A novel CO2 displacement and throughput system and method

Abstract

The application discloses a novel CO2 displacement and throughput system and method. The system can carry out simulation researches on carbonized water displacement, gas injection, water-gas alternating injection displacement, CO2 throughput and the like of oil and gas reservoirs. Under the conditions of formation temperature and pressure, the displacement or throughput development effects of various gases and the like on the underground oil and gas reservoirs are researched, and the effects of the displacement or throughput development of the gases, steam or carbonized water and the like under different conditions, and the influence law of the sensitive factors such as displacement amount, displacement rate, temperature and pressure on the displacement development effect and the throughput development effect are analyzed. The application has the advantages of fast operation control speed, high efficiency, small error and convenient system pipeline cleaning; the modular design is adopted, the application can be widely applied to various research fields according to different experimental targets, and the sensitive factors influencing the displacement effect or the throughput development effect are researched, so as to guide the improvement of the oil and gas reservoir development effect.

Description

Technical Field

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

[0002] Similar displacement and injection systems can be used for evaluating gas injection or water injection in oil and gas reservoirs; to study the displacement and development effects of gas or water on oil-bearing formations under formation conditions; and to analyze the influencing factors of different amounts of gas or water used for displacement and development. Current systems of this type have limited functionality and cannot simulate the impact of carbonated water on displacement effects; their inaccurate temperature and pressure control introduces significant errors; and they do not consider the influence of rock sample length and size on displacement and injection / injection effects. 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 novel CO2 displacement and throughput system and method.

[0005] On the one hand, this invention proposes a novel CO2 displacement and throughput system, comprising:

[0006] A gas injection system, comprising a gas cylinder, a gas booster pump installed on the outlet pipeline of the gas cylinder, a storage tank installed on the outlet pipeline of the gas booster pump, and a pressure regulating valve installed on the outlet pipeline of the storage tank;

[0007] A liquid injection system is located downstream of the gas injection system. The liquid injection system includes a piston stirring container and multiple piston containers. The piston stirring container is connected in parallel with the piston containers. A power pump is connected to the lower part of both the piston stirring container and the piston containers. A stirring device is installed inside the piston stirring container.

[0008] A model system located downstream of the liquid injection system includes an annular pressure pump and at least one core holder. The annular pressure pump is used to adjust the annular pressure of the core holder. The outlet and inlet of the core holder are connected by a connecting pipe.

[0009] A pressure control system, comprising a back pressure valve and a manual pump, wherein the back pressure valve is disposed at the outlet and inlet ends of the core holder, and the manual pump is used to adjust the pressure of the back pressure valve.

[0010] A gas-liquid metering system is installed downstream of the model system. The gas-liquid metering system includes a gas-liquid separator, a first flow meter installed at the upper outlet end of the gas-liquid separator, and a liquid metering device installed at the lower outlet end of the gas-liquid separator.

[0011] A temperature control system, comprising a first temperature control box, a second temperature control box, and a third temperature control box, wherein the first temperature control box is disposed around the gas injection system and the liquid injection system, the second temperature control box is disposed around the core holder, and the third temperature control box is disposed around the gas-liquid separation system;

[0012] A vacuum pumping device is installed on a branch of the outlet pipeline of the piston stirring container.

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

[0014] In some embodiments, a differential pressure sensor is installed on the pipeline between the outlet and inlet ends of the core holder.

[0015] In some embodiments, the back pressure valve includes a first back pressure valve and a second back pressure valve, wherein the first back pressure valve is disposed at the inlet end of the core holder and the second back pressure valve is disposed at the outlet end of the core holder.

[0016] In some embodiments, the output end of the manual pump is connected to a first buffer tank, a first valve is provided on the pipeline between the outlet end of the first buffer tank and the first back pressure valve, and a second valve is provided on the pipeline between the outlet end of the first buffer tank and the second back pressure valve.

[0017] In some embodiments, a first safety valve is provided on a branch of the inlet pipeline of the storage tank, a second safety valve is provided on a branch of the upper pipeline of the piston stirring vessel, and a third safety valve is provided on a branch of the outlet pipeline of the first buffer tank.

[0018] In some embodiments, pressure gauges and thermometers are provided at the inlet end of the storage tank, on the upper pipeline of the piston container, at the outlet and inlet ends of the core holder, at the outlet end of the first buffer tank, and at the inlet end of the gas-liquid separator.

[0019] 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.

[0020] In some embodiments, the liquid metering device includes a balance and a glass container placed on the balance.

[0021] On the other hand, this invention proposes a novel CO2 displacement and throughput method, including displacement simulation experiments and throughput simulation experiments.

[0022] The displacement simulation experiment of carbonized water formed by CO2 dissolution includes the following steps:

[0023] (1) Check the airtightness of the system, load the rock sample saturated with oil into the core holder, and evacuate the system;

[0024] (2) Use a manual pump to adjust the pressure value of the back pressure valve, use a ring pressure pump to adjust the ring pressure value, and set the temperature of the first temperature control box, the second temperature control box and the third temperature control box to the target value.

[0025] (3) The CO2 in the gas cylinder is pressurized by a gas booster pump and then stored in a storage tank;

[0026] (4) Inject the CO2 in the storage tank into the first piston container, and pump the CO2 in the first piston container and the chemical solution in the third piston container into the piston stirring container in a certain proportion to stir and mix evenly to form carbonized water, and record the concentration of carbonized water.

