Nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device and method

Abstract

The present invention relates to a device and method for a nano-silicon dioxide-enhanced carbonated water-heavy oil multiple contact experiment, belonging to the technical field of heavy oil reservoir exploitation. The device comprises a fluid preparation system, a multiple contact experiment system, a test and analysis system, and a temperature control system. The fluid preparation system is used to prepare fluids used in the multiple contact experiment, including preparing nano-SiO2-enhanced carbonated water and preparing formation oil. The multiple contact experiment system is used to control the multiple contact between the nano-SiO2-enhanced carbonated water and the formation oil. The test and analysis system is used to test the properties of the nano-SiO2-enhanced carbonated water and the high-pressure physical properties of the heavy oil after the multiple contact process. The temperature control system is used to provide the temperature required for the multiple contact experiment. The device can simulate the dissolution and mass transfer of CO2 in the carbonated water-heavy oil multiple contact process under the action of nano-SiO2 particles.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy oil reservoir exploitation, and particularly relates to a nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device and method. Background Art

[0002] Water flooding is one of the most commonly used oil recovery methods in oilfields. However, high-viscosity heavy oil is prone to viscous fingering during water flooding, resulting in low oil recovery efficiency. CO2 flooding offers the advantages of reducing viscosity, increasing recovery, and reducing emissions. However, due to gravity overburden, gas channeling forms at the top, resulting in a low sweep coefficient. Carbonated water flooding (i.e., CO2 dissolved in water) combines the advantages of both CO2 and water flooding methods, mitigating viscous fingering and gravity overburden while improving recovery efficiency and achieving superior development results compared to both water and CO2 flooding. When carbonated water is injected into a reservoir to displace heavy oil, the two interact multiple times. During these contact processes, CO2 is transferred from the carbonated water to the oil through mass transfer, reducing the oil's viscosity, expanding its volume, and lowering the oil-water interfacial tension. However, due to the low solubility of CO2 in carbonated water, these effects need to be further improved.

[0003] In recent years, the widespread application of nanotechnology in oil and gas field development has attracted the attention of experts both domestically and internationally. Nano-SiO2-enhanced carbonated water is a novel injection fluid formed by dispersing nano-SiO2 particles in carbonated water. Compared to traditional carbonated water, nano-SiO2-enhanced carbonated water can significantly increase the solubility of CO2 in water and enhance the mass transfer of CO2 from carbonated water to heavy oil, thereby improving heavy oil recovery and CO2 storage capacity. Extensive research has been conducted domestically and internationally on the multiple contact process between CO2 or carbonated water and heavy oil. However, relatively little research has been conducted on this process, due to a lack of effective experimental equipment and methods. The changes in the high-pressure physical properties of heavy oil and nano-SiO2-enhanced carbonated water after multiple contact remain unclear. Furthermore, the influence of CO2 saturation, SiO2 concentration, and salinity in nano-SiO2-enhanced carbonated water on the multiple contact process remains unclear, severely restricting the application of nano-SiO2-enhanced carbonated water CO2 flooding. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a nano-silica enhanced carbonated water-heavy oil multiple contact experimental device and method. The experimental device can be used to study the multiple contact process of nano-SiO2 enhanced carbonated water and heavy oil under high temperature and high pressure conditions, reveal the change pattern of the high-pressure physical properties of heavy oil (density, viscosity, gas-oil ratio, CO2 gas-oil ratio, volume expansion coefficient) and the properties of nano-SiO2 enhanced carbonated water (gas-water ratio, CO2 gas-water ratio) during the multiple contact process of nano-SiO2 enhanced carbonated water and heavy oil, clarify the influence of CO2 saturation, SiO2 concentration, mineralization, etc. on the multiple contact process of nano-SiO2 enhanced carbonated water and heavy oil, and analyze the CO2 mass transfer mechanism during the multiple contact process of nano-SiO2 enhanced carbonated water and heavy oil.

[0005] The technical solution of the present invention is:

[0006] Nano-silica enhanced carbonated water-heavy oil multiple contact experimental device, including fluid preparation system, multiple contact experimental system, test and analysis system, and temperature control system;

[0007] The fluid preparation system is used to prepare fluids used in multiple contact experiments, including the preparation of nano-SiO2 enhanced carbonated water and formation oil;

[0008] The multiple contact experimental system is used to control the multiple contact between nano-SiO2 enhanced carbonated water and formation oil;

[0009] The test and analysis system is used to test the properties of nano-SiO2 enhanced carbonized water and heavy oil high-pressure properties after multiple contact processes; the properties of nano-SiO2 enhanced carbonized water include gas-water ratio and CO2 gas-water ratio, and the high-pressure properties of heavy oil include density, viscosity, gas-oil ratio, CO2 gas-oil ratio, and volume expansion coefficient;

[0010] The temperature control system is used to provide the temperature required for multiple contact experiments.

[0011] Preferably, according to the present invention, the fluid preparation system includes a thick oil container, a CH4 container, a CO2 container, a nano-SiO2 enhanced carbonated water container, a CH4 gas cylinder and a CO2 gas cylinder connected in parallel; the tops of the thick oil container, the CH4 container, the CO2 container and the nano-SiO2 enhanced carbonated water container are all connected to the pipeline through a pressure gauge and a valve, and the bottoms are all connected to a high-precision plunger pump through a valve and a pipeline, and the tops of the CH4 container and the CO2 container are connected to the CH4 gas cylinder and the CO2 gas cylinder respectively through a pressure gauge, a valve and a pipeline.

[0012] Preferably, according to the present invention, the multiple contact experimental system includes a multiple contact model, a multiple contact model stirring device and a stirring block 13; one end of the multiple contact model is connected to the top of the nano-SiO2 enhanced carbonated water container through a pressure gauge, a valve and a pipeline, and the other end is connected to a high-precision plunger pump through a pipeline and a valve; the multiple contact model stirring device is used to control the stirring of the fluid in the multiple contact model.

[0013] Further preferably, the multiple-contact model is a cylindrical container device wrapped with an insulation sleeve, which is used to achieve the contact between nano-SiO2 enhanced carbonated water and formation oil; one end of the multiple-contact model stirring device is fixed on the multiple-contact model, and the other end is connected to a motor, and the multiple-contact model is driven to rotate by the rotation of the motor, so as to stir the nano-SiO2 enhanced carbonated water and formation oil inside the multiple-contact model.

[0014] Further preferably, a multiple-contact model volume meter is provided on the multiple-contact model housing for intuitively displaying the volume changes within the multiple-contact model.

[0015] Further preferably, the rotation speed of the multiple contact model is 2 r / min.

[0016] Further preferably, the total volume of the multiple-contact model is greater than 400 ml.

[0017] Preferably, according to the present invention, a stirring block is placed in the multiple contact model, and the stirring block has a volume greater than 50 ml and a weight not less than 200 g.

