An experimental apparatus and method for evaluating CO2 injection for enhanced oil recovery and geological storage in high-temperature and high-pressure carbonate gas reservoirs.

Abstract

This invention discloses an experimental apparatus and method for evaluating CO2 injection for enhanced oil recovery and geological storage in high-temperature and high-pressure carbonate gas reservoirs. It includes a gas pressurization component, a constant-speed and constant-pressure pump, a piston intermediate container, a high-temperature and high-pressure experimental model container, a backpressure component, a gas metering component, and a constant-temperature chamber, as well as monitoring instruments and a controller. The piston intermediate container and the high-temperature and high-pressure experimental model container are housed within the constant-temperature chamber. The gas pressurization component, piston intermediate container, high-temperature and high-pressure experimental model container, backpressure component, and gas metering component are sequentially connected via pipelines. The constant-speed and constant-pressure pump is connected to the piston intermediate container. The gas metering component, monitoring instruments, and controller are electrically connected, and the monitoring instruments include pressure monitoring instruments and temperature monitoring instruments.

Description

Technical Field

[0001] This invention belongs to the fields of resource environment and petroleum extraction technology, and in particular relates to an experimental method, system, equipment and storage medium for evaluating CO2 injection to enhance the recovery rate and geological storage of high-temperature and high-pressure carbonate gas reservoirs. Background Technology

[0002] In recent years, with the development of carbon capture, utilization and storage (CCUS) technology, CO2 injection into oil and gas reservoirs must balance enhanced oil recovery and geological sequestration to achieve simultaneous progress in economic and environmental benefits. After CO2 is injected into the reservoir, it undergoes a series of physical and chemical reactions in the complex underground space, maintaining a relatively stable state over a long period—this is geological sequestration. The main mechanisms are physical and chemical sequestration. Studies show that China has abundant theoretical CO2 geological sequestration potential, estimated at 1.21-4.13 trillion tons, mainly including saline aquifers and oil and gas fields. China's oilfields are mainly concentrated in the Songliao Basin, Bohai Bay Basin, Ordos Basin, and Junggar Basin, with proven oilfields capable of sequestering approximately 20 billion tons of CO2, of which about 5 billion tons are suitable for sequestration. China's gas reservoirs are mainly distributed in the Ordos Basin, Sichuan Basin, Bohai Bay Basin and Tarim Basin. China has proven gas reservoirs that can eventually store approximately 15 billion tons of CO2.

[0003] In my country, research on CO2 enhanced oil recovery and geological storage primarily focuses on oil-bearing, coal-bearing, and saline-aquifer formations. However, my country possesses numerous inefficient gas reservoirs or those on the verge of abandonment (closed or water-bearing gas reservoirs), making natural gas reservoirs a potential target for underground CO2 storage. For carbonate gas reservoirs operating under typical high-temperature and high-pressure conditions (minimum temperature 100℃, minimum pressure 30MPa), characterized by complex reservoir spaces and uneven fluid distribution, existing experimental methods for evaluating CO2 enhanced oil recovery and geological storage have several shortcomings: core clamp measurement methods cannot simulate the complex reservoir conditions of large-scale carbonate gas reservoirs; large-scale carbonate visualization simulation devices and corresponding methods cannot achieve the real high-temperature and high-pressure conditions of gas reservoirs; and temperature- and pressure-resistant three-dimensional physical simulation experiments and corresponding methods are time-consuming, with most experimental conditions failing to reach the supercritical state of CO2. This invention designs an indoor evaluation device and corresponding evaluation method for CO2 injection enhanced oil recovery and geological storage in high-temperature and high-pressure carbonate gas reservoirs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention designs and proposes an indoor experimental apparatus and method for evaluating CO2 injection for enhanced oil recovery and geological storage in fractured-vuggy gas reservoirs under high temperature and high pressure conditions. By accurately measuring the dynamic changes during gas injection and calculating the injection-production process parameters, the effectiveness of CO2 injection for enhanced oil recovery in carbonate gas reservoirs under high temperature and high pressure conditions can be evaluated, and the geological storage potential of this type of reservoir can be estimated, which has practical significance.