[0027] (5) Use a power pump to inject carbonized water into the core holder to conduct a displacement simulation experiment and record the amount of carbonized water injected.

[0028] (6) Measure the gas and liquid volume at the outlet of the core holder using a gas-liquid metering system and analyze the displacement effect of carbonized water.

[0029] The CO2 throughput simulation experiment includes the following steps:

[0030] (1) Check the airtightness of the system, load the rock sample saturated with oil into the core holder, and evacuate the system;

[0031] (2) Use a manual pump to adjust the pressure value of the back pressure valve, use a ring pressure pump to adjust the ring pressure value, and set the temperature of the first temperature control box, the second temperature control box and the third temperature control box to the target value.

[0032] (3) The CO2 in the gas cylinder is pressurized by a gas booster pump and then stored in a storage tank;

[0033] (4) Inject the CO2 in the storage tank into the first piston container, and use a power pump to inject the CO2 in the first piston container through one end of the core holder.

[0034] (5) Close the valves at both ends of the core holder, simulate well shut-in for a certain period of time, and then open the valve at the end of the core holder that injects the material. The fluid is discharged from the same end of the core holder and flows to the gas-liquid metering system.

[0035] (6) Measure the gas and liquid volume of the fluid using a gas-liquid metering system and analyze the throughput effect. This completes one throughput operation.

[0036] (7) Repeat steps (4) to (6) multiple times until, in three or more consecutive swallowing and spitting operations, the amount of swallowed material injected from one end of the core holder is equal to the amount of swallowed material flowing out from the same end of the core holder, and the amount of oil spit out is zero. Then the swallowing and spitting experiment is completed.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The piston-stirring container of this invention can form a certain proportion of carbonized water, and the stirring device at the bottom of the piston-stirring container can make the liquid and gas fully mixed; the temperature control box and back pressure valve can precisely control the temperature and pressure, and can simulate high-temperature and high-pressure displacement experiments under formation temperature and pressure conditions, so as to make the experimental results accurate and reduce experimental errors; the gas booster pump and storage tank can be used to study the displacement and huff and puff effects of various gases.

[0039] The system of this invention can conduct evaluation experiments such as water carbonate displacement experiments, gas injection and development experiments, water-gas cross-injection experiments, and CO2 huff and puff experiments in oil and gas reservoirs. Through indoor simulation experiments, it studies the displacement or huff and puff effects of various gases on oil-bearing formations under formation temperature and pressure conditions. The analysis reveals the effects of different gases, steam, or water carbonate on displacement or huff and puff development, as well as the influence of sensitive factors such as displacement dosage, discharge rate, temperature, and pressure on the displacement and huff and puff development effects.

[0040] This invention features fast operation and control, high efficiency, small error, and convenient system pipeline cleaning. It adopts a modular design and can be widely applied to various experimental research fields according to different experimental needs. It can study sensitive factors affecting the displacement effect or the churn development effect, thereby guiding the improvement of oil displacement effect. Attached Figure Description

[0041] 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:

[0042] Figure 1 This is a schematic diagram of a novel CO2 displacement and throughput system according to an embodiment of the present invention;

[0043] Explanation of reference numerals in the attached figures:

[0044] 1. Gas cylinder; 2. Gas booster pump; 3. Silent air compressor; 4. Storage tank; 5. First safety valve; 6. First pressure gauge; 7. First thermometer; 8. Pressure regulating valve; 9. Second check valve; 10. First piston container; 11. Second piston container; 12. Third piston container; 13. Piston stirring container; 14. Fourth valve; 15. Power pump; 16. Water tank; 17. Second pressure gauge; 18. Second thermometer; 19. Second safety valve; 20. Vacuum pump; 21. First back pressure valve; 22. Second back pressure valve; 23. Manual pump; 24. First buffer tank; 25. Third safety valve; 26. First valve; 27. Second valve; 28. Fifth pressure gauge; 29. ​​Fifth thermometer. 30. Long core holder 31. Short core holder 32. First differential pressure sensor 33. Second differential pressure sensor 34. Connecting pipe 35. Third valve 36. Fifth valve 37. Sixth valve 38. Seventh valve 39. Eighth valve 30. Ring pressure pump 40. Second buffer tank 41. Third pressure gauge 42. Third thermometer 43. Fourth pressure gauge 44. Fourth thermometer 45. Gas-liquid separator 46. First flow meter 47. Dryer 48. First check valve 49. Glass container 50. Balance 51. Sixth pressure gauge 52. Sixth thermometer 53. First temperature control box 54. Second temperature control box 55. Third temperature control box 56. Detailed Implementation

[0045] 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.

[0046] The novel CO2 displacement and throughput system and method according to embodiments of the present invention are described below with reference to the accompanying drawings.

[0047] like Figure 1 As shown, the novel CO2 displacement and huff / puff system of the present invention includes a gas injection system, a liquid injection system, a model system, a pressure control system, a gas-liquid metering system, a temperature control system, and a vacuum pumping device 20.

[0048] The gas injection system includes a gas cylinder 1, a gas booster pump 2 installed on the outlet pipeline of the gas cylinder 1, a storage tank 4 installed on the outlet pipeline of the gas booster pump 2, and a pressure regulating valve 8 installed on the outlet pipeline of the storage tank 4.

