A multifunctional displacement system and method using co2

Abstract

The application discloses a multifunctional displacement system and method using CO2. The system of the application comprises a gas injection assembly, a core holder and a pressure control system, etc. The gas injection assembly uses a first piston container to measure the amount of gas, and is suitable for quantitative injection of CO2 which is prone to phase change. The core holder is designed with multiple measuring points, and users can arbitrarily set the positions of the measuring points according to requirements. The rubber tube of the core holder is made of epoxy resin material, solving the problem of CO2 swelling of the rubber sleeve. The pressure control system can stably and accurately control the pressure in the core holder. The system of the application is used to simulate dynamic oil displacement processes and supporting process measures, optimize injection and production parameters and process methods under certain temperature and pressure conditions, such as CO2 oil displacement, N2 oil displacement, mixed gas oil displacement, CO2 foam oil displacement, N2 foam oil displacement, steam oil displacement, water oil displacement, water-gas alternating oil displacement, chemical oil displacement, multi-component composite displacement and multi-component alternating displacement.

Description

Technical Field

[0001] This invention relates to the fields of CCUS and oil and gas extraction technology, and in particular to a multifunctional displacement system and method utilizing CO2. Background Technology

[0002] Displacement systems can be applied to CO2 utilization and storage, as well as oil and gas development. Based on displacement mechanisms and similarity principles, they simulate formation pressure and temperature conditions, and utilize the latest advancements in modern science and technology, such as computer technology and advanced sensor technology, to simulate and study dynamic oil displacement processes and corresponding technological methods, including CO2 flooding, N2 flooding, mixed gas flooding, CO2 or N2 foam flooding, steam flooding, water flooding, alternating water-gas flooding, chemical flooding, multi-element composite flooding, alternating multi-element flooding, and multi-element mixed flooding. This guidance helps optimize injection and production parameters, improve oil displacement efficiency, and enhance production results. However, existing displacement systems and methods are limited in function, unable to achieve continuous, quantitative, or alternating injection; inaccurate control of internal pressure and flow rates introduces significant errors into experimental research; and they do not consider multiple gas displacement methods or gas foam displacement. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of the present invention propose a multifunctional displacement system and method utilizing CO2.

[0005] On one hand, this invention proposes a multifunctional displacement system utilizing CO2, comprising:

[0006] A gas injection assembly includes a gas cylinder, a gas booster pump is installed on the outlet pipeline of the gas cylinder, a gas storage tank is installed on the outlet pipeline of the gas booster pump, a first piston container is installed on a branch of the outlet pipeline of the gas storage tank, and a first injection pump is connected to the lower part of the first piston container.

[0007] The displacement source assembly includes a steam generator and several piston containers arranged in parallel, and a second injection pump is connected to the lower part of both the steam generator and the piston containers.

[0008] A foam generator is located downstream of the gas injection assembly, with a stirring device at the bottom of the foam generator and a viewing window located downstream of the foam generator.

[0009] A core holder is located downstream of the viewing window. A temperature control device is installed inside the core holder to control the temperature of the rock sample and other materials inside. A differential pressure sensor is installed on the pipeline between the outlet and inlet ends of the core holder. The annular pressure of the core holder is controlled by an annular pressure pump.

[0010] A pressure control system includes a manual pump and multiple back pressure valves. The back pressure valves are located at the outlet and inlet ends of the core holder and at the outlet end of the gas injection assembly. The manual pump is used to control the pressure of the back pressure valves.

[0011] A gas-liquid metering system is installed downstream of the core holder. The gas-liquid metering system includes a gas-liquid separator, a first flow meter, and a liquid metering device. The first flow meter is installed on the outlet pipeline at the top of the gas-liquid separator, and the liquid metering device is installed at the bottom outlet end of the gas-liquid separator.

[0012] A vacuum pumping device is installed on a branch of the inlet pipeline of the core holder and is used to evacuate the system.

[0013] In some embodiments, the piston container includes a second piston container, a third piston container, and a fourth piston container arranged in parallel, wherein the first piston container, the second piston container, the third piston container, and the fourth piston container are respectively used to store gas, water, crude oil, and chemical solution.

[0014] In some embodiments, the steam generator is connected to a wet nitrogen humidification tank via a pipeline.

[0015] In some embodiments, the foam generator is provided with multiple layers of screens with different pore sizes inside, and the number of screens, pore size, pore density, etc. can be adjusted as needed.

[0016] In some embodiments, the core holder has a rubber sleeve made of epoxy resin, which is resistant to corrosion from CO2 and other substances.

