Method and system for representing CO2 flooding miscible degree based on nuclear magnetic resonance

Abstract

The invention provides a method and system for representing the CO2 flooding miscible degree based on nuclear magnetic resonance, and relates to the technical field of oil and gas exploration and development. The method comprises the steps that the minimum miscible pressure of crude oil and CO2 of a target oil reservoir is tested according to a thin tube method; according to the minimum miscible pressure, a columnar rock core CO2 oil displacement experiment is carried out, and a two-dimensional nuclear magnetic resonance weighted imaging graph and a layering T2 spectrum of fluid in the rock core changing at any time and space are collected in real time; synchronously collecting fluid at the outlet end, and carrying out chromatographic test to obtain chromatographic test data; and carrying out dynamic change qualitative and quantitative characterization on the miscible phase degree according to the two-dimensional nuclear magnetic resonance weighted imaging graph, the layered T2 spectrum and chromatographic test data to obtain a qualitative and quantitative characterization result of the miscible phase degree of CO2 and crude oil. The whole scheme is low in cost and short in time consumption, and the oil-gas miscible phase degree in the CO2 oil displacement process can be accurately and rapidly represented.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration and development, and particularly relates to a method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance. BACKGROUND

[0002] 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 art is prior art nor, that the description is prior art to a currently claimed application.

[0003] In the scene of oil and gas exploration and development, CO2 flooding enhanced oil recovery technology as an effective method is increasingly valued, and this technology has been field tested in multiple oil fields and has been applied on a large scale, and has a good application prospect. 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.

[0004] Compared with immiscible flooding, CO2 and formation crude oil can obtain higher recovery in the 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 to reflect the miscibility degree of CO2 in the formation. However, the pressure at different positions between injection and production wells in the reservoir is changing at different times during the CO2 flooding process, and the pressure in the formation is always part of the pressure higher than the minimum miscibility pressure and part of the pressure lower than the minimum miscibility pressure. The miscible region is dynamically changing during the 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 miscible phenomenon in the high-pressure window, that is, whether there is an obvious interface between oil and gas. This method indirectly judges the miscible state of the fluid in the porous medium by the phase change of the fluid at the outlet end, 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 a large error, and cannot describe the quantitative relationship of the miscibility degree of oil and gas.

[0005] 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 strength change based on the NMR imaging results to obtain the minimum miscibility pressure; some scholars have combined NMR 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 NMR 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 NMR technology.

[0006] 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 miscibility state of oil and gas in porous media, and the differences are 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 NMR 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.

[0007] 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 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.

[0008] 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

[0009] To address the problems existing in current technologies, this invention proposes a method and system for characterizing the miscibility of CO2 flooding based on nuclear magnetic resonance (NMR). This invention utilizes a self-designed NMR-physical model coupling device to simulate the CO2 miscible flooding process under actual high-temperature and high-pressure conditions in formations using crude oil, CO2, and real carbonate rock cores. By combining NMR weighted imaging and layered T2 spectroscopy, the spatiotemporal variation of miscibility during CO2 miscibility flooding is qualitatively determined and quantitatively calculated. This solves the problem of difficulty in determining the degree of miscibility during CO2 displacement within core samples, providing a new approach to the study of miscibility during CO2 miscibility flooding, offering methods and basis for further understanding the dynamics and laws of CO2 flooding development, providing guidance for optimizing injection and production parameters, increasing field applicability, and ultimately improving CO2 flooding efficiency.

[0010] In a first aspect of the present invention, a method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance is proposed, the method comprising:

[0011] The minimum miscibility pressure of crude oil and CO2 in the target reservoir was tested using the capillary tube method.

[0012] Based on the minimum miscibility pressure, a CO2 flooding experiment was conducted using columnar core samples. Two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectra of the fluid in the core were acquired in real time to show the spatiotemporal changes. Simultaneously, the fluid at the outlet end was collected and chromatographically tested to obtain chromatographic test data.

[0013] Based on the two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectrum and chromatographic test data, the dynamic changes in the degree of miscibility were qualitatively and quantitatively characterized, and the qualitative and quantitative characterization results of the degree of miscibility between CO2 and crude oil were obtained.

[0014] In a second aspect of the present invention, a system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance is proposed, the system comprising:

[0015] Minimum miscibility pressure analysis device, used to test the minimum miscibility pressure of crude oil and CO2 in a target reservoir using the capillary method;

[0016] A nuclear magnetic resonance-physical model (NMR-PMMA) coupled device is used to conduct CO2 flooding experiments on columnar cores based on the minimum miscibility pressure. It acquires real-time two-dimensional NMR weighted imaging and layered T2 spectra of the fluid within the core as it changes spatiotemporally. Simultaneously, it acquires fluid at the outlet end and performs chromatographic tests to obtain chromatographic data. Based on the two-dimensional NMR weighted imaging, layered T2 spectra, and chromatographic data, it qualitatively and quantitatively characterizes the dynamic changes in miscibility, obtaining qualitative and quantitative characterization results of the miscibility between CO2 and crude oil.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] The method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance can realize real-time online monitoring of the spatial and temporal variation of the fluid in the core during the CO2 flooding process by using a nuclear magnetic-reservoir model combined device, and can realize intelligent data processing and analysis while quickly and accurately completing the experimental test, 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 the CO2 flooding process can be accurately and quickly characterized. BRIEF DESCRIPTION OF DRAWINGS

[0021] 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.

[0022] Figure 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.

[0023] Figure 2 is an architecture schematic diagram of the nuclear magnetic-reservoir model combined device according to an embodiment of the present application.

[0024] Figure 3 is an architecture deployment relationship schematic diagram of the nuclear magnetic-reservoir model combined device according to a specific embodiment of the present application.

[0025] Figure 4 is a flowchart of testing the minimum miscibility pressure of target oil reservoir crude oil and CO2 according to the slim tube method according to an embodiment of the present application.

[0026] Figure 5 is a flowchart of real-time acquisition of two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectrum of fluid in the core according to the change of space and time according to an embodiment of the present application.

[0027] Figure 6 is a flowchart of chromatographic testing according to an embodiment of the present application.

[0028] Figure 7 is a flowchart of qualitative analysis according to an embodiment of the present application.

[0029] Figure 8 is a flowchart of quantitative analysis according to an embodiment of the present application.

[0030] Figure 9A is a proton density imaging of the initial saturated oil stage according to an embodiment of the present application.

[0031] Figure 9B is a T1 weighted imaging of the initial saturated oil stage according to an embodiment of the present application.

[0032] Figure 9C is a T2 weighted imaging of the initial saturated oil stage according to an embodiment of the present application.

