Laboratory evaluation method and device for carbon dioxide injection oil displacement sweep and coefficient and burying amount

Abstract

The invention relates to the technical field of oil and gas field development, in particular to a laboratory evaluation method and device for a carbon dioxide injection oil displacement wave and coefficient and burying stock, the carbon dioxide injection oil displacement wave and coefficient are carried out according to the following method: carrying out a carbon dioxide displacement experiment on a rock core sample, and recording the volume and return pressure of crude oil in the rock core sample in the displacement experiment; slicing the rock core sample after the carbon dioxide displacement experiment to obtain rock core slices; a color developing agent is dropwise added to the rock core slice for color development, and the CO2 oil displacement swept volume is determined according to a color development area; and according to the crude oil volume and the return pressure in the rock core sample and the CO2 oil displacement swept volume, calculating to obtain a CO2 oil displacement swept coefficient and a CO2 burying amount. According to the method, the carbon dioxide oil displacement sweep efficiency is visually determined, the contradiction in the oil layer is analyzed to determine the carbon dioxide burying potential of the oil layer, and the most real carbon dioxide oil displacement sweep efficiency and burying amount are obtained.

Description

Technical Field

[0001] This invention relates to the technical field of oil and gas field development, and is a laboratory evaluation method and apparatus for the sweep efficiency and burial volume of carbon dioxide flooding. Background Technology

[0002] CO2 miscible flooding is a crucial method for major oilfields to significantly enhance oil recovery and respond to the national "carbon peaking and carbon neutrality" initiative. However, the proximity and over-coverage of supercritical CO2 in oil reservoirs lead to rapid gas breakthroughs in wells, significantly limiting the effectiveness of CO2 miscible flooding in enhancing oil recovery. The sweep efficiency of CO2 flooding refers to the extent to which injected CO2 sweeps through the oil reservoir; that is, the percentage of the total oil reservoir volume (or area) washed by CO2. Visualizing the sweep range and sweep efficiency is of great guiding significance for oilfield management of CO2 channeling and calculation of reservoir storage potential.

[0003] Chinese patent document CN106991223A discloses a method and apparatus for determining the sweep efficiency of water channels in multi-layered oil reservoirs. The method includes: acquiring the physical property parameters of each reservoir within the work area; obtaining the water drive front saturation of each reservoir based on the physical property parameters; determining the water drive injection rate of each reservoir; and determining the water drive front movement velocity, breakthrough time, and sweep efficiency of each reservoir based on the water drive injection rate and water drive front saturation. Chinese patent document CN112561111A discloses a method and apparatus for predicting the water drive sweep efficiency of an oilfield. The method includes: acquiring the water cut of a target oilfield; determining the water drive sweep efficiency of the target oilfield based on the water cut of the target oilfield and a pre-established water drive sweep efficiency prediction model; the water drive sweep efficiency prediction model is pre-established based on historical oilfield production data. Both methods rely on mathematical prediction models based on production characteristics such as bound water saturation, injection volume, and water cut to predict water drive sweep efficiency, but they cannot quantitatively analyze intra-layer contradictions within the oil reservoir. Chinese patent document CN114577837A discloses a device and experimental method for evaluating the effects of carbon dioxide burial and oil displacement on formation pore throat structure and permeability. This method primarily uses T2 spectrum distribution and frequency-area difference to quantitatively evaluate the impact of CO2-water-rock interactions on pore throat and permeability, and to calibrate the degree of reservoir permeability damage. However, it also cannot directly analyze intra-layer contradictions within the oil reservoir. Summary of the Invention

[0004] This invention provides a laboratory evaluation method and apparatus for CO2 flooding sweep efficiency and burial volume, which overcomes the shortcomings of the prior art and can effectively solve the problem that existing methods cannot intuitively analyze the contradictions within the oil layer to determine the CO2 flooding sweep efficiency.

[0005] One of the technical solutions of this invention is achieved through the following measures: a laboratory evaluation method for the sweep efficiency and stock volume of carbon dioxide flooding, comprising the following steps:

[0006] S1, a carbon dioxide displacement experiment was conducted on the core sample, and the crude oil volume V1 and back pressure P1 in the core sample were recorded during the displacement experiment.