[0017] In some embodiments, the back pressure valve includes a first back pressure valve, a second back pressure valve, and a third back pressure valve. The first back pressure valve is disposed at the inlet end of the core holder, the second back pressure valve is disposed at the outlet end of the core holder, and the third back pressure valve is disposed adjacent to the outlet end of the upper part of the first piston container. The output end of the manual pump is connected to a first buffer tank, and the outlet end of the first buffer tank is connected to the first back pressure valve, the second back pressure valve, and the third back pressure valve respectively through pipelines.

[0018] In some embodiments, a dryer is provided between the gas-liquid separator and the first flow meter, and a first one-way valve is provided between the dryer and the first flow meter. The liquid metering device includes a balance and a glass container with a metering scale placed on the balance.

[0019] In some embodiments, safety valves are provided on the branch of the gas storage tank inlet pipeline, the branch of the viewing window outlet pipeline, and the branch of the first buffer tank outlet pipeline.

[0020] In some embodiments, pressure gauges and thermometers are provided on the inlet pipeline of the gas storage tank, the upper pipeline of the first piston container, the top of the foam generator, the outlet and inlet ends of the core holder, the outlet end of the first buffer tank, and the top inlet end of the gas-liquid separator.

[0021] On the other hand, this invention proposes a multifunctional displacement method utilizing CO2, comprising the following steps:

[0022] Check the airtightness of the system, load the rock sample into the core holder, adjust the ring pressure and internal temperature of the core holder, and evacuate the system.

[0023] Inject crude oil into the rock sample until the sample is saturated, and adjust the back pressure valve pressure to the target value according to the plan requirements;

[0024] The displacement agent is injected into the core holder for crude oil displacement. The displacement agent is gas, water vapor, foam, chemical solution, water or a mixture thereof. The mixture is a mixture of at least two substances in the gas, water vapor, foam, chemical solution and water. When the displacement agent is foam, the gas and foaming agent are first quantitatively injected into the foam generator to generate foam. The state of the foam fluid is observed through a viewing window, and the conditions and composition of foam generation are recorded. Then the foam is injected into the core holder for displacement study.

[0025] The gas-liquid metering system is used to measure the gas and liquid volumes and analyze the displacement effect.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The gas injection assembly of this invention uses a first piston container to measure the amount of gas, making it suitable for the quantitative injection of CO2, which is prone to phase changes. Multiple measuring points are designed on the side wall of the core holder, allowing users to arbitrarily set the position of each measuring point according to their needs. The epoxy resin sleeve solves the problem of the sleeve swelling when exposed to CO2. The pressure control system can stably and accurately control the pressure inside the core holder. The safety valve enables better control of the displacement process, reducing safety hazards and greatly facilitating research.

[0028] This invention relates to a multifunctional displacement system used to simulate dynamic oil displacement processes under specific temperature and pressure conditions, including CO2 flooding, N2 flooding, mixed gas flooding, CO2 foam flooding, N2 foam flooding, steam flooding, water flooding, alternating water-gas flooding, chemical flooding, multi-element composite flooding, and alternating multi-element flooding, as well as related technological measures and methods for optimizing injection and production parameters and processes. Simultaneously, it tests porosity, water content, and oil saturation under these temperature and pressure conditions; and investigates the influence of temperature, pressure, injected gas, foam, chemical solution, water, and injection rate on displacement efficiency. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0030] Figure 1 This is a schematic diagram of the multifunctional displacement system of the present invention;

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Gas cylinder; 2. Gas booster pump; 3. Air compressor; 4. Gas storage tank; 5. First piston container; 6. First injection pump; 7. First water tank; 8. Second pressure gauge; 9. Second thermometer; 10. First safety valve; 11. First pressure gauge; 12. First thermometer; 13. Steam generator; 14. Second piston container; 15. Third piston container; 16. Fourth piston container; 17. Second injection pump; 18. Second water tank; 19. Fourth valve; 20. Fifth valve; 21. Second check valve; 22. Foam generator; 23. Viewing window; 24. Third pressure gauge; 25. Third thermometer; 26. Second safety valve; 27. Core holder; 28. Differential pressure sensor. 8. Ring pressure pump 29. Second buffer tank 30. Fourth pressure gauge 31. Fourth thermometer 32. Fifth pressure gauge 33. Fifth thermometer 34. Manual pump 35. First buffer tank 36. First back pressure valve 37. Second back pressure valve 38. Third back pressure valve 39. First valve 40. Second valve 41. Third valve 42. Sixth pressure gauge 43. Sixth thermometer 44. Third safety valve 45. Vacuum device 46. Gas-liquid separator 47. Dryer 48. First check valve 49. First flow meter 50. Glass container 51. Balance 52. Gas collection device 53. Seventh pressure gauge 54. Seventh thermometer 55. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0034] The following description, with reference to the accompanying drawings, describes a multifunctional displacement system and method utilizing CO2 according to embodiments of the present invention.

