aqueous solution with the same salinity as the nanofluid under experimental conditions was preliminarily calculated. n Duan ; Calculate the volume of CO2 in the carbon dioxide container according to formula (I) V 注1 ;

[0026] (I)

[0027] In formula (I), P is the experimental pressure (absolute pressure), MPa; Z Experimental pressure P and experimental temperature T The compression factor of CO2; n Duanis the amount of CO2 dissolved under experimental conditions calculated by the Duan model, mol; R is the thermodynamic constant, with a value of 8.314 J / (mol·K); T is the experimental temperature, K; V 注1 is the volume of CO2 in the carbon dioxide container, mL;

[0028] d. The carbon dioxide container CO2 is injected into the nanofluid enhanced carbonated water container, and the slider is used to stir the nanofluid enhanced carbonated water container fluid;

[0029] A high-precision constant speed and constant pressure pump is used to keep the pressure in the nanofluid enhanced carbonized water container at the experimental pressure. P ;

[0030] When the pressure in the nanofluid-enhanced carbonated water container is P When the flow rate of the high-precision constant speed and constant pressure pump remains unchanged and remains at 0, it indicates that CO2 no longer dissolves into the nanofluid, thereby forming nanofluid-enhanced carbonated water. The gas volume in the nanofluid-enhanced carbonated water container is recorded. V gas ;

[0031] The amount of undissolved CO2 species was calculated by formula (II);

[0032] (II)

[0033] In formula (II), P is the experimental pressure, MPa; V gas is the gas volume in the nanofluid-enhanced carbonized water container, mL; Z 1 is the experimental pressure P and experimental temperature T The compression factor of CO2; R is the thermodynamic constant, with a value of 8.314 J / (mol·K); T is the experimental temperature, K; n 1 is the amount of undissolved CO2 substance, mol;

[0034] The amount of dissolved CO2 substance, mol, was calculated by formula (III);

[0035] (III)

[0036] In formula (III), n Duan is the amount of CO2 dissolved under experimental conditions calculated by the Duan model, mol; n 1 is the amount of undissolved CO2 substance, mol;n 2 is the amount of dissolved CO2, mol;

[0037] The solubility of CO2 was calculated by formula (IV);

[0038] (IV)

[0039] In formula (IV), n 2 is the amount of dissolved CO2, mol; R is the thermodynamic constant, with a value of 8.314 J / (mol·K); T 0 is the indoor temperature, K; P 0 is atmospheric pressure, 0.1 MPa; V N is the volume of the nanofluid, mL; S 计算 is the calculated solubility of CO2, mL / mL;

[0040] e. Maintain the test pressure through the back pressure valve I P , use a high-precision constant speed and constant pressure pump to sequentially displace all undissolved gas and a certain amount of nanofluid enhanced carbonated water into the liquid measuring container, and after the liquid is discharged, start to measure and record the gas output through the gas flow meter I V 气1 , measure and record the liquid output through the liquid measuring container V 液1 , calculate the dissolved amount of CO2 by formula (V) S 测 :

[0041] (V)

[0042] In formula (V), V 气1 is the gas output, mL; V 液1 is the amount of liquid output, mL; S 测 is the measured solubility of CO2, mL / mL;

[0043] f. By comparison S 测 and S 计算 Value, when S 测 and S 计算 When the error is less than 5%, the amount of CO2 dissolved in the nanofluid is considered reliable and the preparation of nanofluid-enhanced carbonated water is completed;

[0044] (2) Simulation of heavy oil reservoir environment: fill the displacement model with quartz sand or artificial core; make the displacement model into a vacuum state; use a high-precision constant speed and constant pressure pump to inject formation water and formation oil, measure the porosity, permeability and original oil saturation of the displacement model; adjust the displacement model pressure to the formation pressure of the heavy oil reservoir to be simulated, and age the saturated formation oil;

[0045] (3) Nanofluid enhanced carbonized water flooding: Inject nanofluid enhanced carbonized water into the displacement model to displace the formation oil, and measure and record the injection volume of nanofluid enhanced carbonized water at different times V 注入 , liquid quality m 液 , oil production quality m 油 , water production, gas production V 气 and stress;

[0046] Calculate the water content at different injection rates f w , CO2 storage S , cumulative production gas-oil ratio R p , cumulative oil production CO i and degree of recovery R , using a high-temperature and high-pressure observation window to observe the microscopic interaction between nanofluid-enhanced carbonized water and heavy oil, and ending when the water cut reached 95% or the cumulative production gas-oil ratio reached 2000;

[0047] (4) Compare the development effects of water flooding, carbonized water flooding, and nanofluid-enhanced carbonized water flooding, and systematically evaluate the feasibility of nanofluid-enhanced carbonized water flooding in heavy oil reservoirs;

[0048] (5) Repeat the above steps (1) to (4) to study the effects of geological parameters and injection and production parameters on the nanofluid enhanced carbonized water flooding effect. Geological parameters and injection and production parameters include permeability, porosity, nanofluid type, nanofluid concentration, CO2 concentration, salinity, injection rate, etc.

