Nuclear-magnetic-resonance-based method and system for characterizing degree of miscibility of co 2 flooding

Abstract

The present invention belongs to the technical field of oil and gas exploration and development. Disclosed are a nuclear-magnetic-resonance-based method and system for characterizing the degree of miscibility of CO2 flooding. The method comprises: on the basis of a slim tube method, testing the minimum miscible pressure of crude oil of a target oil reservoir and CO2 (S101); on the basis of the minimum miscible pressure, conducting CO2 oil displacement experiments using cylindrical cores, collecting, in real time, two-dimensional weighted nuclear magnetic resonance images and multi-component T2 spectra of a fluid in the cores varying over time and space, synchronously collecting an outlet-end fluid, and conducting a chromatographic test to obtain chromatographic test data (S102); and on the basis of the two-dimensional weighted nuclear magnetic resonance images, the multi-component T2 spectra and the chromatographic test data, performing dynamically-changing qualitative and quantitative characterization on the degree of miscibility, so as to obtain qualitative and quantitative characterization results of the degree of miscibility of CO2 and the crude oil (S103).

Description

Method and system for characterizing CO2 flooding miscibility degree based on nuclear magnetic resonance

[0001] Related Applications

[0002] This application claims priority to the Chinese patent application No. 202410612612.X filed on May 16, 2024, and incorporates by reference the entire disclosure of the above patent application as part of this application. TECHNICAL FIELD

[0003] The present application relates to the technical field of oil and gas exploration and development, and in particular to a method and system for characterizing CO2 flooding miscibility degree based on nuclear magnetic resonance. BACKGROUND

[0004] This section is intended to provide background or context to the embodiments of the application recited in the claims. The description herein does not constitute admission that the prior publication is prior art to the present application.

[0005] In the scene of oil and gas exploration and development, CO2 flooding enhanced oil recovery technology as an effective method is increasingly valued, which has been field tested in multiple oilfields and has been applied on a large scale, with good application prospects. According to whether CO2 and formation crude oil can reach miscibility under formation conditions, CO2 flooding technology is divided into miscible flooding and immiscible flooding.

[0006] Compared with immiscible flooding, CO2 and formation crude oil can obtain higher recovery in miscible state, and whether CO2 and formation crude oil can be miscible is a key condition for reservoir screening. However, there is no good test method for judging the miscibility degree, and it is also impossible to realize qualitative and quantitative analysis at the same time. The slim tube method uses the relative size of the average formation pressure value and the MMP (Minimum Miscible Pressure) to reflect the miscibility degree of CO2 in the formation. However, due to the changes in pressure between injection and production wells in different periods during CO2 flooding process, part of the pressure in the formation is higher than the minimum miscible pressure, and part of the pressure is lower than the minimum miscible pressure, and the miscible region is dynamically changing during CO2 flooding process, so it is too general and simplified to judge the CO2 miscibility state by using the average formation pressure. In addition, the miscibility degree is qualitatively judged by observing the miscibility phenomenon in the high-pressure window, i.e. whether there is an obvious interface between oil and gas. This method indirectly judges the miscible state of fluid in porous media by the phase change of outlet fluid, which has too great limitations and can only be used for theoretical research of miscible gas flooding. The bubble rising instrument method can only qualitatively analyze the miscible state of oil and gas, and has large error, and cannot describe the quantitative relationship of the miscibility degree of oil and gas.

[0007] In recent years, nuclear magnetic resonance technology (NMR) has been widely used in core analysis, and plays an important role in oil and gas exploration and development. Some scholars have fitted the signal intensity change of nuclear magnetic resonance imaging results to obtain the minimum miscibility pressure; some scholars have combined nuclear magnetic resonance imaging and CT scanning imaging technology to realize the rapid measurement of the minimum miscibility pressure; in summary, almost all of them are through the measurement and analysis of the minimum miscibility pressure by nuclear magnetic resonance technology, and there are few reports on the qualitative and quantitative research on the space-time variation law of the miscibility degree in the process of CO2 flooding in the core by using nuclear magnetic resonance technology.

[0008] At present, the experimental methods for determining the miscibility degree of oil and gas mainly include fine tube experiment method, interfacial tension disappearance method, steam density method and rising bubble instrument method. However, these methods are indirect to judge the miscible state of oil and gas in porous media, and the difference is large, which cannot truly reflect the miscibility degree of CO2 and crude oil in the formation in the reservoir, and can only be qualitative but not quantitative. In addition, when using nuclear magnetic resonance imaging and CT scanning imaging method to analyze the miscibility degree of oil and gas, only the overall miscibility state of the fluid in the porous medium can be qualitatively analyzed, and the space-time variation law of the fluid in the porous medium cannot be qualitatively and quantitatively described.

[0009] In summary, the existing technology has the following defects: 1. In the existing technology about the dynamic variation characterization of the miscibility degree, only qualitative analysis of the miscibility degree can be carried out, and quantitative analysis cannot be carried out. 2. In-situ real-time monitoring of the miscibility state of the fluid in the core under the real formation temperature and pressure conditions cannot be realized. 3. The traditional test method of the miscibility degree has the problems of less measurement data, large sample consumption, long test time, complex operation, low repeatability and low on-site applicability of the data results.

[0010] Therefore, there is an urgent need for a technical solution which can overcome the above-mentioned defects, can quantitatively and qualitatively analyze the miscibility degree, improve the test efficiency, reduce the test cost, and simplify the test method. SUMMARY

[0011] To solve the problems in the prior art, the application provides a method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance. The nuclear magnetic resonance-mud model combined device independently designed by the application is used to simulate the CO2 miscible flooding process of crude oil, CO2 and real carbonate rock cores under the high temperature and high pressure environment of the actual formation, the qualitative judgment and quantitative calculation of the change of the miscibility degree with time and space in the CO2 miscible flooding process are performed by the technical method combining the nuclear magnetic resonance weighted imaging and the layered T2 spectrum, so as to solve the problem that the miscibility degree in the core internal CO2 displacement process is difficult to judge, provide a new idea for the miscibility degree research in the CO2 miscible flooding process, provide a method and basis for further understanding of the CO2 flooding development dynamic and law, provide guidance for the later injection-production parameter optimization, increase the field applicability, and then improve the CO2 oil displacement efficiency.

[0012] In a first aspect of the embodiments of the application, a method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance is provided, which comprises:

[0013] According to the minimum miscibility pressure of the target oil reservoir crude oil and CO2 tested by the tubular method;

[0014] According to the minimum miscibility pressure, a columnar core CO2 oil displacement experiment is performed, and the two-dimensional nuclear magnetic resonance weighted imaging and the layered T2 spectrum of the fluid in the core changing with time and space are collected in real time; the fluid at the outlet end is synchronously collected, and a chromatographic test is performed to obtain chromatographic test data;

[0015] According to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum and the chromatographic test data, the dynamic change of the miscibility degree is qualitatively and quantitatively characterized, and the qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil are obtained.

[0016] In a second aspect of the embodiments of the application, a system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance is provided, which comprises:

[0017] A minimum miscibility pressure analysis device is used to test the minimum miscibility pressure of the target oil reservoir crude oil and CO2 according to the tubular method;

[0018] A nuclear magnetic resonance-mud model combined device is used to perform a columnar core CO2 oil displacement experiment according to the minimum miscibility pressure, to collect the two-dimensional nuclear magnetic resonance weighted imaging and the layered T2 spectrum of the fluid in the core changing with time and space in real time; the fluid at the outlet end is synchronously collected, and a chromatographic test is performed to obtain chromatographic test data; the dynamic change of the miscibility degree is qualitatively and quantitatively characterized according to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum and the chromatographic test data, and the qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil are obtained.

[0019] In a third aspect of the embodiments of the present application, a computer device is provided, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance when executing the computer program.

[0020] In a fourth aspect of the embodiments of the present application, a computer readable storage medium is provided, which stores a computer program, and the computer program implements the method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance when executed by a processor.

[0021] In a fifth aspect of the embodiments of the present application, a computer program product is provided, which comprises a computer program, and the computer program implements the method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance when executed by a processor.

[0022] The method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance provided in the present application can realize real-time online monitoring of the spatial and temporal variation of fluid in the core during CO2 flooding by using a nuclear magnetic-reservoir model combined device, and can realize intelligent data processing and analysis while quickly and accurately completing experimental testing, thereby greatly improving the experimental efficiency. When the miscibility degree of CO2 flooding is characterized based on nuclear magnetic resonance, the minimum miscibility pressure of the target oil reservoir crude oil and CO2 is tested by using a capillary tube method, a columnar core CO2 flooding experiment is carried out by using the nuclear magnetic-reservoir model combined device, the two-dimensional nuclear magnetic resonance imaging graph and the layered T2 spectrum of the fluid in the core are collected in real time and online, a dynamic variation qualitative and quantitative characterization method of the miscibility degree is established, the experimental cost is low, the time consumption is short, and the miscibility degree of oil and gas during CO2 flooding can be accurately and quickly characterized. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] FIG. 1 is a flowchart of the method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance according to an embodiment of the present application.

[0025] FIG. 2 is a schematic diagram of the architecture of the nuclear magnetic-reservoir model combined device according to an embodiment of the present application.

[0026] FIG. 3 is a schematic diagram of the architecture deployment relationship of the nuclear magnetic-reservoir model combined device according to a specific embodiment of the present application.

[0027] Figure 4 is a flowchart of testing the minimum miscibility pressure of target oil reservoir crude oil and CO2 according to a thin tube method, according to an embodiment of the present application.

[0028] Figure 5 is a flowchart of acquiring a two-dimensional nuclear magnetic resonance weighted image and a layered T2 spectrum of a fluid in a core at a real time according to an embodiment of the present application.