[0035] like Figure 1 As shown, the CO2-based multifunctional displacement system of the present invention includes a gas injection component, a displacement source component, a foam generator 22, a pressure control system, a gas-liquid metering system, and a vacuum pumping device 46.

[0036] The gas injection assembly includes a gas cylinder 1, a gas booster pump 2 installed on the outlet pipeline of the gas cylinder 1, and a gas storage tank 4 installed on the outlet pipeline of the gas booster pump 2.

[0037] Specifically, gas cylinder 1 is used to store gas, and there must be at least one gas cylinder 1. When two gas cylinders 1 are set, they can be used alternately or to store different types of gases or mixed gases. A gas booster pump 2 is installed on the outlet pipeline of gas cylinder 1, and a gas storage tank 4 is installed on the outlet pipeline of gas booster pump 2. The gas is stored in the gas storage tank 4 after being pressurized by gas booster pump 2. The outlet end of the gas storage tank 4 is connected to a first piston container 5. When gas needs to be injected, the gas in the gas storage tank 4 is first injected into the first piston container 5, and then the first injection pump 6 is used to quantitatively inject the gas in the first piston container 5 into the subsequent experimental system. Among them, gas booster pump 2 is mainly used for gas pressurization. An air compressor 3 installed at the input end of gas booster pump 2 provides compressed air to gas booster pump 2. Gas booster pump 2 uses compressed air as a power source and gas booster pump 2 as a pressure source. The output gas pressure is proportional to the driving air source pressure. By adjusting the driving air source pressure, the corresponding pressurized gas pressure can be obtained. When the driving gas source pressure is balanced with the pressurized gas pressure, the gas booster pump 2 stops pressurizing, and the output gas pressure stabilizes at the pre-adjusted pressure. Therefore, it has the characteristics of explosion-proof, adjustable output pressure, small size, light weight, simple operation, reliable performance, and wide applicability.

[0038] In some embodiments, a second pressure gauge 8 and a second thermometer 9 are installed on the inlet pipeline of the gas storage tank 4. The second pressure gauge 8 and the second thermometer 9 are used to test the pressure and temperature of the gas in the gas storage tank 4.

[0039] In some embodiments, a first safety valve 10 is installed on a branch of the inlet pipeline of the gas storage tank 4. When the gas storage tank 4 is overpressurized, it automatically releases pressure to ensure system safety.

[0040] The displacement source assembly includes a steam generator 13 and several piston containers arranged in parallel. The piston containers include a second piston container 14, a third piston container 15, and a fourth piston container 16. The steam generator 13, the second piston container 14, the third piston container 15, and the fourth piston container 16 are arranged in parallel. The first piston container 14, the second piston container 14, the third piston container 15, and the fourth piston container 16 are respectively used to hold gas, water, crude oil, and chemical solution.

[0041] Specifically, a first piston container 5 is installed on the outlet branch of the gas storage tank 4. A first injection pump 6 is connected to the lower part of the first piston container 5. When gas needs to be injected, the gas in the gas storage tank 4 is first injected into the first piston container 5, and then the first injection pump 6 injects a measured amount of gas. A first pressure gauge 11 and a first thermometer 12 are installed on the upper pipeline of the first piston container 5. The first pressure gauge 11 and the first thermometer 12 are used to test the pressure and temperature of the gas flowing out of the first piston container 5. The input end of the first injection pump 6 is connected to a first water tank 7. The amount of gas flowing out of the first piston container 5 is calculated based on the water volume injected by the first injection pump 6 and the test data from the first pressure gauge 11 and the first thermometer 12. It can be understood that the first piston container 5 can be used for measurement regardless of whether the gas is in a gaseous or liquid state. A steam generator 13, a second piston container 14, a third piston container 15, and a fourth piston container 16 are connected in parallel. The lower parts of each container are connected to a second injection pump 17, and their upper parts are connected together. Water is placed in the second piston container 14. When water is needed for crude oil displacement, the second injection pump 17 injects water through a fourth valve 19 into the subsequent core holder 27 for displacement experiments. Crude oil is placed in the third piston container 15. The second injection pump 17 injects crude oil through a fourth valve 19 into the subsequent core holder 27 to saturate the rock sample with crude oil. The fourth piston container 16 is used to hold a chemical solution, which may be a foaming agent or other polymer that affects the displacement effect. Understandably, when conducting foam displacement simulation experiments, the chemical solution acts as a foaming agent, which is injected into the foam generator 22 via the fifth valve 20. When examining the effect of the chemical solution on the displacement effect, the chemical solution acts as a polymer, which is injected into the subsequent core holder 27 via the fourth valve 19. Understandably, the number of the first piston container 5, the second piston container 14, the third piston container 15, and the fourth piston container 16 can be one or two. When there are two, they can be used alternately to allow the experiment to continue. Furthermore, the injection rate of both the first injection pump 6 and the second injection pump 17 is adjustable. Injection can be performed at a constant rate or a variable rate, depending on the experimental needs. Variable rate injection includes, but is not limited to, injection methods with gradually increasing or decreasing rates.