[0049] Furthermore, in step (1) of the experimental method for nanofluid-enhanced carbonated water displacement in heavy oil reservoirs, the nanoparticles in the nanofluid for preparing nanofluid-enhanced carbonated water are selected from one of nano-SiO2, nano-Al2O3, nano-TiO2 and MWCNT; the dispersant is polyvinyl pyrrolidone or sodium dodecyl sulfate; and the soluble metal salt is selected from one of NaCl, KCl, MgCl2, CaCl2 and Na2SO4.

[0050] In the nanofluid, the concentration of nanoparticles is 0.01-1 wt%, the concentration of dispersant is 0.1-5 wt%, and the concentration of soluble metal salt is 0.1-5 wt%.

[0051] The dispersion time of nanofluid is 45~90min.

[0052] Furthermore, in step (2) of the experimental method for nanofluid-enhanced carbonated water displacement in heavy oil reservoirs, the quartz sand particle size is 20-120 meshes, and the artificial core length is 100-1000 mm; the quartz sand particle size can make the permeability of the displacement model after filling consistent with the actual permeability of the heavy oil reservoir, so as to better simulate the loose sandstone formation of the heavy oil reservoir.

[0053] The time for evacuating the displacement model by using a vacuum pump is 24 to 48 hours, and the vacuum pumping rate is 2 to 5 m 3 / h, ultimate vacuum 2~4Pa.

[0054] The displacement model was left at rest for 24 to 48 hours at the formation temperature and pressure of the heavy oil reservoir to allow the saturated formation oil to age.

[0055] Furthermore, in step (2) of the experimental method for enhancing carbonized water displacement in heavy oil reservoirs with nanofluids, the porosity of the displacement model is measured: the displacement model is made to absorb formation water under vacuum, and when the pressure changes from negative pressure to close to atmospheric pressure, the displacement model is changed to injecting formation water. After water is seen, the water output of the displacement model is recorded, and the porosity of the displacement model is calculated by formula (VI): ;

[0056] (VI);

[0057] In formula (VI), V 吸 is the volume of the absorbed formation water, mL; V 注 is the volume of injected formation water, mL; V 产 is the volume of produced formation water, mL; D is the inner diameter of the displacement model, cm; L is the length of the displacement model, cm;

[0058] Penetration: Changing n The simulated formation water is injected into the displacement model at a low injection rate. The pressure at both ends of the displacement model is measured during the injection process. The permeability of the displacement model is then calculated according to Darcy's law shown in formula (VII). k ;

[0059] (VII);

[0060] In formula (VII), Qi Indicates the i injection rate, mL / min; μ represents the simulated formation water viscosity, mPa·s; L is the length of the displacement model, cm; D is the inner diameter of the displacement model, cm; Δ p i Indicates the i The pressure difference between the two ends of the displacement model during the first injection is 10 -1 MPa;

[0061] Initial oil saturation: Inject formation oil into the displacement model at a rate of 1-5 mL / min. Stop injection when the volume of injected formation oil is 2-3 times the pore volume of the displacement model, and record the injected heavy oil volume. V 油注 and produced heavy oil volume V 油采 The pore volume is the volume of the displacement model cavity and the porosity The initial oil saturation is calculated by formula (VIII): S oi ;

[0062] (VIII);

[0063] In formula (VIII), S oi is the initial oil saturation, %; V 油注 is the injected heavy oil volume, mL; V 油采 Volume of produced heavy oil, mL; V 吸 is the volume of the absorbed formation water, mL; V 注 is the volume of injected formation water, mL; V 产 is the volume of produced formation water, mL.

[0064] Furthermore, in step (3) of the experimental method for nanofluid-enhanced carbonated water displacement in heavy oil reservoirs, the injection rate of nanofluid-enhanced carbonated water is 0.5-5 mL / min; this injection rate can better simulate the nanofluid-enhanced carbonated water displacement process. Excessive injection rate will affect the interaction effect between nanofluid-enhanced carbonated water and heavy oil during the displacement process.

[0065] Determination of oil production quality m 油 : Place the displacement output fluid in a high temperature oven at 70-90℃ for 12-48 hours, and then use an electronic balance to weigh the mass of the remaining oil.m 油 ;

[0066] Calculate the water content at different injection rates according to formula (IX) f wi :

[0067] (IX);

[0068] In formula (IX), m 液i Indicates the injection volume i Liquid production measured at , g; m 油i Indicates the injection volume i The product measured at

[0069] Oil amount, g; ρ 水 is the density of water, g / cm 3 ; ρ 油 is the density of oil, g / cm 3 ;

[0070] Calculate the CO2 storage capacity under different injection rates according to formula (X) S i :

[0071] (X);

[0072] In formula (X), V 注i represents the injection amount of nanofluid-enhanced carbonated water at time i, mL; S 测 Expressed as the measured solubility of CO2, mL / mL; V 气i Indicates the i Gas production per measurement, mL;

[0073] The cumulative production gas-oil ratio under different injection rates is calculated according to formula (XI) R pi :

[0074] (XI);

[0075] In formula (XI), V 气i Indicates the i Gas production per measurement, mL; m 油i Indicates the injection volume i Oil production measured at , g; ρ 油is the density of oil, g / cm 3 ;

[0076] Calculate the cumulative oil production at different injection rates according to formula (XII) CO i :

[0077] (XII);

[0078] In formula (XII), m 油i Indicates the injection volume i Oil production measured at , g; ρ 油 is the density of oil, g / cm 3 ;

[0079] Calculate the recovery degree under different injection rates according to formula (XIII) R i :

[0080] (XIII);

[0081] In formula (XIII), m 油i Indicates the injection volume i Oil production measured at , g; ρ 油 is the density of oil, g / cm 3 ; V 油注 is the injected heavy oil volume, mL; V 油采 Volume of produced heavy oil, mL.