[0018] Preferably, according to the present invention, the test and analysis system includes a gas-liquid separator, a gas flow meter, a falling ball viscometer, a gas component analyzer, an electronic balance, a hand pump and several air bags; the top of the gas-liquid separator is connected to the top valve of the multiple contact model through a back pressure valve and a pipeline, the lower part of the gas-liquid separator is an outlet with a valve, and directly below the outlet is a liquid collection container. The liquid collection container is moved to the electronic balance for weighing, which is used to weigh the liquid mass and calculate the gas-liquid ratio; there is also an outlet on the upper part of the gas-liquid separator, which is connected to the gas flow meter. The outlet end of the gas flow meter is connected to a detachable and replaceable air bag through a pipeline, and the separated gas is collected by the air bag, and then the volume percentage of CH4 and CO2 in the separated gas is detected by the gas component analyzer.

[0019] Preferably, according to the present invention, the standard volume of the air bag is not less than 500 ml, and the air bag is evacuated before collecting the gas for gas collection and gas component detection.

[0020] Preferably, according to the present invention, one end of the falling ball viscometer is connected to the top valve of the multiple contact model through a pressure gauge, and the other end is connected to the back pressure valve, which is used to control the pressure of the derived fluid to maintain it under experimental conditions. The falling ball viscometer is used to meet the normal working conditions of 50°C and 18 MPa, and is used to measure the viscosity of the heavy oil before and after multiple contact of nano-SiO2 enhanced carbonated water and heavy oil under high temperature and high pressure conditions. High temperature and high pressure refer to: the high temperature range is 30-50°C, and the high pressure range is 10-18 MPa.

[0021] Preferably, according to the present invention, the temperature control system includes a multiple contact model, a gas-liquid separator, a falling ball viscometer, a nano-SiO2 enhanced carbonated water container and a heavy oil container, and the outside of the pipelines connecting the multiple contact model, the gas-liquid separator, the falling ball viscometer and the nano-SiO2 enhanced carbonated water container is wrapped with a heating belt for heating the above containers and the pipelines connecting the above containers.

[0022] Furthermore, the top of the heavy oil container, CH4 container, CO2 container, nano-SiO2 enhanced carbonated water container and the multiple contact model were all connected to a vacuum pump, and the heavy oil container, CH4 container, CO2 container, nano-SiO2 enhanced carbonated water container and the multiple contact model were evacuated before the experiment.

[0023] The technical solution of the present invention also includes a nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental method, comprising the following steps:

[0024] (1) Preparation of formation oil; determination of formation oil density ;

[0025] (2) Prepare nano-SiO2 fluid; measure the density of nano-SiO2 fluid and record it as , introduce the prepared nano-SiO2 fluid into the nano-SiO2 enhanced carbonated water container;

[0026] (3) Preparation of nano-SiO2 enhanced carbonated water; all CO2 in the CO2 container is introduced into the nano-SiO2 enhanced carbonated water container through a pipeline, and pressure is applied to the nano-SiO2 enhanced carbonated water container by a high-precision plunger pump to dissolve CO2 into the nano-SiO2 fluid until the experimental pressure remains unchanged, thereby obtaining nano-SiO2 enhanced carbonated water;

[0027] (4) Conduct multiple contact experiments between nano-SiO2-enhanced carbonated water and heavy oil;

[0028] Before contact, introduce the prepared formation oil into the falling ball viscometer to measure the viscosity of the formation oil before contact. μ 0;

[0029] Then the formation oil is introduced into the multiple contact model, and then the nano-SiO2 enhanced carbonated water is introduced into the multiple contact model, and the formation oil volume before the i-th contact is recorded. V 0i , record the formation oil volume after the i-th contact V 1i , calculate the volume expansion coefficient ; During the process, the experimental pressure is kept constant by a high-precision plunger pump;

[0030] The fluid in the multiple contact model is stirred by a multiple contact model stirring device. During the process, the pressure in the multiple contact model is controlled until it stabilizes at the experimental pressure. The stirring is stopped and the fluid is allowed to stand for a period of time until the oil and water are separated.

[0031] (5) Calculate the gas-water ratio of nano-SiO2 enhanced carbonated water after contact;

[0032] Draw out nano-SiO2 enhanced carbonized water from the bottom of the multiple contact model to the gas-liquid separator and record the initial reading of the gas flow meter at the beginning. V ai and gas flow meter readings after the separation process is completed V bi , collect the separated gas, and use the gas component analyzer to detect the volume percentage of CO2 in the gas separated by nano-SiO2 enhanced carbonized water, which is recorded as , used to calculate the CO2 gas-water ratio after contact with nano-SiO2 enhanced carbonized water; use an electronic balance to weigh the mass of nano-SiO2 enhanced carbonized water after gas-liquid separation and record it as m wi , discharge all the nano-SiO2 enhanced carbonized water in the multiple contact model until oil is produced;

[0033] (6) Calculate the gas-oil ratio of the heavy oil after contact;

[0034] Drain some of the formation oil from the lower end of the multiple contact model into the gas-liquid separator. When the gas flow meter increases steadily, close the valve at the lower end of the gas-liquid separator and record the volume reading of the multiple contact model before starting the gas-oil ratio test. After draining out some of the formation oil, close the multiple contact model valve and record the volume reading of the multiple contact model after the formation oil is drained out. , while recording the initial reading of the gas flow meter V ci and gas flow meter readings after the separation process is completed V di , use electronic balance to weigh the contacted formation oil mass after gas separation m oi , collect the separated gas, and use the gas component analyzer to detect the volume percentage of CO2 in the separated gas of the formation oil after different contact times, which is recorded as ;

[0035] (7) Repeat steps (4) to (6) to complete the multiple contact experiments of nano-SiO2 enhanced carbonized water and heavy oil; calculate the gas-water ratio of nano-SiO2 enhanced carbonized water under different contact times. , gas-oil ratio of heavy oil , density of formation oil , volume expansion coefficient , Nano-SiO2 enhances the CO2 gas-water ratio of carbonated water , CO2 gas-to-oil ratio of heavy oil After the last contact, part of the heavy oil was drawn from the bottom of the multiple contact model into the falling ball viscometer to measure the viscosity of the heavy oil after multiple contacts. μ ;

[0036] The variation of the above parameters with the increase of contact times was analyzed, the mass transfer effect of nano-SiO2 enhanced carbonized water-heavy oil during multiple contact processes was studied, and the mechanism of nano-SiO2 enhanced carbonized water in improving heavy oil recovery was revealed.

[0037] (8) Repeat steps (1) to (7) to change the property parameters of nano-SiO2 enhanced carbonated water, including salinity, CO2 saturation, nano-SiO2 particle concentration, and salt type, and conduct multiple contact experiments between the nano-SiO2 enhanced carbonated water and heavy oil after the properties are changed to clarify the influence of the property parameters of nano-SiO2 enhanced carbonated water on the gas-water ratio of nano-SiO2 enhanced carbonated water and the high-pressure physical properties of heavy oil.