[0042] In addition, the piston container is designed with an upper and lower trigger mechanism. When the piston moves to the two extreme positions, the computer of the control system will detect that the piston has moved to the two extreme end positions and realize the automatic replenishment of fluid in the piston container.

[0043] In some embodiments, the first piston container 5, the second piston container 14, the third piston container 15, and the fourth piston container 16 are all equipped with temperature control devices to control the temperature of the internal substances; the system pipelines are all wrapped with insulation material.

[0044] Steam generator 13 generates steam for displacement simulation experiments. The input end of the second injection pump 17 is connected to the second water tank 18. Water in the second water tank 18 enters the steam generator 13 under the action of the second injection pump 17 and is heated into steam in the steam generator 13.

[0045] The steam generator 13 mainly consists of a steam generator body, a PLC control system, a safety system, and a pressure and temperature monitoring system. The steam generator body produces steam with a maximum temperature exceeding 300℃. Temperature control probes and pressure sensors are installed inside the steam generator 13. The PLC screen displays the steam temperature and pressure in real time. For safety, a safety valve is installed inside the steam generator 13. The steam generator 13 includes a new type of heating pipe with a double-helix winding structure, using high thermal conductivity metal materials for heat conduction, and ceramic fiber blanket insulation material for external heat preservation. The steam generator 13 adopts a dry heating and conduction structure. This new structure not only improves temperature control accuracy but also increases the service life of the heating element and ensures safety. Compared with traditional liquid conduction heating steam generators, the steam generator 13 has the following characteristics: it uses cast aluminum as the temperature medium instead of liquid, eliminating the need for a liquid heating vessel and thus preventing overpressure caused by vessel heating, resulting in high safety and reliability; the steam generator 13 is designed with a PLC acquisition and control system, giving it both integrated control features and high-precision control.

[0046] In some embodiments, the steam generator 13 is connected to a wet nitrogen humidification tank via a pipeline, the wet nitrogen humidification tank being used to inject wet nitrogen into the steam to adjust the steam dryness.

[0047] The foam generator 22 is located downstream of the gas injection assembly. A stirring device is installed at the bottom of the foam generator 22, and a viewing window 23 is installed downstream of the foam generator 22.

[0048] Specifically, a stirring device is installed at the bottom of the foam generator 22. The foaming agent is injected from the bottom of the foam generator 22 through the fifth valve 20, and the gas is injected from the bottom of the foam generator 22 through the second one-way valve 21. Under the action of the stirring device, the foaming agent and gas are fully stirred and foamed. The stirring device's rotation speed is adjustable. A viewing window 23 is located downstream of the foam generator 22, allowing observation of the foam's stability. The generated foam enters the core holder 27 for displacement experiments. The second one-way valve 21 prevents the foam from flowing towards the gas injection component.

[0049] The foam generator 22 employs a unique design structure, where gas is injected tangentially into the foaming agent, ensuring thorough mixing and foaming of the foaming agent and gas. In some embodiments, the foam generator 22 contains multiple layers of screens with different pore sizes. The screens are arranged sequentially from top to bottom in the foam generator 22 according to the order of increasing pore size, and the foam formed in the foam generator 22 is compressed by passing through the through-holes of the screens with decreasing pore size.

[0050] In some embodiments, the foam squeezed through a screen is transformed into microfoam of the same order of magnitude as the core pore size, which facilitates the foam entering the core channels.

[0051] In some embodiments, the viewing window 23 is made of artificial sapphire, and the stability of the foam can be observed through the viewing window 23.

[0052] In some embodiments, a second safety valve 26 is provided on a branch of the outlet pipeline of the viewing window 23 to automatically release pressure when the viewing window 23 is overpressurized.

[0053] In some embodiments, a third pressure gauge 24 and a third thermometer 25 are provided on the top of the foam generator 22. The third pressure gauge 24 and the third thermometer 25 are used to test the pressure and temperature inside the foam generator 22.

[0054] The core holder 27 is located downstream of the viewing window 23. A temperature control device is installed inside the core holder 27. A differential pressure sensor 28 is installed on the pipeline between the outlet end and the inlet end of the core holder 27. The annular pressure of the core holder 27 is controlled by the annular pressure pump 29.

[0055] Specifically, a displacement simulation experiment is conducted in the core holder 27. A differential pressure sensor 28 is installed on the pipeline connecting the outlet and inlet ends of the core holder 27. The differential pressure sensor 28 is used to measure the pressure difference between the outlet and inlet ends of the core holder 27. The core holder 27 has an internal temperature control device, which is used to heat the core and other materials inside the core holder 27 to simulate formation temperature. The annular pressure of the core holder 27 is controlled by an annular pressure pump 29. The output end of the annular pressure pump 29 is connected to a second buffer tank 30, and the output end of the second buffer tank 30 is connected to the core holder 27.