[0033] Figure 10A is a proton density imaging of the stage of 10 MPa injection pressure according to an embodiment of the present application.

[0034] Figure 10B is a T1 weighted imaging of the stage of 10 MPa injection pressure according to an embodiment of the present application.

[0035] Figure 10C is a T2 weighted imaging of the stage of 10 MPa injection pressure according to an embodiment of the present application.

[0036] Figure 11A is a proton density imaging of the stage of 16 MPa injection pressure according to an embodiment of the present application.

[0037] Figure 11B is a T1 weighted imaging of the stage of 16 MPa injection pressure according to an embodiment of the present application.

[0038] Figure 11C is a T2 weighted imaging of the stage of 16 MPa injection pressure according to an embodiment of the present application.

[0039] Figure 12is a schematic diagram of quantitative calculation of the miscibility degree of CO2 and crude oil according to an embodiment of the present application.

[0040] 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.

[0041] Figure 14 is a schematic diagram of a computer device structure according to an embodiment of the present application.

[0042] BRIEF DESCRIPTION OF THE DRAWINGS

[0043] 1 ring pressure pump 2 displacement pump

[0044] 3 back pressure pump 4 first non-magnetic switch

[0045] 5 second non-magnetic switch 6 third non-magnetic switch

[0046] 7 fourth non-magnetic switch 8 fifth non-magnetic switch

[0047] 9 sixth non-magnetic switch 10 seventh non-magnetic switch

[0048] 11 eighth non-magnetic switch 12 ninth non-magnetic switch

[0049] 13 tenth non-magnetic switch 14 first six-way

[0050] 15 second six-way 16 first piston container

[0051] 17 second piston container 18 third piston container

[0052] 19 first pressure sensor 20 second pressure sensor

[0053] 21 third pressure sensor 22 temperature sensor

[0054] 23 temperature control device 24 permanent magnet

[0055] 25 gradient coil 26 radio frequency coil

[0056] 27 preamplifier 28 spectrometer

[0057] 29 radio frequency amplifier 30 gradient amplifier

[0058] 31 magnetic resonance compatible core holder 32 shielded room

[0059] 33 equipment room 34 input unit

[0060] 35 storage unit 36 display

[0061] 37 central processing unit 38 communication unit

[0062] 39 power supply 40 electronic device

[0063] 41 back pressure valve 42 gas-liquid separator

[0064] 43 oil / gas chromatograph

[0065] 210 nuclear magnetic resonance testing module 220 rock fluid displacement module

[0066] 230 outlet end fluid collection and detection module 240 computer control and data processing module

[0067] 1310 minimum miscibility pressure analysis device 1320 nuclear magnetic-reservoir model combined device

[0068] 1400 computer device 1410 memory

[0069] 1420 processor 1430 computer program DETAILED DESCRIPTION

[0070] The principles and spirits of the present application will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are given only to enable those skilled in the art to better understand and implement the present application, and do not limit the scope of the present application in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0071] 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.

[0072] 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 about dynamic change characterization of miscibility degree, qualitative analysis is usually performed, and quantitative characterization is also indirectly analyzed through changes in pressure, oil displacement efficiency, and output gas composition. The present application improves the accuracy of characterization of the miscibility degree of CO2 and crude oil, and makes the results more consistent with the actual miscibility change in the formation.

[0073] The principles and spirits of the present application will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are given only to enable those skilled in the art to better understand and implement the present application, and do not limit the scope of the present application in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0074] Figure 1 is a method flow diagram for characterizing the miscibility degree of CO2 flooding according to an embodiment of the present application. As shown in Figure 1 , the method comprises:

[0075] S101, testing the minimum miscibility pressure of the target oil reservoir crude oil and CO2 according to the capillary tube method;

[0076] S102, performing a columnar core CO2 flooding experiment according to the minimum miscibility pressure, collecting real-time two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectrum of the fluid in the core with the change of space and time, synchronously collecting the outlet fluid, and performing chromatographic testing to obtain chromatographic testing data;

[0077] Specifically, the nuclear magnetic resonance-physical model combined device can be used to perform the columnar core CO2 flooding experiment.

[0078] S103, qualitatively and quantitatively characterizing the dynamic change of the miscibility degree according to the two-dimensional nuclear magnetic resonance weighted imaging, the layered T2 spectrum and the chromatographic testing data, and obtaining the qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil.

[0079] The overall scheme of the present application has low cost and short time consumption, and can accurately and quickly characterize the oil-gas miscibility degree in the CO2 flooding process.

[0080] Specifically, referring to Figure 2 , the architecture diagram of the nuclear magnetic resonance-physical model combined device according to an embodiment of the present application is shown in Figure 2 . As shown in the figure, the nuclear magnetic resonance-physical model combined device comprises a nuclear magnetic resonance testing module 210, a rock fluid displacement module 220, an outlet fluid collection and detection module 230, and a computer control and data processing module 240.

[0081] The nuclear magnetic resonance testing module 210 is used to perform nuclear magnetic resonance testing to obtain two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectrum.

[0082] The rock fluid displacement module 220 comprises a core holder compatible with nuclear magnetic resonance testing, and is used to perform rock fluid displacement experiments.

[0083] The outlet fluid collection and detection module 230 is used to collect the outlet fluid and perform chromatographic testing to obtain chromatographic testing data.

[0084] The computer control and data processing module 240 is used to collect two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectrum and chromatographic testing data, and qualitatively and quantitatively characterize the dynamic change of the miscibility degree to obtain the qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil.

[0085] The present application integrates the nuclear magnetic resonance testing system, the rock fluid displacement system and the outlet end fluid collection and analysis system into a whole through computer control, measures the nuclear magnetic resonance weighted imaging and the layered T2 spectrum in real time and on line, and obtains rich fluid change information in the CO2 oil displacement process in the core.

[0086] Reference Figure 3 The figure is a schematic diagram of the architecture deployment relationship of the nuclear magnetic-reservoir model combined use device of an embodiment of the present application. Figure 3 The various modules in the nuclear magnetic-reservoir model combined use device (low-field nuclear magnetic-high temperature and high pressure displacement combined use device) are described in detail.

[0087] The nuclear magnetic resonance testing module includes:

[0088] The nuclear magnetic resonance testing module includes 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.

[0089] 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 includes the spectrometer 28, the radio frequency amplifier 29 and the gradient amplifier 30.

[0090] 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 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 the signal is amplified by the preamplifier 27 and collected by the spectrometer 28;

[0091] When the nuclear magnetic resonance imaging scanning and the layered T2 spectrum scanning are performed, a certain gradient strength is applied to the fluid to capture the signal, 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 the fluid in the rock, and the signal is amplified by the preamplifier 27 and collected by the spectrometer 28;

[0092] The shielded room 32 is used to shield the interference source by reflecting and absorbing electromagnetic waves.