[0049] Specifically, gas cylinder 1 is used to hold the gas for displacement and swallowing simulation experiments. One or more gas cylinders 1 can be set, and multiple cylinders 1 can be used alternately to ensure gas supply or to hold different types of gases. A gas booster pump 2 is installed on the outlet pipeline of gas cylinder 1, and a storage tank 4 is installed on the outlet pipeline of gas booster pump 2. The gas in gas cylinder 1 is pressurized by gas booster pump 2 and then stored in storage tank 4. The gas pressurized by gas booster pump 2 is high-pressure gas. To obtain gas at a suitable pressure during the experiment, a pressure regulating valve 8 is installed on the outlet pipeline of storage tank 4.

[0050] The gas booster pump 2 is mainly used for gas pressurization. A silent air compressor 3, located at the input end of the gas booster pump 2, provides compressed air to the gas booster pump 2. The gas booster pump 2 uses compressed air as its power source and is the 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 air source pressure and the pressurized gas pressure are balanced, the gas booster pump 2 stops pressurizing, and the output gas pressure stabilizes at the pre-adjusted pressure. Therefore, it features explosion-proof design, adjustable output pressure, small size, light weight, simple operation, reliable performance, and wide applicability.

[0051] In some embodiments, a first pressure gauge 6 and a first thermometer 7 are installed at the inlet end of the storage tank 4. The first pressure gauge 6 and the first thermometer 7 are used to test the pressure and temperature of the gas inside the storage tank 4. A first safety valve 5 is installed on a branch of the inlet pipeline of the storage tank 4, which automatically releases pressure when the storage tank 4 is overpressurized.

[0052] The liquid injection system is located downstream of the gas injection system. The liquid injection system includes a piston stirring container 13 and multiple piston containers. The piston stirring container 13 and the piston containers are connected in parallel. The lower part of both the piston stirring container 13 and the piston containers is connected to a power pump 15. A stirring device is installed inside the piston stirring container 13.

[0053] Specifically, the liquid injection system is located downstream of the gas injection system. The liquid injection system includes a piston-stirring container 13 and multiple piston containers. The piston containers hold the substances required for the experiment. The piston-stirring container 13 is a piston-type stirring container with a stirring device at its bottom. The piston-stirring container 13 is used to form carbonated water. The piston containers and piston-stirring container 13 are connected in parallel, and their lower parts are connected to a power pump 15, which provides the injection power. When carbonated water needs to be injected into the core holder, the power pump 15 pumps the carbonated water out from the upper outlet end of the piston-stirring container 13. In addition, the piston container is designed with an upper and lower trigger mechanism. When the piston reaches its two extreme positions, the computer detects that the piston has moved to the two extreme ends and automatically replenishes the fluid in the piston container. The injection displacement of the power pump 15 is adjustable. It can inject at a constant displacement or a variable displacement according to experimental needs. Variable displacement injection includes, but is not limited to, injection methods with gradually increasing displacement or injection methods with gradually decreasing displacement.

[0054] In some embodiments, the piston container includes a first piston container 10, a second piston container 11, and a third piston container 12 arranged in parallel, the first piston container 10, the second piston container 11, and the third piston container 12 being used to hold gas, crude oil, and chemical solution, respectively.

[0055] Specifically, the upper part of the first piston container 10 is connected to the outlet end of the pressure regulating valve 8. Gas from the storage tank 4 enters the first piston container 10 after being pressurized by the pressure regulating valve 8. A second pressure gauge 17 and a second thermometer 18 are installed on the upper pipeline of the first piston container 10. The second thermometer 18 and the second pressure gauge 17 are used to test the pressure and temperature of the gas flowing out of the first piston container 10. It is understandable that due to the increase in temperature and pressure, CO2 will undergo a phase change, such as forming a supercritical CO2 state. If a gas mass flow controller is continued to be used, it will definitely cause inaccurate data, because CO2 is no longer CO2 gas and is not suitable for measurement using a gas mass flow controller.

[0056] CO2 is first injected into the first piston container 10. Whether the CO2 is gas or liquid, the injection rate of the power pump 15, combined with the second thermometer 18 and the second pressure gauge 17, allows for the calculation of the CO2 flow rate. Crude oil is placed in the second piston container 11. This crude oil is used to simulate saturated rock samples in the displacement experiment. The power pump 15 pumps the crude oil into the core holder. Similarly, the amount of crude oil injected is measured based on the injection rate of the power pump 15. When the discharge rate of crude oil injected into the rock sample by the power pump 15 is the same as and stable as the discharge rate of crude oil flowing out from the second back pressure valve 22, the rock sample is considered saturated with crude oil. The amount of crude oil flowing out from the second back pressure valve 22 is measured using a glass container 50 and a balance 51. A chemical solution is placed in the third piston container 12. This chemical solution is a salt, a surfactant, or a mixture of both. The salt can be sodium chloride solution, ammonium carbonate solution, etc., and the surfactant can be polyacrylamide or other surfactants. The study investigates the influence of this type of solution on the formation of water carbonate from CO2 in water, and the displacement or huff-and-puff extraction effect. CO2 forms carbonated water, which displaces saturated oil-bearing rock samples under certain formation conditions. Since formation water is saline, this invention uses saline chemical reagents in the water to simulate formation water, making the experimental results closer to actual formation water samples. Furthermore, surfactants are crucial factors affecting the solubility of CO2 in water and the effectiveness of displacement. Adding different types and amounts of surfactants to the simulated formation water sample allows for the investigation of their influence on carbonated water formation and displacement effects, providing a foundation for better utilizing carbonated water for displacement.