[0056] The core holder 27 can be a long-tube core holder or a standard core holder, depending on the design requirements. The core holder 27 is designed with an installation support mechanism. The left end cap, measuring points, rubber sleeve, right core plug, right end cap, support rod, support ring, lead-out rod, and lead-out sealing mechanism are all installed outside the cylinder and then directly inserted into the cylinder, making installation convenient and quick. Materials that are frequently disassembled, such as the end cap, can be made of titanium alloy, making it lightweight and easy to install. The loading and unloading clamp between the core and the rubber sleeve is tilted at a certain angle to facilitate the core's sliding down under gravity. The inner wall of the core holder 27 model cylinder is roughened to prevent crossflow; the inner cavity is designed with a heat insulation device; the plug is designed with a piston compaction structure; and each measuring point and plug is designed with a sand-proof structure. The core holder 27 has multiple measuring points designed on its sidewall for testing technical parameters such as temperature, pressure, and resistance. Users can set the measuring point positions along the axial or radial direction of the core holder 27 on the sidewall as needed, or arbitrarily set the positions of the measuring points according to requirements. In some embodiments, the rubber sleeve of the core holder 27 is made of epoxy resin. Using an epoxy resin rubber sleeve can solve the problem of rubber swelling when the displacing gas is CO2.

[0057] In some embodiments, pressure gauges and thermometers are provided at both the outlet and inlet ends of the core holder 27. Specifically, a fourth pressure gauge 31 and a fourth thermometer 32 are provided at the inlet end of the core holder 27 to test the pressure and temperature of the fluid entering the core holder 27, and a fifth pressure gauge 33 and a fifth thermometer 34 are provided at the outlet end of the core holder 27 to test the pressure and temperature of the fluid flowing out of the core holder 27.

[0058] In addition, during the displacement experiment, the experiment is considered complete when the injection rate of the displacing material from the inlet end of the core holder 27 is equal to and stable with the outflow rate from the outlet end of the core holder 27, and no oil is displaced. The amount of injected displacing material and the amount of oil, gas, and water displaced are recorded to analyze the displacement effect. The displacing material can be CO2, water, N2, water vapor, chemical solutions, polymers, etc.

[0059] The pressure control system includes a manual pump 35 and multiple back pressure valves. The back pressure valves are located at the outlet and inlet ends of the core holder 27 and at the outlet end of the gas injection assembly. The manual pump 35 controls the pressure of the back pressure valves. The back pressure valves include a first back pressure valve 37, a second back pressure valve 38, and a third back pressure valve 39. The first back pressure valve 37 is located at the inlet end of the core holder 27, the second back pressure valve 38 is located at the outlet end of the core holder 27, and the third back pressure valve 39 is located at the upper outlet end of the first piston container 5. The output end of the manual pump 35 is connected to a first buffer tank 36, and the outlet end of the first buffer tank 36 is connected to the first back pressure valve 37, the second back pressure valve 38, and the third back pressure valve 39 via pipelines.

[0060] Specifically, the output end of the manual pump 35 is connected to the first buffer tank 36, and the outlet end of the first buffer tank 36 is connected to the first back pressure valve 37, the second back pressure valve 38, and the third back pressure valve 39 through pipelines. The first back pressure valve 37 is located at the inlet end of the core holder 27, the second back pressure valve 38 is located at the outlet end of the core holder 27, and the third back pressure valve 39 is located at the upper outlet end of the first piston container 5. The first back pressure valve 37 and the second back pressure valve 38 are used to control the pressure entering and exiting the core holder 27, and the third back pressure valve 39 is used to control the minimum outflow pressure of the gas in the gas injection assembly.

[0061] A first valve 40 is installed on the pipeline between the side of the first back pressure valve 37 and the outlet end of the first buffer tank 36. A second valve 41 is installed on the pipeline between the side of the second back pressure valve 38 and the outlet end of the first buffer tank 36. A third valve 42 is installed on the pipeline between the side of the third back pressure valve 39 and the outlet end of the first buffer tank 36. When it is necessary to adjust the pressure value of the first back pressure valve 37, the first valve 40 is opened, and the second valve 41 and the third valve 42 are closed. The pressure value of the first back pressure valve 37 is increased or decreased using a manual pump 35. When it is necessary to adjust the pressure value of the second back pressure valve 38, the second valve 41 is opened, and the first valve 40 and the third valve 42 are closed. The pressure value of the second back pressure valve 38 is increased or decreased using a manual pump 35. When it is necessary to adjust the pressure value of the third back pressure valve 39, the third valve 42 is opened, and the second valve 41 and the first valve 40 are closed. The pressure value of the third back pressure valve 39 is increased or decreased using a manual pump 35.