[0082] The water content under different injection rates is calculated by the above formula f wi , CO2 storage S i , cumulative production gas-oil ratio R pi , cumulative oil production CO i and degree of recovery R i The displacement process of the experiment was fully recorded, including the CO2 storage S i It is of great significance to study the CO2 storage of nanofluid-enhanced carbonized water flooding.

[0083] The beneficial effects of the present invention are:

[0084] 1. The experimental device for nanofluid-enhanced carbonized water flooding in heavy oil reservoirs proposed in this invention can realize the experimental process of nanofluid-enhanced carbonized water flooding in heavy oil reservoirs, and observe the microscopic interaction between nanofluid-enhanced carbonized water and heavy oil in real time under high-temperature and high-pressure reservoir conditions, while meeting the requirements of other experiments such as nanofluid flooding, CO2 flooding, and carbonized water flooding.

[0085] 2. The experimental method described in this paper addresses the limitations of conventional carbonized water flooding by introducing nanofluids, providing an effective technical means for the efficient development of heavy oil reservoirs. This experimental method can be used to study the effects of geological and injection / production parameters, such as permeability, porosity, nanofluid type, nanofluid concentration, CO2 concentration, salinity, and injection rate, on the development results during nanofluid-enhanced carbonized water flooding. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 Schematic diagram of the structure of the experimental device of the present invention.

[0087] Figure 2 This is the variation of cumulative oil production with injection volume in the experimental method of the present invention.

[0088] Figure 3 This is the variation of the recovery degree with the injection volume in the experimental method of the present invention.

[0089] Figure 4 This is the change of water content with injection volume in the experimental method of the present invention.

[0090] Among them, 1 is a high-precision constant speed and constant pressure pump, 2 is a carbon dioxide container, 3 is a nanofluid enhanced carbonated water container, 4 is a formation oil container, 5 is a formation water container, 6 is a control valve, 7 is a heating jacket, 8 is a pressure gauge, 9 is a back pressure valve I, 10 is a liquid metering container, 11 is a gas flow meter I, 12 is an injection port, 13 is an inlet cover, 14 is an outer body, 15 is a head end pressure measuring point, 16 is a middle end pressure measuring point, 17 is a terminal pressure measuring point, 18 is an outlet cover Plate, 19 is the production outlet, 20 is the pressure sensor, 21 is the temperature controller, 22 is the heating plate, 23 is the insulation sleeve, 24 is the computer, 25 is the vacuum pump, 26 is the high-temperature and high-pressure observation window, 27 is the high-definition camera, 28 is the light source, 29 is the back pressure control pump, 30 is the back pressure valve II, 31 is the gas-liquid separator, 32 is the gas flow meter II, 33 is the electronic balance, 34 is the liquid collection container, 35 is the constant temperature box, and 36 is the displacement model. DETAILED DESCRIPTION

[0091] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0092] Example 1

[0093] The nanofluid enhanced carbonated water flooding experimental device for heavy oil reservoirs comprises a nanofluid enhanced carbonated water preparation system, a fluid injection system, a displacement experimental system, an oil and gas measurement system, and a data acquisition and temperature control system.

[0094] The nanofluid-enhanced carbonated water preparation system includes two containers connected in parallel, namely a carbon dioxide container 2 and a nanofluid-enhanced carbonated water container 3; the bottoms of both containers are connected to a high-precision constant-speed and constant-pressure pump 1 through a control valve 6 and a pipeline; the tops of both containers are connected to one end of a back-pressure valve I9 through a pressure gauge 8, a control valve 6 and a pipeline, and the other end of the back-pressure valve I9 is connected to a liquid metering container 10; the upper part of the liquid metering container 10 is connected to a gas flow meter I11.

[0095] The fluid injection system includes three containers connected in parallel: a formation oil container 4, a formation water container 5, and the nanofluid-enhanced carbonated water container 3 in the nanofluid-enhanced carbonated water preparation system. The bottoms of the formation oil container 4 and the formation water container 5 are connected to a high-precision constant-speed and constant-pressure pump 1 via a control valve 6 and pipelines. The tops of the formation oil container 4, the formation water container 5, and the nanofluid-enhanced carbonated water container 3 are connected to an injection port 12 at one end of a displacement model 36 in the displacement experimental system via a pressure gauge 8, a control valve 6, and pipelines. This is used to inject nanofluid-enhanced carbonated water, formation oil, and formation water into the displacement model 36.