[0029] Figure 6 is a flowchart of chromatographic testing, according to an embodiment of the present application.

[0030] Figure 7 is a flowchart of qualitative analysis, according to an embodiment of the present application.

[0031] Figure 8 is a flowchart of quantitative analysis, according to an embodiment of the present application.

[0032] Figure 9A is a proton density image of an initial saturated oil stage, according to an embodiment of the present application.

[0033] Figure 9B is a T1 weighted image of an initial saturated oil stage, according to an embodiment of the present application.

[0034] Figure 9C is a T2 weighted image of an initial saturated oil stage, according to an embodiment of the present application.

[0035] Figure 10A is a proton density image of a stage with an injection pressure of 10 MPa, according to an embodiment of the present application.

[0036] Figure 10B is a T1 weighted image of a stage with an injection pressure of 10 MPa, according to an embodiment of the present application.

[0037] Figure 10C is a T2 weighted image of a stage with an injection pressure of 10 MPa, according to an embodiment of the present application.

[0038] Figure 11A is a proton density image of a stage with an injection pressure of 16 MPa, according to an embodiment of the present application.

[0039] Figure 11B is a T1 weighted image of a stage with an injection pressure of 16 MPa, according to an embodiment of the present application.

[0040] Figure 11C is a T2 weighted image of a stage with an injection pressure of 16 MPa, according to an embodiment of the present application.

[0041] Figure 12 is a schematic diagram of quantitative calculation of the miscibility degree of CO2 and crude oil, according to an embodiment of the present application.

[0042] Figure 13 is a schematic diagram of a system architecture for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance, according to an embodiment of the present application.

[0043] Figure 14 is a schematic diagram of a computer device structure, according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] The principles and spirits of the present application will be described below with reference to several exemplary embodiments. It should be understood that the embodiments are given only so that those skilled in the art can better understand and implement the present application, and do not limit the scope of the present application in any way. On the contrary, the embodiments are provided so that the present disclosure is more thorough and complete, and the scope of the present disclosure is fully conveyed to those skilled in the art.

[0045] Those skilled in the art know that the embodiments of the present application can be implemented as a system, device, apparatus, method or computer program product. Therefore, the present disclosure can be embodied in the form of a complete hardware, complete software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

[0046] According to the embodiments of the present application, a method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance are proposed, which relates to the technical field of oil and gas exploration and development. In the prior art for dynamic characterization of miscibility degree, qualitative analysis is usually performed, and even if quantitative analysis exists, the quantitative characterization is indirectly analyzed through the changes of pressure, oil displacement efficiency, and output gas composition, which cannot achieve the visualization of the spatial and temporal changes of the miscibility degree of CO2 flooding in the actual formation temperature and pressure environment. The present application improves the accuracy of the characterization of the miscibility degree of CO2 and crude oil, and makes the results more consistent with the actual formation miscibility change.

[0047] The principles and spirits of the present application will be described below with reference to several exemplary embodiments. It should be understood that the embodiments are given only so that those skilled in the art can better understand and implement the present application, and do not limit the scope of the present application in any way. On the contrary, the embodiments are provided so that the present disclosure is more thorough and complete, and the scope of the present disclosure is fully conveyed to those skilled in the art.

[0048] Figure 1 is a flowchart of a method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance according to an embodiment of the present application. As shown in Figure 1, the method comprises:

[0049] S101, determining the minimum miscibility pressure of the target oil reservoir crude oil and CO2 according to the slim tube test;

[0050] S102, performing a columnar core CO2 flooding experiment according to the minimum miscibility pressure, and collecting the two-dimensional nuclear magnetic resonance weighted imaging and the layered T2 spectrum of the fluid in the core in real time;

[0051] Specifically, the nuclear magnetic resonance-physical model combined device can be used to perform the columnar core CO2 flooding experiment.

[0052] S103, qualitatively and quantitatively characterizing the dynamic changes of the miscibility degree according to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum and the chromatographic test data, and obtaining the qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil.

[0053] The whole scheme of the application has low cost and short time consumption, and can accurately and quickly characterize the oil-gas miscibility degree in the CO2 oil displacement process.

[0054] Specifically, referring to FIG. 2, it is a schematic diagram of the architecture of the nuclear magnetic-fluid model combined device according to an embodiment of the application. As shown in FIG. 2, the nuclear magnetic-fluid model combined device comprises a nuclear magnetic resonance test module 210, a rock fluid displacement module 220, an outlet end fluid collection and detection module 230, and a computer control and data processing module 240.

[0055] The nuclear magnetic resonance test module 210 is configured to perform nuclear magnetic resonance test to obtain two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectrum.

[0056] The rock fluid displacement module 220 comprises a core holder compatible with nuclear magnetic resonance test, and is configured to perform rock fluid displacement experiment.

[0057] The outlet end fluid collection and detection module 230 is configured to collect outlet end fluid and perform chromatographic test to obtain chromatographic test data.

[0058] The computer control and data processing module 240 is configured to collect two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectrum and chromatographic test data from the nuclear magnetic resonance test module 210 and the outlet end fluid collection and detection module 230, and perform dynamic change qualitative and quantitative characterization of miscibility degree to obtain qualitative and quantitative characterization results of CO2 and crude oil miscibility degree.

[0059] The application integrates the nuclear magnetic resonance test system, the rock fluid displacement system and the outlet end fluid collection and analysis system into a whole through computer control, and realizes real-time online measurement of nuclear magnetic resonance weighted imaging and layered T2 spectrum to obtain rich fluid change information in the CO2 oil displacement process in the core.

[0060] Referring to FIG. 3, it is a schematic diagram of the architecture deployment relationship of the nuclear magnetic-fluid model combined device according to a specific embodiment of the application. The following will describe each module in the nuclear magnetic-fluid model combined device (low-field nuclear magnetic-high temperature and high pressure displacement combined device) in detail in combination with FIG. 3.

[0061] For the nuclear magnetic resonance test module:

[0062] The nuclear magnetic resonance test module comprises a permanent magnet 24, a gradient coil 25, a radio frequency coil 26, a preamplifier 27, a spectrometer 28, a radio frequency amplifier 29, a gradient amplifier 30, a shielded room 32 and an equipment room 33.

[0063] The permanent magnet 24, the gradient coil 25, the radio frequency coil 26 and the preamplifier 27 are arranged in the shielded room 32; the equipment room 33 comprises the spectrometer 28, the radio frequency amplifier 29 and the gradient amplifier 30.

[0064] The permanent magnet 24 is compatible with multiple online displacement scanning modes; the signal generated by the magnetic resonance effect of the fluid in the rock is excited by applying a certain radio frequency signal through the spectrometer 28, amplified through the radio frequency amplifier 29, and applied to the radio frequency coil 26 to excite the signal generated by the magnetic resonance effect of the fluid in the rock, and then amplified through the preamplifier 27 and collected by the spectrometer 28;

[0065] When performing the nuclear magnetic resonance imaging scan and the layered T2 spectrum scan, a certain gradient strength is applied to the fluid to capture the signal, a certain gradient signal is applied through the spectrometer 28, the signal is amplified through the gradient amplifier 30 and applied to the gradient coil 25 to excite the signal generated by the magnetic resonance effect of the fluid in the rock, and then amplified through the preamplifier 27 and collected by the spectrometer 28; and

[0066] The shielding room 32 is used to shield the interference source by reflecting and absorbing electromagnetic waves.

[0067] Specifically, the permanent magnet 24, the gradient coil 25, the radio frequency coil 26, the preamplifier 27, the spectrometer 28, the radio frequency amplifier 29, the gradient amplifier 30, the shielding room 32, and the equipment room 33 are arranged according to the experimental needs. The magnet designed by the applicant is convenient for pipeline connection, solves the problem of placing the high-temperature and high-pressure core holder, has small magnet temperature drift, and is compatible with X, Y, and Z three online displacement scanning modes. The signal generated by the magnetic resonance effect of the fluid in the rock is excited by applying a certain radio frequency signal through the spectrometer 28, amplified through the radio frequency amplifier 29, and applied to the radio frequency coil 26 to excite the signal generated by the magnetic resonance effect of the fluid in the rock, and then amplified through the preamplifier 27 and collected by the spectrometer 28. When performing the nuclear magnetic resonance imaging scan and the layered T2 spectrum scan, a certain gradient strength needs to be applied to the fluid to capture the signal. This process is performed by applying a certain gradient signal through the spectrometer 28, amplifying the signal through the gradient amplifier 30, and applying it to the gradient coil 25 to excite the signal generated by the magnetic resonance effect of the fluid in the rock, and then amplifying the signal through the preamplifier 27 and collecting it by the spectrometer 28.

[0068] There are various frequency bands of electromagnetic waves in nature. During the magnetic resonance high-temperature and high-pressure online displacement experiment, the peripheral injection system, the ring pressure system, the constant temperature system, etc. can also bring electromagnetic wave interference, resulting in a decrease in the signal-to-noise ratio or the appearance of an error signal during core testing, causing testing errors. To solve this problem, the system is equipped with a transparent and reusable nuclear magnetic resonance shielding room 32. The magnetic resonance shielding room is composed of a metal shielding body, which shields the influence of the interference source by reflecting and absorbing electromagnetic waves. At the same time, all cables and displacement pipelines are connected through high-power filters and waveguides, which can greatly improve the signal-to-noise ratio and measurement accuracy of core analysis, and can protect the safety of experimental personnel during high-temperature and high-pressure displacement experiments.