[0038] According to the present invention, preferably, the ratio of the volume of the nano-SiO2 enhanced carbonized water introduced into the multiple-contact model each time to the volume of the formation oil in the multiple-contact model is 1:1.

[0039] According to the preferred embodiment of the present invention, the standing time is not less than 6 hours, until the oil and water are separated into separate layers.

[0040] According to the preferred embodiment of the present invention, the volume expansion coefficient of the heavy oil after each contact is calculated according to formula (I): :

[0041] ;

[0042] In formula (I), is the volume expansion coefficient of the formation oil after the i-th contact, dimensionless; V 1i For the i After the first contact, all the oil volume in the formation after the nano-SiO2 enhanced carbonated water was extracted; V 0i For the i Secondary contact of nano-SiO2 enhanced formation oil volume before carbonization water.

[0043] According to the preferred embodiment of the present invention, the gas-water ratio of nano-SiO2 enhanced carbonated water after contact at different contact times is calculated by formula (II): ;

[0044] ;

[0045] In formula (II), For the i Gas-water ratio of nano-SiO2 enhanced carbonated water after the first contact, ml / ml; V bi is the flow meter reading after the gas-liquid separation process is completed, ml; V ai is the initial reading of the flow meter at the beginning of gas-liquid separation, ml; m wi For the i The mass of nano-SiO2 enhanced carbonated water collected by the separator after the first contact, g; The density of carbonated water enhanced by nano-SiO2 g / cm 3 ;

[0046] The CO2 gas-water ratio of nano-SiO2 enhanced carbonated water after contact was calculated according to formula (III) ;

[0047] ;

[0048] In formula (III), For the i The volume percentage of CO2 in the gas separated by carbonization enhanced by nano-SiO2 after the first contact, dimensionless; For the i CO2 gas-water ratio of nano-SiO2 enhanced carbonated water after the first contact, ml / ml.

[0049] According to the present invention, the volume of formation oil extracted in each contact is preferably 15-25 ml;

[0050] The gas-oil ratio of heavy oil after each contact is calculated by the following formula (IV): ;

[0051] ;

[0052] In formula (IV), For the i Gas-oil ratio of heavy oil after the first contact, ml / ml; V ci is the initial reading of the flow meter at the beginning of gas-liquid separation, ml; V di is the flow meter reading after the gas-liquid separation process is completed, ml; moi For the i Mass of formation oil collected during the secondary contact gas-liquid separation process, g; is the degassed formation oil density, g / cm 3 ;

[0053] Calculate the density of the formation oil after each contact according to formula (V) :

[0054] ;

[0055] In formula (V), is the formation oil density after the i-th contact, g / cm 3 ; For the i The volume of the multiple contact model before the start of the gas-oil ratio test, ml; For the i The volume of the multiple contact model after the formation oil is extracted after the first contact, ml;

[0056] Calculate the CO2 gas-oil ratio of heavy oil after contact according to formula (VI) :

[0057] ;

[0058] In formula (VI), For the i CO2 gas-to-oil ratio of heavy oil after the first contact, ml / ml; For the i The volume percentage of CO2 in the gas separated from the heavy oil after the first contact, dimensionless.

[0059] The beneficial effects of the present invention are:

[0060] 1. The nano-SiO2 enhanced carbonated water-heavy oil multiple contact experimental device proposed in the present invention can realize the multiple contact process between heavy oil and nano-SiO2 enhanced carbonated water, and can simulate the dissolution and mass transfer of CO2 in the carbonated water-heavy oil multiple contact process under the action of nano-SiO2 particles.

[0061] 2. The nano-SiO2 enhanced carbonated water-heavy oil multiple contact experimental method proposed in the present invention can reveal the changing patterns of heavy oil high-pressure physical properties (density, viscosity, gas-oil ratio, CO2 gas-oil ratio, volume expansion coefficient) and nano-SiO2 enhanced carbonated water properties (gas-water ratio, CO2 gas-water ratio) during the multiple contact process between nano-SiO2 enhanced carbonated water and heavy oil, clarify the influence of CO2 saturation, SiO2 concentration, mineralization, etc. on the multiple contact process between nano-SiO2 enhanced carbonated water and heavy oil, analyze the CO2 mass transfer mechanism during the multiple contact process between nano-SiO2 enhanced carbonated water and heavy oil, and contribute to the application of nano-SiO2 enhanced carbonated water CO2 flooding technology in oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a schematic structural diagram of the nano-silicon dioxide enhanced carbonized water-heavy oil multiple contact experimental device in Example 2.

[0063] Among them, 1. high-precision plunger pump, 2. CH4 container, 3. heavy oil container, 4. CO2 container, 5. nano-SiO2 enhanced carbonated water container, 6. CO2 gas cylinder, 7. CH4 gas cylinder, 8. insulation cover, 9. valve, 10. pressure gauge, 11. multiple contact model stirring device, 12. multiple contact model volume meter, 13. stirring block, 14. multiple contact model, 15. back pressure valve, 16. gas-liquid separator, 17. liquid collection container, 18. electronic balance, 19. gas flow meter, 20. air bag, 21. hand pump, 22. falling ball viscometer, 23. vacuum pump, 24. gas component analyzer.

[0064] Figure 2 This is a graph showing the change in the gas-to-water ratio of nano-SiO2 enhanced carbonized water with the number of contacts in the experimental method of the present invention.

[0065] Figure 3 This is a graph showing the change in formation oil-gas-oil ratio with the number of contacts in the experimental method of the present invention.

[0066] Figure 4 This is a graph showing the change in the CO2 gas-water ratio of carbonized water enhanced by nano-SiO2 as a function of the number of contacts in the experimental method of the present invention.

[0067] Figure 5 This is a graph showing the change in the CO2 gas-to-oil ratio of formation oil with the number of contacts in the experimental method of the present invention.

[0068] Figure 6 This is a graph showing how the volume expansion coefficient of formation oil changes with the number of contacts in the experimental method of the present invention.

[0069] Figure 7 This is a graph showing how formation oil density changes with the number of contacts in the experimental method of the present invention. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0071] Example 1

[0072] Nano-silica enhanced carbonated water-heavy oil multiple contact experimental device, including fluid preparation system, multiple contact experimental system, test and analysis system, and temperature control system;

[0073] The fluid preparation system is used to prepare fluids used in multiple contact experiments, including the preparation of nano-SiO2 enhanced carbonated water and formation oil;

[0074] The multiple contact experimental system is used to control the multiple contact between nano-SiO2 enhanced carbonated water and formation oil;

[0075] The test and analysis system is used to test the properties of nano-SiO2 enhanced carbonized water and heavy oil high-pressure properties after multiple contact processes; the properties of nano-SiO2 enhanced carbonized water include gas-water ratio and CO2 gas-water ratio, and the high-pressure properties of heavy oil include density, viscosity, gas-oil ratio, CO2 gas-oil ratio, and volume expansion coefficient;

[0076] The temperature control system is used to provide the temperature required for multiple contact experiments.