[0007] S2, the core samples after the carbon dioxide displacement experiment are sliced ​​to obtain core slices;

[0008] S3, add a colorimetric agent to the core slice for color development, and determine the CO2 flooding sweep volume V2 based on the color development area;

[0009] S4. The CO2 sweep efficiency and CO2 storage amount are calculated based on the crude oil volume V1, back pressure P1, and CO2 sweep volume V2 in the core sample.

[0010] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0011] The above CO2 displacement sweep efficiency is calculated using the following formula:

[0012]

[0013] In the formula, E v V1 represents the sweep efficiency of CO2 flooding, V2 represents the volume of crude oil in the core sample during the displacement experiment, and V2 represents the sweep volume of CO2 flooding.

[0014] The CO2 displacement sweep volume V2 mentioned above is determined according to the following steps:

[0015] Establish a rectangular coordinate system with the center point of the core sample as the origin, the length direction of the core sample as the X-axis, and the diameter direction of the core sample as the Y-axis. Plot the colorimetric boundaries of each core slice in the rectangular coordinate system. Integrate the area within the boundary using the following formula (see...). Figure 3 That is to Figure 3 Integrating the shaded area, we obtain the CO2 displacement sweep volume V2:

[0016]

[0017] The above-mentioned CO2 storage volume is calculated using the following formula:

[0018]

[0019] V 标 T represents CO2 storage capacity. 标 P represents the temperature of CO2 under standard conditions. 标V1 represents the CO2 pressure under standard conditions, V1 represents the crude oil volume in the core sample during the displacement experiment, P1 represents the back pressure during the displacement experiment, and T1 represents the temperature of the simulated reservoir during the displacement experiment.

[0020] The colorimetric reagents mentioned above are acid-base indicators, including bromothymol blue solution (mass concentration 0.1% to 2%).

[0021] The above core slices are slices taken along the diameter of the core sample, with a slice thickness of 0.2 mm to 0.8 mm.

[0022] The above-mentioned carbon dioxide displacement experiment was conducted on the core samples, and the crude oil volume V1 and back pressure P1 within the core samples were recorded during the displacement experiment; including:

[0023] Step 1: Prepare formation crude oil;

[0024] Step 2: Establish the bound water saturation of the core sample using formation water, then inject formation crude oil into the core sample under constant temperature and pressure, and record the volume of formation crude oil V1 in the core sample.

[0025] Step 3: Under the set back pressure, carbon dioxide is injected into the core sample to carry out the carbon dioxide displacement experiment, and the back pressure P1 is recorded at the same time.

[0026] The second technical solution of the present invention is achieved through the following measures: an apparatus for implementing a laboratory evaluation method for the sweep efficiency and burial volume of carbon dioxide flooded oil, comprising: a core holder, a crude oil sampler, a formation water sampler, a carbon dioxide storage tank, a backpressure nitrogen storage tank, a gas-liquid two-phase separator, a gas meter, a first booster pump, a second booster pump, and a backpressure valve. A first booster pipeline is fixedly connected between the outlet of the first booster pump and the crude oil sampler; a second booster pipeline is fixedly connected between the first booster pipeline and the formation water sampler; a third booster pipeline is fixedly connected between the first booster pipeline (connected to the second booster pipeline and the crude oil sampler) and the carbon dioxide storage tank; and a third booster pipeline is fixedly connected between the outlet of the formation water sampler and the inlet of the displacement fluid of the core holder. A first injection pipeline is fixedly connected between the outlet of the crude oil sampler and the first injection pipeline. A second injection pipeline is fixedly connected between the outlet of the carbon dioxide storage tank and the first injection pipeline between the core holder and the second injection pipeline. A third injection pipeline is fixedly connected between the outlet of the core holder displacement fluid and the first inlet of the back pressure valve. A first discharge pipeline is fixedly connected between the outlet of the back pressure valve and the inlet of the gas-liquid two-phase separator. A gas discharge pipeline is fixedly connected between the outlet of the gas-liquid two-phase separator and the gas meter. A first back pressure regulating pipeline is fixedly connected between the second booster pump and the back pressure nitrogen storage tank. A second back pressure regulating pipeline is fixedly connected between the outlet of the back pressure nitrogen storage tank and the second inlet of the back pressure valve.