[0069] For the rock fluid displacement module:

[0070] The rock fluid displacement module comprises: a confining pressure pump 1, a displacement pump 2, a first non-magnetic switch 4, a second non-magnetic switch 5, a third non-magnetic switch 6, a fourth non-magnetic switch 7, a fifth non-magnetic switch 8, a sixth non-magnetic switch 9, a seventh non-magnetic switch 10, a first six-way valve 14, a second six-way valve 15, a first piston container 16, a second piston container 17, a third piston container 18, a first pressure sensor 19, a second pressure sensor 20, a temperature sensor 22, a temperature control device 23, and a magnetic resonance compatible core holder 31.

[0071] The required injection fluid for the core in the magnetic resonance compatible core holder 31 is provided by the second piston container 17 and the third piston container 18, and the displacement pump 2 is connected to the first six-way valve 14 and the third non-magnetic switch 6 in sequence, so that the fluid in the second piston container 17 flows into the core in the magnetic resonance compatible core holder 31 through the fourth non-magnetic switch 7, the second six-way valve 15, and the fifth non-magnetic switch 8 in sequence.

[0072] The displacement pump 2 is connected to the first six-way valve 14 and the sixth non-magnetic switch 9 in sequence, so that the fluid in the third piston container 18 flows into the core in the magnetic resonance compatible core holder 31 through the seventh non-magnetic switch 10, the second six-way valve 15, and the fifth non-magnetic switch 8 in sequence.

[0073] The required fluid in the confining pressure cavity of the magnetic resonance compatible core holder 31 is provided by the first piston container 16, and the displacement pump 1 is connected to the first non-magnetic switch 4, so that the fluid in the first piston container 16 flows into the core in the confining pressure cavity of the magnetic resonance compatible core holder 31 through the second non-magnetic switch 5.

[0074] The monitoring of the confining pressure is feedback through the connection of the second pressure sensor 20 and the inlet end of the confining pressure cavity of the magnetic resonance compatible core holder 31.

[0075] The monitoring of the injection pressure of the fluid in the core is feedback through the connection of the first pressure sensor 19 and the inlet end of the magnetic resonance compatible core holder 31.

[0076] The heating of the magnetic resonance compatible core holder 31 is temperature-adjusted by the temperature control device 23, and the temperature is detected by the temperature sensor 22.

[0077] Specifically, according to the experimental needs, the loop pressure pump 1, the displacement pump 2, the first non-magnetic switch 4, the second non-magnetic switch 5, the third non-magnetic switch 6, the fourth non-magnetic switch 7, the fifth non-magnetic switch 8, the sixth non-magnetic switch 9, the seventh non-magnetic switch 10, the first six-way 14, the second six-way 15, the first piston container 16, the second piston container 17, the third piston container 18, the first pressure sensor 19, the second pressure sensor 20, the temperature sensor 22, the temperature control device 23 and the magnetic resonance compatible core holder 31 are arranged. The loop pressure pump 1 adopts a high-precision multi-stage plunger displacement pump (Teledyne Isco 100-DX), the loop pressure fluid adopts fluorine oil injection, and the fluorine oil is reusable. After the experiment is completed, the fluorine oil is recovered to avoid affecting the nuclear magnetic resonance results. The displacement pump 2 adopts a high-pressure high-precision plunger pump (Teledyne Isco 260D), which can be set to a constant injection flow or a constant injection pressure displacement mode. The pump flow is 0.01-50.00 mL / min (pressure less than 70 MPa), and the flow rate accuracy is ±0.3% (maximum sealing leakage is 0.25 μL / min). The first pressure sensor 19 and the second pressure sensor 20 can adopt a DXD high-precision digital pressure sensor. Under the condition of 0℃-100℃, the test accuracy is ±0.04%.

[0078] The required injection fluid in the magnetic resonance compatible core holder 31 is provided by the piston container 17 and the piston container 18. The displacement pump 2 is connected with the first six-way 14 and the third non-magnetic switch 6 in sequence, and the fluid in the second piston container 17 flows into the magnetic resonance compatible core holder 31 in sequence through the fourth non-magnetic switch 7, the second six-way 15 and the fifth non-magnetic switch 8. The displacement pump 2 is connected with the first six-way 14 and the sixth non-magnetic switch 9 in sequence, and the fluid in the third piston container 18 flows into the magnetic resonance compatible core holder 31 in sequence through the seventh non-magnetic switch 10, the second six-way 15 and the fifth non-magnetic switch 8. The required fluid in the loop pressure cavity of the magnetic resonance compatible core holder 31 is provided by the first piston container 16. The displacement pump 1 is connected with the first non-magnetic switch 4, and the fluid in the first piston container 16 flows into the loop pressure cavity of the magnetic resonance compatible core holder 31 through the second non-magnetic switch 5. The monitoring of the loop pressure is feedback through the connection of the second pressure sensor 20 and the inlet end of the loop pressure cavity of the magnetic resonance compatible core holder 31. The monitoring of the injection pressure of the fluid in the core is feedback through the connection of the first pressure sensor 19 and the inlet end of the magnetic resonance compatible core holder 31. The heating of the magnetic resonance compatible core holder 31 is realized by the temperature control device 23, and the temperature is detected by the temperature sensor 22.

[0079] The magnetic resonance compatible core holder 31 is a self-designed non-magnetic core holder which does not affect the magnetic field distribution of the magnet. The core holder is a titanium alloy core holder with a coil built-in, and the coil is built-in in the annulus of the core holder. Compared with the external coil commonly used at home and abroad, the signal-to-noise ratio SNR (Signal-to-noise Ratio) of the core holder is improved by more than 3 times, while the magnetic compatibility and high temperature and pressure are considered, and the maximum temperature and pressure that can be withstood are 150 DEG C and 70 MPa respectively.

[0080] For the outlet end fluid collection and detection module:

[0081] The outlet end fluid collection and detection module comprises a back pressure pump 3, an eighth non-magnetic switch 11, a ninth non-magnetic switch 12, a tenth non-magnetic switch 13, a third pressure sensor 21, a back pressure valve 41, a gas-liquid separator 42 and an oil / gas chromatograph 43;

[0082] The back pressure pump 3 is connected with the ninth non-magnetic switch 12, and the fluid is input to the back pressure valve 41; the monitoring of back pressure is feedbacked after the fluid flowing through the eighth non-magnetic switch 11 flows into the back pressure valve 41 through the third pressure sensor 21;

[0083] The collection and measurement of the outlet end fluid are carried out by gas-liquid separation, collection and measurement through the gas-liquid separator 42; the gas-liquid separator 42 is a container with a visual window and a piston, which is used to measure the volume of crude oil, gas phase and water phase; and

[0084] The detection of fluid chromatography detects the gas-liquid collected by the gas-liquid separator 42 through the tenth non-magnetic switch 13 into the oil / gas chromatograph 43, which simultaneously considers oil phase component analysis and gas component analysis.

[0085] In the actual application scene, the back pressure pump 3, the eighth non-magnetic switch 11, the ninth non-magnetic switch 12, the tenth non-magnetic switch 13, the third pressure sensor 21, the back pressure valve 41, the gas-liquid separator 42 and the oil / gas chromatograph 43 are deployed according to the experimental needs. The back pressure valve 41 adopts the BP-100 air spring back pressure valve produced by a certain core company.

[0086] The back pressure pump 3 is connected with the ninth non-magnetic switch 12, and the fluid required by the back pressure valve 41 is input through the back pressure pump 3 and the ninth non-magnetic switch 12; the monitoring of back pressure is feedbacked after the fluid flowing through the eighth non-magnetic switch 11 flows into the back pressure valve 41 through the pressure sensor 21;

[0087] The collection and measurement of the outlet end fluid are carried out by gas-liquid separation, collection and measurement through the gas-liquid separator 42; the gas-liquid separator 42 is a container with a visual window and a piston, which is used to measure the volume of crude oil, gas phase and water phase, the maximum bearing pressure is 30 MPa, and the accuracy is 0.01 mL;

[0088] The fluid chromatography detection involves the gas and liquid phases collected by the gas-liquid separator 42 flowing into the oil / gas chromatograph 43 through the tenth non-magnetic switch 13 for detection. The chromatograph simultaneously performs oil phase component analysis and gas component analysis, greatly improving experimental efficiency.

[0089] Computer control and data processing module:

[0090] The computer control and data processing module includes: an input unit 34, a storage unit 35, a display 36, a central processing unit 37, a communication unit 38, a power supply 39, and electronic devices 40;

[0091] Electronic device 40 includes an input unit 34, a storage unit 35, a display 36, a central processing unit 37, a communication unit 38, and a power supply 39; the communication unit 38 is used for information transmission between devices; the collected data is transmitted to the central processing unit 37 through the input unit 34, the central processing unit 37 automatically processes the data and analyzes the results based on deep learning and AI (Artificial Intelligence) large models, and stores them in the storage unit 35 and displays them on the display 36; the collected data includes at least: nuclear magnetic resonance test data and chromatographic test data.

[0092] This application effectively combines nuclear magnetic resonance (NMR) technology with CO2 flooding physical simulation experiments, proposing a combined approach of low-field NMR and high-temperature, high-pressure displacement device to conduct CO2 flooding experiments. The core samples used in the experiment are... Columnar core samples were used for CO2 flooding, with high-purity CO2 used for displacement. Real-time online monitoring of fluid changes within the core was employed to qualitatively and quantitatively characterize the degree of miscibility. The advantage of this method lies in utilizing nuclear magnetic resonance weighted imaging and layered T2 spectroscopy to obtain the spatiotemporal variation of oil-gas miscibility during CO2 flooding, which is more consistent with actual conditions than other methods. The overall experimental scheme in this application is simple to operate, low in cost, short in time, highly repeatable, and provides intuitive data processing, enabling accurate and rapid qualitative and quantitative characterization of oil-gas miscibility.

[0093] To provide a clearer explanation of the above method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance, each step will be described in detail in conjunction with the above system.

