Carbon dioxide migration front three-dimensional dynamic tracking method based on fiber grating

Abstract

This invention discloses a three-dimensional dynamic tracking method for the carbon dioxide migration front based on fiber Bragg gratings (FBGs). The method involves constructing a core displacement experimental device based on FBG sensing; preparing homogeneous cores of different permeability types; determining core porosity using CT scanning; attaching the FBG; conducting a carbon dioxide displacement experiment based on the FBG and testing the wavelength of the FBG; performing CT again on the extracted cores after the experiment to determine the carbon dioxide displacement front; constructing a pressure differential-permeability-displacement front strain chart; and determining the three-dimensional morphology of the carbon dioxide displacement front based on the actual core. This invention constructs a pressure differential-permeability-displacement front strain chart. Based on this chart, the three-dimensional dynamics of the carbon dioxide migration front during displacement are tracked using FBG strain monitoring, improving the accuracy of dynamic monitoring of the carbon dioxide front. This method is easy to implement and operate, providing technical support for safe and efficient carbon dioxide injection and production technology in heterogeneous reservoirs.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide geological storage technology, and in particular to a method for predicting the fluid transport front based on fiber optic sensing. Background Technology

[0002] Carbon dioxide geological sequestration (CCUS) technology refers to the capture of carbon dioxide generated during industrial and energy conversion processes before its emission, followed by transportation via pipelines or ships to a storage site, compression, and injection into suitable deep underground formations. Through physical and chemical processes, it is then isolated from the atmosphere for an extended period. Monitoring the carbon dioxide displacement front is crucial for guiding the regulation of injection and production parameters in heterogeneous saline aquifers or oil and gas reservoirs, effectively addressing the challenge of low displacement efficiency in these reservoirs.

[0003] Carbon dioxide displacement experiments possess energy, environmental, economic, and scientific value, serving as a core technological support for promoting low-carbon oil and gas development and achieving carbon neutrality. Future breakthroughs are needed in areas such as deep reservoir monitoring and long-term storage verification to further expand their application scale. Currently, carbon dioxide displacement experiments utilize X-CT or low-field NMR to monitor the displacement process in real time (Doi.org / 10.1007 / s00723-020-01280-4, Doi.org / 10.1016 / j.fuel.2021. 121606), while water-driven oil recovery experiments monitor the oil-water front using resistivity (see Chinese Patent CN 115436433 A). However, X-CT and low-field NMR are relatively expensive; furthermore, each imaging monitoring session in low-field NMR requires several minutes to tens of minutes, while X-CT requires even longer, making it impossible to achieve three-dimensional dynamic real-time tracking and evaluation of the carbon dioxide displacement front in low-permeability reservoirs.

[0004] Chinese patent CN 117723447 A discloses a CO2 plume transport simulation and monitoring device and method based on fiber optic gratings. It proposes to use fiber optic monitoring of pressure changes to determine the transport and distribution of CO2 in the core. However, the pressure front and the fluid front in the fluid displacement process are usually inconsistent (Weijermars et al., Comparison of pressure front with tracer front advance and principal flow regimes in hydraulically fractured wells in unconventional reservoirs, Journal of Petroleum Science and Engineering). Therefore, the pressure obtained by monitoring cannot represent the plume transport front. On the other hand, the fiber optic grating monitoring principle is to obtain strain by monitoring the wavelength of the fiber, which cannot directly monitor pressure as described in the patent.

[0005] Therefore, there is an urgent need to invent a high-precision three-dimensional dynamic tracking method for the carbon dioxide transport front, so as to provide technical support for the safe and efficient injection and production of carbon dioxide geological storage. Summary of the Invention

[0006] The main objective of this invention is to provide a three-dimensional dynamic tracking method for the carbon dioxide migration front based on fiber Bragg gratings. This method can achieve high-precision three-dimensional dynamic tracking of the carbon dioxide migration front, and it is simple and easy to use, providing technical support for the safe and efficient injection and production of carbon dioxide in geological storage.