[0027] The following are further optimizations and / or improvements to the second technical solution of the above invention:

[0028] The aforementioned laboratory evaluation device for the sweep efficiency and burial volume of carbon dioxide flooding also includes an insulated box, with the core holder installed inside the insulated box.

[0029] The aforementioned laboratory evaluation device for the sweep efficiency and burial volume of carbon dioxide flooding also includes a confining pressure pump and a confining pressure nitrogen storage tank. A confining pressure boosting pipeline is fixedly connected between the confining pressure pump and the confining pressure nitrogen storage tank. A first confining pressure pipeline is fixedly connected between the confining pressure nitrogen storage tank and the top port of the core holder. A second confining pressure pipeline is fixedly connected between the first confining pressure pipeline and the right port of the core holder.

[0030] This invention provides a laboratory evaluation method for the sweep efficiency and storage capacity of carbon dioxide flooding. This method visualizes the detection results of carbon dioxide flowing in the core sample after carbon dioxide flooding, and then uses the core slicing method to observe the carbon dioxide sweep range in different directions of the core sample and judge the pore throat connectivity of the core sample. The sweep efficiency of carbon dioxide flooding is determined intuitively, and the intralayer contradictions of the oil layer are analyzed to determine the carbon dioxide storage potential of the oil layer, thus obtaining the most accurate sweep efficiency and storage capacity of carbon dioxide flooding. Attached Figure Description

[0031] Appendix Figure 1 This is a schematic diagram of the process flow of Embodiment 8 of the present invention.

[0032] Appendix Figure 1 The codes in the diagram are as follows: 1 for core holder, 2 for crude oil sample mixing device, 3 for formation water sample mixing device, 4 for carbon dioxide storage tank, 5 for nitrogen storage tank, 6 for gas-liquid two-phase separator, 7 for gas meter, 8 for first booster pump, 9 for second booster pump, 10 for first booster pipeline, 11 for second booster pipeline, 12 for third booster pipeline, 13 for first injection pipeline, 14 for second injection pipeline, and 15 for third injection pipeline. 16 is the first discharge pipeline, 17 is the second discharge pipeline, 18 is the gas discharge pipeline, 19 is the first back pressure regulating pipeline, 20 is the second back pressure regulating pipeline, 21 is the confining pressure pump, 22 is the confining pressure nitrogen storage tank, 23 is the confining pressure boosting pipeline, 24 is the first confining pressure pipeline, 25 is the second confining pressure pipeline, 26 is the first three-way valve, 27 is the second three-way valve, 28 is the third three-way valve, 29 is the fourth three-way valve, and 30 is the back pressure valve.

[0033] Appendix Figure 2 This is a schematic diagram of a core slice according to the present invention. In the diagram, A is the core sample, B is the core slice, and C is the colorimetric experimental stage.

[0034] Appendix Figure 3 This is a schematic diagram of the CO2 sweep boundary and integral of the present invention. Detailed Implementation

[0035] This invention is not limited to the following embodiments; specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, the equipment and apparatus used in this invention are all existing, publicly known, and commonly used equipment and apparatus in the art.

[0036] The present invention will be further described below with reference to embodiments:

[0037] Example 1: The laboratory evaluation method for the sweep efficiency and stock volume of carbon dioxide flooding is carried out according to the following steps:

[0038] S1, a carbon dioxide displacement experiment was conducted on the core sample, and the crude oil volume V1 and back pressure P1 in the core sample were recorded during the displacement experiment.

[0039] S2, the core samples after the carbon dioxide displacement experiment are sliced ​​to obtain core slices;

[0040] S3, add a colorimetric agent to the core slice for color development, and determine the CO2 flooding sweep volume V2 based on the color development area;

[0041] S4. The CO2 sweep efficiency and CO2 storage amount are calculated based on the crude oil volume V1, back pressure P1, and CO2 sweep volume V2 in the core sample.

[0042] Example 2: As an optimization of the above example, the CO2 displacement sweep efficiency is calculated using the following formula:

[0043]

[0044] In the formula, E v V1 represents the sweep efficiency of CO2 flooding, V2 represents the volume of crude oil in the core sample during the displacement experiment, and V2 represents the sweep volume of CO2 flooding.