[0057] During the operation, the chemical solution in the third piston container 12 is first injected into the piston-stirred container 13 via the upper pipeline using a power pump 15. Then, CO2 gas from the first piston container 10 is quantitatively injected into the piston-stirred container 13 via the upper pipeline. The mixture is stirred and homogenized in the piston-stirred container 13 to form carbonated water. Finally, the carbonated water is used for subsequent displacement experiments. It is understood that pumping CO2 and the chemical solution into the piston-stirred container 13 in a certain proportion will yield carbonated water of a certain concentration.

[0058] In some embodiments, the power pump 15 is a constant speed and constant pressure pump. The input end of the power pump 15 is connected to a water tank 16, which contains clean water free of chemical reagents. The clean water can be used for cleaning system equipment and for examining the displacement effect of carbonized water formed by CO2 dissolving in the clean water. When CO2 is dissolved in clean water to form carbonized water, the power pump 15 first pumps the clean water in the water tank 16 into the piston stirring container 13 through the fourth valve 14 via the upper pipeline, filling the piston stirring container 13 with clean water. Then, the CO2 gas in the first piston container 10 is quantitatively injected into the piston stirring container 13 through the upper pipeline. The mixture is stirred and mixed evenly in the piston stirring container 13 to form carbonized water. Excess CO2 flows to the first flow meter 47 through the connecting pipe 34. The amount of CO2 injected into the first piston container 10 minus the amount of CO2 flowing out of the first flow meter 47 is the amount of CO2 dissolved in the saturated carbonized water. Finally, the carbonized water is used for subsequent displacement experiments. The fourth valve 14 is connected in parallel with the piston-stirred container 13. Furthermore, under certain temperature and pressure conditions, CO2 and water are pumped into the piston-stirred container 13 in a specific ratio to prepare a carbonized aqueous solution of a certain concentration.

[0059] In some embodiments, a second check valve 9 is provided on the pipeline between the pressure regulating valve 8 and the upper part of the first piston container 10. The provision of the second check valve 9 avoids measurement errors caused by gas backflow.

[0060] In some embodiments, a second safety valve 19 is provided on a branch of the upper pipeline of the piston stirring container 13. Specifically, a second safety valve 19 is provided on a branch of the upper pipeline of the piston stirring container 13. The second safety valve 19 is mainly used to prevent gas overpressure. When gas flowing out from the first piston container 10 enters the piston stirring container 13 through the upper pipeline of the piston stirring container 13, it will automatically release pressure if gas overpressure occurs.

[0061] The model system is located downstream of the liquid injection system. The model system includes an annular pressure pump 40 and at least one core holder. The annular pressure pump 40 is used to adjust the annular pressure of the core holder. The outlet and inlet of the core holder are connected by a connecting pipe 34, and a third valve 35 is installed on the connecting pipe 34.

[0062] Specifically, the model system is used for displacement and huff-and-puff experiments. Located downstream of the liquid injection system, the model system includes at least one core holder and an annular pressure pump 40. The annular pressure pump 40 regulates the annular pressure of the core holder. The output of the annular pressure pump 40 is connected to a second buffer tank 41, and the output of the second buffer tank 41 is connected to the core holder via a pipeline. It is understood that when multiple core holders are present, the outlet of the second buffer tank 41 is connected to each of the multiple core holders via multiple pipelines. A connecting pipe 34 connects the outlet and inlet of the core holder. During the huff-and-puff experiment, fluid flows into or out of the core holder through the connecting pipe 34. A differential pressure sensor is installed on the pipeline between the inlet and outlet of the core holder to measure the pressure difference across the core holder.

[0063] In some embodiments, pressure gauges and thermometers are provided at both the outlet and inlet ends of the core holder. Specifically, a third pressure gauge 42 and a third thermometer 43 are provided at the inlet end of the core holder to test the pressure and temperature of the fluid entering the core holder, and a fourth pressure gauge 44 and a fourth thermometer 45 are provided at the outlet end of the core holder to test the pressure and temperature of the fluid exiting the core holder.

[0064] The ring pressure pump 40 is used for ring pressure loading and can automatically track the ring pressure, subjecting the rock sample to stress conditions similar to those of underground oil reservoirs. The pump speed, pressure protection, injection pressure tracking, and differential pressure maintenance can be controlled by a computer.

[0065] The type and size of the core holder are selected according to requirements. The core holder 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 placed 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 them 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 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.

[0066] The model system is illustrated below using the example of setting up two core holders. The model system includes a long core holder 30 and a short core holder 31, which are connected in parallel. Core holders of different sizes are used to investigate the influence of different sample sizes on displacement and throughput effects. A connecting pipe 34 is also connected in parallel with the long core holder 30 and the short core holder 31, and a third valve 35 is installed on the connecting pipe 34. A first differential pressure sensor 32 is installed on the pipeline between the outlet and inlet ends of the long core holder 30, and a second differential pressure sensor 33 is installed on the pipeline between the outlet and inlet ends of the short core holder 31. A fifth valve 36 is installed at the inlet end of the long core holder 30, a sixth valve 37 at the outlet end of the long core holder 30, a seventh valve 38 at the inlet end of the short core holder 31, and an eighth valve 39 at the outlet end of the short core holder 31. The output end of the ring pressure pump 40 is connected to the second buffer tank 41. The output end of the second buffer tank 41 is connected to the long core holder 30 and the short core holder 31 through two pipelines, so that the ring pressure of the long core holder 30 and the short core holder 31 can be controlled by the ring pressure pump 40.