[0005] To achieve the aforementioned objectives, the present invention employs the following experimental method: an experimental apparatus for evaluating CO2 injection to enhance oil recovery and geological storage in high-temperature, high-pressure carbonate gas reservoirs, comprising the following:

[0006] It includes a gas cylinder, a compression component, a gas pressurization component, a constant speed and constant pressure pump, a piston intermediate container, a high temperature and high pressure experimental model container, a back pressure component, a gas metering component, and a constant temperature chamber, as well as monitoring instruments and a controller; the piston intermediate container and the high temperature and high pressure experimental model container are built into the constant temperature chamber;

[0007] The gas cylinder, compression component, gas pressurization component, piston intermediate container, high temperature and high pressure experimental model container, back pressure component, and gas metering component are connected in sequence through pipelines; the constant speed and constant pressure pump is connected to the piston intermediate container; and valves are also included on the pipelines.

[0008] Electrical connections for gas metering components, monitoring instruments, and controllers.

[0009] Furthermore, the monitoring instruments include pressure sensors and temperature sensors.

[0010] Furthermore, the pressure sensor includes a first pressure sensor, a second pressure sensor, a third pressure sensor, and a fourth pressure sensor; the first and second pressure sensors are respectively installed on the inlet and outlet pipes of the piston intermediate container; the third and fourth pressure sensors are respectively installed on the inlet and outlet pipes of the high-temperature and high-pressure experimental model container.

[0011] Furthermore, the gas metering component includes a gas flow meter and a gas chromatograph connected in sequence.

[0012] Furthermore, the piston intermediate container comprises three intermediate containers connected in parallel, and the gas cylinder is a gas cylinder assembly of three connected in parallel.

[0013] Furthermore, the valves on the pipeline include control valves, which are electrically connected to the controller; the control valves include a first control valve, a second control valve, a third control valve, and a fourth control valve, which are respectively disposed in front of the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor.

[0014] Furthermore, a gas filtration and purification component and a one-way valve are provided on the pipeline connecting the outlet of the gas pressurizing component and the inlet of the piston intermediate container; the gas filtration and purification component is used to purify and filter impurity gases unrelated to the experiment; the one-way valve is used to control the gas in the gas pressurizing component to flow into the piston intermediate container in only one direction.

[0015] The back pressure component is used to control the outflow of high-pressure gas from the outlet of the high-temperature and high-pressure experimental model container;

[0016] The gas metering component is used to measure the gas flow rate and composition at the outlet of the high-temperature and high-pressure experimental model container;

[0017] The gas flow meter is used to measure the gas flow rate at the outlet of the back pressure component;

[0018] The gas chromatograph is used to measure the composition of the gas exiting the gas flow meter.

[0019] Furthermore, in the aforementioned experimental apparatus, the piston intermediate container, the high-temperature and high-pressure experimental model container, and the back pressure component are high-temperature and high-pressure resistant components; they can withstand temperatures above 100°C and pressures above 20MPa. The high-temperature and high-pressure experimental model container has a height of 700mm, a diameter of 64.5mm, and a volume of 2287.22mL.

[0020] Furthermore, an experimental method for enhancing oil recovery and geological storage through CO2 injection in high-temperature, high-pressure carbonate gas reservoirs includes the following steps:

[0021] Step 1: Clean the high-temperature and high-pressure piston intermediate container, high-temperature and high-pressure corrosion-resistant piston gas tank, high-temperature and high-pressure sealed container and connected pipelines with petroleum ether and dry them; connect the device and introduce high-purity nitrogen gas at a certain pressure. After the monitored pressure stabilizes, complete the device airtightness test.

[0022] Step two: Design, fabricate, and clean the fractured-vuggy carbonate gas reservoir storage space. Vacuum the entire apparatus, turn on the constant temperature chamber, set the experimental temperature, and ensure all components within the chamber reach stability. Inject formation water using a constant pressure and speed pump. Once no more air bubbles are generated at the outlet, accumulate the injected water volume using the pump. Record the difference between this volume and the volume of liquid collected at the outlet as the pore volume V. pore Gas from the gas reservoir is injected into a high-temperature, high-pressure sealed container from the opposite direction of the water injection port. The volume of produced water is measured and considered as the initial gas-bearing volume of the gas reservoir, V. 气1 And obtain the initial gas saturation of the gas reservoir;