[0093] 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 requirements. The magnet designed by the present application is convenient for pipeline connection, solves the problem of placing the high-temperature and high-pressure core holder, has small 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 applied 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 the fluid in the rock, and then the signal is amplified by the preamplifier 27 and collected by the spectrometer 28. When performing nuclear magnetic resonance imaging scanning and layered T2 spectrum scanning, a certain gradient intensity needs to be applied to the fluid to capture the signal. This process applies a certain gradient signal through the spectrometer 28, amplifies the signal through the gradient amplifier 30, and applies it to the gradient coil 25 to excite the signal generated by the magnetic resonance effect of the fluid in the rock. Then the signal is amplified by the preamplifier 27 and collected by the spectrometer 28.

[0094] 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 and the constant temperature system also bring electromagnetic wave interference, which leads to a decrease in the signal-to-noise ratio or the appearance of an error signal during the core test, and causes a test error. In view of this problem, the system is equipped with a transparent and reusable nuclear magnetic resonance special shielding room 32. The magnetic resonance shielding room is composed of a metal shielding body, and the influence of the interference source is shielded through reflection and absorption of 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 in the high-temperature and high-pressure displacement experiment.

[0095] Rock fluid displacement module:

[0096] 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 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.

[0097] The fluid required 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. The displacement pump 2 is connected with the first six-way valve 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 valve 15 and the fifth non-magnetic switch 8 in sequence.

[0098] Displacement pump 2 is connected with the first six-way valve 14 and the sixth non-magnetic switch 9 in sequence, and the fluid in the third piston container 18 is sequentially flowed 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;

[0099] The fluid required in the hoop stress 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, and the fluid in the first piston container 16 is flowed into the core in the hoop stress cavity of the magnetic resonance compatible core holder 31 through the second non-magnetic switch 5;

[0100] The monitoring of the hoop stress is fed back by connecting the second pressure sensor 20 with the inlet end of the hoop stress cavity of the magnetic resonance compatible core holder 31;

[0101] 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;

[0102] The heating of the magnetic resonance compatible core holder 31 is temperature-regulated by the temperature control device 23, and the temperature is detected by the temperature sensor 22.

[0103] Specifically, the hoop stress 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 valve 14, the second six-way valve 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 according to the experimental requirements. The hoop stress pump 1 adopts a high-precision multi-stage plunger displacement pump (Teledyne Isco 100-DX), the hoop stress 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, and the test accuracy is ±0.04% under the condition of 0 ℃-100 ℃.

[0104] The required injection fluid in the magnetic resonance compatible core holder 31 is provided by the piston container 17 and the 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. 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. The required fluid in the annular 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 core in the annular pressure cavity of the magnetic resonance compatible core holder 31 through the second non-magnetic switch 5. The monitoring of the annular pressure is fed back through the connection of the second pressure sensor 20 and the inlet end of the annular 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 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.

[0105] 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 built-in coil, and the coil is built in the annular space of the core holder. Compared with the external coil commonly used at home and abroad, the signal-to-noise ratio SNR of the core holder is improved by more than 3 times, and the magnetic compatibility and high temperature and high pressure are also considered, and the maximum temperature and pressure that can be withstood are 150℃ and 70MPa respectively.

[0106] Outlet end fluid collection and detection module:

[0107] 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.

[0108] 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 through the third pressure sensor 21 after the fluid flowing through the eighth non-magnetic switch 11 flows into the back pressure valve 41;

[0109] The collection and metering of the outlet end fluid are carried out by gas-liquid separation, collection and metering through 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 aqueous phase;

[0110] The gas-liquid separator 42 collects the gas-liquid and sends them to the oil / gas chromatograph 43 through the tenth non-magnetic switch 13 for detection.

[0111] In actual application scenarios, 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 experimental needs.

[0112] The back pressure pump 3 is connected to 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 fed back through the pressure sensor 21 and the fluid flowing through the eighth non-magnetic switch 11 into the back pressure valve 41;

[0113] The collection and metering of the fluid at the outlet end are carried out by the gas-liquid separator 42 for gas-liquid separation, collection and metering. The gas-liquid separator 42 is a container with a visible window and a piston, which can be used to measure the volume of crude oil, gas and water. The maximum bearing pressure is 30 MPa, and the accuracy is 0.01 mL.

[0114] The fluid chromatography detection sends the gas-liquid collected by the gas-liquid separator 42 to the oil / gas chromatograph 43 through the tenth non-magnetic switch 13 for detection. The chromatograph simultaneously considers oil phase component analysis and gas component analysis functions, greatly improving experimental efficiency.

[0115] Computer control and data processing module:

[0116] 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 an electronic device 40.

[0117] The 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 large models, and stores them in the storage unit 35, which is displayed on the display 36. The collected data at least includes nuclear magnetic test data and chromatography test data.

[0118] The present application effectively combines nuclear magnetic resonance technology with CO2 flooding physical simulation experiment, and proposes a method of using low-field nuclear magnetic resonance-high temperature and high pressure displacement device combination to carry out CO2 flooding experiment. The core used in the experiment is 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 of this invention 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.

[0119] 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.

[0120] In one embodiment, for S101, the minimum miscibility pressure of crude oil and CO2 in the target reservoir is tested using the capillary method, with reference to... Figure 4 The specific process is as follows:

[0121] S401, Select the target oil reservoir formation crude oil, and simulate the reservoir temperature based on the target oil reservoir formation crude oil.

[0122] S402, based on the simulated reservoir temperature, establish the relationship curves between different pressures and oil displacement efficiency using the capillary method, and obtain the minimum miscibility pressure of crude oil and CO2 in the target reservoir.

[0123] In practical applications, the specific procedure for testing minimum miscibility pressure based on the capillary method is as follows: Select crude oil from the target reservoir formation, simulate reservoir temperature, establish the relationship curve between different pressures and oil displacement efficiency based on the capillary method, and determine the minimum miscibility pressure of crude oil and carbon dioxide in the target reservoir. The operating standard for the capillary method is SY / T6573-2016 "Experimental Determination Method of Minimum Miscibility Pressure - Capillary Method", and the minimum miscibility pressure of crude oil and CO2 is determined to be 15.5 MPa.

[0124] In one embodiment, for S102, a columnar core CO2 flooding experiment is conducted based on the minimum miscibility pressure, and two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectra of the fluid in the core are collected in real time to show the spatiotemporal changes; the fluid at the outlet end is collected simultaneously and chromatographic tests are performed to obtain chromatographic test data.