[0067] During displacement experiments, when using the long core holder 30 to displace carbonated water, valves 36 and 37 are open, while valves 38, 39, and 35 are closed. Carbonated water enters the long core holder 30 through valve 36 for displacement, and the gas-liquid mixture flows out through valve 37. When using the short core holder 31, valves 38 and 39 are open, while valves 36, 37, and 35 are closed. Carbonated water enters the short core holder 31 through valve 38 for displacement, and the gas-liquid mixture flows out through valve 39. The long core holder 30 and the short core holder 31 can be used individually or simultaneously for displacement experiments. When the long core holder 30 and the short core holder 31 are subjected to displacement experiments at the same time, the annular pressure of the long core holder 30 and the short core holder 31 can be the same or different.

[0068] 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 is equal to and stable with the outflow rate from the outlet end of the core holder, 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, carbonated water, or a chemical solution, etc.

[0069] During the huff and puff experiment, the long core holder 30 and the short core holder 31 operate independently. When using the long core holder 30 for CO2 huff and puff experiments, there are two paths. One path involves first opening the fifth valve 36, then closing the sixth valve 37 and the third valve 35. CO2 is injected into the core holder through the fifth valve 36. Then, the fifth valve 36 is closed, simulating a well shut-in period. After that, the third valve 35 and the fifth valve 36 are opened, and the fluid flowing from the long core holder 30 flows out through the fifth valve 36 and then through the connecting pipe 34. The CO2 flows downstream to the gas-liquid metering system via the third valve 35 and the second back pressure valve 22. Alternatively, the sixth valve 37 and the third valve 35 are opened first, and the fifth valve 36 is closed. CO2 is injected into the long core holder 30 via the connecting pipe 34, passing through the third valve 35 and the sixth valve 37 in sequence. Then, the sixth valve 37 and the third valve 35 are closed. After simulating a well shut-in period, the sixth valve 37 is opened, and the fluid flowing from the long core holder 30 flows out through the sixth valve 37 and then through the second back pressure valve 22 to the downstream gas-liquid metering system. When using the short core holder 31 for CO2 huff and puff experiments, there are also two paths, and the principle is the same as when using the long core holder 30 for CO2 huff and puff experiments, so it will not be described again here.

[0070] In addition, multiple huff and puff operations are required throughout the entire huff and puff experiment. The experiment is considered complete when, in three or more consecutive huff and puff operations, the amount of material injected from one end of the core holder is equal to the amount of material flowing out from the same end of the core holder, and the amount of oil expelled is zero. The injected huff and puff materials and the amounts of oil, gas, and water expelled are recorded to analyze the huff and puff effect. The huff and puff materials can include CO2, N2, etc.

[0071] The pressure control system includes a back pressure valve and a manual pump 23. The back pressure valve is located at both the outlet and inlet ends of the core holder, and the manual pump 23 is used to regulate the pressure of the back pressure valve. The back pressure valve includes a first back pressure valve 21 and a second back pressure valve 22. The first back pressure valve 21 is located at the inlet end of the core holder, and the second back pressure valve 22 is located at the outlet end of the core holder. The output end of the manual pump 23 is connected to a first buffer tank 24. A first valve 26 is installed on the pipeline between the outlet end of the first buffer tank 24 and the first back pressure valve 21, and a second valve 27 is installed on the pipeline between the outlet end of the first buffer tank 24 and the second back pressure valve 22.

[0072] Specifically, a pressure control system is used to control the pressure entering and exiting the model system, i.e., the pressure entering and exiting the core holder. The pressure control system mainly includes a manual pump 23 and a back pressure valve. The manual pump 23 is used to adjust the pressure value of the back pressure valve, thereby controlling the pressure entering and exiting the core holder. The back pressure valve includes a first back pressure valve 21 and a second back pressure valve 22. The first back pressure valve 21 is located at the inlet end of the core holder and is used to control the pressure entering the core holder. The second back pressure valve 22 is located at the outlet end of the core holder and is used to control the pressure exiting the core holder. The output end of the manual pump 23 is connected to a first buffer tank 24. The output end of the first buffer tank 24 is connected to the first back pressure valve 21 and the second back pressure valve 22 through pipelines. A first valve 26 is located on the pipeline between the outlet end of the first buffer tank 24 and the first back pressure valve 21, and a second valve 27 is located on the pipeline between the outlet end of the first buffer tank 24 and the second back pressure valve 22. When it is necessary to adjust the pressure of the first back pressure valve 21, open the first valve 26, close the second valve 27, and increase or decrease the pressure of the first back pressure valve 21 by using the manual pump 23; when it is necessary to adjust the pressure of the second back pressure valve 22, open the second valve 27, close the first valve 26, and increase or decrease the pressure of the second back pressure valve 22 by using the manual pump 23.

[0073] The back pressure valve adopts a piston structure, mainly composed of a valve body and a valve core. This valve has advantages such as high adjustment sensitivity, high pressure resistance, high control accuracy, and light weight. The valve body is provided with a back pressure port and liquid inlet and outlet ports at the top and bottom, respectively. The valve core adopts a piston structure, with a plunger protrusion extending axially at the bottom of the piston. The lower part of the valve body has a pre-drilled cylindrical hole that mates with the plunger protrusion. The liquid inlet and outlet ports are connected to the bottom of the cylindrical hole in the valve body below the piston protrusion through a guide cavity. An auxiliary liquid inlet port connected to the inlet pipe is also provided on one side of the valve body. The auxiliary liquid inlet port is connected to the joint between the lower part of the valve body and the piston body through a guide cavity.