[0077] Example 2

[0078] According to the nano-silicon dioxide enhanced carbonized water-heavy oil multiple contact experimental device described in Example 1, Figure 1 As shown, the difference is:

[0079] The fluid preparation system includes a parallel-connected thick oil container 3, a CH4 container 2, a CO2 container 4, a nano-SiO2-enhanced carbonated water container 5, a CH4 gas cylinder 7, and a CO2 gas cylinder 6; the tops of the thick oil container 3, the CH4 container 2, the CO2 container 4, and the nano-SiO2-enhanced carbonated water container 5 are connected to the pipeline via a pressure gauge 10 and a valve 9, and the bottoms are connected to a high-precision plunger pump 1 via a valve 9 and a pipeline. The tops of the CH4 container 2 and the CO2 container 4 are connected to the CH4 gas cylinder 7 and the CO2 gas cylinder 6, respectively, via a pressure gauge 10, a valve 9, and a pipeline.

[0080] The multiple-contact experimental system includes a multiple-contact model 14, a multiple-contact model stirring device 11 and a stirring block 13; one end of the multiple-contact model 14 is connected to the top of the nano-SiO2 enhanced carbonated water container 5 through a pressure gauge 10, a valve 9 and a pipeline, and the other end is connected to a high-precision plunger pump 1 through a pipeline and a valve 9; the fluid in the multiple-contact model 14 is stirred by controlling the multiple-contact model stirring device 11.

[0081] The multiple-contact model 14 is a cylindrical container device wrapped with an insulation sleeve 8, which is used to achieve the contact between nano-SiO2 enhanced carbonated water and formation oil; one end of the multiple-contact model stirring device 11 is fixed on the multiple-contact model 14, and the other end is connected to the motor. The multiple-contact model 14 is driven to rotate by the rotation of the motor, and is used to stir the nano-SiO2 enhanced carbonated water and formation oil inside the multiple-contact model 14.

[0082] A multi-contact model volume meter 12 is also provided on the housing of the multi-contact model 14, which is used to visually display volume changes within the multi-contact model 14. The multi-contact model 14 rotates at a speed of 2 r / min. The total volume of the multi-contact model 14 is greater than 400 ml, ensuring that sufficient heavy oil can be extracted after each contact for property analysis.

[0083] A stirring block 13 is placed in the multiple contact model 14. The stirring block 13 has a volume greater than 50 ml and a weight not less than 200 g to enhance the stirring effect and improve the contact efficiency between the heavy oil and the nano-SiO2 enhanced carbonized water.

[0084] The test and analysis system includes a gas-liquid separator 16, a gas flow meter 19, a falling ball viscometer 22, a gas component analyzer 24, an electronic balance 18, a hand pump 21 and several air bags 20; the top of the gas-liquid separator 16 is connected to the top valve 9 of the multiple contact model 14 through a back pressure valve 15 and a pipeline, the lower part of the gas-liquid separator 16 is an outlet with a valve 9, and directly below the outlet is a liquid collection container 17. The liquid collection container 17 is moved to the electronic balance 18 for weighing, which is used to weigh the liquid mass and calculate the gas-liquid ratio; there is also an outlet at the top of the gas-liquid separator 16, which is connected to the gas flow meter 19. The outlet end of the gas flow meter 19 is connected to a detachable and replaceable air bag 20 through a pipeline. The separated gas is collected by the air bag 20, and then the volume percentage of CH4 and CO2 in the separated gas is detected by the gas component analyzer 24.

[0085] The standard volume of the gas bag 20 is not less than 500 ml to reduce component detection errors. The gas bag 20 is vacuumed before collecting the gas for gas collection and gas component detection.

[0086] One end of the falling ball viscometer 22 is connected to the valve 9 at the top of the multiple contact model 14 through the pressure gauge 10, and the other end is connected to the back pressure valve 15, which is used to control the pressure of the output fluid to maintain it under the experimental conditions. The operating conditions of the falling ball viscometer 22 meet the normal working conditions of 50°C and 18 MPa, and are used to measure the viscosity of the heavy oil before and after multiple contact between nano-SiO2 enhanced carbonated water and heavy oil under high temperature and high pressure conditions.

[0087] The temperature control system includes a multiple contact model 14, a gas-liquid separator 16, a falling ball viscometer 22, a nano-SiO2 enhanced carbonated water container 5 and a heavy oil container 3. The outside of the pipeline connecting the multiple contact model 14, the gas-liquid separator 16, the falling ball viscometer 22, and the nano-SiO2 enhanced carbonated water container 5 is wrapped with a heating belt for heating the above containers and the pipelines connecting the above containers.

[0088] The pipeline should meet the requirements of high temperature and high pressure use. Use multiple heating belts connected to the temperature controller to wrap all the pipelines through which the experimental fluid passes and is exposed to the air, so that the experimental fluid is always under experimental conditions, maintains good fluidity, and avoids premature precipitation of dissolved gas.

[0089] The tops of the heavy oil container 3, CH4 container 2, CO2 container 4, nano-SiO2 enhanced carbonated water container 5, and multiple contact model 14 are all connected to a vacuum pump 23. Before the experiment, the heavy oil container 3, CH4 container 2, CO2 container 4, nano-SiO2 enhanced carbonated water container 5, and multiple contact model 14 are evacuated.

[0090] Example 3

[0091] The difference between the nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device described in Example 2 is that:

[0092] The total volume of the multi-contact model 14 is 450 ml. The stirring block 13 has a volume of 83 ml and a mass of 314 g. The standard volume of the air bag 20 is 500 ml. The upper temperature limit of the falling ball viscometer 22 is 120°C and the upper pressure limit is 45.0 MPa.

[0093] Example 4

[0094] The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental method is implemented using the nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device described in Example 3, and includes the following steps:

[0095] (1) Prepare formation oil; prepare degassed formation oil, measure the density of degassed formation oil, and record it as The degassed formation oil is introduced into the heavy oil container 3. CH4 is prepared in the CH4 container 2 according to the dissolved gas-oil ratio of the formation oil and the gas compressibility factor. The CH4 is introduced into the heavy oil container 3 and controlled under the formation pressure and temperature conditions until the CH4 is fully dissolved and the pressure in the heavy oil container 3 is stable. The formation oil is obtained and the formation oil density is measured. In this embodiment, the degassed formation oil density =0.9803g / cm 3 ; Formation temperature 40℃, pressure 12.0MPa; formation oil density =0.9412g / cm3 ;

[0096] (2) Preparation of nano-SiO2 fluid: Sodium chloride, polyvinyl pyrrolidone, and nano-SiO2 particles were added to distilled water in sequence, stirred with a glass rod, and the stirred fluid was transferred to an ultrasonic disperser for dispersion to obtain a uniformly dispersed nano-SiO2 fluid. The density of the nano-SiO2 fluid was measured and recorded as , introduce the prepared nano-SiO2 fluid into the nano-SiO2 enhanced carbonated water container 5;

[0097] The frequency of the ultrasonic disperser is not less than 25kHz, the number of dispersions is not less than 3 times, and each dispersion time is 15 to 20 minutes. The temperature change caused by the dispersion time is too long to achieve a better dispersion effect and avoid the precipitation of nano-SiO2 particles. In this embodiment, the concentration of nano-SiO2 is 0.1wt%, the concentration of polyvinyl pyrrolidone is 1wt%, the concentration of NaCl is 0.5wt%, and the density of the nano-SiO2 fluid is =1.0162g / cm 3 .