[0096] The displacement experimental system includes a displacement model 36 equipped with an injection port 12, an inlet cover plate 13, an outlet cover plate 18, and a production port 19. The outer body 14 of the displacement model 36 is placed in a constant temperature chamber 35. The other end of the displacement model 36 is connected to a vacuum pump 25 via a control valve 6 and a pipeline. The displacement model 36 is connected in series with a high-temperature, high-pressure observation window 26 and a back-pressure valve II 30. The back-pressure valve II 30 is connected to a back-pressure control pump 29 and a pressure gauge 8 to control the pressure within the displacement model. A high-definition camera 27 is located above the high-temperature, high-pressure observation window 26, and a light source 28 is located below the high-temperature, high-pressure observation window 26 to observe and record the microscopic interaction between the nanofluid-enhanced carbonated water and the heavy oil during the nanofluid-enhanced carbonated water displacement process. A vacuum pump 25 is located between the displacement model 36 and the high-temperature, high-pressure observation window 26 to maintain a vacuum throughout the experimental setup. The high-temperature, high-pressure observation window 26 can withstand temperatures and pressures exceeding 70°C and 15 MPa, simulating the conditions of heavy oil reservoirs.

[0097] The displacement model 36 has an inner diameter of 40 mm and a length of 100 mm. This size range is the optimal size obtained through extensive simulation experiments and theoretical calculations, and can better reflect the oil, gas, and water seepage process at the scale of heavy oil reservoirs.

[0098] The displacement model 36 is provided with a head pressure measuring point 15, a middle pressure measuring point 16, and a terminal pressure measuring point 17. This allows accurate detection of pressure changes at different locations of the displacement model during the experiment, avoiding the inability to detect certain areas of the displacement model due to too few pressure measuring points.

[0099] The high-definition camera 27 has a pixel greater than 12 million and a frame rate greater than 30 frames per second; the light source 28 is a white light source.

[0100] The visible range of the high-temperature and high-pressure observation window 26 is between 50 mm in length, 5 mm in width and 1 mm in thickness. This thickness can ensure that the nanofluid-enhanced carbonated water and heavy oil can flow in the high-temperature and high-pressure viewing window, and can also enable the light source and high-definition camera to cooperate to obtain clear pictures.

[0101] The oil and gas measurement system includes a gas-liquid separator 31, the upper part of which is connected to a gas flow meter II32 for measuring the gas production during the nanofluid-enhanced carbonized water displacement process; the bottom of the gas-liquid separator 31 is connected to a liquid collection container 34, which is placed on an electronic balance 33 for measuring the liquid production quality during the nanofluid-enhanced carbonized water displacement process.

[0102] The data acquisition and temperature control system includes a computer 24, which is connected to the pressure sensor 20 of the displacement model 36 to measure pressure changes within the displacement model during nanofluid-enhanced carbonated water displacement. The computer 24 is also connected to the temperature controller 21 of the displacement model 36, as well as the heating plate 22 and insulation jacket 23 surrounding the displacement model 36. These control the temperature of the heated displacement model and simulate a heavy oil reservoir temperature of 40°C.

[0103] Example 2

[0104] The experimental method for nanofluid enhanced carbonated water displacement in heavy oil reservoirs includes the following steps:

[0105] (1) Preparation of injection fluids: Preparation of formation oil, formation water, and nanofluid-enhanced carbonated water;

[0106] Preparation of formation oil: Based on the dissolved gas-to-oil ratio and gas compressibility of the reservoir's heavy oil, formation oil is prepared at the reservoir pressure and temperature to simulate the heavy oil in the actual reservoir. The prepared formation oil is then introduced from the sample preparation container into the formation oil container. The formation oil prepared in this embodiment has a pressure of 5080 mPa·s.

[0107] Preparation of nanofluid-enhanced carbonated water:

[0108] a. NaCl, polyvinyl pyrrolidone, and nano-SiO2 were added to distilled water and stirred until the soluble metal salt and dispersant were completely dissolved and the nanoparticles were uniformly dispersed to prepare a nanofluid, wherein the concentration of nano-SiO2 was 0.1wt%, the concentration of polyvinyl pyrrolidone was 1wt%, and the concentration of NaCl was 0.5wt%. The nanofluid was dispersed using an ultrasonic disperser with an output power of 150W and an operating frequency of 25kHz for 45 minutes.

[0109] b. Set the volume to V N The nanofluid is introduced into the nanofluid enhanced carbonated water container to discharge the air in the container;

[0110] c. According to the experimental pressure P and experimental temperature T Based on the Duan model, the amount of CO2 dissolved in a pure soluble metal salt aqueous solution with the same salinity as the nanofluid under experimental conditions was preliminarily calculated. n Duan ; Calculate the volume of CO2 in the carbon dioxide container according to formula (I) V 注1 ;

[0111] (I);

[0112] In formula (I), P =12.1MPa; Z =0.3055; n Duan =1.607mol; R =8.314 J / (mol·K); T =313K;

[0113] Calculated V 注1 =158.4mL.