[0062] In some embodiments, a sixth pressure gauge 43 and a sixth thermometer 44 are provided at the outlet end of the first buffer tank 36. The sixth pressure gauge 43 and the sixth thermometer 44 are used to test the pressure and temperature at the outlet end of the first buffer tank 36. In some embodiments, a third safety valve 45 is provided on a branch of the outlet pipeline of the first buffer tank 36 to automatically release pressure when the first buffer tank 36 is overpressurized.

[0063] The gas-liquid metering system is located downstream of the core holder 27. The system includes a gas-liquid separator 47, a first flow meter 50, and a liquid metering device. The first flow meter 50 is located on the outlet pipeline at the top of the gas-liquid separator 47, and the liquid metering device is located at the bottom outlet of the gas-liquid separator 47. A dryer 48 is installed between the gas-liquid separator 47 and the first flow meter 50, and a first one-way valve 49 is installed between the dryer 48 and the first flow meter 50. The liquid metering device includes a balance 52 and a graduated glass container 51 placed on the balance 52.

[0064] Specifically, the gas-liquid metering system is used to measure the amount of gas and liquid flowing out from the outlet of the core holder 27. The gas-liquid metering device includes a gas-liquid separator 47, a first flow meter 50, and a liquid metering device. The first flow meter 50 is installed on the outlet pipeline at the top of the gas-liquid separator 47 to measure the gas flow rate. A dryer 48 is installed between the gas-liquid separator 47 and the first flow meter 50 to remove water vapor from the gas, avoiding metering errors caused by water vapor. A first one-way valve 49 is installed between the dryer 48 and the first flow meter 50 to prevent metering errors caused by gas backflow. The liquid metering device is located at the bottom outlet of the gas-liquid separator 47. The liquid metering device includes a balance 52 and a glass container 51. The glass container 51 is placed on the balance 52. After the gas-liquid mixture is separated by the gas-liquid separator 47, the liquid flows into the glass container 51. The volume of the liquid can be measured using the glass container 51, and the mass of the liquid can be measured using the balance 52. The glass container 51 has measuring scales on its side wall, and the oil-water mixture can easily separate into layers inside, making it convenient to measure the amount of oil and water separately.

[0065] In some embodiments, a gas collection device 53 is provided at the outlet end of the first flow meter 50. The gas collection device 53 is used to collect gas for further processing of gas that cannot be directly discharged.

[0066] In some embodiments, a seventh pressure gauge 54 and a seventh thermometer 55 are provided at the inlet end of the top of the gas-liquid separator 47. The seventh pressure gauge 54 and the seventh thermometer 55 are used to test the temperature and pressure of the gas-liquid mixture flowing into the gas-liquid separator 47.

[0067] A vacuum pumping device 46 is installed on the inlet pipeline of the core holder 27 to evacuate the system. In some embodiments, the vacuum pumping device 46 is a vacuum pump.

[0068] The CO2-based multifunctional displacement method and the CO2-based multifunctional displacement system of this invention include the following steps: loading a rock sample into a core holder 27 and adjusting the annular pressure and internal temperature of the core holder 27; injecting crude oil into the rock sample until it is saturated and adjusting the back pressure valve to the target value; injecting a displacement agent into the core holder 27 to displace the crude oil, wherein the displacement agent is a gas, water vapor, foam, water, or chemical solution, or a mixture thereof, wherein the gas is CO2 or N2, and the mixture is a mixture of at least two substances from the gas, water vapor, foam, chemical solution, and water. When the displacement agent is foam, firstly, a gas and a foaming agent are quantitatively injected into a foam generator 22 to generate foam, and the state of the foam fluid is observed through a viewing window 23. Then, the foam is injected into the core holder 27 for displacement experiments; the gas-liquid metering system is used to measure the gas-liquid volume and analyze the displacement effect.

[0069] The method of the present invention is illustrated below using water-driven oil recovery as an example, and includes the following steps:

[0070] (1) Check the airtightness of the system and load the rock sample into the core holder 27;

[0071] (2) Use a vacuum pump to evacuate the system, use a ring pressure pump 29 to adjust the ring pressure of the core holder 27, and use a temperature control device to adjust the internal temperature of the core holder 27.

[0072] (3) The crude oil in the third piston container 15 is injected into the core holder 27 through the fourth valve 19 and the first back pressure valve 37 using the second injection pump 17 until the rock sample is saturated. The pressure of the first back pressure valve 37 and the second back pressure valve 38 is adjusted to adjust the internal pressure of the core holder 27 to the target value. When the crude oil injected by the second injection pump 17 is the same as the discharge of the crude oil flowing out of the second back pressure valve 38 and is stable, the rock sample is considered to be saturated. The amount of crude oil flowing out of the second back pressure valve 38 is measured by the glass container 51 and the balance 52.