[0023] Step 3: Using a gas pressurization device, CO2 is pumped into the intermediate container of the high-temperature, high-pressure piston. After the pressure stabilizes, a constant-speed, constant-pressure pump is turned on to inject CO2 from the intermediate container into the high-temperature, high-pressure experimental model at a certain speed. The outlet of the high-temperature, high-pressure model is then opened, and the extracted gas is measured using a gas metering device. The cumulative volume of natural gas extracted is recorded as V. 气2 The cumulative volume of CO2 extracted is denoted as V. 二氧化碳1 ;

[0024] Step four: Record the experimental data changes using a gas flow meter and a gas chromatograph at intervals of 0.5-10 minutes. When the CO2 content at the collection end reaches 90%, the experiment is considered complete, and CO2 displacement is stopped. The cumulative injection volume during the entire displacement process using a constant-speed, constant-pressure pump is considered the CO2 injection volume under experimental conditions and is denoted as V. 二氧化碳2 .

[0025] Furthermore, according to the experimental method, the target gas includes one or more of nitrogen-C1-C4 gaseous hydrocarbons; the carbonate gas reservoir includes one or more of fracture-cavity structures, cavern structures, and fracture-cavity structures.

[0026] Furthermore, according to the experimental method described above, the calculation steps for determining the CO2-enhanced gas storage capacity of carbonate rock reservoirs using the mass conservation method are as follows:

[0027] Determine the volume V of the carbonate reservoir; measure the volume of produced formation water, V pore ;V represents the initial gas-bearing volume of a fractured-vuggy carbonate gas reservoir under a certain pressure condition. 气1 ; Cumulative gas production volume V 二氧化碳2

[0028] The calculation for CO2 enhancing the recovery rate of natural gas from carbonate rocks is as follows:

[0029] RF = V 气2 V 气1 ×100% Equation (1)

[0030] The CO2 retention rate of carbonate natural gas reservoirs is calculated as follows:

[0031] GS=V 二氧化碳1 V 二氧化碳2 ×100% Equation (2)

[0032] This invention provides an experimental method for evaluating CO2 injection to enhance oil recovery and geological storage in high-temperature, high-pressure carbonate gas reservoirs:

[0033] 1. It broadened the experimental conditions for CO2 injection to enhance oil recovery and geological preservation in carbonate gas reservoirs.

[0034] 2. Improved the accuracy of CO2 injection for enhanced oil recovery and geological preservation in carbonate gas reservoirs.

[0035] 3. It is beneficial to inject CO2 to improve the recovery rate and realize the long-term storage of CO2, reducing greenhouse gas emissions and achieving a win-win situation for both economic and social benefits. Attached Figure Description

[0036] Figure 1 This is a flowchart of the experimental process of the present invention.

[0037] Figure 2 A graph showing the carbon dioxide content of produced gas at different displacement stages in an application example of this invention.

[0038] Figure 3 Recovery rate curves at different displacement stages in application examples of this invention

[0039] Figure 4 This is a diagram showing the proportion of carbon dioxide remaining in the storage tank at different displacement stages, representing an application example of the present invention. Detailed Implementation

[0040] In the following, the terms “comprising” or “may include” as used in various embodiments of the invention indicate the presence of an inventive function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of the invention, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0041] The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of the invention. Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. The terms (such as those defined in commonly used dictionaries) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning unless clearly defined in the various embodiments of the invention.

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining this invention and are not intended to limit this invention.

[0043] CO2 Displacement-Storage Experiment of Sandstone Filler in Carbonate Gas Reservoir under High Temperature and High Pressure Conditions

[0044] (1) Experimental materials

[0045] Experimental gases: high-purity CO2, with a purity of 99.99%; simulated natural gas, including CH4 with a purity of 99.9%; and nitrogen.

[0046] Experimental water: simulated formation water from an oilfield, with a salinity of 120.86 g / L, CaCl2 type.

[0047] Experimental model: Outcrop core of a certain carbonate gas reservoir.

[0048] Experimental temperature: The experiment was conducted at a simulated formation temperature of 60℃ and a pressure of 10MPa.

[0049] (2) Experimental instruments and procedures

[0050] This invention establishes Figure 1 The experimental flowchart is shown.

[0051] The specific experimental equipment includes:

[0052] Gas cylinder 1, compressor 2, booster pump 3, HW-Ⅲ type self-controlled constant temperature chamber 17, ISCO (100DX) constant speed and constant pressure pump 5, first high temperature and high pressure piston intermediate container 7, second high temperature and high pressure piston intermediate container 9, third high temperature and high pressure piston intermediate container 10, high temperature and high pressure experimental model container (12), four-way valve 6, high temperature and high pressure corrosion resistant pipeline, back pressure component 14, gas flow meter 15, gas chromatograph 16, high precision pressure sensor (4,8,11,13) and controller.