[0007] The technical solution adopted in this invention is: A three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating includes the following steps: S1. Construct a core displacement experimental device based on FBG fiber grating sensing; S2. Prepare multiple homogeneous cores of the same size but with different permeabilities; S3. For multiple core samples from S2, CT scans were performed. By processing the three-dimensional pore structure images obtained from the scans, the radial porosity of the core samples was determined based on the gray level of the CT images. The radial permeability of the core samples was obtained by analyzing the relationship between permeability and porosity. S4. Before the experiment begins, M FBG fiber gratings are pasted in the radial direction of each core, and N FBG fiber gratings are pasted in the circumferential direction of the core. S5. Install the core with the FBG fiber grating attached to it into the experimental setup built in S1, and carry out the core carbon dioxide displacement experiment. During the experiment, the strain of each part of the core is calculated by measuring the wavelength of the fiber grating. S6. After the experiment, the core was removed and a CT scan was performed again to determine the location of the carbon dioxide transport front. S7. Combining the results of S5 and S6, determine the relationship between the location of the carbon dioxide transport front and the strain. Then, using the pressure difference between the injection pressure and the outlet back pressure set in the experiment, and the core permeability, construct a "pressure difference-permeability-displacement front strain" chart. S8. Using the core samples taken on-site, conduct core displacement experiments according to the S3-S5 procedure, monitor the strain on the core surface, and simultaneously use the "pressure difference-permeability-displacement front strain" chart obtained in S7 to achieve real-time three-dimensional dynamic tracking of the carbon dioxide transport front.

[0008] In the above scheme, in S1, the core displacement experimental device based on FBG fiber grating sensing includes a carbon dioxide cylinder, an ISCO plunger pump, a core holder, a pressure gauge, a back pressure valve, a confining pressure pump, a temperature control system, a fluid collection and metering device, and a fiber optic demodulator. The carbon dioxide cylinder, ISCO plunger pump, core holder, and fluid collection and metering device are connected sequentially via pipelines. The pressure gauge is installed on the inlet pipeline of the core holder, and the back pressure valve is installed on the outlet pipeline of the core holder. The confining pressure pump is connected to the confining pressure inlet of the core holder via a pipeline for applying confining pressure. The temperature control system is used to control the temperature of the core holder. The core is installed in the core holder, and each FBG fiber grating on the core is electrically connected to the fiber optic demodulator.

[0009] In the above scheme, the steps of the core carbon dioxide displacement experiment in S5 include: S51. Before the experiment, place the core into the core holder and apply pressure to the experimental conditions. Let it stand for 24-48 hours to allow the confining pressure to be fully applied to the core. The standard for ending the loading is when the confining pressure value stabilizes. S52. Inject the prepared saline water into the core using an ISCO plunger pump and observe the wavelength data in the fiber optic demodulator. If the wavelength data does not change after being injected into the fiber optic cable, the core is fully saturated with saline water. S53. Use the electric heating temperature control system to load the temperature to the experimental set temperature, and record the strain of each optical fiber at this time as the reference value. S54. Inject carbon dioxide into the core holder using an ISCO plunger pump and record the strain values ​​at different time intervals.

[0010] In the above scheme, the relationship between strain and wavelength is ε=Δλ / (K×L), where ε is strain, Δλ is wavelength change, K is strain sensitivity coefficient, and L is grating length.

[0011] In the above scheme, S8 specifically includes the following steps: S81. Following S3, perform a CT scan on the core to determine its permeability; S82. Following S4-S5, conduct a core displacement experiment based on FBG fiber grating, record the difference between the injection pressure at the injection end and the back pressure at the outlet end during the experiment, and obtain the strain value of the three-dimensional surface of the core through wavelength. S83. Query the chart to locate the front: Based on the strain values, combined with the "pressure difference-permeability-displacement front strain" chart obtained in S7, the core carbon dioxide migration front can be obtained. S84. Three-dimensional dynamic tracking: As the injection time progresses, repeat steps S81-S83 to achieve real-time, dynamic three-dimensional tracking of the spatiotemporal evolution of the leading edge during the entire displacement process.

[0012] In the above scheme, step S83 specifically includes: (1) Based on the obtained real-time pressure difference and core permeability, find the corresponding strain value in the "Pressure Difference-Permeability-Displacement Front Strain" chart; (2) By querying the chart, the strain value measured by each FBG sensor is converted into the arrival status of the displacement leading edge at the location of the sensor.