[0073] (4) Under the action of the second injection pump 17, the water in the second piston container 14 is injected into the core holder 27 through the fourth valve 19 and the first back pressure valve 37, and the water displaces the crude oil inside the rock sample.

[0074] (5) Use gas-liquid separator 47 to separate oil and water, and measure the amount of separated oil and water through glass container 51 and balance 52.

[0075] (6) Change the injection displacement, cumulative input, injection timing, experimental temperature, and ring pressure of the second injection pump 17 respectively, conduct comparative experiments, and analyze the displacement pressure;

[0076] (7) Clean the experimental equipment and the experiment is over.

[0077] The methods for oil displacement using CO2, water vapor, and chemical solutions are similar to those using water displacement.

[0078] Taking foam displacement of oil as an example, the method of the present invention includes the following steps:

[0079] (1) Check the airtightness of the system and load the rock sample into the core holder 27;

[0080] (2) Use a vacuum pump to evacuate the system, use a ring pressure pump 29 to adjust the ring pressure of the core holder 27, and use a temperature control device to adjust the internal temperature of the core holder 27.

[0081] (3) The crude oil in the third piston container 15 is injected into the core holder 27 through the fourth valve 19 and the first back pressure valve 37 using the second injection pump 17 until the rock sample is saturated. The pressure of the first back pressure valve 37 and the second back pressure valve 38 is adjusted to adjust the internal pressure of the core holder 27 to the target value. When the crude oil injected by the second injection pump 17 is the same as the crude oil flowing out of the second back pressure valve 38 and is stable, the rock sample is saturated. The amount of crude oil flowing out of the second back pressure valve 38 is measured by the glass container 51 and the balance 52.

[0082] (4) Under the action of the second injection pump 17, the foaming agent in the fourth piston container 16 is injected into the foam generator 22 through the fifth valve 20. Under the action of the first injection pump 6, the gas in the first piston container 5 is injected into the foam generator 22 through the third back pressure valve 39 and the second check valve 21. The gas and foaming agent generate foam under the action of the stirring device. The state of the foam fluid is observed through the viewing window 23, and the conditions and composition of foam generation are recorded. The bubbles are injected into the core holder 27 through the first back pressure valve 37. The foam displaces the crude oil inside the rock sample.

[0083] (5) Use gas-liquid separator 47 to separate oil and water, and measure the amount of separated oil and water through glass container 51 and balance 52.

[0084] (6) Clean the experimental equipment and the experiment is over.

[0085] Understandably, in displacement simulation experiments, comparative experiments can be conducted and the displacement effect analyzed by changing the displacement or cumulative injection volume of the first injection pump 6, the displacement or cumulative injection volume of the second injection pump 17, the experimental temperature, and the annular pressure. In foam displacement simulation experiments, the gas can be CO2, N2, etc.

[0086] In the displacement experiment, the rock sample is considered saturated, i.e., saturated oil, when the displacement of crude oil injected from the core holder 27 is equal to and stable with the displacement of crude oil flowing out of the core holder 27. Specifically, crude oil in the third piston container 15 is injected into the core holder 27 at a certain displacement through the fourth valve 19 and the first back pressure valve 37 using the second injection pump 17. When the displacement of the injected crude oil is equal to and stable with the displacement flowing out of the outlet of the core holder 27 through the second back pressure valve 38, the rock sample is saturated. The amount of crude oil flowing out of the outlet of the core holder 27 through the second back pressure valve 38 is measured using a glass container 51 and a balance 52.

[0087] The multifunctional displacement system of this invention can be used to simulate dynamic oil displacement processes such as CO2 flooding, N2 flooding, mixed gas flooding, CO2 foam flooding, N2 foam flooding, steam flooding, water flooding, water-gas alternating flooding, chemical flooding, multi-element composite flooding, and multi-element alternating flooding under certain temperature and pressure conditions, as well as related process measures and methods for optimizing injection and production parameters and processes. Simultaneously, it tests porosity, water content, and oil saturation under these temperature and pressure conditions; and studies the influence of temperature, pressure, injected gas, foam, chemical solution, water, and injection rate on displacement efficiency.

[0088] The system of this invention can conduct foam displacement simulation experiments, and can verify and further illustrate the temporary plugging and diversion characteristics of foam fluid and the diversion characteristics of chemical particles through indoor simulation. The main experiments include: parallel comparative experiments on the foam plugging performance of single water-bearing cores with different permeabilities; research on the pressure change trends, outlet flow rate, and core gas phase saturation changes during foam displacement and subsequent foaming agent solution and water displacement of single cores, analyzing the plugging performance of foam on single cores; parallel comparative experiments on the foam plugging performance of single oil-bearing cores with different permeabilities; selective plugging experiments of foam on water-bearing and oil-bearing cores; selective plugging experiments of foam on high-permeability and low-permeability cores; experimental research on the influence of gas-liquid ratio on foam plugging capacity; and CO2 foam diversion experiments.