[0045] Example 3: As an optimization of the above examples, the CO2 displacement sweep volume V2 is determined according to the following steps:

[0046] Establish a rectangular coordinate system with the center point of the core sample as the origin, the length direction of the core sample as the X-axis, and the diameter direction of the core sample as the Y-axis. Plot the colorimetric boundaries of each core slice in the rectangular coordinate system. Integrate the area within the boundary using the following formula (see...). Figure 3 That is to Figure 3 Integrating the shaded area, we obtain the CO2 displacement sweep volume V2:

[0047]

[0048] Example 4: As an optimization of the above examples, the CO2 storage capacity is calculated using the following formula:

[0049]

[0050] V 标 T represents CO2 storage capacity. 标 P represents the temperature of CO2 under standard conditions. 标 V1 represents the CO2 pressure under standard conditions, V1 represents the crude oil volume in the core sample during the displacement experiment, P1 represents the back pressure during the displacement experiment, and T1 represents the temperature of the simulated reservoir during the displacement experiment.

[0051] Example 5: As an optimization of the above examples, the colorimetric agent is an acid-base indicator, including bromothymol blue solution (mass concentration 0.1% to 2%).

[0052] Example 6: As an optimization of the above example, the core slice is sliced ​​along the diameter direction of the core sample, and the slice thickness is 0.2 mm to 0.8 mm.

[0053] Example 7: As an optimization of the above examples, a carbon dioxide displacement experiment was conducted on the core sample, and the crude oil volume V1 and back pressure P1 in the core sample were recorded during the displacement experiment; including:

[0054] Step 1: Prepare formation crude oil;

[0055] Step 2: Establish the bound water saturation of the core sample using formation water, then inject formation crude oil into the core sample under constant temperature and pressure, and record the volume of formation crude oil V1 in the core sample.

[0056] Step 3: Under the set back pressure, carbon dioxide is injected into the core sample to carry out the carbon dioxide displacement experiment, and the back pressure P1 is recorded at the same time.

[0057] In this invention, the formation crude oil is prepared in accordance with the national standard GB / T26981-2020 "Methods for Analysis of Fluid Properties in Oil and Gas Reservoirs".

[0058] Example 8: As Figure 1 As shown, the laboratory evaluation device for CO2 flooding sweep efficiency and stockpile includes:

[0059] The system comprises a core holder 1, a crude oil sampler 2, a formation water sampler 3, a carbon dioxide storage tank 4, a backpressure nitrogen storage tank 5, a gas-liquid two-phase separator 6, a gas meter 7, a first booster pump 8, a second booster pump 9, and a backpressure valve 30. A first booster pipeline 10 is fixedly connected between the outlet of the first booster pump 8 and the crude oil sampler 2. A second booster pipeline 11 is fixedly connected between the first booster pipeline 10 and the formation water sampler 3. A third booster pipeline 12 is fixedly connected between the first booster pipeline 10 and the crude oil sampler 2, and between the second booster pipeline 11 and the first booster pipeline 10 and the carbon dioxide storage tank 4. A first injection pipeline 13 is fixedly connected between the outlet of the formation water sampler 3 and the displacement fluid inlet of the core holder 1. The outlet of the crude oil sampler 2 is connected to the first injection pipeline 13. A second injection pipeline 14 is fixedly connected between the outlet of the carbon dioxide storage tank 4 and the first injection pipeline 13 between the core holder 1 and the second injection pipeline 14. A third injection pipeline 15 is fixedly connected between the outlet of the core holder 1 and the first inlet of the back pressure valve 30. A first discharge pipeline 16 is fixedly connected between the outlet of the back pressure valve 30 and the inlet of the gas-liquid two-phase separator 6. A gas discharge pipeline 18 is fixedly connected between the outlet of the gas-liquid two-phase separator 6 and the gas meter 7. A first back pressure regulating pipeline 19 is fixedly connected between the second booster pump 9 and the back pressure nitrogen storage tank 5. A second back pressure regulating pipeline 20 is fixedly connected between the outlet of the back pressure nitrogen storage tank 5 and the second inlet of the back pressure valve 30.

[0060] Example 9: As Figure 1 As shown, as an optimization of the above embodiment, the laboratory evaluation device for carbon dioxide flooding sweep efficiency and burial volume also includes an insulated box, and the core holder 1 is installed inside the insulated box.