[0053] Among them, gas cylinder 1 has three types, including high-purity CO2 cylinder, simulated natural gas cylinder, and nitrogen cylinder. All three types of high-temperature and high-pressure piston intermediate containers and high-temperature and high-pressure experimental model containers are sealed with corrosion-resistant reinforced graphite self-sealing ring structures. This not only enhances the overall sealing structure of the device but also reduces abnormal pressure changes caused by gas leakage during the experiment, increasing the accuracy of measurements.

[0054] The connection relationships of the above experimental equipment are as follows:

[0055] Three gas cylinders 1 are connected in parallel to form a gas cylinder assembly. The first high-temperature and high-pressure piston intermediate container 7, the second high-temperature and high-pressure piston intermediate container 9, and the third high-temperature and high-pressure piston intermediate container are connected in parallel to form an intermediate container. Then, the gas cylinder assembly, compression component, gas pressurization component, piston intermediate container, high-temperature and high-pressure experimental model container, back pressure component, gas flow meter, and gas chromatograph are connected in sequence through pipelines. The outlet of the constant speed and constant pressure pump is connected to the inlet of the piston intermediate container. Corresponding valves and monitoring instruments are also installed on the pipelines.

[0056] The controller collects and monitors data such as the inlet and outlet pressures of the piston intermediate container and the inlet and outlet pressures of the high-temperature and high-pressure experimental model container, as well as gas volume and content and liquid volume, through pressure and temperature sensors, gas flow meters, and gas chromatographs.

[0057] (3) Experimental steps

[0058] Step 1: Equipment preparation and airtightness test

[0059] (1) Clean the high-temperature and high-pressure piston intermediate container, the experimental model container, and the connected pipelines with petroleum ether, and then dry them;

[0060] (2) Connect the experimental equipment together according to the experimental flowchart, put the prepared carbonate gas reservoir model into the high temperature and high pressure experimental model container, ensure that the size of the model does not hinder the sealing of the model container, cover the top cover and close all valves.

[0061] (3) Open the corresponding valves and open the nitrogen cylinder. Through the compressor and booster, inject high-purity nitrogen (usually 10MPa) at a certain pressure into the connected container. Observe the pressure change at the corresponding pressure measuring point through the computer display connected to the controller. If the pressure remains stable within 3 hours, it indicates that the containers and pipelines are well sealed.

[0062] 2) Carbonate reservoir treatment

[0063] Step 1: Based on the physical properties of the filling medium, construct the corresponding fractured-vuggy carbonate gas reservoir space. The model medium is made from the outcrop core of the corresponding strata. Clean the carbonate reservoir model with ethanol and petroleum ether.

[0064] Step two, fluid preparation: Open the simulated carbon dioxide cylinder and the corresponding pipeline valves, and inject carbon dioxide into the first high-temperature, high-pressure piston intermediate container through the compressor and booster. Similarly, inject natural gas into the third high-temperature, high-pressure piston intermediate container.

[0065] Formation water is injected into the intermediate container of the second high-temperature and high-pressure piston.

[0066] Turn on the incubator and set the simulated gas reservoir temperature. Use a pressure gauge to measure the pressure in each of the three piston containers. Once the pressure stabilizes and becomes similar at the set temperature, the fluid preparation is considered complete. Evacuate the entire apparatus, turn on the incubator, set the experimental temperature, and allow all components within the incubator to stabilize.

[0067] Step 3: Establish formation water saturation under gas reservoir conditions: Connect the production outlet to the back pressure valve. Taking an initial gas reservoir pressure of 20 MPa as an example, set the back pressure to 20 MPa. Open the valve at the top of the model container and inject formation water from the intermediate container of the second high-temperature and high-pressure piston into the model container through the model water injection port using a constant pressure and constant speed pump. Once there is continuous water production without air bubbles at the outlet of the model container, the difference between the cumulative volume of formation water injected by the pump and the liquid collected at the outlet is recorded as the pore volume V. pore .