[0125] refer to Figure 5 Based on the minimum miscibility pressure, a CO2 flooding experiment was conducted using columnar core samples. Two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectra of the fluid within the core were acquired in real time, reflecting the spatiotemporal changes in fluid composition. The specific procedure is as follows:

[0126] S501, select the formation outcrop of the target oil reservoir core well for core drilling and cutting, wash and dry the core and measure the core's analytical parameters.

[0127] Specifically, the stratum outcrop of the target oil reservoir coring well is selected for core drilling and cutting, the core is washed and dried according to the national standard GB / T 29172-2012 Core Analysis Method, and the length L, diameter d, porosity and permeability K of the core are measured.

[0128] S502, the pipeline is cleaned with petroleum ether and dried, the high-pressure CO2 gas for the experiment is placed in the third piston container 18, the crude oil is placed in the second piston container 17, the fluorine oil is placed in the first piston container 16, and the temperature is warmed to the set temperature for the experiment.

[0129] S503, the sampling core is loaded into the magnetic resonance compatible core holder 31 and placed in the shielded room 32.

[0130] S504, the ring pressure pump 1, the first non-magnetic switch 4, and the second non-magnetic switch 5 are opened in turn, the air in the ring cavity of the magnetic resonance compatible core holder 31 is discharged with fluorine oil, and then the ring pressure pump 1 is closed, and the ring pressure is increased to the set value.

[0131] S505, the temperature control system 23 is opened, and the temperature of the magnetic resonance compatible core holder 31 is raised to the formation temperature.

[0132] S506, 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 turn, 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 turn 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.

[0133] S507, 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 turn to inject CO2 into the core, and the CO2 is used to displace the crude oil, and the pressure is increased to the first set pressure and the 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 holder are tested respectively under the initial saturated oil state and after each pressure increase.

[0134] 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).

[0135] Reference Figure 6 , the outlet fluid is collected synchronously, and chromatographic test is performed to obtain chromatographic test data, and the specific process is as follows:

[0136] S601, when 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.​

[0137] S602, after being processed and analyzed by the central processing unit 37, the data are stored in the storage unit 35 and displayed by the display 36, and when the change rate of the components in the oil phase chromatogram and the gas phase chromatogram is less than the set range, the eighth non-magnetic switch 11 is closed and the experiment is stopped.

[0138] In an embodiment, for S103, qualitative and quantitative characterization of dynamic changes in the miscibility degree is performed according to the two-dimensional nuclear magnetic resonance weighted imaging image, the layered T2 spectrum and the chromatographic test data, to obtain qualitative and quantitative characterization results of the CO2 and the crude oil miscibility degree.

[0139] Reference Figure 7 The specific process of the qualitative analysis is as follows:

[0140] S701, based on different weighted imaging techniques, 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 viscosity change of the fluid caused by the dissolution and extraction of CO2 in the crude oil.

[0141] S702, combined with the results of the chromatographic analysis of the fluid component change rule, the qualitative judgment of the change of the oil-gas miscibility degree with time and space during the CO2 flooding process is performed; wherein, according to the minimum miscibility pressure of CO2 and crude oil measured by the slim tube experiment, layered two-dimensional imaging scanning is performed on the core at different positions along the axial direction at the initial saturated oil stage, the injection pressure at the first set pressure stage and the injection pressure at the second set pressure stage, respectively, and each stage is respectively subjected to proton density imaging scanning and T1 weighted imaging scanning, 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.

[0142] Reference Figure 8 The specific process of the quantitative analysis is as follows:

[0143] S801, layered T2 spectrum scanning is performed along the axial direction of the core, the shift rule of the T2 spectrum of the corresponding layer position at each stage is taken as the judgment standard of whether miscible or not, and the shift amount of the T2 spectrum of the corresponding layer position is taken as the calculation standard of the miscibility degree, with the layered T2 spectrum at the initial saturated oil stage as the reference;

[0144] S802, 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.

[0145] Specifically, the two-dimensional nuclear magnetic resonance weighted imaging image, the layered T2 spectrum data and the chromatographic test data are processed, and the qualitative and quantitative characterization of the dynamic changes in the miscibility degree is performed.

[0146] In theory, the signal amplitude of a MRI image can be expressed as:

[0147]

[0148] where S is the signal amplitude; se is the signal amplitude;

[0149] N(H) is the proton density of H in the sample, which is a constant for a given sample;

[0150] TR is the repetition time of the sequence;

[0151] T1 is the longitudinal relaxation time;

[0152] T2 is the transverse relaxation time;

[0153] TE is the echo time.

[0154] According to the above formula, T1 and T2 have a very large impact on the signal; in addition to T1 and T2, the signal strength S se is mainly affected by three factors, namely N(H), TR and TE.

[0155] From the above formula, T1 weighting is to increase the impact of T1 on the signal S, and to reduce the impact of different T2 on the signal;

[0156] Similarly, T2 weighting is to increase the impact of T2 relaxation on the signal S, and to reduce the impact of different T1 on the signal;

[0157] The proton density image tries to make the signal S mainly determined by the proton density of H in the sample, and to reduce the impact of T1 relaxation and T2 relaxation.

[0158] T1 weighted imaging, the gray level (light and dark) of the image is mainly determined by the speed of T1 relaxation of the sample, so it is necessary to reduce the impact of T2 on the 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 different T1 can be reflected; therefore, for T1 weighted imaging, "short TR and short TE" should be used.

[0159] T2 weighted imaging, the gray level (light and dark) of the image is mainly determined by the speed of T2 relaxation of the sample, so it is necessary to reduce the impact of T1 on the signal S as much as possible; in , only when TR >> T1 (>> means much greater than), the item approaches 1; and for When TE is large, the image difference caused by different T2 can be reflected; therefore, for T2 weighted imaging, "long TR and long TE" should be used.

[0160] For proton density imaging, the gray scale (light and dark degree) of the image is mainly determined by the proton density of the sample; therefore, the second and third terms in the formula should be close to 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.

[0161] Qualitative analysis of the degree of miscibility:

[0162] 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, and the changes in fluid viscosity caused by the dissolution and extraction of CO2 in crude oil.

[0163] In combination with the results of analyzing the fluid component variation law by chromatography of the produced fluid, the variation of the degree of oil-gas miscibility with time and space during the CO2 oil displacement process is qualitatively judged.

[0164] Specifically, the minimum miscibility pressure of CO2 and crude oil measured by the slim tube experiment is 15.7 MPa, layered two-dimensional imaging scanning is performed at different positions along the axial direction of the core at the initial saturated oil stage, the injection pressure of 10 MPa stage and the injection pressure of 16 MPa stage, respectively, and T1 weighted imaging scanning and proton density imaging scanning are performed at each stage, 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, and the T2 weighted imaging scanning image is obtained by "image subtraction method" by using the inherent characteristics of the software.