[0098] The ultrasonic disperser frequency is not less than 25kHz, the number of dispersions is not less than 3 times, and each dispersion time is 15 to 20 minutes. This is to avoid temperature changes caused by excessive dispersion time, thereby achieving a better dispersion effect and preventing the precipitation of nano-SiO2 particles. In this embodiment, the ultrasonic disperser frequency is 25kHz, the number of dispersions is 3 times, and each dispersion time is 15 minutes.

[0099] (3) Preparation of Nano-SiO2 Enhanced Carbonated Water: All CO2 in CO2 container 4 is introduced into nano-SiO2 enhanced carbonated water container 5 through a pipeline. Pressure is applied to nano-SiO2 enhanced carbonated water container 5 by a high-precision plunger pump 1 to dissolve CO2 into the nano-SiO2 fluid until the experimental pressure remains constant, thereby obtaining nano-SiO2 enhanced carbonated water. Nano-SiO2 enhanced carbonated water needs to be prepared each time nano-SiO2 enhanced carbonated water contacts heavy oil to prevent precipitation of nano-SiO2 particles in the nano-SiO2 enhanced carbonated water with increasing contact times. In this embodiment, the gas-water ratio of the nano-SiO2 enhanced carbonated water is 29.6 ml / ml.

[0100] (4) Conduct multiple contact experiments between nano-SiO2-enhanced carbonated water and heavy oil;

[0101] Before contact, the prepared formation oil is introduced into the falling ball viscometer 22 to measure the viscosity of the formation oil before contact. μ 0;

[0102] Then, the formation oil is introduced into the multiple contact model 14, and then the nano-SiO2 enhanced carbonated water is introduced into the multiple contact model 14, and the formation oil volume before the i-th contact is recorded.V 0i , record the formation oil volume after the i-th contact V 1i , calculate the volume expansion coefficient During the process, the experimental pressure is kept constant by a high-precision plunger pump 1;

[0103] The fluid in the multiple contact model 14 is stirred by the multiple contact model stirring device 11. During the process, the pressure in the multiple contact model 14 is controlled until it stabilizes at the experimental pressure. The stirring is stopped and the mixture is allowed to stand for a period of time until the oil and water are separated. In this embodiment, i =1, formation oil viscosity before contact μ 0=3561.9 mPa . s, formation oil volume before the first contact V 0i =200ml, the volume of formation oil after the first contact V 1i =220.006ml.

[0104] The ratio of the volume of the nano-SiO2 enhanced carbonated water introduced into the multiple-contact model 14 each time to the volume of the formation oil in the multiple-contact model 14 is 1:1. In this embodiment, the volume of the heavy oil before the first contact is 200 ml, so the volume of the nano-SiO2 enhanced carbonated water introduced into the multiple-contact model 14 is 200 ml.

[0105] The standing time should be no less than 6 hours, until the oil and water separate into separate layers. The standing time should be 8 hours.

[0106] The volume expansion coefficient of heavy oil after each contact is calculated according to formula (I): :

[0107] ;

[0108] In formula (I), is the volume expansion coefficient of the formation oil after the i-th contact, dimensionless; V 1i For the i After the first contact, all the oil volume in the formation after the nano-SiO2 enhanced carbonated water was extracted; V 0i For the i The volume of oil in the formation before the first contact with nano-SiO2 enhanced carbonized water. i =1; V 1i =220.006ml; V 0i =200ml; =1.11.

[0109] (5) Calculate the gas-water ratio of nano-SiO2 enhanced carbonated water after contact;

[0110] The nano-SiO2 enhanced carbonized water is led out from the lower end of the multiple contact model 14 to the gas-liquid separator 16, and the initial reading of the gas flow meter 19 is recorded at the beginning. V ai After the separation process is completed, the gas flow meter 19 reading V bi , collect the separated gas, and use the gas component analyzer 24 to detect the volume percentage of CO2 in the gas separated by nano-SiO2 enhanced carbonized water, which is recorded as , used to calculate the CO2 gas-water ratio after contact with nano-SiO2 enhanced carbonated water; use an electronic balance 18 to weigh the mass of nano-SiO2 enhanced carbonated water after gas-liquid separation and record it as m wi , discharge all the nano-SiO2 enhanced carbonized water in the multiple contact model 14 until oil is produced; in this embodiment, i =1; Gas flow meter 19 initial reading V ai =176ml, after the separation process, the gas flow meter 19 reading V bi =832ml, CO2 volume percentage =34.82%, nano-SiO2 enhances the quality of carbonated water m wi =48.667g.

[0111] The gas-water ratio of nano-SiO2 enhanced carbonated water after different contact times was calculated by formula (II) ;

[0112] ;

[0113] In formula (II), For the i Gas-water ratio of nano-SiO2 enhanced carbonated water after the first contact, ml / ml; V bi is the flow meter reading after the gas-liquid separation process is completed, ml; V ai is the initial reading of the flow meter at the beginning of gas-liquid separation, ml; m wi For the i The mass of nano-SiO2 enhanced carbonated water collected by the separator after the first contact, g; The density of carbonated water enhanced by nano-SiO2 g / cm 3 In this embodiment, i =1; V bi =832ml; V ai=176ml; m wi =48.667g; =1.0162g / cm 3 , calculated =13.70ml / ml.

[0114] The CO2 gas-water ratio of nano-SiO2 enhanced carbonated water after contact was calculated according to formula (III) ;

[0115] ;

[0116] In formula (III), For the i The volume percentage of CO2 in the gas separated by carbonization enhanced by nano-SiO2 after the first contact, dimensionless; For the i After the first contact, the CO2 gas-water ratio of the nano-SiO2 enhanced carbonated water is ml / ml. In this embodiment, i =1; =0.3482; calculated =4.77ml / ml.