[0094] In one embodiment, for S101, the minimum miscibility pressure of crude oil and CO2 in the target reservoir is tested using the capillary tube method. Referring to Figure 4, the specific process is as follows:

[0095] S401, Select crude oil from the target reservoir formation, and simulate reservoir temperature based on the crude oil from the target reservoir formation.

[0096] S402, based on the simulated reservoir temperature, a curve of different pressures and oil displacement efficiency is established based on the slim tube method to obtain the minimum miscibility pressure of the target reservoir crude oil and CO2.

[0097] In an actual application scenario, the specific process of testing the minimum miscibility pressure based on the slim tube method is as follows: selecting target reservoir formation crude oil, simulating reservoir temperature, establishing a curve of different pressures and oil displacement efficiency based on the slim tube method, determining the minimum miscibility pressure of the target reservoir crude oil and carbon dioxide, and the operation standard of the slim tube method can be determined according to the actual situation (for example, SY / T 6573-2016 "Minimum miscibility pressure experimental determination method-slim tube method"). The minimum miscibility pressure of the crude oil and CO2 is 15.5 MPa.

[0098] In an embodiment, for S102, according to the minimum miscibility pressure, a CO2 oil displacement experiment of a columnar core is carried out, and a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum of the fluid in the core are collected in real time. The fluid at the outlet end is collected synchronously, and a chromatographic test is carried out to obtain chromatographic test data.

[0099] Referring to FIG. 5, according to the minimum miscibility pressure, a CO2 oil displacement experiment of a columnar core is carried out, and a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum of the fluid in the core are collected in real time. The specific process is as follows:

[0100] S501, selecting a formation outcrop of a target reservoir coring well to drill and cut a core, washing and drying the core, and measuring the analysis parameters of the core.

[0101] Specifically, the formation outcrop of the target reservoir coring well is selected to drill and cut a core, which can be washed and dried according to the actual situation. The length L, diameter d, porosity and permeability K of the core are measured.

[0102] S502, using petroleum ether to clean the pipeline and blow dry, placing the high-pressure CO2 gas used for the experiment in the third piston container 18, placing the crude oil in the second piston container 17, placing the fluorine oil in the first piston container 16, and warming to the experimental set temperature.

[0103] S503, loading the sampling core into the magnetic resonance compatible core holder 31 and placing it in the shielding room 32.

[0104] S504, opening the ring pressure pump 1, the first non-magnetic switch 4, and the second non-magnetic switch 5 in turn, using fluorine oil to discharge the air in the ring cavity of the magnetic resonance compatible core holder 31, then closing the ring pressure pump 1, and increasing the ring pressure to the set value.

[0105] S505, open the temperature control system 23, and raise the temperature of the magnetic resonance compatible core holder 31 to the formation temperature.

[0106] S506, open the displacement pump 2, the second piston container 17, the fourth non-magnetic switch 7, the second six-way valve 15, and the fifth non-magnetic switch 8 in sequence; then open the back pressure pump 3, the ninth non-magnetic switch 12, the back pressure valve 41, and the eighth non-magnetic switch 11 in sequence to control the back pressure, and establish a constant pressure difference to inject the crude oil into the core until the pressure difference between the two ends of the core tends to be stable.

[0107] S507, open the displacement pump 3, the first six-way valve 14, the sixth non-magnetic switch 9, the seventh non-magnetic switch 10, the second six-way valve 15, and the fifth non-magnetic switch 8 in sequence to inject the CO2 into the core, and use the CO2 to displace the crude oil, and pressurize to a first set pressure and a second set pressure, respectively, and the second set pressure is 0.5 MPa higher than the minimum miscibility pressure, and test the two-dimensional nuclear magnetic resonance imaging and the layered T2 spectrum of the initial saturated oil state and the fluid in the holder after each pressurization, respectively.

[0108] Specifically, the first set pressure is 10 MPa, and the second set pressure is 16 MPa (0.5 MPa higher than the minimum miscibility pressure).

[0109] Referring to FIG. 6, the outlet end fluid is synchronously collected, and a chromatographic test is performed to obtain chromatographic test data, and the specific process is as follows:

[0110] S601, when the gas continuously flows out of the gas-liquid separator 42, the test result data of the oil / gas chromatograph 43 is sent to the central processing unit 37 through the communication unit 38 and the input unit 34.

[0111] S602, after being processed and analyzed by the central processing unit 37, the data is stored in the storage unit 35 and displayed through the display 36, and when the change rate of the components in the oil and gas chromatograms displayed is less than the set range, the eighth non-magnetic switch 11 is closed, and the experiment is stopped.

[0112] In an embodiment, for S103, qualitative and quantitative characterization of the dynamic change of the miscibility degree is performed according to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum, and the chromatographic test data, and qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil are obtained.

[0113] Referring to FIG. 7, the specific process of qualitative analysis is as follows:

[0114] S701, based on different weighted imaging techniques, the layered two-dimensional imaging scanning is performed on the core at different positions along the axial direction, and the non-miscible region, the near-miscible region, and the miscible region are identified according to the viscosity difference between CO2 and crude oil during the experiment, and the change of fluid viscosity caused by the dissolution and extraction of CO2 in the crude oil.

[0115] S702, in combination with the result of analyzing the fluid component variation law of the produced fluid by chromatography, qualitatively judging the variation of the miscibility degree of oil and gas in the CO2 flooding process with time and space; wherein, according to the minimum miscibility pressure of CO2 and crude oil measured by the slim tube experiment, performing layered two-dimensional imaging scanning at different positions along the axial direction of the core in the initial saturated oil stage, the injection pressure being the first set pressure stage and the injection pressure being the second set pressure stage respectively, performing proton density imaging scanning and T1 weighted imaging scanning respectively in each stage, according to the set layer thickness and layer spacing, dividing the test core into multiple layers for imaging scanning, and obtaining the T2 weighted imaging scanning image by image subtraction method.

[0116] Referring to FIG. 8, the specific process of quantitative analysis is as follows:

[0117] S801, performing layered T2 spectrum scanning along the axial direction of the core, taking the layered T2 spectrum of the initial saturated oil stage as the benchmark, taking the shift law of the T2 spectrum of the corresponding layer position in each stage as the judgment standard of whether miscible, and taking the shift amount of the T2 spectrum of the corresponding layer position as the calculation standard of the miscibility degree.

[0118] S802, according to the judgment standard and the calculation standard, quantitatively calculating the miscibility degree of CO2 and crude oil by the shift law and the shift amount of the T2 spectrum of each layer along the axial direction in the layered T2 spectrum.

[0119] Specifically, the application processes two-dimensional nuclear magnetic resonance weighted imaging image, layered T2 spectrum data and chromatography test data, and performs dynamic variation qualitative and quantitative characterization of the miscibility degree.

[0120] According to the theoretical analysis combined with the nuclear magnetic image, the signal amplitude of the nuclear magnetic image can be represented as:

[0121] In the formula, S se is the signal amplitude;

[0122] N(H) is the proton density of H in the sample, which is a constant value for a certain sample;

[0123] TR is the repetition time of the sequence;

[0124] T1 is the longitudinal relaxation time;

[0125] T2 is the transverse relaxation time;

[0126] TE is the echo time.

[0127] According to the above formula, T1 and T2 have a very great influence on the signal; in addition to T1 and T2, the signal intensity S se is mainly affected by three factors, i.e. N(H), TR and TE.

[0128] From the above formula, T1 weighting is to increase the influence of T1 on signal S and reduce the influence of T2 on signal S.

[0129] Similarly, T2 weighting is to increase the influence of T2 relaxation on signal S and reduce the influence of T1 on signal S.

[0130] The proton density image tries to make signal S mainly determined by the proton density of H in the sample, and reduce the influence of T1 relaxation and T2 relaxation.

[0131] T1 weighted imaging, the gray scale (light and dark) of the image is mainly determined by the T1 relaxation speed of the sample, so it is necessary to reduce the influence of T2 on signal S as much as possible; in , only when TE is as small as possible, TE << T2 (<< means much smaller than), approaches 1; at the same time, in , only when TR is also small, the image difference caused by the difference of T1 can be reflected; therefore, for T1 weighted imaging, "short TR and short TE" should be used.

[0132] T2 weighted imaging, the gray scale (light and dark) of the image is mainly determined by the T2 relaxation speed of the sample, so it is necessary to reduce the influence of T1 on signal S as much as possible; in , only when TR >> T1 (>> means much greater than), the term approaches 1; and for , only when TE is large, the image difference caused by the difference of T2 can be reflected; therefore, for T2 weighted imaging, "long TR and long TE" should be used.

[0133] Proton density imaging, the gray scale (light and dark) of the image is mainly determined by the proton density of the sample; therefore, the second term and the third term in the formula should approach 1, at which time S Se = N(H), so that TR >> T1; so that TE << T2; therefore, for proton density weighted imaging, "long TR and short TE" should be used.

[0134] Qualitative analysis of the degree of miscibility:

[0135] Based on different weighted imaging techniques, by performing layered two-dimensional imaging scanning at different positions along the axial direction of the core, the non-miscible region, the near-miscible region and the miscible region are identified according to the viscosity difference between CO2 and crude oil during the experiment, as well as the changes in fluid viscosity caused by the dissolution and extraction of CO2 in crude oil.

[0136] Combined with the results of analyzing the variation of fluid components by chromatography of the produced fluid, the variation of the degree of oil-gas miscibility with space and time during the CO2 flooding process is qualitatively judged.

[0137] Specifically, the minimum miscibility pressure of CO2 and crude oil measured by the slim tube experiment is 15.7 MPa, and the core is subjected to layered two-dimensional imaging scanning at different positions along the axial direction at the initial saturated oil stage, the stage of 10 MPa injection pressure and the stage of 16 MPa injection pressure, respectively. Proton density imaging scanning and T1 weighted imaging scanning are performed at each stage, respectively. The test core is divided into 8 layers with a layer thickness of 5 mm and a layer spacing of 2 mm for imaging scanning. The T2 weighted imaging scanning image is obtained by using the inherent characteristics of the software through "image subtraction method".