[0074] In some embodiments, a fifth pressure gauge 28 and a fifth thermometer 29 are provided at the outlet end of the first buffer tank 24. The fifth pressure gauge 28 and the fifth thermometer 29 are used to test the pressure and temperature at the outlet end of the first buffer tank 24.

[0075] In some embodiments, a third safety valve 25 is provided on a branch of the outlet pipeline of the first buffer tank 24 to automatically release pressure when the first buffer tank 24 is overpressurized.

[0076] The gas-liquid metering system is located downstream of the model system. The system includes a gas-liquid separator 46, a first flow meter 47 located at the upper outlet of the gas-liquid separator 46, and a liquid metering device located at the lower outlet of the gas-liquid separator 46. A dryer 48 is installed between the gas-liquid separator 46 and the first flow meter 47, and a first check valve 49 is installed between the dryer 48 and the first flow meter 47. The liquid metering device includes a balance 51 and a glass container 50 placed on the balance 51.

[0077] Specifically, a gas-liquid metering system is located downstream of the model system to test the volume of gas and liquid flowing out of the model system. The gas-liquid metering system includes a gas-liquid separator 46, a first flow meter 47, and a liquid metering device. The first flow meter 47 is located on the upper outlet pipeline of the gas-liquid separator 46. A dryer 48 is installed on the pipeline between the gas-liquid separator 46 and the first flow meter 47. The dryer 48 is used to dry the gas separated by the gas-liquid separator 46. A first one-way valve 49 is installed on the pipeline between the dryer 48 and the first flow meter 47. The first one-way valve 49 prevents gas metering errors caused by gas backflow, and the dryer 48 prevents gas metering errors caused by water vapor carried by the gas. The liquid metering device is located at the lower outlet end of the gas-liquid separator 46. The liquid metering device includes a balance 51 and a glass container 50. The glass container 50 is placed on the balance 51, and the balance 51 is used to measure the mass of the liquid in the glass container 50. The glass container 50 can be a container with a metering scale, and the volume of the liquid is read through the scale of the glass container 50. In addition, when the liquid is a mixture of water and oil, the volumes of water and oil can be read separately through the measuring scale of the glass container 50 because the water and oil separate into layers.

[0078] In some embodiments, a sixth pressure gauge 52 and a sixth thermometer 53 are provided at the upper inlet end of the gas-liquid separator 46. The sixth pressure gauge 52 and the sixth thermometer 53 are provided on the inlet pipeline of the gas-liquid separator 46 and are used to test the pressure and temperature of the fluid entering the gas-liquid separator 46.

[0079] The temperature control system includes a first temperature control chamber 54, a second temperature control chamber 55, and a third temperature control chamber 56. The first temperature control chamber 54 is located outside the gas injection system and the liquid injection system, the second temperature control chamber 55 is located outside the core holder, and the third temperature control chamber 56 is located outside the gas-liquid metering system. Specifically, the first temperature control chamber 54 is used to simulate the formation temperature of carbonated water, the second temperature control chamber 55 is used to simulate certain formation temperature conditions, and the third temperature control chamber 56 is used to simulate the surface temperature.

[0080] In some embodiments, the gas cylinder 1 and the power pump 15 are disposed outside the first temperature control chamber 54. In some embodiments, the balance 51 and the glass container 50 are disposed outside the third temperature control chamber 55.

[0081] The vacuum pumping device 20 is used to evacuate the experimental system, and is installed on a branch of the outlet pipeline of the piston stirring vessel 13. In some embodiments, the vacuum pumping device 20 is a vacuum pump.

[0082] A novel CO2 displacement and throughput method utilizes the novel CO2 displacement and throughput system of this invention, including displacement simulation experiments and throughput simulation experiments.

[0083] The following uses water carbonate displacement as an example to illustrate the specific process of the displacement simulation experiment, including the following steps:

[0084] (1) Check the airtightness of the system, load the rock sample saturated with oil into the core holder, and evacuate the system;

[0085] (2) Use manual pump 23 to adjust the pressure values ​​of the first back pressure valve 21 and the second back pressure valve 22 to the target value, use ring pressure pump 40 to adjust the ring pressure value to the target value, and set the temperatures of the first temperature control box 54, the second temperature control box 55 and the third temperature control box 56 to the target value.

[0086] (3) The CO2 in gas cylinder 1 is pressurized by gas booster pump 2 and then stored in storage tank 4;

[0087] (4) Inject the CO2 in the storage tank 4 into the first piston container 10, and pump the CO2 in the first piston container 10 and the chemical solution in the third piston container 12 into the piston stirring container 13 in a certain proportion to stir and mix evenly to form carbonized water, and record the concentration of carbonized water.

[0088] (5) Use power pump 15 to inject carbonized water into the core holder to carry out displacement simulation experiment and record the amount of carbonized water injected.

[0089] (6) The gas-liquid mixture flowing out of the core holder outlet is measured by the gas-liquid metering system. The gas-liquid mixture flowing out of the core holder outlet is separated into gas and liquid by the gas-liquid separator 46. The gas is measured by the first flow meter 47 and the liquid is measured by the liquid metering device to analyze the displacement effect.