[0114] d. Inject the CO2 in the carbon dioxide container into the nanofluid enhanced carbonated water container, use the slider to stir the fluid in the nanofluid enhanced carbonated water container to increase the dissolution rate of CO2 in the nanofluid, and the pressure in the nanofluid enhanced carbonated water container will continue to decrease. Use a high-precision constant speed and constant pressure pump to keep the pressure in the nanofluid enhanced carbonated water container at the experimental pressure. P , when the pressure in the nanofluid enhanced carbonized water container is P When the flow rate of the high-precision constant speed and constant pressure pump remains unchanged and remains at 0, it indicates that CO2 no longer dissolves into the nanofluid, thereby forming nanofluid-enhanced carbonated water. Record the gas volume in the nanofluid-enhanced carbonated water container. V gas;

[0115] The amount of undissolved CO2 species was calculated by formula (II);

[0116] (II);

[0117] In formula (II), V gas =32.42mL; Z 1=0.3055; P =12.1MPa; R =8.314 J / (mol·K); T =313K;

[0118] Calculated, n 1=0.493mol.

[0119] The amount of dissolved CO2 substance, mol, was calculated by formula (III);

[0120] (III);

[0121] In formula (III), n 1=0.493mol; n Duan =1.607mol;

[0122] Calculated, n 2=1.918mol.

[0123] The solubility of CO2 was calculated by formula (IV);

[0124] (IV);

[0125] In formula (IV), T 0=298.1K; P 0=0.1MPa; R =8.314 J / (mol·K); n 2=1.918mol; V N =1300mL;

[0126] Calculated, S 计算 =36.563mL / mL.

[0127] e. Maintain the test pressure through the back pressure valve I P , use a constant speed and constant pressure pump to sequentially displace all undissolved gas and a certain amount of nanofluid enhanced carbonized water into the gas separation device, and start measuring and recording the gas output after the liquid is discharged V气1 and fluid output V 液1 , calculate the dissolved amount of CO2 by formula (V) S 测 :

[0128] (V);

[0129] In formula (V), V 气1 =678.1mL; V 液1 =18.9mL;

[0130] Calculated, S 测 =35.88mL / mL.

[0131] f. By comparison S 测 and S 计算 value, S 测 and S 计算 When the error is (36.563-35.88) / 35.88=1.90%<5%, it is considered that the amount of CO2 dissolved in the nanofluid is reliable and the preparation of nanofluid-enhanced carbonated water is completed;

[0132] (2) Simulation of heavy oil reservoir environment: Fill the displacement model with 120-mesh quartz sand or an artificial core with a length of 100 mm; use a vacuum pump to evacuate the displacement model for 24 hours to make the displacement model a vacuum state; use a high-precision constant speed and constant pressure pump to inject formation water and formation oil, and measure the porosity, permeability and original oil saturation of the displacement model;

[0133] Measure the porosity of the displacement model: Under vacuum, the displacement model is made to absorb formation water. When the pressure changes from negative pressure to close to atmospheric pressure, the displacement model is injected with formation water. After water is produced, the water output of the displacement model is recorded and the porosity of the displacement model is calculated using formula (VI). ;

[0134] (VI);

[0135] In formula (VI), V 吸 =9.8mL; V 注 =85.5mL; V 产 =51.2mL; D =4cm; L =10cm;

[0136] Calculation yields: = 35.1%.

[0137] Penetration: Changing n The simulated formation water is injected into the displacement model at a low injection rate. The pressure at both ends of the displacement model is measured during the injection process. The permeability of the displacement model is then calculated according to Darcy's law shown in formula (7). k ;

[0138] (VII);

[0139] In formula (VII), Q i Indicates the i injection rate, mL / min; μ =1mPa·s;Δ p i Indicates the i The pressure difference between the two ends of the displacement model during the first injection is 10 -1 MPa.

[0140] Table 1 Permeability at different injection rates

[0141]

[0142] The final permeability of the displacement model is k 3.35μm 2 .

[0143] Initial oil saturation: Inject formation oil into the displacement model at a rate of 1-5 mL / min. Stop injection when the volume of injected formation oil is 2-3 times the pore volume of the displacement model, and record the injected heavy oil volume. V 油注 and produced heavy oil volume V 油采 The pore volume is the volume of the displacement model cavity and the porosity The initial oil saturation is calculated by formula (VIII): S oi ;

[0144] (VIII);

[0145] In formula (VIII), S oi is the initial oil saturation, %; V 油注 =110.3mL; V 油采 =69.7mL; V 吸 =9.8mL;V 注 =85.5mL; V 产 =51.2mL;

[0146] Calculated S oi =92.1%.

[0147] Adjust the displacement model pressure to the formation pressure of the heavy oil reservoir to be simulated, and leave the displacement model at the formation temperature and pressure of the heavy oil reservoir for 24 hours to allow the saturated formation oil to age;

[0148] (3) Nanofluid enhanced carbonized water flooding: Nanofluid enhanced carbonized water was injected into the displacement model at an injection rate of 2 mL / min to displace the formation oil. The injection volume of nanofluid enhanced carbonized water at different times was measured and recorded. V 注入 , liquid quality m 液 , oil production quality m 油 , water production, gas production V 气 and pressure; wherein the oil production quality is determined m 油 : Place the displacement output fluid in a high-temperature oven at 90°C for 48 hours, and then use an electronic balance to weigh the mass of the remaining oil. m 油 ;