[0138] Taking the layered two-dimensional weighted imaging image of the third layer core as an example, referring to FIGS. 9A, 9B and 9C, they are respectively the proton density imaging image, the T1 weighted imaging image and the T2 weighted imaging image of the initial saturated oil stage of the embodiment of the application.

[0139] Referring to FIGS. 10A, 10B and 10C, they are respectively the proton density imaging image, the T1 weighted imaging image and the T2 weighted imaging image of the stage of 10 MPa injection pressure of the embodiment of the application.

[0140] Referring to FIGS. 11A, 11B and 11C, they are respectively the proton density imaging image, the T1 weighted imaging image and the T2 weighted imaging image of the stage of 16 MPa injection pressure of the embodiment of the application.

[0141] Based on the above imaging images, the average gray value of each image is roughly calculated. The size of the gray value represents the amount of fluid content. The greater the gray value, the more the fluid content, and vice versa. Taking the gray value of the image at the initial saturated oil stage as a reference, the gray value of the proton density imaging image represents the oil content (including light components and heavy components) of the core at this layer. The ratio of the gray value of the T1 weighted imaging image (which represents the content of heavy components) to the gray value of the T2 weighted imaging image (which represents the content of light components) is about 1:1. At the stage of 10 MPa injection pressure, the gray value of the proton density imaging image decreases, but the ratio of the gray value of the T1 weighted imaging image to the gray value of the T2 weighted imaging image is still 1:1, indicating that at this stage, under the action of CO2 displacement, only the oil content of the core at this layer decreases, and the crude oil and CO2 do not have any effect, so the oil and gas do not have miscibility, and the miscibility degree is 0. At the stage of 16 MPa injection pressure, the gray value of the proton density imaging image continues to decrease, but the ratio of the gray value of the T1 weighted imaging image to the gray value of the T2 weighted imaging image is 2:1, indicating that at this stage, under the action of CO2 displacement, the oil content of the core at this layer further decreases, and the light components in the crude oil are extracted by CO2, resulting in an increase in the proportion of heavy components and a decrease in the proportion of light components. Therefore, the oil and gas are miscible. The greater the difference between the ratio of the two and the ratio at the initial saturated oil stage, the greater the miscibility degree.

[0142] Quantitative analysis of the miscibility degree:

[0143] In the quantitative analysis of the miscibility degree of CO2 and crude oil, the layered T2 spectrum scanning is performed along the axial direction of the core. The shift rule of the T2 spectrum of each stage corresponding to the layered T2 spectrum of the initial oil saturation stage is taken as the judgment standard of miscibility, and the shift amount of the T2 spectrum corresponding to the layered T2 spectrum is taken as the calculation standard of the miscibility degree.

[0144] Referring to FIG. 12, it is a schematic diagram of the quantitative calculation of the miscibility degree of CO2 and crude oil according to an embodiment of the present application. As shown in FIG. 12, in the miscibility process, if CO2 is dissolved into the oil phase, the viscosity of the crude oil is reduced, the fluidity is enhanced, the T2 relaxation time is lengthened, the T2 spectrum is shifted to the right, and the miscibility of CO2 and crude oil occurs; if CO2 extracts the light components of the crude oil, the heavy components of the remaining oil are highlighted, the viscosity of the crude oil is increased, the fluidity is deteriorated, the T2 relaxation time is shortened, the T2 spectrum is shifted to the left, and the miscibility of CO2 and crude oil occurs; when CO2 and crude oil are completely miscible, no dissolution and extraction occurs, the T2 relaxation time no longer changes, and the T2 spectrum no longer shifts. Since the viscosity changes, the T2 spectrum still shifts compared with the T2 spectrum of the initial oil saturation stage, and therefore the miscibility degree of CO2 and crude oil is quantitatively calculated by the shift rule and the shift amount of the T2 spectrum of each layer along the axial direction in the layered T2 spectrum.

[0145] It should be noted that although the operations of the method of the present application are described in a specific order in the above embodiments and the accompanying drawings, this does not require or imply that the operations must be performed in this specific order, or that all the shown operations must be performed to achieve the desired results. Additionally or alternatively, certain steps can be omitted, a plurality of steps can be combined into one step, and / or one step can be divided into a plurality of steps.

[0146] The method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance proposed in the present application can realize real-time online monitoring of the space-time variation of the fluid in the core during the CO2 flooding process by using a nuclear magnetic resonance-physical model combined device. The experimental test is completed quickly and accurately, and intelligent data processing and analysis are performed at the same time, which greatly improves the experimental efficiency. In the characterization of the miscibility degree of CO2 miscible flooding based on nuclear magnetic resonance, the minimum miscibility pressure of the target oil reservoir crude oil and CO2 is tested by the capillary tube method, the CO2 flooding experiment of the columnar core is carried out by using the nuclear magnetic resonance-physical model combined device, the two-dimensional nuclear magnetic resonance imaging and the layered T2 spectrum of the fluid in the core are collected in real time, the dynamic variation of the miscibility degree is qualitatively and quantitatively characterized, the experimental cost is low, the time consumption is short, and the miscibility degree of oil and gas in the CO2 flooding process can be accurately and quickly characterized.

[0147] In the prior art about the characterization of the dynamic change of the miscibility degree, almost all are qualitative analysis. Even if there is quantitative analysis, the quantitative characterization is indirect analysis through the changes of pressure, oil displacement efficiency, output gas composition, etc. It is impossible to achieve the visualization characterization of the CO2 flooding miscibility degree changing with space and time in the actual formation temperature and pressure environment. In the actual formation, due to the "pressure funnel" between injection and production wells, part of the formation pressure is higher than the minimum miscibility pressure, and part of the formation pressure is lower than the minimum miscibility pressure. The miscible region is dynamically changing in the CO2 flooding process. Therefore, it is necessary to qualitatively and quantitatively understand the change rule of the miscibility degree with space and time, and further analyze the influence of the miscibility degree on the development effect. The method and system for characterizing the CO2 flooding miscibility degree based on nuclear magnetic resonance provided in the present application solve the problem of qualitative and quantitative characterization of the dynamic change of the miscibility degree with space and time, provide support for understanding the relationship between the miscible range and the oil displacement effect, are closer to the actual formation, and the miscible flooding is not miscible in the whole formation. The non-miscible flooding also exists in part of the formation.

[0148] After introducing the method of the exemplary embodiments of the present application, next, with reference to FIG. 13, the system for characterizing the CO2 flooding miscibility degree based on nuclear magnetic resonance of the exemplary embodiments of the present application is introduced.

[0149] The implementation of the system for characterizing the CO2 flooding miscibility degree based on nuclear magnetic resonance can refer to the implementation of the above method, and the repeated parts will not be described again. The term "module" or "unit" used below can be a combination of software and / or hardware that realizes a predetermined function. Although the system described in the following embodiments is preferably realized in software, the realization of hardware, or a combination of software and hardware is also possible and conceived.

[0150] Based on the same inventive concept, the present application also provides a system for characterizing the CO2 flooding miscibility degree based on nuclear magnetic resonance, as shown in FIG. 13, which comprises:

[0151] A minimum miscibility pressure analysis device 1310 is configured to test the minimum miscibility pressure of the target oil reservoir crude oil and CO2 according to the tube method;

[0152] A nuclear magnetic resonance-physical model combined device 1320 is configured to perform a columnar core CO2 flooding experiment according to the minimum miscibility pressure, to collect a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum of the fluid in the core changing with space and time in real time, to synchronously collect the fluid at the outlet end and perform a chromatographic test to obtain chromatographic test data, and to perform qualitative and quantitative characterization of the dynamic change of the miscibility degree according to the two-dimensional nuclear magnetic resonance weighted imaging graph, the layered T2 spectrum and the chromatographic test data, to obtain the qualitative and quantitative characterization results of the CO2 and crude oil miscibility degree.

[0153] For characterizing the CO2 flooding miscibility degree by using the system for characterizing the CO2 flooding miscibility degree based on nuclear magnetic resonance

[0154] In an embodiment, the architecture of the nuclear magnetic-fluid model combined device can refer to Figure 2. Specifically, the nuclear magnetic-fluid model combined device comprises a nuclear magnetic resonance test module, a rock fluid displacement module, an outlet end fluid collection and detection module, a computer control and data processing module;

[0155] The nuclear magnetic resonance test module is used for performing nuclear magnetic resonance test to obtain two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectrum;

[0156] The rock fluid displacement module comprises a core holder compatible with nuclear magnetic resonance test, and is used for performing rock fluid displacement experiment;

[0157] The outlet end fluid collection and detection module is used for collecting outlet end fluid and performing chromatographic test to obtain chromatographic test data;

[0158] The computer control and data processing module is used for collecting two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectrum and chromatographic test data, and performing qualitative and quantitative characterization of dynamic change of miscibility to obtain qualitative and quantitative characterization results of miscibility of CO2 and crude oil.