[0117] (6) Calculate the gas-oil ratio of the heavy oil after contact;

[0118] Draw out some of the formation oil from the lower end of the multiple contact model 14 to the gas-liquid separator 16. When the growth rate of the gas flow meter 19 stabilizes, close the valve 9 at the lower end of the gas-liquid separator 16 and record the volume reading of the multiple contact model 14 before starting the gas-oil ratio test. After draining out some of the formation oil, close the valve 9 of the multiple contact model 14 and record the volume reading of the multiple contact model 14 after the formation oil is drained out. , while recording the initial reading of gas flow meter 19 V ci After the separation process is completed, the gas flow meter 19 reading V di , use electronic balance 18 to weigh the contacted formation oil mass after gas separation m oi , collect the separated gas, and use the gas component analyzer 24 to detect the volume percentage of CO2 in the separated gas of the formation oil after different contact times, which is recorded as In this embodiment, i =1; =214.343ml, =189.08ml, initial reading of gas flow meter 19 V ci =1264ml, after the separation process, the gas flow meter 19 reading Vdi =1768ml, formation oil mass m oi =21.335g, CO2 volume percentage =56.95%.

[0119] The volume of formation oil extracted during each contact is 15-25 ml. The volume of the extracted oil is controlled to avoid excessively small volumes, which can lead to large errors in the calculated gas-oil ratio, and excessively large volumes, which can reduce the number of contacts. In this embodiment, the volume of formation oil extracted during each contact is 20 ml.

[0120] The gas-oil ratio of heavy oil after each contact is calculated by the following formula (IV): ;

[0121] ;

[0122] In formula (IV), For the i Gas-oil ratio of heavy oil after the first contact, ml / ml; V ci is the initial reading of the flow meter at the beginning of gas-liquid separation, ml; V di is the flow meter reading after the gas-liquid separation process is completed, ml; m oi For the i Mass of formation oil collected during the secondary contact gas-liquid separation process, g; is the degassed formation oil density, g / cm 3 In this embodiment, i =1; V ci =1264ml; V di =1768ml; m oi =21.335g; =0.9803g / cm 3 , calculated =23.158ml / ml.

[0123] Calculate the density of the formation oil after each contact according to formula (V) :

[0124]

[0125] In formula (V), is the formation oil density after the i-th contact, g / cm 3 ; For the iThe volume of the multiple contact model 14 before the start of the test gas-oil ratio is shown in ml; For the i After the first contact, the formation oil is extracted and the volume of the model 14 is shown multiple times, ml; in this embodiment, i =1; =214.343ml; =189.08ml; calculated =0.9167g / cm 3 .

[0126] Calculate the CO2 gas-oil ratio of heavy oil after contact according to formula (VI) :

[0127]

[0128] In formula (VI), For the i CO2 gas-to-oil ratio of heavy oil after the first contact, ml / ml; For the i The volume percentage of CO2 in the separated gas of heavy oil after the first contact is dimensionless. In this embodiment, =56.95%; calculated =13.188ml / ml.

[0129] In steps (5) and (6), a hand pump is used to control the pressure of the back-pressure valve 15, in conjunction with a high-precision plunger pump 1, to ensure that each contact with the heavy oil is maintained at the experimental pressure, thereby avoiding calculation errors caused by the pressure drop caused by the derivation of the fluid from the cavity of the multiple contact model 14. In this embodiment, the pressure of the multiple contact model 14 is controlled to be 12.0 MPa, and the hand pump pressure range is 10-12 MPa.

[0130] (7) Repeat steps (4) to (6) to complete the multiple contact experiments of nano-SiO2 enhanced carbonized water and heavy oil; calculate the gas-water ratio of nano-SiO2 enhanced carbonized water under different contact times. , gas-oil ratio of heavy oil , density of formation oil , volume expansion coefficient , Nano-SiO2 enhances the CO2 gas-water ratio of carbonated water , CO2 gas-to-oil ratio of heavy oil After the last contact, the heavy oil was extracted from the lower end of the multiple contact model 14 to the falling ball viscometer 22 to measure the viscosity of the heavy oil after multiple contacts. μ ;

[0131] The variation of the above parameters with the increase of contact times was analyzed, and the mass transfer effect of nano-SiO2 enhanced carbonized water-heavy oil during multiple contacts was studied to reveal the mechanism of nano-SiO2 enhancing carbonized water to improve the recovery rate of heavy oil; in this embodiment, the viscosity of heavy oil after multiple contacts was μ =1883.1mPa·s, the calculation results during multiple contact processes are as follows Figures 2 to 7 shown.

[0132] like Figures 2 to 7 As shown in the figure, during the multiple contacts of nano-SiO2 enhanced carbonated water and heavy oil, as the number of contacts increases, the gas-oil ratio of heavy oil gradually increases, the gas-oil ratio of CO2 in heavy oil also gradually increases, and the increase of CO2 gas-oil ratio gradually decreases. The gas-water ratio and CO2 gas-water ratio of nano-SiO2 enhanced carbonated water decrease significantly after the initial contact. During the multiple contacts, the gas-water ratio gradually increases, but it is still lower than the initial gas-water ratio. This shows that during the multiple contacts, CO2 transfers from nano-SiO2 enhanced carbonated water to heavy oil. At the beginning of the contact, the gas-oil ratio of heavy oil and CO2 decreases. The oil-gas ratio is low, the gas-water ratio of nano-SiO2 enhanced carbonized water is high, and the mass transfer rate of CO2 from nano-SiO2 enhanced carbonized water to heavy oil is fast. During multiple contacts, the gas-oil ratio of heavy oil increases, and the CO2 mass transfer effect slows down; with the increase of the number of contacts, the volume expansion coefficient of heavy oil increases, and the density and viscosity of heavy oil decrease, indicating that the mass transfer of CO2 from nano-SiO2 enhanced carbonized water to heavy oil improves the high-pressure physical properties of heavy oil, but with the multiple contacts, the CO2 mass transfer effect slows down, and the improvement of the high-pressure physical properties of heavy oil gradually decreases.

[0133] (8) Repeat steps (1) to (7), changing the property parameters of nano-SiO2 enhanced carbonated water including salinity, CO2 saturation, nano-SiO2 particle concentration and salt type, and conduct multiple contact experiments between nano-SiO2 enhanced carbonated water and heavy oil after changing the property parameters, to clarify the influence of the property parameters of nano-SiO2 enhanced carbonated water on the gas-water ratio of nano-SiO2 enhanced carbonated water and the high-pressure physical properties of heavy oil (density, viscosity, gas-oil ratio, CO2 gas-oil ratio, volume expansion coefficient). In this example, the 100% CO2 saturation is changed to 50% CO2 saturation. The viscosity calculation results before and after the multiple contact process are shown in Table 1:

[0134] Table 1 Viscosity measurement results of heavy oil before and after contact at different CO2 saturations;

[0135]

[0136] Figure 2 This is a graph showing the change in the gas-to-water ratio of nano-SiO2 enhanced carbonized water with the number of contacts in the experimental method of the present invention. Figure 3 This is a graph showing the change in formation oil-gas-oil ratio with the number of contacts in the experimental method of the present invention. Figure 4This is a graph showing the change in the CO2 gas-water ratio of carbonized water enhanced by nano-SiO2 as a function of the number of contacts in the experimental method of the present invention. Figure 5 This is a graph showing the change in the CO2 gas-to-oil ratio of formation oil with the number of contacts in the experimental method of the present invention. Figure 6 This is a graph showing how the volume expansion coefficient of formation oil changes with the number of contacts in the experimental method of the present invention. Figure 7 The graph of formation oil density changing with the number of contacts in the experimental method of the present invention is shown in FIG. Figures 2 to 7 As shown in the figure, compared with 50% CO2 saturation, after multiple contacts between nano-SiO2 enhanced carbonized water and heavy oil, the gas-oil ratio of heavy oil is higher at different contact times. In addition, after contact between nano-SiO2 enhanced carbonized water and heavy oil, the density and viscosity of heavy oil are lower, the volume expansion coefficient is larger, and the expansion and viscosity reduction effect is better. This shows that increasing the CO2 saturation in nano-SiO2 enhanced carbonized water can improve the mass transfer effect of CO2 from nano-SiO2 enhanced carbonized water to heavy oil, and better improve the high-pressure physical properties of heavy oil.