[0013] In the above scheme, if the real-time pressure difference is not on the standard curve of the chart, the displacement leading edge position corresponding to the current strain value under that pressure difference needs to be estimated by using a linear interpolation method.

[0014] In the above scheme, step S84 specifically includes: (1) Collect the “leading edge position” information obtained by all FBG sensors at the same time; (2) Using the data from these discrete points, the three-dimensional spatial morphology of the carbon dioxide displacement front inside the core was reconstructed through a spatial interpolation algorithm. (3) As the injection time progresses, repeat steps S81-S83 to achieve real-time, dynamic three-dimensional tracking of the spatiotemporal evolution of the leading edge during the entire displacement process.

[0015] In the above scheme, in S4, M≥1 and N≥1. The values ​​of M and N are determined by the accuracy requirements of carbon dioxide front monitoring and are adjusted according to the size of the test core and the rationality of the test results.

[0016] In the above scheme, the rock core used in the experiment is cylindrical, and the size of the rock core taken in the field is consistent with the size of the experimental rock core.

[0017] The beneficial effects of this invention are: Before the experiment, the permeability of the core was obtained by CT scanning. During the experiment, the strain of different parts of the core was monitored by fiber optic grating during the displacement process. After the experiment, the position of the carbon dioxide migration front was obtained by CT scanning again, thus obtaining the relationship between the position of the carbon dioxide migration front and the strain. Finally, a "pressure difference-permeability-displacement front strain" chart was constructed. Based on this chart, the three-dimensional dynamics of the carbon dioxide migration front during the displacement process were tracked by fiber optic grating strain monitoring, which improved the accuracy of carbon dioxide front dynamic monitoring.

[0018] The method of this invention enables real-time monitoring of the carbon dioxide migration front. The method is easy to implement and simple to operate, providing technical support for safe and efficient carbon dioxide injection and production technology in heterogeneous reservoirs. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the three-dimensional dynamic tracking method for carbon dioxide transport front based on fiber Bragg grating according to the present invention; Figure 2 This is a schematic diagram of the core displacement experimental device constructed in an embodiment of the present invention; Figure 3 This is a schematic diagram of the FBG fiber grating arrangement along the radial direction of the core in an embodiment of the present invention; Figure 4 This is a schematic diagram of the FBG fiber grating arrangement along the circumferential direction of the core in an embodiment of the present invention; Figure 5 This is a schematic diagram of the pressure difference-permeability-strain chart constructed in an embodiment of the present invention.

[0021] In the figure: 10. Core displacement experimental apparatus; 11. Carbon dioxide cylinder; 12. ISCO plunger pump; 13. Core holder; 14. Pressure gauge; 15. Back pressure valve; 16. Confining pressure pump; 17. Temperature control system; 18. Fluid collection and metering device; 19. Fiber optic demodulator; 20. Core; 21. FBG fiber grating. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] In this invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0025] Furthermore, it should be noted that the features of the various embodiments of the present invention can be combined or integrated in whole or in part, and as those skilled in the art will understand, they can interact and operate in different ways. Each embodiment can be implemented independently of each other or in association with one another.

[0026] like Figure 1 As shown, this invention proposes a three-dimensional dynamic tracking method for the carbon dioxide transport leading edge based on a fiber Bragg grating, comprising the following steps: S1. Construct a core displacement experimental device based on FBG fiber grating sensing.

[0027] like Figure 2As shown, the core displacement experimental apparatus based on FBG fiber grating sensing includes a carbon dioxide cylinder 11, an ISCO plunger pump 12, a core holder 13, a pressure gauge 14, a back pressure valve 15, a confining pressure pump 16, a temperature control system 17, a fluid collection and metering device 18, and a fiber optic demodulator 19. The carbon dioxide cylinder 11, ISCO plunger pump 12, core holder 13, and fluid collection and metering device 18 are connected sequentially via pipelines, with the ISCO plunger pump 12 providing the injection pressure. The pressure gauge 14 is installed on the inlet pipeline of the core holder 13, and the back pressure valve 15 is installed on the outlet pipeline of the core holder 13. The confining pressure pump 16 is connected to the confining pressure inlet of the core holder 13 via a pipeline for applying confining pressure. The temperature control system 17 is used to control the temperature of the core holder 13. The core 20 is installed in the core holder 13, and each FBG fiber grating 21 on the core is electrically connected to the fiber demodulator 19.