[0061] Example 10: As Figure 1 As shown, as an optimization of the above embodiment, the laboratory evaluation device for the sweep efficiency and burial volume of carbon dioxide flooding also includes a confining pressure pump 21 and a confining pressure nitrogen storage tank 22. A confining pressure boosting pipeline 23 is fixedly connected between the confining pressure pump 21 and the confining pressure nitrogen storage tank 22. A first confining pressure pipeline 24 is fixedly connected between the confining pressure nitrogen storage tank 22 and the top port of the core holder 1. A second confining pressure pipeline 25 is fixedly connected between the first confining pressure pipeline 24 and the right port of the core holder 1.

[0062] As required, the laboratory evaluation device for CO2 flooded oil sweep efficiency and stock volume also includes multiple three-way valves. The first booster line 10 and the second booster line 11 are connected via the first three-way valve 26; the first booster line 10 and the third booster line 12 are connected via the second three-way valve 27; the first injection line 13 and the second injection line 14 are connected via the third three-way valve 28; and the first injection line 13 and the third injection line 15 are connected via the fourth three-way valve 29. Valves are installed on the first back pressure regulating line 19, the second back pressure regulating line 20, the confining pressure boosting line 23, the first confining pressure line 24, and the second confining pressure line 25. Furthermore, instruments to ensure the normal operation of the CO2 flooded oil sweep efficiency and stock volume laboratory evaluation device are fixedly installed on each pipeline.

[0063] Example 11: The specific implementation process of the laboratory evaluation method for the sweep efficiency and stock volume of carbon dioxide flooding is as follows:

[0064] The first step is to prepare formation crude oil (V0, mL) by adding associated gas and degassed crude oil to crude oil sampler 2, in accordance with the national standard GB / T26981-2020 "Methods for Analysis of Fluid Properties in Oil and Gas Reservoirs".

[0065] The second step is to measure the length (H, cm), diameter (D, cm), and porosity (POR, %) of the core sample.

[0066] The third step involves connecting the laboratory evaluation device for carbon dioxide flooding sweep efficiency and burial volume, raising the constant temperature chamber to the reservoir formation temperature (T1, ℃), and establishing the bound water saturation of the core sample using formation water according to the field data.

[0067] The fourth step involves using a booster pump to slowly inject the prepared formation crude oil into the core sample while maintaining its temperature and pressure, and recording the volume of formation crude oil in the core sample (V1, mL). This volume is equal to the compression volume of the booster pump.

[0068] The fifth step is to use the booster pump to set the injection pressure and back pressure to conduct a laboratory carbon dioxide displacement experiment, and record the back pressure (P1, MPa) at the same time, based on the on-site production data.

[0069] Step 6: After the displacement experiment, quickly remove the core sample. To prevent CO2 diffusion from the core sample, wrap the core sample with plastic wrap. Then slice the core sample along the core sample, with a slice thickness of no more than 0.8 mm. Place the core slice on the experimental table and evenly drop bromothymol blue solution onto the core slice. Observe the yellow area in the plane of the core slice with a microscope and draw the boundary of the yellow area.

[0070] Step 7: Establish a rectangular coordinate system with the center point of the core sample as the origin of the coordinate axis, the length direction of the core sample as the X-axis, and the diameter direction of the core sample as the Y-axis. Plot the yellow boundary lines recorded in each core slice in this coordinate system. The degree of connection of the yellow boundary lines represents the degree of pore throat connection of the core sample.

[0071] Step 8: Integrate the boundary lines within the coordinate axes according to Equation 2 to obtain the CO2 displacement sweep volume V2, and then calculate the CO2 displacement sweep coefficient according to Equation 1; at the same time, calculate the CO2 stockpile according to the equation of state (Equation 3).

[0072] Example 12: The experimental procedure of the laboratory evaluation device for the sweep efficiency and stock volume of carbon dioxide flooding is as follows:

[0073] The first step is to prepare core samples and record information such as the length, diameter, and porosity of the core samples. Place the core samples in core holder 1. According to the national standard GB / T26981-2020 "Methods for Fluid Property Analysis of Oil and Gas Reservoirs", add associated gas and degassed crude oil to crude oil sampler 2 to prepare formation crude oil (V0, mL).