[0165] Taking the layered two-dimensional weighted imaging image of the third layer core as an example, referring to Figure 9A , Figure 9B , Figure 9C , the proton density imaging image, the T1 weighted imaging image and the T2 weighted imaging image of the initial saturated oil stage of the specific embodiment of the present application are respectively shown.

[0166] Referring to Figure 10A , Figure 10B , Figure 10C , the proton density imaging image, the T1 weighted imaging image and the T2 weighted imaging image of the injection pressure of 10 MPa stage of the specific embodiment of the present application are respectively shown.

[0167] Referring to Figure 11A , Figure 11B , Figure 11C, respectively, are the proton density imaging graph, the T1 weighted imaging graph and the T2 weighted imaging graph of the injection pressure of 16 MPa stage of the embodiment of the present application.

[0168] Based on the above imaging graphs, the average gray value of each image is roughly calculated, and the size of the gray value represents the amount of fluid content, the larger the gray value represents the more fluid content, and vice versa, the smaller the gray value represents the less fluid content. Taking the gray value of the initial saturated oil stage image as the reference, the gray value of the proton density imaging graph represents the oil content (including light components and heavy components) of the core layer, the ratio of the gray value of the T1 weighted imaging graph (which represents the content of heavy components) and the T2 weighted imaging graph (which represents the content of light components) is about 1:1; in the stage of injection pressure of 10 MPa, the gray value of the proton density imaging graph decreases, but the ratio of the gray value of the T1 weighted imaging graph and the T2 weighted imaging graph is still 1:1, which shows that in this stage, under the action of CO2 displacement, only the oil content of the core 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; in the stage of injection pressure of 16 MPa, the gray value of the proton density imaging graph continues to decrease, but the ratio of the gray value of the T1 weighted imaging graph and the T2 weighted imaging graph is 2:1, which shows that in this stage, under the action of CO2 displacement, the oil content of the core layer further decreases, and the light components in the crude oil are extracted by CO2, resulting in the increase of the proportion of heavy components and the decrease of the proportion of light components, so the oil and gas have miscibility, and the larger the difference between the ratio of the two and the ratio of the initial saturated oil stage, the larger the miscibility degree.

[0169] For quantitative analysis of the miscibility degree:

[0170] In the quantitative exploration of the miscibility degree of CO2 and crude oil, the layered T2 spectrum scanning is carried out along the axial direction of the core, and the shift rule of the T2 spectrum of the corresponding layer position in each stage is taken as the judgment standard of miscibility, and the shift amount of the T2 spectrum of the corresponding layer position is taken as the calculation standard of the miscibility degree.

[0171] Reference Figure 12 , the schematic diagram for quantitative calculation of the miscibility degree of CO2 and crude oil of the embodiment of the present application. As Figure 12As shown, in the miscible process, if CO2 is dissolved into the oil phase, it leads to the decrease of crude oil viscosity, the increase of flowability, the increase of T2 relaxation time, the right shift of T2 spectrum, and the miscible action of CO2 and crude oil; if CO2 extracts light components of crude oil, the heavy components of remaining oil are highlighted, the viscosity of crude oil increases, the flowability becomes poor, the T2 relaxation time becomes shorter, the T2 spectrum shifts to the left, and the miscible action of CO2 and crude oil occurs; when CO2 and crude oil are completely miscible, no dissolution and extraction occur, 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 saturated oil stage. Therefore, the miscibility degree of CO2 and crude oil is quantitatively calculated by the shift rule and shift amount of the T2 spectrum of each layer along the axial direction in the layered T2 spectrum.

[0172] 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 drawings, this does not require or imply that the operations must be performed in this specific order, or that all of the shown operations must be performed to achieve the desired result. Additionally or alternatively, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be divided into multiple steps.

[0173] 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 fluid in the core during CO2 flooding 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, which greatly improves the experimental efficiency. When the miscibility degree of CO2 miscible flooding is characterized based on nuclear magnetic resonance, the minimum miscibility pressure of target oil reservoir crude oil and CO2 is tested by a capillary tube method, a columnar core CO2 flooding experiment is carried out by using a nuclear magnetic resonance-physical model combined device, two-dimensional nuclear magnetic resonance imaging and layered T2 spectrum of fluid in the core are collected in real time and online, a dynamic variation qualitative and quantitative characterization method of miscibility degree is established, 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.

[0174] In the prior art about the characterization of the dynamic change of the miscibility degree, almost all are qualitative analysis, and the quantitative characterization is also indirect analysis through the change of pressure, oil displacement efficiency, output gas composition, etc., and it is impossible to realize the visualization characterization of the change of the miscibility degree of CO2 flooding in the actual formation temperature and pressure environment. In the actual formation, due to the existence of the "pressure funnel" between the 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, and the miscible region is dynamically changed in the process of CO2 flooding. Therefore, it is necessary to qualitatively and quantitatively understand the change rule of the miscibility degree with time and space, 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 by the present application solve the problem of qualitative and quantitative characterization of the dynamic change of the miscibility degree with time and space, 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, and the non-miscible flooding also exists in the miscible range in part of the formation.

[0175] After introducing the method of the exemplary embodiments of the present application, next, with reference to Figure 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.

[0176] 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 herein. The term "module" or "unit" used below can be a combination of software and / or hardware for realizing 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.

[0177] 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 Figure 13 The system comprises:

[0178] 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;

[0179] A nuclear magnetic-mechanical 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 in real time, to synchronously collect the fluid at the outlet end and perform a chromatographic test to obtain chromatographic test data, 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, and to obtain qualitative and quantitative characterization results of the miscibility degree of CO2 and the crude oil.

[0180] For characterizing the miscibility degree of CO2 flooding by using the system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance

[0181] In an embodiment, the architecture of the nuclear magnetic-physical model combined device can refer to Figure 2 Specifically, the nuclear magnetic-physical model combined device comprises a nuclear magnetic resonance testing module, a rock fluid displacement module, an outlet end fluid collection and detection module, a computer control and data processing module.

[0182] The nuclear magnetic resonance testing module is used for performing nuclear magnetic resonance testing to obtain two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectrum.

[0183] The rock fluid displacement module comprises a core holder compatible with nuclear magnetic resonance testing, and is used for performing rock fluid displacement experiments.

[0184] The outlet end fluid collection and detection module is used for collecting outlet end fluid and performing chromatographic testing to obtain chromatographic testing data.