[0149] Calculate the water content at different injection rates f w , CO2 storage S , cumulative production gas-oil ratio R p , cumulative oil production CO i and degree of recovery R , using a high-temperature and high-pressure observation window to observe the microscopic interaction between nanofluid-enhanced carbonized water and heavy oil, and ending when the water cut reached 95% or the cumulative production gas-oil ratio reached 2000;

[0150] Calculate the water content at different injection rates according to formula (IX) f wi :

[0151] (IX),

[0152] In formula (IX), m 液i Indicates the injection volume i Liquid production measured at , g; m 油i Indicates the injection volumei Measured

[0153] Oil yield, g; ρ 水 is the density of water, g / cm 3 ; ρ 油 is the density of oil, g / cm 3 ;

[0154] Calculate the CO2 storage capacity under different injection rates according to formula (X) S i :

[0155] (X),

[0156] In formula (X), V 注i represents the injection amount of nanofluid-enhanced carbonated water at time i, mL; S 测 Expressed as the measured solubility of CO2, mL / mL; V 气i Indicates the i Gas production per measurement, mL;

[0157] The cumulative production gas-oil ratio under different injection rates is calculated according to formula (XI) R pi :

[0158] (XI),

[0159] In formula (XI), V 气i Indicates the i Gas production per measurement, mL; m 油i Indicates the injection volume i Oil production measured at , g; ρ 油 is the density of oil, g / cm 3 ;

[0160] Calculate the cumulative oil production at different injection rates according to formula (XII) CO i :

[0161] (XII),

[0162] In formula (XII), m 油i Indicates the injection volume i Oil production measured at , g; ρ 油 is the density of oil, g / cm3 ;

[0163] Calculate the recovery degree under different injection rates according to formula (XIII) R i :

[0164] (XIII),

[0165] In formula (XIII), m 油i Indicates the injection volume i Oil production measured at , g; ρ 油 is the density of oil, g / cm 3 ; V 油注 is the injected heavy oil volume, mL; V 油采 Volume of produced heavy oil, mL.

[0166] (4) Compare the development effects of water flooding, carbonized water flooding, and nanofluid-enhanced carbonized water flooding, and systematically evaluate the feasibility of nanofluid-enhanced carbonized water flooding in heavy oil reservoirs;

[0167] In this example, the cumulative oil production, recovery degree and water content are recorded during the displacement process. Figure 2 , Figure 3 and Figure 4 .

[0168] After the water flooding was completed, the cumulative oil production was 13.8 cm 3 , the recovery degree of water drive is 26.1%;

[0169] After the carbonized water flooding was completed, the cumulative oil production was 13.32 cm 3 , the recovery degree of carbonized water flooding is 33.29%;

[0170] After the nanofluid-enhanced carbonized water flooding was completed, the cumulative oil production was 15.83 cm 3 , the recovery degree of nanofluid enhanced carbonized water flooding is 38.83%.

[0171] (5) Repeat the above steps (1) to (4) to study the effects of geological parameters and injection and production parameters on the nanofluid enhanced carbonized water flooding effect. Geological parameters and injection and production parameters include permeability, porosity, nanofluid type, nanofluid concentration, CO2 concentration, salinity, injection rate, etc.

[0172] Combine Figure 2 、 Figure 3 and Figure 4The cumulative oil production, recovery degree, and water cut change with injection volume show that, compared with nanofluid-enhanced carbonated water flooding, water flooding and carbonated water flooding achieve lower recovery degrees than nanofluid-enhanced carbonated water flooding for the same injection volume. The ultimate recovery of nanofluid-enhanced carbonated water flooding is 12.735% and 5.54% higher than that of water flooding and carbonated water flooding, respectively. This is because the solubility of CO2 in nanofluid-enhanced carbonated water is higher than that in carbonated water. Furthermore, during the displacement process, the enhanced mass transfer effect of nanoparticles increases the solubility of CO2 in heavy oil, which facilitates viscosity reduction and expansion of the heavy oil, improves the mobility ratio, and delays breakthrough of the injected fluid. Furthermore, nanofluid-enhanced carbonated water flooding can reduce oil-water interfacial tension, change the wettability of the rock surface, and make crude oil more easily stripped from the rock surface, which helps to increase the ultimate recovery.