[0090] It is understandable that if the proportion of the chemical solution is 0 in step (4), it is a simulation experiment of CO2 displacing crude oil. In addition, when conducting the displacement experiment, a long core holder 30 or a short core holder 31 can be selected.

[0091] The following uses a CO2 throughput simulation experiment as an example to illustrate the specific process of a throughput simulation experiment, including the following steps:

[0092] (1) Check the airtightness of the system, load the rock sample saturated with oil into the core holder, and evacuate the system;

[0093] (2) Use manual pump 23 to adjust the pressure values ​​of the first back pressure valve 21 and the second back pressure valve 22 to the target value, use ring pressure pump 40 to adjust the ring pressure value to the target value, and set the temperature of the first temperature control box 54, the second temperature control box 55 and the third temperature control box 56 to the target value.

[0094] (3) The CO2 in gas cylinder 1 is pressurized by gas booster pump 2 and then stored in storage tank 4;

[0095] (4) Inject the CO2 in the storage tank 4 into the first piston container 10, and use the power pump 15 to inject the CO2 in the first piston container 10 through one end of the core holder.

[0096] (5) Close the valves at both ends of the core holder, simulate well shut-in for a certain period of time, and then open the valve at the end of the core holder that injects the material. The fluid is discharged from the same end of the core holder and flows to the gas-liquid metering system.

[0097] (6) The gas and liquid volume of the fluid is measured by the gas-liquid metering system. The gas and liquid fluid discharged from the outlet of the core holder are separated into gas and liquid by the gas-liquid separator 46. The gas is measured by the first flow meter 47 and the liquid is measured by the liquid metering device. The throughput effect is analyzed. Thus, one throughput operation is completed.

[0098] (7) Repeat steps (4) to (6) multiple times until, in three or more consecutive swallowing and spitting operations, the amount of swallowed material injected from one end of the core holder is equal to the amount of swallowed material flowing out from the same end of the core holder, and the amount of oil spit out is zero. The swallowing and spitting experiment is completed. Record the amount of injected swallowed material and swallowed oil, gas, water and other substances, and analyze the swallowing and spitting effect.

[0099] In the CO2 huff and puff simulation experiment, taking the long core holder 30 as an example, steps (4) and (5) are as follows: CO2 in the storage tank 4 is injected into the first piston container 10, the sixth valve 37 and the third valve 35 are closed, and the CO2 in the first piston container 10 is injected into the long core holder 30 through the fifth valve 36 using the power pump 15; the fifth valve 36 is closed, at which time both the fifth valve 36 and the sixth valve 37 are closed. After simulating well shut-in for a certain period of time, the third valve 35 and the fifth valve 36 are opened, and the fluid flows out of the long core holder 30 through the fifth valve 36, and then flows to the downstream gas-liquid metering system through the connecting pipe 34 and the third valve 35. It can be understood that when using the system of the present invention to conduct the huff and puff simulation experiment, either the long core holder 30 or the short core holder 31 can be selected.

[0100] The following uses the alternating water-air displacement experiment as an example to illustrate the specific process of the displacement simulation experiment, including the following steps:

[0101] (1) Check the airtightness of the system, load the rock sample saturated with oil into the core holder, and evacuate the system;

[0102] (2) Use manual pump 23 to adjust the pressure values ​​of the first back pressure valve 21 and the second back pressure valve 22 to the target value, use ring pressure pump 40 to adjust the ring pressure value to the target value, and set the temperature of the first temperature control box 54, the second temperature control box 55 and the third temperature control box 56 to the target value.

[0103] (3) The CO2 in gas cylinder 1 is pressurized by gas booster pump 2 and then stored in storage tank 4;

[0104] (4) Inject CO2 from storage tank 4 into first piston container 10. S1: Use power pump 15 to inject a certain amount of gas from first piston container 10 into core holder through first back pressure valve 21 for displacement. S2: Use power pump 15 to inject a certain amount of clean water from water tank 16 into core holder through fourth valve 14 and first back pressure valve 21 for displacement. Repeat steps S1 and S2 for water-gas alternating displacement.

[0105] (5) The gas-liquid mixture flowing out of the core holder outlet is measured by the gas-liquid metering system. The gas-liquid mixture flowing out of the core holder outlet is separated into gas and liquid by the gas-liquid separator 46. The gas is measured by the first flow meter 47 and the liquid is measured by the liquid metering device to analyze the displacement effect.

[0106] When conducting water-gas alternating displacement experiments, either a long core holder 30 or a short core holder 31 can be selected.

[0107] In addition to conducting carbonized water displacement simulation experiments, the system of this invention can also be used for displacement simulation experiments of other gases and liquids. For example, it can be used to conduct comparative evaluation experiments on the oil displacement effects of gas drive and water-gas alternating drive, optimize gas injection parameters (experimental temperature, pressure, injection displacement, injection timing, injection volume, gas injection method, etc.), calculate and study the characteristics of gas drive oil displacement (displacement pressure, produced oil and gas composition, water cut, oil displacement efficiency variation law, etc.), and study the mobility control during the gas drive process. The injection displacement can be constant, or it can increase, decrease, or follow other irregular patterns.