[0089] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0090] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0091] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A multifunctional displacement system utilizing CO2, characterized in that, include: A gas injection assembly includes a gas cylinder, a gas booster pump is installed on the outlet pipeline of the gas cylinder, a gas storage tank is installed on the outlet pipeline of the gas booster pump, a first piston container is installed on a branch of the outlet pipeline of the gas storage tank, a first injection pump is connected to the lower part of the first piston container, and the piston container includes a second piston container, a third piston container and a fourth piston container arranged in parallel, the first piston container, the second piston container, the third piston container and the fourth piston container are respectively used to store gas, water, crude oil and chemical solution; The displacement source assembly includes a steam generator and several piston containers arranged in parallel. The lower part of the steam generator and the piston containers are both connected to a second injection pump. The steam generator is connected to a wet nitrogen humidification tank through a pipeline. A foam generator is located downstream of the gas injection assembly, with a stirring device at the bottom of the foam generator and a viewing window located downstream of the foam generator. The core holder is located downstream of the viewing window. A temperature control device is installed inside the core holder. A differential pressure sensor is installed on the pipeline between the outlet and inlet ends of the core holder. The annular pressure of the core holder is controlled by an annular pressure pump. A pressure control system includes a manual pump and multiple back pressure valves. The back pressure valves are located at the outlet and inlet ends of the core holder and at the outlet end of the gas injection assembly. The manual pump is used to control the pressure of the back pressure valves. The back pressure valves include a first back pressure valve, a second back pressure valve, and a third back pressure valve. The first back pressure valve is located at the inlet end of the core holder, the second back pressure valve is located at the outlet end of the core holder, and the third back pressure valve is located at the upper outlet end of the first piston container. The output end of the manual pump is connected to a first buffer tank, and the outlet end of the first buffer tank is connected to the first back pressure valve, the second back pressure valve, and the third back pressure valve respectively through pipelines. A gas-liquid metering system is installed downstream of the core holder. The gas-liquid metering system includes a gas-liquid separator, a first flow meter, and a liquid metering device. The first flow meter is installed on the outlet pipeline at the top of the gas-liquid separator, and the liquid metering device is installed at the bottom outlet end of the gas-liquid separator. A dryer is installed between the gas-liquid separator and the first flow meter, and a first one-way valve is installed between the dryer and the first flow meter. The liquid metering device includes a balance and a glass container with metering scale placed on the balance. A vacuum pumping device is installed on a branch of the inlet pipeline of the core holder and is used to pump a vacuum for the multifunctional displacement system utilizing CO2.

2. The multifunctional displacement system utilizing CO2 as described in claim 1, characterized in that, The foam generator is equipped with multiple layers of screens with different pore sizes inside.

3. The multifunctional displacement system utilizing CO2 as described in claim 1, characterized in that, The core holder has a rubber sleeve made of epoxy resin.

4. The multifunctional displacement system utilizing CO2 as described in claim 1, characterized in that, Safety valves are installed on the branch of the gas storage tank inlet pipeline, the branch of the visible window outlet pipeline, and the branch of the first buffer tank outlet pipeline.

5. The multifunctional displacement system utilizing CO2 as described in claim 1, characterized in that, Pressure gauges and thermometers are installed on the inlet pipeline of the gas storage tank, the upper pipeline of the first piston container, the top of the foam generator, the outlet and inlet ends of the core holder, the outlet end of the first buffer tank, and the top inlet end of the gas-liquid separator.

6. A multifunctional displacement method utilizing CO2, characterized in that, The multifunctional displacement system utilizing CO2 as described in any one of claims 1-5 includes the following steps: To check the airtightness of the CO2-based multifunctional displacement system, the rock sample was loaded into the core holder, and the ring pressure and internal temperature of the core holder were adjusted. The CO2-based multifunctional displacement system was then evacuated. Inject crude oil into the rock sample until the sample is saturated, and adjust the back pressure valve pressure to the target value; The displacement agent is injected into the core holder to displace crude oil. The displacement agent is gas, water vapor, foam, chemical solution, water or a mixture thereof. The mixture is a mixture of at least two substances in the gas, water vapor, foam, chemical solution and water. When the displacement agent is foam, the gas and foaming agent are first quantitatively injected into the foam generator to generate foam. The state of the foam fluid is observed through a viewing window, and the conditions and composition of foam generation are recorded. Then the foam is injected into the core holder for displacement experiment research. The gas-liquid metering system is used to measure the gas and liquid volumes and analyze the displacement effect.

Images