[0068] Step 4: Establishing Natural Gas Saturation under Gas Reservoir Conditions: Using a constant pressure and speed pump, natural gas from the intermediate container of the third high-temperature and high-pressure piston is injected into the high-temperature and high-pressure sealed model container from the opposite direction (outlet) of the water inlet. The extracted liquid is collected. Once the produced end is pure gas, the total produced liquid volume is measured, which is the initial gas-bearing volume of the fractured-vuggy carbonate gas reservoir under 20 MPa conditions, V. 气1 And the corresponding gas saturation. Close all outlets, age for 5 hours, and establish the initial spatial distribution relationship of gas reservoir fluids.

[0069] Step 5: CO2 Displacement of Natural Gas Experiment: Open the CO2 cylinder and corresponding pipeline valves. Through the compressor and booster, inject CO2 into the first high-temperature, high-pressure piston intermediate container. Turn on the constant flow pump and set a specific displacement rate. Under the conditions of this case, the displacement rate is 1.5 mL / min. Inject CO2 into the model container, open the back pressure component outlet, and measure the cumulative produced gas volume (V). 气2 V 二氧化碳1 The study measured the displacement time and outlet gas composition, calculated the CO2 enhanced oil recovery effect and the injected pore volume, V. 二氧化碳2 .

[0070] Step Six: Calculation of CO2 Enhanced Natural Gas Recovery and Retention Rate: Process the experimental data measured during the experiment, and calculate the CO2 enhanced natural gas recovery rate and CO2 retention rate of carbonate natural gas reservoirs using equations (1) and (2). The displacement dynamic characteristic curve is shown in the figure. Figures 2-4 As shown.

[0071] This experimental setup and method broaden the range of experimental conditions, with a maximum test temperature of 150℃ and a test pressure of 50MPa. The high temperature and high pressure conditions of the setup cover most oil reservoir conditions in my country, especially high temperature and high pressure fractured-vuggy carbonate reservoirs, making the test results more applicable. Secondly, this invention improves existing experimental evaluation methods for CO2 injection to enhance oil recovery and geological sequestration in gas reservoirs. It increases the size of traditional displacement physical models; the device model of this invention can accommodate physical models with a diameter of 6.5 cm and a height of 70 cm, reducing errors caused by boundary and end-face instability and increasing measurement accuracy. The addition of a full-air bath device reduces phase transitions and temperature changes caused by high-speed flow in the initial injection phase. It also increases the flexibility of model design, allowing for the simulation of various reservoir space types in fractured-vuggy carbonate gas reservoirs, including karst, etched, various filling types, and reservoirs with different filling degrees. It can not only meet the requirements for enhancing oil recovery with a single type of gas, such as non-hydrocarbon gases like carbon dioxide and nitrogen, but also meet the experimental research requirements for enhancing oil recovery in carbonate gas reservoirs with different proportions of mixed gases. These mixed gases can be non-hydrocarbon, hydrocarbon, or a combination of hydrocarbon and non-hydrocarbon gases, better reflecting actual injection conditions and reservoir conditions. Furthermore, the fractured-vuggy carbonate model contains a rich fluid phase, capable of saturating formation water with different salinity levels or filling media with different water saturation levels.

[0072] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. An experimental apparatus for evaluating CO2 injection for enhanced oil recovery and geological storage in high-temperature and high-pressure carbonate gas reservoirs, characterized in that, It includes a gas cylinder assembly, a compression component, a gas pressurization component, a constant speed and constant pressure pump, a piston intermediate container, a high temperature and high pressure experimental model container, a back pressure component, a gas metering component, and a constant temperature chamber, as well as monitoring instruments and a controller; the piston intermediate container and the high temperature and high pressure experimental model container are built into the constant temperature chamber; The gas cylinder assembly, compression component, gas pressurization component, piston intermediate container, high temperature and high pressure experimental model container, back pressure component, and gas metering component are sequentially connected by pipelines; the constant speed and constant pressure pump is connected to the piston intermediate container; and valves are also included on the pipelines. Electrical connections for gas metering components, monitoring instruments, and controllers.

2. The apparatus as claimed in claim 1, characterized in that, The monitoring instruments include a pressure sensor and a temperature sensor, and the gas metering components include a gas flow meter and a gas chromatograph connected in sequence.

3. The apparatus as described in claim 2, characterized in that, The pressure sensors include a first pressure sensor, a second pressure sensor, a third pressure sensor, and a fourth pressure sensor; the first and second pressure sensors are respectively installed on the inlet and outlet pipes of the piston intermediate container; the third and fourth pressure sensors are respectively installed on the inlet and outlet pipes of the high-temperature and high-pressure experimental model container.