[0185] The computer control and data processing module is used for collecting two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectrum and chromatographic testing data, and performing dynamic change qualitative and quantitative characterization of miscibility degree to obtain qualitative and quantitative characterization results of the miscibility degree of CO2 and crude oil.

[0186] In an embodiment, the architecture deployment relationship of the nuclear magnetic-physical model combined device can refer to Figure 3 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 shielded room 32 and an equipment room 33.

[0187] 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.

[0188] 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 by the spectrometer 28 to exert a certain radio frequency signal, the signal is 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 the signal is amplified by the preamplifier 27 and collected by the spectrometer 28.

[0189] When the NMR imaging scan and the layered T2 spectrum scan are performed, the signal of the fluid is captured by applying a certain gradient strength, the 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, and the signal is amplified by the preamplifier 27 and collected by the spectrometer 28;

[0190] The shielding space 32 is used to shield the interference source by reflecting and absorbing electromagnetic waves.

[0191] In an embodiment, 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 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.

[0192] 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 valve 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 valve 15 and the fifth non-magnetic switch 8 in sequence.

[0193] The displacement pump 2 is connected with the first six-way valve 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 valve 15 and the fifth non-magnetic switch 8 in sequence.

[0194] 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 core in the ring pressure cavity of the magnetic resonance compatible core holder 31 through the second non-magnetic switch 5.

[0195] The monitoring of the ring pressure is feedback connected with the ring pressure cavity inlet end of the magnetic resonance compatible core holder 31 through the second pressure sensor 20.

[0196] The monitoring of the injection pressure of the fluid in the core is feedback connected with the inlet end of the magnetic resonance compatible core holder 31 through the first pressure sensor 19.

[0197] 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.

[0198] 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.

[0199] 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 back pressure is performed by the third pressure sensor 21 and the feedback of fluid flowing through the eighth non-magnetic switch 11 and then flowing into the back pressure valve 41;

[0200] The collection and metering of outlet end fluid is performed by 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 volume of crude oil, gas phase and water phase;

[0201] The detection of fluid chromatography is performed by the tenth non-magnetic switch 13 to input the gas-liquid collected by the gas-liquid separator 42 into the oil / gas chromatograph 43 for detection, which simultaneously considers oil phase component analysis and gas component analysis.

[0202] 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.

[0203] 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, which are displayed on the display 36; wherein the collected data at least comprises nuclear magnetic test data and chromatography test data.

[0204] 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 foregoing detailed description, such division is merely 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 several modules.

[0205] Compared with the prior art, the main improvement of the present application at least lies in:

[0206] 1. The present application realizes the simultaneous qualitative and quantitative characterization of the miscibility degree of CO2 and crude oil.

[0207] 2. Compared with existing testing methods, data processing based on two-dimensional nuclear magnetic resonance imaging and layered T2 spectrum is more intuitive and less affected by human factors.

[0208] 3. The experiment utilizes a low-field NMR-physical model coupling device, which enables real-time monitoring of the miscibility characteristics of CO2 and crude oil during the injection process. This effectively solves the problem of indirectly reflecting the miscibility of oil and gas through pressure, recovery rate, and changes in fluid at the outlet end, ensuring the accuracy of the experiment and reducing errors caused by pressurization, depressurization, and repeated core disassembly and assembly during conventional testing.

[0209] 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.

[0210] 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.

[0211] 6. This invention 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.

[0212] Based on the aforementioned inventive concept, such as Figure 14 As shown, the present invention 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.

[0213] Based on the aforementioned inventive concept, the present invention 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.

[0214] Based on the aforementioned inventive concept, the present invention 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.

[0215] The method and system for characterizing the miscibility degree of CO2 flooding based on nuclear magnetic resonance provided by the application can realize real-time online monitoring of the space-time variation law of fluid in the core during CO2 flooding, 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 target oil reservoir crude oil and CO2 is tested by a capillary tube method, a columnar core CO2 flooding experiment is carried out by using the nuclear magnetic resonance-substitute model combined device, two-dimensional nuclear magnetic resonance imaging and layered T2 spectrum of fluid in the core are collected in real time, 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.

[0216] The acquisition, storage, use, processing and the like of data in the technical solution of the application comply with relevant provisions of laws and regulations.

[0217] Those skilled in the art will understand that embodiments of the application can be provided as methods, systems, or computer program products. Therefore, the application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0218] The application is described with reference to flowcharts and / or block diagrams of the methods and computer program products according to embodiments of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts 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, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a device that implements the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the function specified in the flow or flows and / or block or blocks.

[0219] These computer program instructions can also be stored in a computer-readable memory that can cause the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction apparatus, which implements the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the function specified in the flow or flows and / or block or blocks.

[0220] These computer program instructions can also be loaded into 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 block or blocks. Figure 1 one or more flowcharts and / or blocks Figure 1 Figure 1 one or more flowcharts and / or blocks

[0221] Finally, it should be noted that the above-described embodiments are merely exemplary embodiments of the present application, and are used to explain the technical solutions of the present application, but not to limit the same. The protection scope of the present application is not limited to this. 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 modification or easy-to-think change to the technical solutions recorded in the foregoing embodiments, or equivalent replacement of part of the technical features, without changing the essence of the corresponding technical solutions, 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

1. A method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance, characterized in that, The method includes: The minimum miscibility pressure of crude oil and CO2 in the target reservoir was tested using the capillary tube method. Based on the minimum miscibility pressure, a CO2 flooding experiment was conducted using columnar core samples. Two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectra of the fluid in the core were acquired in real time to show the spatiotemporal changes. Simultaneously, the fluid at the outlet end was collected and chromatographically tested to obtain chromatographic test data. Based on the two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectrum and chromatographic test data, the dynamic changes in the degree of miscibility were qualitatively and quantitatively characterized, and the qualitative and quantitative characterization results of the degree of miscibility between CO2 and crude oil were obtained.

2. The method for characterizing the degree of CO2 flooding based on nuclear magnetic resonance according to claim 1, characterized in that, The minimum miscibility pressure of crude oil and CO2 in the target reservoir was tested using the capillary method, including: Select crude oil from the target reservoir formation and simulate reservoir temperature based on the crude oil from the target reservoir formation; Based on the simulated reservoir temperature, curves showing the relationship between different pressures and oil displacement efficiency were established using the capillary method, yielding the minimum miscibility pressure between crude oil and CO2 in the target reservoir.

3. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, A columnar core CO2 flooding experiment was conducted using a nuclear magnetic resonance-physical model (NMR-physical model) device, which includes: a nuclear magnetic resonance testing module, a rock fluid displacement module, an outlet fluid acquisition and detection module, and a computer control and data processing module. The nuclear magnetic resonance testing module is used to perform nuclear magnetic resonance testing to obtain a two-dimensional nuclear magnetic resonance weighted imaging map and a layered T2 spectrum; The rock fluid displacement module includes a core holder compatible with nuclear magnetic resonance testing for conducting rock fluid displacement experiments. The outlet fluid acquisition and detection module is used to acquire the outlet fluid and perform chromatographic testing to obtain chromatographic test data. The computer control and data processing module is used to acquire two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectra and chromatographic test data, and to perform qualitative and quantitative characterization of the dynamic changes in the degree of miscibility, so as to obtain the qualitative and quantitative characterization results of the degree of miscibility between CO2 and crude oil.

4. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 3, characterized in that, The nuclear magnetic resonance testing module includes: 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); The permanent magnet (24), gradient coil (25), radio frequency coil (26) and preamplifier (27) are deployed in the shielded room (32); the equipment room (33) includes the spectrometer (28), radio frequency amplifier (29) and gradient amplifier (30); The permanent magnet (24) is compatible with multiple online displacement scanning methods; the signal generated by the magnetic resonance effect of the fluid in the rock is generated by applying a certain radio frequency signal through the spectrometer (28), amplifying the signal through the radio frequency amplifier (29) and applying it to the radio frequency coil (26) to excite the magnetic resonance effect of the fluid in the rock to generate a signal, which is then amplified by the preamplifier (27) and collected by the spectrometer (28); When performing nuclear magnetic resonance imaging and layered T2 spectrum scanning, a certain gradient intensity is applied to the fluid to capture the signal. A certain gradient signal is applied through the spectrometer (28), and 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 then collected by the spectrometer (28). The shielding chamber (32) is used to shield interference sources by reflecting and absorbing electromagnetic waves.

5. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 4, characterized in that, The rock fluid displacement module includes: 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 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). The fluid required to inject into 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 in sequence to the first six-way (14) and the third non-magnetic switch (6), and the fluid in the second piston container (17) flows into the core of 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 in sequence to the first six-way (14) and the sixth non-magnetic switch (9), and the fluid in the third piston container (18) flows into the core of 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). The fluid required in the annular cavity of the magnetic resonance compatible core holder (31) is provided by the first piston container (16). The displacement pump (1) is connected to the first non-magnetic switch (4) and the fluid in the first piston container (16) flows into the core of the annular cavity of the magnetic resonance compatible core holder (31) through the second non-magnetic switch (5). The ring pressure is monitored and feedback is provided by connecting the second pressure sensor (20) to the inlet end of the ring pressure chamber of the magnetic resonance compatible core holder (31); The monitoring of the injection pressure of the fluid in the core is fed back through the first pressure sensor (19) connected to the inlet end of the magnetic resonance compatible core holder (31); The heating of the magnetic resonance compatible core holder (31) is regulated by a temperature control device (23) and the temperature is detected by a temperature sensor (22).

6. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 5, characterized in that, The outlet fluid acquisition and detection module includes: 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 to the ninth non-magnetic switch (12) to input fluid into the back pressure valve (41); the back pressure is monitored by the third pressure sensor (21) and feedback is given after the fluid flows into the back pressure valve (41) through the eighth non-magnetic switch (11); The collection and measurement of fluid at the outlet end are carried out by gas-liquid separation, collection and measurement through gas-liquid separator (42). Gas-liquid separator (42) is a container with a viewing window and piston, used to measure the volume of crude oil, gas phase and water phase. The gas and liquid collected by the gas-liquid separator (42) are respectively flowed into the oil phase / gas phase chromatograph (43) through the tenth non-magnetic switch (13) for detection. The oil phase / gas phase chromatograph (43) simultaneously performs oil phase component analysis and gas component analysis.

7. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 6, characterized in that, 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 an electronic device (40); The 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 big models, and stores them in the storage unit (35), and displays them on the display (36); among them, the collected data includes at least: nuclear magnetic resonance test data and chromatographic test data.

8. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 7, characterized in that, Based on the stated minimum miscibility pressure, a CO2 flooding experiment was conducted using columnar core samples. Two-dimensional nuclear magnetic resonance weighted imaging and layered T2 spectra of the fluid within the core were acquired in real time, reflecting spatiotemporal variations. Cores were drilled and cut from the formation outcrops of the target reservoir core wells, and the cores were washed, dried, and their analytical parameters were measured. The pipeline was cleaned and dried with petroleum ether. The high-pressure CO2 gas used in the experiment was placed in the third piston container (18), the crude oil was placed in the second piston container (17), and the fluorinated oil was placed in the first piston container (16). The mixture was then heated to the temperature set for the experiment. The sampled core is placed in a magnetic resonance compatible core holder (31) and placed in a shielded room (32); Turn on the ring pressure pump (1), the first non-magnetic switch (4), and the second non-magnetic switch (5) in sequence. Use fluorinated oil to purge the air from the annular cavity of the magnetic resonance compatible core holder (31) and then turn off the ring pressure pump (1) to increase the ring pressure to the set value. Turn on the temperature control system (23) to raise the temperature of the magnetic resonance compatible core holder (31) to the formation temperature; 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, establish a constant pressure difference, and inject crude oil into the core until the pressure difference at both ends of the core tends to stabilize. 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) were turned on in sequence to inject CO2 into the core. The CO2 was used to displace the crude oil. The pressure was increased to the first set pressure and the second set pressure, respectively. The second set pressure was 0.5 MPa higher than the minimum miscibility pressure. The two-dimensional nuclear magnetic resonance imaging and layered T2 spectrum of the fluid in the clamp after each pressurization were tested in the initial saturated oil state.

9. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 8, characterized in that, Simultaneously collect fluid from the outlet end and perform chromatographic testing to obtain chromatographic test data, including: When gas continuously flows out of the gas-liquid separator (42), the test result data of the oil phase / gas phase chromatograph (43) is sent to the central processing unit (37) through the communication unit 38 and the input unit 34. After being processed and analyzed by the central processing unit (37), the data is stored in the storage unit (35) and displayed on the display (36). When the component change rate in the displayed oil chromatogram and gas chromatogram is less than the set range, the eighth non-magnetic switch (11) is turned off and the experiment is stopped.

10. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, Based on the two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectra, and chromatographic test data, the dynamic changes in the degree of miscibility were qualitatively analyzed, resulting in a qualitative characterization of the degree of miscibility between CO2 and crude oil, including: Based on different weighted imaging techniques, layered two-dimensional imaging scans were performed on the core at different locations along the axial direction. Based on 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, immiscible, near-miscible, and miscible regions were identified. Based on the results of chromatographic analysis of the fluid composition changes in the produced fluid, the spatiotemporal variation of oil-gas miscibility during CO2 flooding was qualitatively determined. Specifically, based on the minimum miscibility pressure of CO2 and crude oil measured by the capillary tube experiment, layered two-dimensional imaging scans were performed on the core at different locations along the axial direction in the initial saturated oil stage, the stage with the first set injection pressure, and the stage with the second set injection pressure. Proton density imaging scans and T1-weighted imaging scans were performed in each stage. According to the set layer thickness and interlayer spacing, the test core was divided into multiple layers for imaging scans, and T2-weighted imaging scan images were obtained by image subtraction.

11. The method for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 1, characterized in that, Based on the two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectra, and chromatographic test data, the dynamic changes in the degree of miscibility were quantitatively characterized, and the quantitative characterization results of the degree of miscibility between CO2 and crude oil were obtained, including: Layered T2 spectrum scanning was performed along the core axis. The layered T2 spectrum of the initial saturated oil stage was used as the benchmark. The shift pattern of the T2 spectrum of the corresponding layer in each stage was used as the criterion for judging whether it is miscible, and the shift of the T2 spectrum of the corresponding layer was used as the criterion for calculating the degree of miscibility. Based on the aforementioned judgment and calculation criteria, the degree of miscibility between CO2 and crude oil is quantitatively calculated by observing the shift patterns and changes in the shift amount of the T2 spectra along the axial direction in the layered T2 spectra.

12. A system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance, characterized in that, The system includes: Minimum miscibility pressure analysis device, used to test the minimum miscibility pressure of crude oil and CO2 in a target reservoir using the capillary method; A nuclear magnetic resonance-physical model (NMR-PMMA) coupled device is used to conduct CO2 flooding experiments on columnar cores based on the minimum miscibility pressure. It acquires real-time two-dimensional NMR weighted imaging and layered T2 spectra of the fluid within the core as it changes spatiotemporally. Simultaneously, it acquires fluid at the outlet end and performs chromatographic tests to obtain chromatographic data. Based on the two-dimensional NMR weighted imaging, layered T2 spectra, and chromatographic data, it qualitatively and quantitatively characterizes the dynamic changes in miscibility, obtaining qualitative and quantitative characterization results of the miscibility between CO2 and crude oil.

13. The system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 12, characterized in that, The nuclear magnetic resonance-physical model combined device includes: a nuclear magnetic resonance testing module, a rock fluid displacement module, an outlet fluid acquisition and detection module, and a computer control and data processing module; The nuclear magnetic resonance testing module is used to perform nuclear magnetic resonance testing to obtain a two-dimensional nuclear magnetic resonance weighted imaging map and a layered T2 spectrum; The rock fluid displacement module includes a core holder compatible with nuclear magnetic resonance testing for conducting rock fluid displacement experiments. The outlet fluid acquisition and detection module is used to acquire the outlet fluid and perform chromatographic testing to obtain chromatographic test data. The computer control and data processing module is used to acquire two-dimensional nuclear magnetic resonance weighted imaging, layered T2 spectra and chromatographic test data, and to perform qualitative and quantitative characterization of the dynamic changes in the degree of miscibility, so as to obtain the qualitative and quantitative characterization results of the degree of miscibility between CO2 and crude oil.

14. The system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 13, characterized in that, The nuclear magnetic resonance testing module includes: 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); The permanent magnet (24), gradient coil (25), radio frequency coil (26) and preamplifier (27) are deployed in the shielded room (32); the equipment room (33) includes the spectrometer (28), radio frequency amplifier (29) and gradient amplifier (30); The permanent magnet (24) is compatible with multiple online displacement scanning methods; the signal generated by the magnetic resonance effect of the fluid in the rock is generated by applying a certain radio frequency signal through the spectrometer (28), amplifying the signal through the radio frequency amplifier (29) and applying it to the radio frequency coil (26) to excite the magnetic resonance effect of the fluid in the rock to generate a signal, which is then amplified by the preamplifier (27) and collected by the spectrometer (28); When performing nuclear magnetic resonance imaging and layered T2 spectrum scanning, a certain gradient intensity is applied to the fluid to capture the signal. A certain gradient signal is applied through the spectrometer (28), and 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 then collected by the spectrometer (28). The shielding chamber (32) is used to shield interference sources by reflecting and absorbing electromagnetic waves.

15. The system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 13, characterized in that, The rock fluid displacement module includes: 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 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). The fluid required to inject into 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 in sequence to the first six-way (14) and the third non-magnetic switch (6), and the fluid in the second piston container (17) flows into the core of 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 in sequence to the first six-way (14) and the sixth non-magnetic switch (9), and the fluid in the third piston container (18) flows into the core of 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). The fluid required in the annular cavity of the magnetic resonance compatible core holder (31) is provided by the first piston container (16). The displacement pump (1) is connected to the first non-magnetic switch (4) and the fluid in the first piston container (16) flows into the core of the annular cavity of the magnetic resonance compatible core holder (31) through the second non-magnetic switch (5). The ring pressure is monitored and feedback is provided by connecting the second pressure sensor (20) to the inlet end of the ring pressure chamber of the magnetic resonance compatible core holder (31); The monitoring of the injection pressure of the fluid in the core is fed back through the first pressure sensor (19) connected to the inlet end of the magnetic resonance compatible core holder (31); The heating of the magnetic resonance compatible core holder (31) is regulated by a temperature control device (23) and the temperature is detected by a temperature sensor (22).

16. The system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 13, characterized in that, The outlet fluid acquisition and detection module includes: 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 to the ninth non-magnetic switch (12) to input fluid into the back pressure valve (41); the back pressure is monitored by the third pressure sensor (21) and feedback is given after the fluid flows into the back pressure valve (41) through the eighth non-magnetic switch (11); The collection and measurement of fluid at the outlet end are carried out by gas-liquid separation, collection and measurement through gas-liquid separator (42). Gas-liquid separator (42) is a container with a viewing window and piston, used to measure the volume of crude oil, gas phase and water phase. The gas and liquid collected by the gas-liquid separator (42) are respectively flowed into the oil phase / gas phase chromatograph (43) through the tenth non-magnetic switch (13) for detection. The oil phase / gas phase chromatograph (43) simultaneously performs oil phase component analysis and gas component analysis.

17. The system for characterizing the degree of CO2-driven miscibility based on nuclear magnetic resonance according to claim 13, characterized in that, 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 an electronic device (40); The 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 big models, and stores them in the storage unit (35), and displays them on the display (36); among them, the collected data includes at least: nuclear magnetic resonance test data and chromatographic test data.

18. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 11.

19. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method of any one of claims 1 to 11.

20. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method of any one of claims 1 to 11.

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