[0074] The second step is to connect the evaluation device and set the temperature of the constant temperature chamber to the reservoir formation temperature (T1, ℃), which is the temperature of the reservoir simulated in the displacement experiment.

[0075] The third step is to adjust the first three-way valve 26, the third three-way valve 28, and the fourth three-way valve 29 to connect the pipeline between the first booster pump 8, the formation water sampler 3, and the core holder 1. Through the first booster pump 8, the formation water in the formation water sampler 3 is slowly injected into the core sample to establish the bound water saturation.

[0076] Fourth step, adjust the first three-way valve 26 and the third three-way valve 28 to connect the pipeline between the first booster pump 8, the crude oil sampler 2 and the core holder 1. The first booster pump 8 injects the formation crude oil in the crude oil sampler 2 into the core sample while keeping it warm and pressurized, slowly saturating the core sample, and recording the volume of formation crude oil in the core sample (V1, mL). V1 is equal to the compression volume of the first booster pump 8.

[0077] Fifth step: Open the valves on the confining pressure boosting pipeline 23, the first confining pressure pipeline 24, and the second confining pressure pipeline 25, and use the confining pressure pump 21 to inject nitrogen from the confining pressure nitrogen storage tank 22 into the core holder 1 to control the confining pressure in the displacement experiment.

[0078] Step 6: Open the valves on the first back pressure regulating pipeline 19 and the second back pressure regulating pipeline 20. Use the second booster pump 9 to inject nitrogen from the back pressure nitrogen storage tank 5 into the back pressure valve to control the back pressure (P1, MPa). Adjust the pipeline connecting the second three-way valve 27, the fourth three-way valve 29, the first booster pump 8, the carbon dioxide storage tank 4, and the core holder 1. Use the first booster pump 8 to inject supercritical CO2 from the carbon dioxide storage tank 4 into the core sample to carry out the carbon dioxide displacement experiment. During the experiment, the displaced fluid is separated by the gas-liquid two-phase separator 6. The liquid part is measured by the gas-liquid two-phase separator 6, and the gas part is measured by the gas meter 7. When no fluid flows into the gas-liquid two-phase separator 6, the displacement experiment ends.

[0079] Step 7: After the displacement experiment is completed, shut down the experimental system and slice, develop color, and calculate the CO2 flooding sweep efficiency and CO2 storage amount according to Example 12 above.

[0080] The parameter values ​​obtained during the experiment can be used to calculate other parameters in the carbon dioxide displacement experiment, guiding actual production.

[0081] This invention visualizes the detection results of carbon dioxide flowing within core samples after carbon dioxide flooding. Then, by using core slicing, it observes the carbon dioxide sweep range in different directions of the core sample and determines the degree of pore-throat connectivity. Finally, it calculates the most accurate CO2 flooding sweep efficiency and CO2 storage, maximizing the reproduction of the actual on-site production process. The invention is well-designed and highly practical, providing important technical guidance for on-site control of gas channeling in carbon dioxide flooding.

[0082] In summary, this invention provides a laboratory evaluation method for the sweep efficiency and burial volume of carbon dioxide flooding. This method closely aligns with the actual situation of field production, the calculation method for the sweep efficiency and burial volume of carbon dioxide flooding is reliable, and the experimental process is simple and easy to operate, which is of great significance for oil reservoir development.

[0083] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooded oil, characterized in that... Follow these steps: S1, a carbon dioxide displacement experiment was conducted on the core sample, and the crude oil volume V1 and back pressure P1 in the core sample were recorded during the displacement experiment. S2, the core samples after the carbon dioxide displacement experiment are sliced ​​to obtain core slices; S3, add a colorimetric agent to the core slice for color development, and determine the CO2 flooding sweep volume V2 based on the color development area; S4. The CO2 sweep efficiency and CO2 storage amount are calculated based on the crude oil volume V1, back pressure P1, and CO2 sweep volume V2 in the core sample.

2. The laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooding as described in claim 1, characterized in that... The CO2 sweep efficiency is calculated using the following formula: In the formula, E v V1 represents the sweep efficiency of CO2 flooding, V2 represents the volume of crude oil in the core sample during the displacement experiment, and V2 represents the sweep volume of CO2 flooding.