[0028] S2. Prepare multiple homogeneous cores of the same size but with different permeabilities.

[0029] Reservoirs with a permeability ≥ 500 mD are classified as ultra-high permeability reservoirs; those with a permeability of 100~500 mD are classified as high permeability reservoirs; those with a permeability of 10~100 mD are classified as medium permeability reservoirs; those with a permeability of 0.1~10 mD are classified as low permeability reservoirs; and those with a permeability < 0.1 mD are classified as ultra-low permeability reservoirs.

[0030] In this embodiment, cylindrical cores with a diameter of 25 mm and a length of 50 mm were used. Since there are no high-permeability or ultra-high-permeability reservoirs in this geological block, two cores were selected from each of the medium-permeability, low-permeability, and ultra-low-permeability reservoirs.

[0031] S3. For multiple core samples from S2, CT scans were performed. By processing the three-dimensional pore structure images obtained from the scans, the radial porosity of the core samples was determined based on the gray level of the CT images (Wang Yu et al., Calculation and Application of Porosity Based on Image Gray Level, 2015). The radial permeability of the core samples was obtained through the relationship between permeability and porosity (Carman-Kozeny equation).

[0032] In this embodiment, the CT scan accuracy along the core radial direction is 1 mm, and the layer spacing is 0.5 mm.

[0033] S4. Before the experiment begins, M FBG fiber gratings are pasted in the radial direction of each core sample, and N FBG fiber gratings are pasted in the circumferential direction of the core sample.

[0034] M≥1, N≥1. The values ​​of M and N depend on the required accuracy of carbon dioxide front monitoring and can be adjusted based on the size of the test core and the reasonableness of the test results. In this embodiment, as... Figure 3As shown, M=5, meaning five FBG fiber gratings are evenly pasted in the radial direction of the core. The position is determined by dividing the core of length L into six equal parts. The FBG fiber gratings are pasted at 1 / 6L, 2 / 6L, 3 / 6L, 4 / 6L, and 5 / 6L to avoid unreliable results caused by pasting the FBG fiber gratings at both ends. Figure 4 As shown, N=3, that is, three FBG fiber gratings are uniformly pasted in the radial direction of the core. The method for determining the position is as follows: divide the 360-degree circumference into three equal parts, and use Aibida 6005 epoxy resin AB glue to paste the FBG fiber gratings at the positions of 0°, 120° and 240° respectively.

[0035] S5. Install the core with the FBG fiber grating attached onto it into the experimental setup constructed in S1, and conduct the core carbon dioxide displacement experiment. During the experiment, the wavelength of the fiber grating is measured and converted into strain using the relationship between strain and wavelength: ε = Δλ / (K × L) (Fan Chengkai, Fiber Grating Monitoring and Numerical Simulation of Strain Response at the CO2 Core Discharge Front, 2019). Here, ε is the strain, Δλ is the wavelength change, K is the strain sensitivity coefficient, and L is the grating length.

[0036] The steps of a core carbon dioxide displacement experiment include: S51. Before the experiment, place the core in the core holder 13 and apply pressure to the experimental conditions. Let it stand for 24~48 h to allow the confining pressure to be fully applied to the core. S52. Inject the prepared saline water into the core using the ISCO plunger pump 12 and observe the wavelength data in the fiber optic demodulator 19. If the wavelength data does not change after being injected into the fiber optic cable, the core is fully saturated with saline water. S53. Use the electric heating temperature control system 17 to apply the temperature to the experimental set temperature, and record the strain of each optical fiber at this time as the reference value. S54. Carbon dioxide is injected into the core holder 13 through the ISCO plunger pump 12, and the strain values ​​at different time periods are recorded.

[0037] S6. After the experiment, the core was removed, and then a CT scan was performed again according to step S3. The location of the carbon dioxide transport front was determined based on the gray level of the measured CT image.

[0038] S7. Combining the results of S5 and S6, the relationship between the location of the carbon dioxide transport front and strain was determined. Then, using the pressure difference between the injection pressure and the outlet back pressure set in the experiment, and the core permeability, a "pressure difference-permeability-displacement front strain" chart was constructed.