Claims

1. Nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device, characterized by: Including fluid preparation system, multiple contact experiment system, test analysis system, temperature control system; The fluid preparation system is used to prepare fluids used in multiple contact experiments, including the preparation of nano-SiO2 enhanced carbonated water and formation oil; The multiple contact experimental system is used to control the multiple contact between nano-SiO2 enhanced carbonated water and formation oil; The test and analysis system is used to test the properties of nano-SiO2 enhanced carbonized water and heavy oil high-pressure properties after multiple contact processes; the properties of nano-SiO2 enhanced carbonized water include gas-water ratio and CO2 gas-water ratio, and the high-pressure properties of heavy oil include density, viscosity, gas-oil ratio, CO2 gas-oil ratio, and volume expansion coefficient; The temperature control system is used to provide the temperature required for multiple contact experiments; The fluid preparation system includes a parallel connection of a heavy oil container, a CH4 container, a CO2 container, a nano-SiO2 enhanced carbonated water container, a CH4 gas cylinder, and a CO2 gas cylinder; the tops of the heavy oil container, the CH4 container, the CO2 container, and the nano-SiO2 enhanced carbonated water container are all connected to pipelines via pressure gauges and valves, and the bottoms are all connected to high-precision plunger pumps via valves and pipelines; the tops of the CH4 container and the CO2 container are respectively connected to the CH4 gas cylinder and the CO2 gas cylinder via pressure gauges, valves, and pipelines; The multiple contact experimental system includes a multiple contact model, a multiple contact model stirring device, and a stirring block; one end of the multiple contact model is connected to the top of the nano-SiO2 enhanced carbonated water container via a pressure gauge, a valve, and a pipeline, and the other end is connected to a high-precision plunger pump via a pipeline and a valve; the multiple contact model stirring device controls the stirring of the fluid in the multiple contact model; The test and analysis system includes a gas-liquid separator, a gas flow meter, a falling ball viscometer, a gas component analyzer, an electronic balance, a hand pump, and several air bags; the top of the gas-liquid separator is connected to the top valve of the multiple contact model via a back pressure valve and a pipeline; the lower part of the gas-liquid separator is an outlet with a valve, and directly below the outlet is a liquid collection container. The liquid collection container is moved to the electronic balance for weighing, which is used to weigh the liquid mass and calculate the gas-liquid ratio; the upper part of the gas-liquid separator also has an outlet connected to the gas flow meter, and the outlet end of the gas flow meter is connected to a detachable and replaceable air bag via a pipeline. The separated gas is collected by the air bag, and then the volume percentage of CH4 and CO2 in the separated gas is detected by the gas component analyzer; The temperature control system includes a multiple contact model, a gas-liquid separator, a falling ball viscometer, a nano-SiO2 enhanced carbonated water container, and a heavy oil container. The pipelines connecting the multiple contact model, the gas-liquid separator, the falling ball viscometer, and the nano-SiO2 enhanced carbonated water container are wrapped with a heating tape on the outside for heating the above containers and the pipelines connecting the above containers. The heavy oil container, CH4 container, CO2 container, nano-SiO2 enhanced carbonated water container, and the top of the multiple contact model were all connected to a vacuum pump. Before the experiment, the heavy oil container, CH4 container, CO2 container, nano-SiO2 enhanced carbonated water container, and the multiple contact model were evacuated. The total volume of the multiple contact model is greater than 400 ml; A stirring block is placed in the multiple contact model, and the stirring block has a volume greater than 50 ml and a weight not less than 200 g.

2. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device according to claim 1, characterized in that: The multiple-contact model is a cylindrical container device wrapped in an insulation sleeve, which is used to achieve contact between nano-SiO2 enhanced carbonated water and formation oil; one end of the multiple-contact model stirring device is fixed to the multiple-contact model, and the other end is connected to a motor, and the multiple-contact model is driven to rotate by the rotation of the motor, which is used to stir the nano-SiO2 enhanced carbonated water and formation oil inside the multiple-contact model.

3. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device according to claim 1, characterized in that: A multiple contact model volume meter is also provided on the shell of the multiple contact model for visually displaying the volume change within the multiple contact model.

4. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device according to claim 1, characterized in that: The rotation speed of the multiple contact model is 2 r / min.

5. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device according to claim 4, characterized in that: The standard volume of the gas bag is not less than 500ml. The gas bag should be evacuated before collecting the gas for gas collection and gas component detection. One end of the falling ball viscometer is connected to the top valve of the multiple contact model through a pressure gauge, and the other end is connected to the back pressure valve, which is used to control the pressure of the exported fluid to maintain it under experimental conditions. The use conditions of the falling ball viscometer meet the normal operation conditions of 50°C and 18MPa. It is used to measure the viscosity of the heavy oil before and after multiple contacts of nano-SiO2 enhanced carbonated water and heavy oil under high temperature and high pressure conditions. High temperature and high pressure refer to: the high temperature value range is 30-50°C, and the high pressure value range is 10-18Mpa.