4. The apparatus as claimed in claim 1, characterized in that, The piston intermediate container comprises three intermediate containers connected in parallel, and the gas cylinder assembly consists of three gas cylinders connected in parallel.

5. The apparatus as claimed in claim 1, characterized in that, The valves on the pipeline include control valves, which are electrically connected to the controller; the control valves include a first control valve, a second control valve, a third control valve, and a fourth control valve, which are respectively installed in front of the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor.

6. The apparatus as claimed in claim 1, characterized in that, A gas filtration and purification component and a one-way valve are installed on the pipeline connecting the outlet of the gas pressurizing component and the inlet of the piston intermediate container; the gas filtration and purification component is used to purify and filter impurity gases unrelated to the experiment; the one-way valve is used to control the gas in the gas pressurizing component to flow into the piston intermediate container in only one direction.

7. The apparatus as claimed in claim 1, characterized in that, The back pressure component is used to control the outflow of high-pressure gas from the outlet of the high-temperature and high-pressure experimental model container.

8. An experimental method for enhancing oil recovery and geological storage of high-temperature, high-pressure carbonate gas reservoirs by CO2 injection, characterized in that, The experimental method involves using any of the experimental apparatuses described herein and includes the following steps: Step 1: Clean the high-temperature and high-pressure piston intermediate container, high-temperature and high-pressure corrosion-resistant piston gas tank, high-temperature and high-pressure sealed container and connected pipelines with petroleum ether and dry them; connect the device and introduce high-purity nitrogen gas at a certain pressure. After the monitored pressure stabilizes, complete the device airtightness test. Step two: Design, fabricate, and clean the fractured-vuggy carbonate gas reservoir storage space. Vacuum the entire apparatus, set the experimental temperature in the constant temperature chamber, and ensure all components within the chamber stabilize. Open the valve at the top of the model and inject formation water from the bottom using a constant-pressure, constant-speed pump. Once continuous water is produced from the outlet without air bubbles, the difference between the cumulative volume of water injected by the pump and the volume of liquid collected at the outlet is recorded as the pore volume Vpore. Gas from the reservoir is injected into a high-temperature, high-pressure sealed container from the opposite direction of the water injection port. The volume of produced water is measured and considered as the initial gas-bearing volume of the reservoir, Vgas1, and the initial gas saturation of the reservoir is obtained. Step 3: Using a gas pressurization device, CO2 is pumped into the intermediate container of the high-temperature, high-pressure piston. After the pressure stabilizes, a constant-speed, constant-pressure pump is turned on to inject CO2 from the intermediate container into the high-temperature, high-pressure experimental model at a certain speed. The outlet of the high-temperature, high-pressure model is then opened, and the extracted gas is measured using a gas metering device. The cumulative volume of natural gas extracted is recorded as V. 气2 The cumulative volume of CO2 extracted is denoted as V. 二氧化碳1 ; Step four: Record the experimental data changes using a gas flow meter and a gas chromatograph at intervals of 0.5-10 minutes. When the CO2 content at the collection end reaches 90%, the experiment is considered complete, and CO2 displacement is stopped. The cumulative injection volume during the entire displacement process using a constant-speed, constant-pressure pump is considered the CO2 injection volume under experimental conditions and is denoted as V. 二氧化碳2 .

9. The method as described in claim 8, characterized in that, The calculation steps for determining CO2-enhanced carbonate gas reservoirs are as follows: Determine the volume V of the carbonate reservoir; measure the volume of produced formation water, V pore ;V represents the initial gas-bearing volume of a fractured-vuggy carbonate gas reservoir under a certain pressure condition. 气1 ; Metered cumulative injected gas volume V 二氧化碳2 The calculation for CO2 enhancing the recovery rate of natural gas from carbonate rocks is as follows: RF = V 气2 / V 气1 × 100% Equation (1) The CO2 retention rate of carbonate natural gas reservoirs is calculated as follows: GS = V 二氧化碳1 / V 二氧化碳2 × 100% Equation (2) 10. The method as described in claim 9, characterized in that, The target gas includes one or more of nitrogen-C1-C4 gaseous hydrocarbons; the carbonate gas reservoir storage space includes one or more of fracture-cavity structures, cavern structures, and fracture-cavity structures.

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