[0159] In an embodiment, the architecture deployment relationship of the nuclear magnetic-fluid model combined device can refer to Figure 3. The nuclear magnetic resonance test module comprises a permanent magnet 24, a gradient coil 25, a radio frequency coil 26, a preamplifier 27, a spectrometer 28, a radio frequency amplifier 29, a gradient amplifier 30, a shielded room 32 and an equipment room 33;

[0160] The permanent magnet 24, the gradient coil 25, the radio frequency coil 26 and the preamplifier 27 are deployed in the shielded room 32; the equipment room 33 comprises the spectrometer 28, the radio frequency amplifier 29 and the gradient amplifier 30;

[0161] The permanent magnet 24 is compatible with multiple online displacement scanning modes; the signal generated by the magnetic resonance effect of fluid in the rock is applied with a certain radio frequency signal by the spectrometer 28, amplified by the radio frequency amplifier 29 and applied to the radio frequency coil 26 to excite the signal generated by the magnetic resonance effect of fluid in the rock, and amplified by the preamplifier 27 and collected by the spectrometer 28;

[0162] When performing nuclear magnetic resonance imaging scanning and layered T2 spectrum scanning, a certain gradient strength is applied to the fluid for signal capture, a certain gradient signal is applied by the spectrometer 28, the signal is amplified by the gradient amplifier 30 and applied to the gradient coil 25 to excite the signal generated by the magnetic resonance effect of fluid in the rock, and the signal is amplified by the preamplifier 27 and collected by the spectrometer 28;

[0163] The shielded room 32 is used for shielding interference sources by reflecting and absorbing electromagnetic waves.

[0164] In an embodiment, the rock fluid displacement module comprises: a confining pressure pump 1, a displacement pump 2, a first non-magnetic switch 4, a second non-magnetic switch 5, a third non-magnetic switch 6, a fourth non-magnetic switch 7, a fifth non-magnetic switch 8, a sixth non-magnetic switch 9, a seventh non-magnetic switch 10, a first six-way valve 14, a second six-way valve 15, a first piston container 16, a second piston container 17, a third piston container 18, a first pressure sensor 19, a second pressure sensor 20, a temperature sensor 22, a temperature control device 23, and a magnetic resonance compatible core holder 31;

[0165] The injection fluid required by the core in the magnetic resonance compatible core holder 31 is provided by the second piston container 17 and the third piston container 18, and the displacement pump 2 is connected with the first six-way valve 14 and the third non-magnetic switch 6 in sequence, so that the fluid in the second piston container 17 flows into the core in the magnetic resonance compatible core holder 31 through the fourth non-magnetic switch 7, the second six-way valve 15, and the fifth non-magnetic switch 8 in sequence;

[0166] The displacement pump 2 is connected with the first six-way valve 14 and the sixth non-magnetic switch 9 in sequence, so that the fluid in the third piston container 18 flows into the core in the magnetic resonance compatible core holder 31 through the seventh non-magnetic switch 10, the second six-way valve 15, and the fifth non-magnetic switch 8 in sequence;

[0167] The fluid required in the confining pressure cavity of the magnetic resonance compatible core holder 31 is provided by the first piston container 16, and the displacement pump 1 is connected with the first non-magnetic switch 4, so that the fluid in the first piston container 16 flows into the confining pressure cavity of the magnetic resonance compatible core holder 31 through the second non-magnetic switch 5;

[0168] The monitoring of the confining pressure is fed back by connecting the second pressure sensor 20 with the inlet end of the confining pressure cavity of the magnetic resonance compatible core holder 31;

[0169] The monitoring of the injection pressure of the fluid in the core is fed back by connecting the first pressure sensor 19 with the inlet end of the magnetic resonance compatible core holder 31;

[0170] The heating of the magnetic resonance compatible core holder 31 is temperature-adjusted by the temperature control device 23, and the temperature is detected by the temperature sensor 22.

[0171] In an embodiment, the outlet end fluid collection and detection module comprises: a back pressure pump 3, an eighth non-magnetic switch 11, a ninth non-magnetic switch 12, a tenth non-magnetic switch 13, a third pressure sensor 21, a back pressure valve 41, a gas-liquid separator 42, and an oil / gas chromatograph 43;

[0172] The back pressure pump 3 is connected with the ninth non-magnetic switch 12, so that the fluid is input to the back pressure valve 41; the monitoring of the back pressure is fed back by connecting the third pressure sensor 21 with the fluid flowing through the eighth non-magnetic switch 11 and then flowing into the back pressure valve 41;

[0173] The collection and metering of the outlet end fluid is carried out by gas-liquid separation, collection and metering by a gas-liquid separator 42, which is a container with a visual window and a piston for metering the volume of crude oil, gas phase and water phase;

[0174] The detection of the fluid chromatogram is carried out by flowing the gas-liquid collected by the gas-liquid separator 42 into the oil / gas chromatograph 43 through the tenth non-magnetic switch 13 for detection, and the oil / gas chromatograph 43 simultaneously considers oil phase component analysis and gas component analysis.

[0175] In an embodiment, the computer control and data processing module comprises an input unit 34, a storage unit 35, a display 36, a central processing unit 37, a communication unit 38, a power supply 39 and an electronic device 40.

[0176] The electronic device 40 comprises the input unit 34, the storage unit 35, the display 36, the central processing unit 37, the communication unit 38 and the power supply 39; the communication unit 38 is used for information transmission between devices; the collected data is transmitted to the central processing unit 37 through the input unit 34, the central processing unit 37 automatically processes the data and analyzes the results based on deep learning and AI large model, and stores them in the storage unit 35, and displays them on the display 36; wherein the collected data at least includes nuclear magnetic test data and chromatographic test data.

[0177] It should be noted that although several modules of the system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance are mentioned in the above detailed description, such division is only exemplary and not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided into modules embodied by multiple modules.

[0178] Compared with the prior art, the main improvement of the present application is at least:

[0179] 1. The present application realizes the simultaneous qualitative and quantitative characterization of the miscibility degree of CO2 and crude oil.

[0180] 2. Compared with the existing test method, the data processing based on two-dimensional nuclear magnetic imaging and layered T2 spectrum is more intuitive and less affected by human factors.

[0181] 3. The experiment uses a low-field nuclear magnetic-mockup combined device, which can realize real-time monitoring of the miscibility characteristics of CO2 and crude oil during injection, effectively solves the problem of indirectly reflecting the oil-gas miscibility law through pressure, recovery rate, outlet end fluid change and the like, ensures the accuracy of the experiment, and reduces the errors caused by pressurization and depressurization and repeated disassembly and assembly of the core in the conventional test process.

[0182] 4. The CO2 flooding experiment simulates the high temperature and high pressure environment in real formations, and the experimental results are more consistent with the actual situation, and the operation is also simpler.

[0183] 5. The experiment requires less oil and gas samples, is energy-saving and environmentally friendly, takes less time, is highly efficient, and the experimental method is highly reproducible.

[0184] 6. This application can not only determine and calculate the degree of miscibility between CO2 and crude oil in the core, but also conduct qualitative and quantitative studies on the migration law and occurrence characteristics of fluids in the core pore space, as well as experiments involving the microscopic seepage mechanism of reservoirs.

[0185] Based on the aforementioned inventive concept, as shown in FIG14, this application also proposes a computer device 1400, including a memory 1410, a processor 1420, and a computer program 1430 stored in the memory 1410 and executable on the processor 1420. When the processor 1420 executes the computer program 1430, it implements the aforementioned method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance.

[0186] Based on the aforementioned inventive concept, this application proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the aforementioned method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance.

[0187] Based on the aforementioned inventive concept, this application proposes a computer program product, which includes a computer program that, when executed by a processor, implements a method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance.

[0188] The method and system proposed in this application for characterizing the miscibility of CO2 flooding based on nuclear magnetic resonance (NMR) employs a combined NMR-physical model device to monitor the spatiotemporal changes of fluid within the core during CO2 flooding in real time. This allows for rapid and accurate experimental testing while simultaneously performing intelligent data processing and analysis, significantly improving experimental efficiency. In characterizing the miscibility of CO2 flooding based on NMR, the minimum miscibility pressure between crude oil and CO2 in the target reservoir is tested using a thin-tube method. A columnar core CO2 flooding experiment is conducted using the combined NMR-physical model device. By acquiring real-time online two-dimensional NMR images and layered T2 spectra of the fluid within the core, a qualitative and quantitative characterization method for the dynamic changes in miscibility is established. This method is low-cost, time-efficient, and can accurately and rapidly characterize the degree of oil and gas miscibility during CO2 flooding.

[0189] The acquisition, storage, use, and processing of data in this application comply with relevant laws and regulations.

[0190] Those skilled in the art will appreciate that embodiments of the application can be readily used as a method, a system or a computer program product. Accordingly, the application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer-readable program code.

[0191] The application is described in reference to the flowchart illustrations and / or block diagrams of methods and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams block or blocks.

[0192] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart illustrations and / or block diagrams block or blocks.

[0193] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams block or blocks.