[0039] In the “Pressure Difference-Permeability-Displacement Front Strain” chart, the pressure difference refers to the difference between the injection pressure at the injection end and the back pressure at the outlet end in the S5 experiment; the permeability is obtained from the data analysis of CT scans in S3; and the strain is the wavelength obtained by testing the FBG fiber grating during the S5 experiment, which is obtained through the relationship between strain and wavelength.

[0040] The "pressure difference-permeability-displacement front strain" chart constructed in this embodiment is as follows: Figure 5 As shown, it should be noted that if the pressure difference measured in the core during the experiment is 2.2 MPa, which is not on the standard pressure curves such as 2 MPa and 2.5 MPa, then it is necessary to use the position between 2 MPa and 2.5 MPa to perform difference processing to obtain the strain and permeability curves corresponding to 2.2 MPa.

[0041] S8. Using core samples taken on-site, conduct core displacement experiments according to procedures S3-S5, monitor the strain on the core surface, and simultaneously utilize the "pressure difference-permeability-displacement front strain" chart obtained in S7 to achieve real-time three-dimensional dynamic tracking of the carbon dioxide transport front. Specifically, this includes the following steps: S81. According to S3, perform CT scanning on the core to determine the permeability of the core in the radial direction; S82. Following the procedures in S4 and S5, conduct a core displacement experiment based on FBG fiber grating, record the difference between the injection pressure at the injection end and the back pressure at the outlet end during the experiment, and obtain the strain value of the three-dimensional surface of the core through wavelength. S83. Refer to the chart to locate the leading edge. Based on the strain values ​​and combined with the "pressure difference-permeability-displacement front strain" chart obtained in S7, the core carbon dioxide migration front can be obtained. The specific method is as follows: (1) Based on the obtained real-time pressure difference and core permeability, find the corresponding strain value in the "Pressure Difference-Permeability-Displacement Front Strain" chart; (2) By consulting the chart, the strain value measured by each FBG sensor can be converted into the arrival status of the displacement leading edge at the location of the sensor (e.g., whether the leading edge has advanced to the point).

[0042] (3) If the real-time pressure difference (e.g., 2.2 MPa) is not on the standard curve of the chart (e.g., 2 MPa, 2.5 MPa), then the displacement leading edge position corresponding to the current strain value under the pressure difference needs to be estimated by linear interpolation.

[0043] S84, 3D dynamic tracking. The specific method is as follows: (1) Collect the “leading edge position” information obtained from all FBG sensors (M radial points and N circumferential points) at the same time; (2) Using the data from these discrete points, the three-dimensional spatial morphology of the carbon dioxide displacement front inside the core can be reconstructed through a spatial interpolation algorithm. (3) As the injection time progresses, repeat steps S81-S83 to achieve real-time, dynamic three-dimensional tracking of the spatiotemporal evolution of the leading edge during the entire displacement process.

[0044] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0045] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0046] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating, characterized in that, Includes the following steps: S1. Construct a core displacement experimental device based on FBG fiber grating sensing; S2. Prepare multiple homogeneous cores of the same size but with different permeabilities; S3. For multiple core samples from S2, CT scans were performed. By processing the three-dimensional pore structure images obtained from the scans, the radial porosity of the core samples was determined based on the gray level of the CT images. The radial permeability of the core samples was obtained by analyzing the relationship between permeability and porosity. S4. Before the experiment begins, M FBG fiber gratings are pasted in the radial direction of each core, and N FBG fiber gratings are pasted in the circumferential direction of the core. S5. Install the core with the FBG fiber grating attached to it into the experimental setup built in S1, and carry out the core carbon dioxide displacement experiment. During the experiment, the strain of each part of the core is calculated by measuring the wavelength of the fiber grating. S6. After the experiment, the core was removed and a CT scan was performed again to determine the location of the carbon dioxide transport front. S7. Combining the results of S5 and S6, determine the relationship between the location of the carbon dioxide transport front and the strain. Then, using the pressure difference between the injection pressure and the outlet back pressure set in the experiment, and the core permeability, construct a "pressure difference-permeability-displacement front strain" chart. S8. Using the core samples taken on-site, conduct core displacement experiments according to the S3-S5 procedure, monitor the strain on the core surface, and simultaneously use the "pressure difference-permeability-displacement front strain" chart obtained in S7 to achieve real-time three-dimensional dynamic tracking of the carbon dioxide transport front.

2. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 1, characterized in that, In S1, the core displacement experimental device based on FBG fiber grating sensing includes a carbon dioxide cylinder, an ISCO plunger pump, a core holder, a pressure gauge, a back pressure valve, a confining pressure pump, a temperature control system, a fluid collection and metering device, and a fiber optic demodulator. The carbon dioxide cylinder, ISCO plunger pump, core holder, and fluid collection and metering device are connected sequentially via pipelines. The pressure gauge is installed on the inlet pipeline of the core holder, and the back pressure valve is installed on the outlet pipeline of the core holder. The confining pressure pump is connected to the confining pressure inlet of the core holder via a pipeline for applying confining pressure. The temperature control system is used to control the temperature of the core holder. The core is installed in the core holder, and each FBG fiber grating on the core is electrically connected to the fiber optic demodulator.

3. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 2, characterized in that, In S5, the steps of the core carbon dioxide displacement experiment include: S51. Before the experiment, place the core into the core holder and apply pressure to the experimental conditions. Let it stand for 24-48 hours to allow the confining pressure to be fully applied to the core. The standard for ending the loading is when the confining pressure value stabilizes. S52. Inject the prepared saline water into the core using an ISCO plunger pump and observe the wavelength data in the fiber optic demodulator. If the wavelength data does not change after being injected into the fiber optic cable, the core is fully saturated with saline water. S53. Use the electric heating temperature control system to load the temperature to the experimental set temperature, and record the strain of each optical fiber at this time as the reference value. S54. Inject carbon dioxide into the core holder using an ISCO plunger pump and record the strain values ​​at different time intervals.

4. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 3, characterized in that, The relationship between strain and wavelength is ε=Δλ / (K×L), where ε is the strain, Δλ is the wavelength change, K is the strain sensitivity coefficient, and L is the grating length.

5. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 1, characterized in that, S8 specifically includes the following steps: S81. Following S3, perform a CT scan on the core to determine its permeability; S82. Following S4-S5, conduct a core displacement experiment based on FBG fiber grating, record the difference between the injection pressure at the injection end and the back pressure at the outlet end during the experiment, and obtain the strain value of the three-dimensional surface of the core through wavelength. S83. Query the chart to locate the front: Based on the strain values ​​and combined with the "pressure difference-permeability-displacement front strain" chart obtained in S7, the core carbon dioxide migration front can be obtained. S84. Three-dimensional dynamic tracking: As the injection time progresses, repeat steps S81-S83 to achieve real-time, dynamic three-dimensional tracking of the spatiotemporal evolution of the leading edge during the entire displacement process.

6. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 5, characterized in that, Step S83 specifically includes: (1) Based on the obtained real-time pressure difference and core permeability, find the corresponding strain value in the "Pressure Difference-Permeability-Displacement Front Strain" chart; (2) By querying the chart, the strain value measured by each FBG sensor is converted into the arrival status of the displacement leading edge at the location of the sensor.

7. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 6, characterized in that, If the real-time differential pressure is not on the standard curve of the chart, then the displacement leading edge position corresponding to the current strain value under that differential pressure needs to be estimated by using a linear interpolation method.

8. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 5, characterized in that, Step S84 specifically includes: (1) Collect the "leading edge position" information obtained by all FBG sensors at the same time; (2) Using the data from these discrete points, the three-dimensional spatial morphology of the carbon dioxide displacement front inside the core was reconstructed through a spatial interpolation algorithm. (3) As the injection time progresses, repeat steps S81-S83 to achieve real-time, dynamic three-dimensional tracking of the spatiotemporal evolution of the leading edge during the entire displacement process.

9. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 1, characterized in that, In S4, M≥1 and N≥1. The values ​​of M and N are determined by the accuracy requirements of carbon dioxide front monitoring and are adjusted according to the size of the test core and the rationality of the test results.

10. The three-dimensional dynamic tracking method for carbon dioxide transport leading edge based on fiber Bragg grating according to claim 1, characterized in that, The core used in the experiment was cylindrical, and the size of the core taken in the field was consistent with the size of the experimental core.

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