[0108] In addition to CO2 huff and puff simulation experiments, the system of this invention can also conduct huff and puff simulation experiments of other gases. For example, the system of this invention can be used to conduct comparative evaluation experiments on the oil displacement effects of water vapor / CO2 / N2 huff and puff, optimize gas injection huff and puff parameters (experimental temperature, pressure, injection displacement, injection timing, injection volume, gas injection method, etc.), study oil displacement characteristics (displacement pressure, produced oil and gas composition, water content, oil displacement efficiency variation law, etc.), and study the flow control during the gas drive process.

[0109] In this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are 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.

[0110] 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.

[0111] 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 novel CO2 displacement and throughput system, characterized in that, include: A gas injection system, comprising a gas cylinder, a gas booster pump installed on the outlet pipeline of the gas cylinder, a storage tank installed on the outlet pipeline of the gas booster pump, and a pressure regulating valve installed on the outlet pipeline of the storage tank; A liquid injection system is located downstream of the gas injection system. The liquid injection system includes a piston stirring container and multiple piston containers. The piston stirring container is connected in parallel with the piston containers. A power pump is connected to the lower part of both the piston stirring container and the piston containers. A stirring device is installed inside the piston stirring container. The piston containers include a first piston container, a second piston container, and a third piston container connected in parallel. The first piston container, the second piston container, and the third piston container are used to hold gas, crude oil, and chemical solution, respectively. A model system is located downstream of the liquid injection system. The model system includes an annular pressure pump and at least one core holder. The annular pressure pump is used to adjust the annular pressure of the core holder. The outlet and inlet of the core holder are connected by a connecting pipe. A differential pressure sensor is installed on the pipeline between the outlet and inlet of the core holder. A pressure control system includes a back pressure valve and a manual pump. The back pressure valve is located at the outlet and inlet of the core holder. The manual pump is used to adjust the pressure of the back pressure valve. The back pressure valve includes a first back pressure valve and a second back pressure valve. The first back pressure valve is located at the inlet of the core holder, and the second back pressure valve is located at the outlet of the core holder. The output end of the manual pump is connected to a first buffer tank. A first valve is installed on the pipeline between the outlet of the first buffer tank and the first back pressure valve. A second valve is installed on the pipeline between the outlet of the first buffer tank and the second back pressure valve. A first safety valve is installed on a branch of the inlet pipeline of the storage tank. A second safety valve is installed on a branch of the upper pipeline of the piston stirring vessel. A third safety valve is installed on a branch of the outlet pipeline of the first buffer tank. A gas-liquid metering system is installed downstream of the model system. The gas-liquid metering system includes a gas-liquid separator, a first flow meter installed at the upper outlet end of the gas-liquid separator, and a liquid metering device installed at the lower outlet end of the gas-liquid separator. A temperature control system, comprising a first temperature control box, a second temperature control box, and a third temperature control box, wherein the first temperature control box is disposed around the gas injection system and the liquid injection system, the second temperature control box is disposed around the core holder, and the third temperature control box is disposed around the gas-liquid metering system; A vacuum pumping device is installed on a branch of the outlet pipeline of the piston stirring container.

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

3. The novel CO2 displacement and throughput system as described in claim 1, characterized in that, 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.

4. The novel CO2 displacement and throughput system as described in claim 1, characterized in that, The liquid metering device includes a balance and a glass container placed on the balance.

5. A novel CO2 displacement and throughput method, characterized in that, Using the novel CO2 displacement and throughput system as described in any one of claims 1-4, including displacement simulation experiments and throughput simulation experiments, The displacement simulation experiment for CO2 dissolution to form carbonated water includes the following steps: (a) Check the airtightness of the system, load the oil-saturated rock sample into the core holder, and evacuate the system; (b) Adjust the back pressure valve using a manual pump and adjust the ring pressure using a ring pressure pump to set the temperatures of the first, second, and third temperature control chambers to the target values. (c) The CO2 in the gas cylinder is pressurized by a gas booster pump and then stored in a storage tank; (d) Inject CO2 from the storage tank into the first piston container, and pump the CO2 in the first piston container and the chemical solution in the third piston container into the piston stirring container in a certain proportion to stir and mix evenly to form carbonated water, and record the concentration of carbonated water. (e) A displacement simulation experiment was conducted by injecting carbonized water into the core holder using a power pump, and the amount of carbonized water injected was recorded. (f) Measure the gas and liquid volume at the outlet of the core holder using a gas-liquid metering system and analyze the displacement effect of carbonized water. The CO2 throughput simulation experiment includes the following steps: (1) Check the airtightness of the system, load the rock sample saturated with oil into the core holder, and evacuate the system; (2) Adjust the back pressure valve using a manual pump and adjust the ring pressure using a ring pressure pump to set the temperatures of the first, second, and third temperature control boxes to the target values. (3) The CO2 in the gas cylinder is pressurized by a gas booster pump and then stored in a storage tank; (4) Inject the CO2 in the storage tank into the first piston container, and use a power pump to inject the CO2 in the first piston container through one end of the core holder; (5) Close the valves at both ends of the core holder, simulate well shut-in for a certain period of time, and then open the valve at the end of the core holder that injects the material. The fluid is discharged from the same end of the core holder and flows to the gas-liquid metering system. (6) Measure the gas and liquid volume of the fluid using a gas-liquid metering system and analyze the throughput effect. This completes one throughput operation. (7) Repeat steps (4) to (6) multiple times until, in three or more consecutive swallowing and spitting operations, the amount of swallowed material injected from one end of the core holder is equal to the amount of swallowed material flowing out from the same end of the core holder, and the amount of oil spit out is zero. Then the swallowing and spitting experiment is completed.

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