[0194] Finally, it should be noted that the above-described embodiments are merely specific embodiments of the present application, which are used to illustrate the technical solutions of the present application, but not to limit the same. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that any skilled person in the art can still modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features, within the technical scope disclosed by the present application. The modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

A method for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance, characterized in that, The method comprises: According to the tubular method, the minimum miscibility pressure of the target oil reservoir crude oil and CO2 is tested; According to the minimum miscibility pressure, a columnar core CO2 oil displacement experiment is performed, and a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum of the fluid in the core are collected in real time according to the change of space and time; the fluid at the outlet end is synchronously collected, and a chromatographic test is performed to obtain chromatographic test data; and According to the two-dimensional nuclear magnetic resonance weighted imaging graph, the layered T2 spectrum and the chromatographic test data, dynamic change qualitative and quantitative characterization of the miscibility degree is performed to obtain qualitative and quantitative characterization results of the miscibility degree of CO2 and the crude oil. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, According to the tubular method, the minimum miscibility pressure of the target oil reservoir crude oil and CO2 is tested, which comprises: The target oil reservoir crude oil is selected, and the target oil reservoir temperature is simulated according to the target oil reservoir crude oil; and According to the simulated oil reservoir temperature, a relationship curve between different pressures and oil displacement efficiencies is established based on the tubular method to obtain the minimum miscibility pressure of the target oil reservoir crude oil and CO2. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, A nuclear magnetic resonance-physical model combined device is used to perform a columnar core CO2 oil displacement experiment, and the nuclear magnetic resonance-physical model combined device comprises a nuclear magnetic resonance test module, a rock fluid displacement module, an outlet fluid collection and detection module, a computer control and data processing module; The nuclear magnetic resonance test module is used to perform nuclear magnetic resonance test to obtain a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum; The rock fluid displacement module comprises a core holder compatible with nuclear magnetic resonance test, and is used to perform rock fluid displacement experiment; The outlet fluid collection and detection module is used to collect the fluid at the outlet end, and perform chromatographic test to obtain chromatographic test data; and The computer control and data processing module is used to collect the two-dimensional nuclear magnetic resonance weighted imaging graph, the layered T2 spectrum and the chromatographic test data, and perform dynamic change qualitative and quantitative characterization of the miscibility degree to obtain qualitative and quantitative characterization results of the miscibility degree of CO2 and the crude oil. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 3, characterized in that, The nuclear magnetic resonance test module comprises a permanent magnet (24), a gradient coil (25), a radio frequency coil (26), a preamplifier (27), a spectrometer (28), a radio frequency amplifier (29), a gradient amplifier (30), a shield room (32) and an equipment room (33); The permanent magnet (24), the gradient coil (25), the radio frequency coil (26) and the preamplifier (27) are arranged in the shield room (32); the equipment room (33) comprises the spectrometer (28), the radio frequency amplifier (29) and the gradient amplifier (30); The permanent magnet (24) is compatible with multiple online displacement scanning modes; the signal generated by the magnetic resonance effect of the fluid in the rock is amplified by the radio frequency amplifier (29) after a certain radio frequency signal is applied by the spectrometer (28), and is applied to the radio frequency coil (26) to excite the signal generated by the magnetic resonance effect of the fluid in the rock, which is amplified by the preamplifier (27) and collected by the spectrometer (28); When the nuclear magnetic resonance imaging scanning and the layered T2 spectrum scanning are performed, the signal capturing of the fluid is performed by applying a certain gradient strength, a certain gradient signal is applied by the spectrometer (28), the signal is amplified by the gradient amplifier (30) and applied to the gradient coil (25) to excite the magnetic resonance effect of the fluid in the rock to generate a signal, the signal is amplified by the preamplifier (27) and collected by the spectrometer (28); and The shielded space (32) is used for shielding the interference source by reflecting and absorbing electromagnetic waves. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 4, characterized in that, The rock fluid displacement module comprises a ring pressure pump (1), a displacement pump (2), a first non-magnetic switch (4), a second non-magnetic switch (5), a third non-magnetic switch (6), a fourth non-magnetic switch (7), a fifth non-magnetic switch (8), a sixth non-magnetic switch (9), a seventh non-magnetic switch (10), a first six-way (14), a second six-way (15), a first piston container (16), a second piston container (17), a third piston container (18), a first pressure sensor (19), a second pressure sensor (20), a temperature sensor (22), a temperature control device (23) and a magnetic resonance compatible core holder (31); The required injection fluid of the core in the magnetic resonance compatible core holder (31) is provided by the second piston container (17) and the third piston container (18), the displacement pump (2) is connected with the first six-way (14) and the third non-magnetic switch (6) in sequence, and the fluid in the second piston container (17) flows into the core in the magnetic resonance compatible core holder (31) through the fourth non-magnetic switch (7), the second six-way (15) and the fifth non-magnetic switch (8) in sequence; The displacement pump (2) is connected with the first six-way (14) and the sixth non-magnetic switch (9) in sequence, and the fluid in the third piston container (18) flows into the core in the magnetic resonance compatible core holder (31) through the seventh non-magnetic switch (10), the second six-way (15) and the fifth non-magnetic switch (8) in sequence; The required fluid in the ring pressure cavity of the magnetic resonance compatible core holder (31) is provided by the first piston container (16), the displacement pump (1) is connected with the first non-magnetic switch (4), and the fluid in the first piston container (16) flows into the ring pressure cavity core of the magnetic resonance compatible core holder (31) through the second non-magnetic switch (5); The monitoring of the ring pressure is performed by connecting the second pressure sensor (20) with the inlet end of the ring pressure cavity of the magnetic resonance compatible core holder (31) to feed back; The monitoring of the injection pressure of the fluid in the core is performed by connecting the first pressure sensor (19) with the inlet end of the magnetic resonance compatible core holder (31) to feed back; and The heating of the magnetic resonance compatible core holder (31) is adjusted by the temperature control device (23), and the temperature is detected by the temperature sensor (22). The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 5, characterized in that, The outlet end fluid collection and detection module comprises a back pressure pump (3), an eighth non-magnetic switch (11), a ninth non-magnetic switch (12), a tenth non-magnetic switch (13), a third pressure sensor (21), a back pressure valve (41), a gas-liquid separator (42) and an oil / gas chromatograph (43). The back pressure pump (3) is connected with the ninth non-magnetic switch (12) to input fluid to the back pressure valve (41); the monitoring of the back pressure is fed back through the third pressure sensor (21) after the fluid flows through the eighth non-magnetic switch (11) and then flows into the back pressure valve (41); The collection and metering of the outlet end fluid are carried out through gas-liquid separation, collection and metering by the gas-liquid separator (42), which is a container with a visible window and a piston for metering the volumes of the crude oil, the gas phase and the water phase; and The detection of the fluid chromatography is carried out by flowing the gas-liquid collected by the gas-liquid separator (42) into the oil / gas chromatograph (43) through the tenth non-magnetic switch (13) for detection, and the oil / gas chromatograph (43) simultaneously considers the oil phase component analysis and the gas component analysis. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 6, characterized in that, The computer control and data processing module comprises an input unit (34), a storage unit (35), a display (36), a central processing unit (37), a communication unit (38), a power supply (39) and an electronic device (40); and The electronic device (40) comprises the input unit (34), the storage unit (35), the display (36), the central processing unit (37), the communication unit (38) and the power supply (39); the communication unit (38) is used for information transmission between devices; the collected data is transmitted to the central processing unit (37) through the input unit (34), the central processing unit (37) automatically processes the data and analyzes the results based on deep learning and AI large models, and stores them in the storage unit (35) for display on the display (36); wherein the collected data at least includes nuclear magnetic test data and chromatographic test data. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 7, characterized in that, According to the minimum miscibility pressure, a columnar core CO2 flooding experiment is carried out, and a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum of the fluid in the core are collected in real time, including: The stratum outcrop of the target reservoir coring well is selected to drill and cut the core, the core is washed, dried and measured for analysis parameters, and the core is measured for analysis parameters; The pipeline is cleaned with petroleum ether and dried, high-pressure CO2 gas for experiment is placed in the third piston container (18), crude oil is placed in the second piston container (17), and fluorine oil is placed in the first piston container (16) and warmed to the set temperature for experiment; The sampling core is loaded into the magnetic resonance compatible core holder (31) and placed in the shielding room (32); The back pressure pump (3) is connected with the ninth non-magnetic switch (12) to input fluid to the back pressure valve (41); the monitoring of the back pressure is fed back through the third pressure sensor (21) after the fluid flows through the eighth non-magnetic switch (11) and then flows into the back pressure valve (41); The temperature control system (23) is opened, and the temperature of the magnetic resonance compatible core holder (31) is increased to the stratum temperature; The displacement pump (2), the second piston container (17), the fourth non-magnetic switch (7), the second six-way valve (15) and the fifth non-magnetic switch (8) are opened in sequence, then the back pressure pump (3), the ninth non-magnetic switch (12), the back pressure valve (41) and the eighth non-magnetic switch (11) are opened in sequence to control the back pressure, a constant pressure difference is established to inject crude oil into the core until the pressure difference at both ends of the core tends to be stable; and The back pressure pump (3) is connected with the ninth non-magnetic switch (12) to input fluid to the back pressure valve (41); the monitoring of the back pressure is fed back through the third pressure sensor (21) after the fluid flows through the eighth non-magnetic switch (11) and then flows into the back pressure valve (41); The displacement pump (3), the first six-way valve (14), the sixth non-magnetic switch (9), the seventh non-magnetic switch (10), the second six-way valve (15) and the fifth non-magnetic switch (8) are opened in sequence, CO2 is injected into the core, CO2 is used to displace the crude oil, and the crude oil is pressurized to a first set pressure and a second set pressure respectively, the second set pressure is 0.5 MPa higher than the minimum miscibility pressure, and the two-dimensional nuclear magnetic resonance imaging and the layered T2 spectrum of the fluid in the gripper after each pressurization are tested respectively. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 8, characterized in that, The outlet fluid is synchronously collected and subjected to chromatographic testing to obtain chromatographic testing data, including: When gas continuously flows out of the gas-liquid separator (42), the test result data of the oil / gas chromatograph (43) is transmitted to the central processing unit (37) through the communication unit 38 and the input unit 34; and After being processed and analyzed by the central processing unit (37), the data is stored in the storage unit (35) and displayed through the display (36), and when the component change rate in the displayed oil and gas chromatograms is less than the set range, the eighth non-magnetic switch (11) is closed and the experiment is stopped. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, According to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum and the chromatographic test data, the dynamic change of the miscibility degree is qualitatively determined, and the qualitative characterization result of the miscibility degree of CO2 and crude oil is obtained, including: Based on different weighted imaging techniques, the layered two-dimensional imaging scanning is performed on the core at different positions along the axial direction, the non-miscible region, the near-miscible region and the miscible region are identified according to the viscosity difference between CO2 and crude oil, and the viscosity change of the fluid caused by the dissolution and extraction of CO2 in the crude oil; and The results of the chromatographic analysis of the produced fluid are combined to qualitatively determine the change of the miscibility degree of oil and gas with time and space during the CO2 oil displacement process; wherein, according to the minimum miscibility pressure of CO2 and crude oil measured by the capillary tube experiment, the layered two-dimensional imaging scanning is performed on the core at different positions along the axial direction at the initial saturated oil stage, the stage of the first set pressure and the stage of the second set pressure, respectively, the proton density imaging scanning and the T1 weighted imaging scanning are performed at each stage, the test core is divided into multiple layers for imaging scanning according to the set layer thickness and layer spacing, and the T2 weighted imaging scanning image is obtained by image subtraction method. The method for characterizing the degree of CO2 flooding miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, According to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum and the chromatographic test data, the dynamic change of the miscibility degree is quantitatively characterized, and the quantitative characterization result of the miscibility degree of CO2 and crude oil is obtained, including: The layered T2 spectrum scanning is performed along the axial direction of the core, the shift rule of the T2 spectrum of each stage corresponding to the layer position is taken as the judgment standard of whether miscible or not, and the shift amount of the T2 spectrum corresponding to the layer position is taken as the calculation standard of the miscibility degree; and According to the judgment standard and the calculation standard, the miscibility degree of CO2 and crude oil is quantitatively calculated by the shift rule and the shift amount of the T2 spectrum of each layer along the axial direction in the layered T2 spectrum. A system for characterizing the miscibility of CO2 flooding based on nuclear magnetic resonance, characterized in that it comprises: The system comprises: A minimum miscibility pressure analysis device is configured to determine the minimum miscibility pressure of the target oil reservoir and CO2 according to a capillary tube method; and A minimum miscibility pressure analysis device is configured to determine the minimum miscibility pressure of the target oil reservoir and CO2 according to a capillary tube method; and The nuclear magnetic resonance-physical model combined device is used for carrying out a columnar core CO2 oil displacement experiment according to the minimum miscibility pressure, collecting a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum of fluid in the core changing with time and space in real time, synchronously collecting fluid at an outlet end and carrying out chromatographic testing to obtain chromatographic testing data, qualitatively and quantitatively representing dynamic changes of a miscibility degree according to the two-dimensional nuclear magnetic resonance weighted imaging graph, the layered T2 spectrum and the chromatographic testing data, and obtaining qualitative and quantitative representation results of the miscibility degree of CO2 and crude oil. The system for characterizing the degree of miscibility of CO2 flooding based on nuclear magnetic resonance according to claim 12, characterized in that, The nuclear magnetic resonance-physical model combined device comprises a nuclear magnetic resonance testing module, a rock fluid displacement module, an outlet end fluid collection and detection module and a computer control and data processing module. The nuclear magnetic resonance testing module is used for carrying out nuclear magnetic resonance testing to obtain a two-dimensional nuclear magnetic resonance weighted imaging graph and a layered T2 spectrum. The rock fluid displacement module comprises a core holder compatible with nuclear magnetic resonance testing and is used for carrying out rock fluid displacement experiments. The outlet end fluid collection and detection module is used for collecting fluid at an outlet end, carrying out chromatographic testing and obtaining chromatographic testing data. The computer control and data processing module is used for collecting a two-dimensional nuclear magnetic resonance weighted imaging graph, a layered T2 spectrum and chromatographic testing data, qualitatively and quantitatively representing dynamic changes of a miscibility degree, and obtaining qualitative and quantitative representation results of the miscibility degree of CO2 and crude oil. The system for characterizing the degree of miscibility of CO2 flooding based on nuclear magnetic resonance according to claim 13, characterized in that, The nuclear magnetic resonance testing module comprises a permanent magnet (24), a gradient coil (25), a radio frequency coil (26), a preamplifier (27), a spectrometer (28), a radio frequency amplifier (29), a gradient amplifier (30), a shield room (32) and an equipment room (33). The permanent magnet (24), the gradient coil (25), the radio frequency coil (26) and the preamplifier (27) are arranged in the shield room (32); the equipment room (33) comprises the spectrometer (28), the radio frequency amplifier (29) and the gradient amplifier (30). The permanent magnet (24) is compatible with multiple online displacement scanning modes; signals generated by the magnetic resonance effect of fluid in the rock are amplified by the radio frequency amplifier (29) and applied to the radio frequency coil (26) to excite signals generated by the magnetic resonance effect of fluid in the rock, and the signals are amplified by the preamplifier (27) and collected by the spectrometer (28); When carrying out nuclear magnetic resonance imaging scanning and layered T2 spectrum scanning, a certain gradient strength is applied to the fluid to capture signals, a certain gradient signal is applied by the spectrometer (28), the signals are amplified by the gradient amplifier (30) and applied to the gradient coil (25) to excite signals generated by the magnetic resonance effect of fluid in the rock, and the signals are amplified by the preamplifier (27) and collected by the spectrometer (28); and The shield room (32) is used for shielding interference sources by reflecting and absorbing electromagnetic waves. The system for characterizing the degree of miscibility of CO2 flooding based on nuclear magnetic resonance according to claim 13, characterized in that, The rock fluid displacement module comprises a ring pressure pump (1), a displacement pump (2), a first non-magnetic switch (4), a second non-magnetic switch (5), a third non-magnetic switch (6), a fourth non-magnetic switch (7), a fifth non-magnetic switch (8), a sixth non-magnetic switch (9), a seventh non-magnetic switch (10), a first six-way (14), a second six-way (15), a first piston container (16), a second piston container (17), a third piston container (18), a first pressure sensor (19), a second pressure sensor (20), a temperature sensor (22), a temperature control device (23), and a magnetic resonance compatible core holder (31); The required injection fluid in the core in the magnetic resonance compatible core holder (31) is provided by the second piston container (17) and the third piston container (18), the displacement pump (2) is connected with the first six-way (14) and the third non-magnetic switch (6) in sequence, and the fluid in the second piston container (17) flows into the core in the magnetic resonance compatible core holder (31) through the fourth non-magnetic switch (7), the second six-way (15), and the fifth non-magnetic switch (8) in sequence; The displacement pump (2) is connected with the first six-way (14) and the sixth non-magnetic switch (9) in sequence, and the fluid in the third piston container (18) flows into the core in the magnetic resonance compatible core holder (31) through the seventh non-magnetic switch (10), the second six-way (15), and the fifth non-magnetic switch (8) in sequence; The required fluid in the ring pressure cavity of the magnetic resonance compatible core holder (31) is provided by the first piston container (16), the displacement pump (1) is connected with the first non-magnetic switch (4), and the fluid in the first piston container (16) flows into the ring pressure cavity of the magnetic resonance compatible core holder (31) through the second non-magnetic switch (5); The monitoring of the ring pressure is fed back by connecting the second pressure sensor (20) with the inlet end of the ring pressure cavity of the magnetic resonance compatible core holder (31); The monitoring of the injection pressure of the fluid in the core is fed back by connecting the first pressure sensor (19) with the inlet end of the magnetic resonance compatible core holder (31); and The heating of the magnetic resonance compatible core holder (31) is adjusted by the temperature control device (23), and the temperature is detected by the temperature sensor (22). The system for characterizing the degree of miscibility of CO2 flooding based on nuclear magnetic resonance according to claim 13, characterized in that, The outlet end fluid collection and detection module comprises a back pressure pump (3), an eighth non-magnetic switch (11), a ninth non-magnetic switch (12), a tenth non-magnetic switch (13), a third pressure sensor (21), a back pressure valve (41), a gas-liquid separator (42), and an oil / gas chromatograph (43); The back pressure pump (3) is connected with the ninth non-magnetic switch (12), and the fluid is input to the back pressure valve (41); the monitoring of the back pressure is fed back by the third pressure sensor (21) after the fluid flowing through the eighth non-magnetic switch (11) flows into the back pressure valve (41); The collection and metering of the outlet end fluid are carried out by gas-liquid separation, collection, and metering by the gas-liquid separator (42), which is a container with a visual window and a piston, used for metering the volume of crude oil, gas phase, and water phase; and The collection and metering of the outlet end fluid are carried out by gas-liquid separation, collection, and metering by the gas-liquid separator (42), which is a container with a visual window and a piston, used for metering the volume of crude oil, gas phase, and water phase; and The detection of fluid chromatography will separate the gas-liquid separator (42) collected gas-liquid through the tenth non-magnetic switch (13) into the oil phase / gas chromatograph (43) for detection, and the oil phase / gas chromatograph (43) can analyze oil phase components and gas components at the same time. The system for characterizing the degree of miscibility of CO2 flooding based on nuclear magnetic resonance according to claim 13, characterized in that, The computer control and data processing module comprises an input unit (34), a storage unit (35), a display (36), a central processing unit (37), a communication unit (38), a power supply (39) and an electronic device (40); and The electronic device (40) comprises an input unit (34), a storage unit (35), a display (36), a central processing unit (37), a communication unit (38) and a power supply (39); the communication unit (38) is used for information transmission between devices; the collected data is transmitted to the central processing unit (37) through the input unit (34), the central processing unit (37) automatically processes the data and analyzes the results based on deep learning and AI large model, and stores them in the storage unit (35) and displays them on the display (36); wherein the collected data at least comprises nuclear magnetic test data and chromatographic test data. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that The processor executes the computer program to realize the method of any one of claims 1-11. A computer-readable storage medium, characterized by The computer readable storage medium stores a computer program, and the computer program is executed by the processor to realize the method of any one of claims 1-11. A computer program product, characterized in that The computer program product comprises a computer program, and the computer program is executed by the processor to realize the method of any one of claims 1-11. The computer program product comprises a computer program, and the computer program is executed by the processor to realize the method of any one of claims 1-11.

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