6. A nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental method, implemented by the nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental device according to any one of claims 1 to 5, characterized in that: The steps are as follows: (1) Preparation of formation oil; determination of formation oil density ρ o ; (2) Prepare nano-SiO2 fluid; measure the density of the nano-SiO2 fluid and record it as ρ w , introduce the prepared nano-SiO2 fluid into the nano-SiO2 enhanced carbonated water container; (3) preparing nano-SiO2 enhanced carbonated water; introducing all the CO2 in the CO2 container into the nano-SiO2 enhanced carbonated water container through a pipeline, applying pressure to the nano-SiO2 enhanced carbonated water container by a high-precision plunger pump to dissolve the CO2 into the nano-SiO2 fluid until the experimental pressure remains unchanged, thereby obtaining nano-SiO2 enhanced carbonated water; (4) Conduct multiple contact experiments between nano-SiO2 enhanced carbonated water and heavy oil; Before contact, the prepared formation oil is introduced into the falling ball viscometer to measure the viscosity μ0 of the formation oil before contact; Then the formation oil is introduced into the multiple contact model, and then the nano-SiO2 enhanced carbonated water is introduced into the multiple contact model, and the formation oil volume V before the i-th contact is recorded. 0i , record the formation oil volume V after the i-th contact 1i , calculate the volume expansion coefficient λ i ; During the process, the experimental pressure is kept constant by a high-precision plunger pump; The fluid in the multiple contact model is stirred by a multiple contact model stirring device. During the process, the pressure in the multiple contact model is controlled until it stabilizes at the experimental pressure. The stirring is stopped and the fluid is allowed to stand for a period of time until the oil and water are separated into layers. (5) Calculate the gas-water ratio of nano-SiO2 enhanced carbonated water after contact; Lead the nano-SiO2 enhanced carbonized water from the lower end of the multiple contact model to the gas-liquid separator, and record the initial reading V of the gas flow meter at the beginning. ai After the separation process, the gas flow meter reading V bi , collect the separated gas, and use the gas component analyzer to detect the volume percentage of CO2 in the gas separated by nano-SiO2 enhanced carbonized water, which is recorded as ω 水i (CO2) is used to calculate the CO2 gas-water ratio after contact with nano-SiO2 enhanced carbonated water; the mass of nano-SiO2 enhanced carbonated water after gas-liquid separation is weighed using an electronic balance and recorded as m wi , discharge all the nano-SiO2 enhanced carbonized water in the multiple contact model until oil is produced; (6) Calculate the gas-oil ratio of the heavy oil after contact; Drain some of the formation oil from the lower end of the multiple contact model into the gas-liquid separator. When the gas flow meter increases steadily, close the valve at the lower end of the gas-liquid separator and record the volume reading V of the multiple contact model before starting the gas-oil ratio test. 2i After draining out some of the formation oil, close the multiple contact model valve and record the volume indication V of the multiple contact model after the formation oil is drained out. 3i , and record the initial reading of the gas flow meter V ci After the separation process, the gas flow meter reading V di , use electronic balance to weigh the mass of contacted formation oil after gas separation m oi , collect the separated gas, and use the gas component analyzer to detect the volume percentage of CO2 in the separated gas of the formation oil after different contact times, which is recorded as ω oi (CO2); (7) Repeat steps (4) to (6) to complete the multiple contact experiments of nano-SiO2 enhanced carbonized water and heavy oil; calculate the gas-water ratio R of nano-SiO2 enhanced carbonized water under different contact times. wi , Gas-oil ratio R of heavy oil oi , the density of formation oil ρ i , volume expansion coefficient λ i , Nano-SiO2 enhanced CO2 gas-water ratio R of carbonated water wi (CO2), CO2 gas-oil ratio R of heavy oil oi (CO2); After the last contact, a portion of the heavy oil was drawn from the lower end of the multiple contact model into a falling ball viscometer to measure the viscosity μ of the heavy oil after multiple contacts; The variation of the above parameters with the increase of contact times was analyzed, the mass transfer effect of nano-SiO2 enhanced carbonized water-heavy oil during multiple contact processes was studied, and the mechanism of nano-SiO2 enhanced carbonized water in improving heavy oil recovery was revealed. (8) Repeat steps (1) to (7), change the property parameters of nano-SiO2 enhanced carbonated water including mineralization, CO2 saturation, nano-SiO2 particle concentration and salt type, and conduct multiple contact experiments between the nano-SiO2 enhanced carbonated water and heavy oil after the properties are changed to clarify the influence of the property parameters of nano-SiO2 enhanced carbonated water on the gas-water ratio of nano-SiO2 enhanced carbonated water and the high-pressure physical properties of heavy oil.

7. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental method according to claim 6, characterized in that: The ratio of the volume of nano-SiO2 enhanced carbonized water introduced into the multiple contact model each time to the volume of formation oil in the multiple contact model was 1:1; The standing time should be no less than 6 hours, until the oil and water separate into layers; The volume expansion coefficient λ of the heavy oil after each contact is calculated according to formula (I): i : In formula (I), λ i is the volume expansion coefficient of the formation oil after the i-th contact, dimensionless; V 1i V is the volume of oil in the formation after all the nano-SiO2 enhanced carbonated water is extracted after the i-th contact; 0i is the formation oil volume before the i-th contact with nano-SiO2 enhanced carbonized water.

8. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental method according to claim 6, characterized in that: The gas-water ratio R of nano-SiO2 enhanced carbonated water after different contact times was calculated by formula (II) wi ; In formula (II), R wi is the gas-water ratio of nano-SiO2 enhanced carbonated water after the i-th contact, ml / ml; V bi is the flow meter reading after the gas-liquid separation process is completed, ml; V ai is the initial flow meter reading at the beginning of gas-liquid separation, ml; m wi is the mass of nano-SiO2 enhanced carbonated water collected by the separator after the i-th contact, g; ρ w The density of carbonated water enhanced by nano-SiO2 g / cm 3 ; The CO2 gas-water ratio R of the carbonized water enhanced by nano-SiO2 after contact was calculated according to formula (III) wi (CO2); R wi (CO2)=R wi ×ω 水i (CO2) (III); In formula (III), ω 水i (CO2) is the volume percentage of CO2 in the carbonized water separation gas enhanced by nano-SiO2 after the i-th contact, dimensionless; R wi (CO2) is the CO2 gas-water ratio of nano-SiO2 enhanced carbonated water after the i-th contact, ml / ml; The volume of formation oil extracted per contact was 15-25 ml.

9. The nano-silicon dioxide enhanced carbonated water-heavy oil multiple contact experimental method according to claim 6, characterized in that: The gas-oil ratio R of heavy oil after each contact is calculated by the following formula (IV): oi ; In formula (IV), R oi is the gas-oil ratio of heavy oil after the ith contact, ml / ml; V ci V is the initial flow meter reading at the beginning of gas-liquid separation, ml; di is the flow meter reading after the gas-liquid separation process is completed, ml; m oi is the mass of formation oil collected during the i-th contact gas-liquid separation process, g; ρ is the density of degassed formation oil, g / cm 3； Calculate the density of the formation oil after each contact according to formula (V): i : In formula (V), ρ i is the formation oil density after the i-th contact, g / cm 3 ; V 2i V is the volume of the multiple contact model before the start of the gas-oil ratio test at the i-th contact, ml; 3i The volume of the multiple contact model after the formation oil is extracted after the i-th contact, ml; Calculate the CO2 gas-oil ratio R of the heavy oil after contact according to formula (VI) oi (CO2): R oi (CO2)=R oi ×ω oi (CO2)(VI); In formula (VI), R oi (CO2) is the CO2 gas-to-oil ratio of the heavy oil after the i-th contact, ml / ml; ω oi (CO2) is the volume percentage of CO2 in the heavy oil separation gas after the i-th contact, dimensionless.

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