[0173] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. An experimental device for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs, characterized in that: It includes nanofluid enhanced carbonated water preparation system, fluid injection system, displacement experiment system, oil and gas measurement system, and data acquisition and temperature control system; The nanofluid-enhanced carbonated water preparation system includes two containers connected in parallel: a carbon dioxide container and a nanofluid-enhanced carbonated water container. The bottoms of both containers are connected to a high-precision constant-speed and constant-pressure pump via a control valve and pipeline. The tops of both containers are connected to one end of a back-pressure valve (I) via a pressure gauge, a control valve, and pipelines. The other end of the back-pressure valve (I) is connected to a liquid metering container. The upper portion of the liquid metering container is connected to a gas flow meter (I). The fluid injection system includes three containers connected in parallel: a formation oil container, a formation water container, and a nanofluid-enhanced carbonated water container from the nanofluid-enhanced carbonated water preparation system. The bottoms of the formation oil container and formation water container are connected to a high-precision constant-speed and constant-pressure pump via control valves and pipelines. The tops of the formation oil container, formation water container, and nanofluid-enhanced carbonated water container are connected to one end of the displacement model in the displacement experimental system via pressure gauges, control valves, and pipelines. The displacement experiment system includes a displacement model, the other end of which is connected to a vacuum pump via a control valve and pipeline. The displacement model is connected in series with a high-temperature and high-pressure observation window and a back-pressure valve II, which is connected to a back-pressure control pump and a pressure gauge. A high-definition camera is installed above the high-temperature and high-pressure observation window, and a light source is installed below the high-temperature and high-pressure observation window. The vacuum pump is located between the displacement model and the high-temperature and high-pressure observation window. Oil and gas measurement system: including a gas-liquid separator connected to a back pressure valve II, a gas flow meter II connected to the upper part of the gas-liquid separator, and a liquid collection container connected to the bottom of the gas-liquid separator, which is placed on an electronic balance; Data acquisition and temperature control system: including a computer, the computer is connected to the pressure sensor of the displacement model; the computer is also connected to the temperature controller of the displacement model and the heating plate and insulation cover wrapped around the outside of the displacement model.

2. The experimental device for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 1, characterized in that: The displacement model has an inner diameter of 25-50 mm and a length of 100-1000 mm.

3. The experimental device for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 1, characterized in that: The pixel of the high-definition camera is greater than 12 million, and the frame rate is greater than 30 frames per second; the light source is a white light source.

4. The experimental device for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 1, characterized in that: The displacement model is provided with a head end pressure measuring point, a middle end pressure measuring point and a terminal end pressure measuring point.

5. The experimental device for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 1, characterized in that: The visual range of the high-temperature and high-pressure observation window is between 50 and 200 mm in length, 5 and 30 mm in width, and 1 and 5 mm in thickness.

6. An experimental method for enhancing carbonated water displacement in heavy oil reservoirs using nanofluids using the experimental device according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparation of injection fluids: Preparation of formation oil, formation water, and nanofluid-enhanced carbonated water; Preparation of formation oil: Based on the dissolved gas-oil ratio and gas compressibility factor of the reservoir heavy oil, formation oil is prepared at the reservoir pressure and temperature to simulate the heavy oil in the actual reservoir. The prepared formation oil is then introduced from the sample preparation container into the formation oil container. The viscosity of the formation oil under formation conditions is greater than 5000 mPa·s. Preparation of nanofluid-enhanced carbonated water: a. Adding a soluble metal salt, a dispersant, and nanoparticles to distilled water and stirring until the soluble metal salt and the dispersant are completely dissolved and the nanoparticles are uniformly dispersed to obtain a nanofluid; dispersing the nanofluid using an ultrasonic disperser; b. Set the volume to V N The nanofluid is introduced into the nanofluid enhanced carbonated water container to discharge the air in the container; c. According to the experimental pressure P and experimental temperature T Based on the Duan model, the amount of CO2 dissolved in a pure soluble metal salt aqueous solution with the same salinity as the nanofluid under experimental conditions was preliminarily calculated. n Duan ; Calculate the volume of CO2 in the carbon dioxide container according to formula (I) V 注1 ; （I）； In formula (I), P is the experimental pressure, MPa; Z Experimental pressure P and experimental temperature T The compression factor of CO2; R is the thermodynamic constant, with a value of 8.314 J / (mol·K); T is the experimental temperature, K; V 注1 is the volume of CO2 in the carbon dioxide container, mL; d. The carbon dioxide container CO2 is injected into the nanofluid enhanced carbonated water container, and the slider is used to stir the nanofluid enhanced carbonated water container fluid; A high-precision constant speed and constant pressure pump is used to keep the pressure in the nanofluid enhanced carbonized water container at the experimental pressure. P ; When the pressure in the nanofluid-enhanced carbonated water container is P When the flow rate of the high-precision constant speed and constant pressure pump remains unchanged and remains at 0, it indicates that CO2 no longer dissolves into the nanofluid, thereby forming nanofluid-enhanced carbonated water. The gas volume in the nanofluid-enhanced carbonated water container is recorded. V gas ; The amount of undissolved CO2 species was calculated by formula (II); (II); In formula (II), P is the experimental pressure, MPa; V gas is the gas volume in the nanofluid-enhanced carbonized water container, mL; Z 1 is the experimental pressure P and experimental temperature T The compression factor of CO2; R is the thermodynamic constant, with a value of 8.314 J / (mol·K); T is the experimental temperature, K; n 1 is the amount of undissolved CO2 substance, mol; The amount of dissolved CO2 species was calculated by formula (III); (III); In formula (III), n 1 is the amount of undissolved CO2 substance, mol; n 2 is the amount of dissolved CO2, mol; The solubility of CO2 was calculated by formula (IV); (IV); In formula (IV), n 2 is the amount of dissolved CO2, mol; R is the thermodynamic constant, with a value of 8.314 J / (mol·K); T 0 is the indoor temperature, K; P 0 is atmospheric pressure, 0.1 MPa; V N is the volume of the nanofluid, mL; S 计算 is the calculated solubility of CO2, mL / mL; e. Maintain the test pressure through the back pressure valve I P , use a high-precision constant speed and constant pressure pump to sequentially displace all undissolved gas and a certain amount of nanofluid enhanced carbonated water into the liquid measuring container, and after the liquid is discharged, start to measure and record the gas output through the gas flow meter I V 气1 , measure and record the liquid output through the liquid measuring container V 液1 , calculate the dissolved amount of CO2 by formula (V) S 测 : （V）； In formula (V), V 气1 is the gas output, mL; V 液1 is the amount of liquid output, mL; S 测 is the measured solubility of CO2, mL / mL; f. By comparison S 测 and S 计算 Value, when S 测 and S 计算 When the error is less than 5%, the amount of CO2 dissolved in the nanofluid is considered reliable and the preparation of nanofluid-enhanced carbonated water is completed; (2) Simulation of heavy oil reservoir environment: fill the displacement model with quartz sand or artificial core; make the displacement model into a vacuum state; use a high-precision constant speed and constant pressure pump to inject formation water and formation oil, measure the porosity, permeability and original oil saturation of the displacement model; adjust the displacement model pressure to the formation pressure of the heavy oil reservoir to be simulated, and age the saturated formation oil; (3) Nanofluid enhanced carbonized water flooding: Inject nanofluid enhanced carbonized water into the displacement model to displace the formation oil, and measure and record the injection volume of nanofluid enhanced carbonized water at different times V 注入 , liquid quality m 液 , oil production quality m 油 , water production, gas production V 气 and stress; Calculate the water content at different injection rates f w , CO2 storage S , cumulative production gas-oil ratio R p , cumulative oil production CO i and recovery degree, using a high-temperature and high-pressure observation window to observe the microscopic interaction between nanofluid-enhanced carbonized water and heavy oil, and ending when the water cut reached 95% or the cumulative production gas-oil ratio reached 2000; (4) Compare the development effects of water flooding, carbonized water flooding, and nanofluid-enhanced carbonized water flooding, and systematically evaluate the feasibility of nanofluid-enhanced carbonized water flooding in heavy oil reservoirs; (5) Repeat the above steps (1)-(4) to study the effects of geological parameters and injection and production parameters on the nanofluid enhanced carbonized water flooding effect.