3. The laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooding according to claim 1 or 2, characterized in that... The CO2 displacement sweep volume V2 is determined according to the following steps: A rectangular coordinate system is established with the center point of the core sample as the origin, the length direction of the core sample as the X-axis, and the diameter direction of the core sample as the Y-axis. The colorimetric boundaries of each core slice are then plotted in the rectangular coordinate system. The CO2 swept volume V2 is obtained by integrating the area within the boundary using the following formula:

4. The laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooding according to any one of claims 1 to 3, characterized in that... The CO2 stockpile is calculated using the following formula: V 标 T represents CO2 storage capacity. 标 Let P be the temperature of CO2 under standard conditions. 标 V1 represents the CO2 pressure under standard conditions, V1 represents the crude oil volume in the core sample during the displacement experiment, P1 represents the back pressure during the displacement experiment, and T1 represents the temperature of the simulated reservoir during the displacement experiment.

5. The laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooding according to any one of claims 1 to 4, characterized in that... The colorimetric reagent is an acid-base indicator, including bromothymol blue solution.

6. The laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooding according to any one of claims 1 to 5, characterized in that... The core slices are slices taken along the diameter of the core sample, with a slice thickness of 0.2 mm to 0.8 mm.

7. The laboratory evaluation method for sweep efficiency and stock volume of carbon dioxide flooding according to any one of claims 1 to 6, characterized in that... Carbon dioxide displacement experiments were conducted on core samples, and the crude oil volume v1 and back pressure P1 within the core samples were recorded during the displacement experiments, including: Step 1: Prepare formation crude oil; Step 2: Establish the bound water saturation of the core sample using formation water, then inject formation crude oil into the core sample under constant temperature and pressure, and record the volume of formation crude oil V1 in the core sample. Step 3: Under the set back pressure, carbon dioxide is injected into the core sample to carry out the carbon dioxide displacement experiment, and the back pressure P1 is recorded at the same time.

8. An apparatus for laboratory evaluation of sweep efficiency and stock volume of carbon dioxide flooding oil recovery system according to any one of claims 1 to 7, characterized in that... include: The system includes a core holder, a crude oil sampler, a formation water sampler, a carbon dioxide storage tank, a backpressure nitrogen storage tank, a gas-liquid two-phase separator, a gas meter, a first booster pump, a second booster pump, and a backpressure valve. A first booster pipeline is fixedly connected between the outlet of the first booster pump and the crude oil sampler. A second booster pipeline is fixedly connected between the first booster pipeline and the formation water sampler. A third booster pipeline is fixedly connected between the first booster pipeline (connected to the second booster pipeline and the crude oil sampler) and the carbon dioxide storage tank. A first injection pipeline is fixedly connected between the outlet of the formation water sampler and the displacing fluid inlet of the core holder. The outlet of the crude oil sampler is connected to the first injection pipeline... A second injection pipeline is fixedly connected between the outlet of the carbon dioxide storage tank and the first injection pipeline between the core holder and the second injection pipeline. A third injection pipeline is fixedly connected between the outlet of the core holder displacement fluid and the first inlet of the back pressure valve. A second discharge pipeline is fixedly connected between the outlet of the back pressure valve and the inlet of the gas-liquid two-phase separator. A gas discharge pipeline is fixedly connected between the outlet of the gas-liquid two-phase separator and the gas meter. A first back pressure regulating pipeline is fixedly connected between the second booster pump and the back pressure nitrogen storage tank. A second back pressure regulating pipeline is fixedly connected between the outlet of the back pressure nitrogen storage tank and the second inlet of the back pressure valve.

9. The apparatus for the laboratory evaluation method of sweep efficiency and stock volume of carbon dioxide flooding according to claim 8, characterized in that... It also includes an insulated box, inside which the core holder is placed.

10. The apparatus for the laboratory evaluation method of sweep efficiency and stock volume of carbon dioxide flooding according to claim 8 or 9, characterized in that... It also includes a confining pressure pump and a confining pressure nitrogen storage tank. A confining pressure boosting pipeline is fixedly connected between the confining pressure pump and the confining pressure nitrogen storage tank. A first confining pressure pipeline is fixedly connected between the confining pressure nitrogen storage tank and the top port of the core holder. A second confining pressure pipeline is fixedly connected between the first confining pressure pipeline and the right port of the core holder.

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