7. The experimental method for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 6, characterized in that: In the step (1), the nanoparticles in the nanofluid for preparing the nanofluid-enhanced carbonated water are selected from one of nano-SiO2, nano-Al2O3, nano-TiO2 and MWCNT; the dispersant is polyvinyl pyrrolidone or sodium dodecyl sulfate; and the soluble metal salt is selected from one of NaCl, KCl, MgCl2, CaCl2 and Na2SO4; In the nanofluid, the concentration of nanoparticles is 0.01~1wt%, the concentration of dispersant is 0.1~5wt%, and the concentration of soluble metal salt is 0.1~5wt%; The dispersion time of nanofluid is 45~90min.

8. The experimental method for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 6, characterized in that: In step (2), the quartz sand has a particle size of 20 to 120 meshes and the length of the artificial core is 100 to 1000 mm; The time for evacuating the displacement model by using a vacuum pump is 24 to 48 hours, and the vacuum pumping rate is 2 to 5 m 3 / h, ultimate vacuum 2~4Pa; The displacement model was left at rest for 24 to 48 hours at the formation temperature and pressure of the heavy oil reservoir to allow the saturated formation oil to age.

9. The experimental method for nanofluid-enhanced carbonized water displacement in heavy oil reservoirs according to claim 6, characterized in that: In step (2), the porosity of the displacement model is measured by allowing the displacement model to absorb formation water under vacuum. When the pressure changes from negative pressure to close to atmospheric pressure, formation water is injected. After water is produced, the water output of the displacement model is recorded, and the porosity of the displacement model is calculated using formula (VI): ; (WE); In formula (VI), V 吸 is the volume of the absorbed formation water, mL; V 注 is the volume of injected formation water, mL; V 产 is the volume of produced formation water, mL; D is the inner diameter of the displacement model, cm; L is the length of the displacement model, cm; Penetration: Changing n The formation water is injected into the displacement model at a certain injection rate. The pressure at both ends of the displacement model is measured during the injection process. The permeability of the displacement model is then calculated according to Darcy's law shown in formula (VII). k ; (VII); In formula (VII), Q i Indicates the i injection rate, mL / min; μ represents the formation water viscosity, mPa·s; L is the length of the displacement model, cm; D is the inner diameter of the displacement model, cm; Δ p i Indicates the i The pressure difference between the two ends of the displacement model during the first injection is 10 -1 MPa; Initial oil saturation: Inject formation oil into the displacement model at a rate of 1-5 mL / min. Stop injection when the volume of injected formation oil is 2-3 times the pore volume of the displacement model, and record the injected heavy oil volume. V 油注 and produced heavy oil volume V 油采 , calculate the initial oil saturation using formula (VIII) S oi ; (VIII); In formula (VIII), S oi is the initial oil saturation, %; V 油注 is the injected heavy oil volume, mL; V 油采 Volume of produced heavy oil, mL; V 吸 is the volume of the absorbed formation water, mL; V 注 is the volume of injected formation water, mL; V 产 is the volume of produced formation water, mL.

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