Hydrate saturation fine characterization device and method based on time domain reflectometry

Abstract

The invention belongs to the technical field of marine natural gas hydrate resource exploration and development engineering, and particularly provides a hydrate saturation fine characterization device and method based on a time domain reflection method.The device comprises a reaction kettle, a dielectric property testing module and a data collecting and processing module; the dielectric property testing module comprises a time domain reflection tester and a time domain reflection sensor assembly which are connected, the time domain reflection sensor assembly vertically penetrates through the bottom of the reaction kettle and is inserted into the reaction kettle, a marine sediment sample is arranged in the reaction kettle, and the marine sediment sample is virtually divided into a plurality of layers in the length direction of the reaction kettle; the time-domain reflection sensor assembly is composed of one or more groups of time-domain reflection sensors, each group of time-domain reflection sensors is composed of time-domain reflection sensors with the number equal to that of the layers, the lengths of all the groups of time-domain reflection sensors are different, and the top ends of all the groups of time-domain reflection sensors are located at different layers, so that the saturation degrees of hydrates at different positions in the sediment sample can be obtained; the fine characterization of the saturation of the hydrate in the sediment sample can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of marine natural gas hydrate resource exploration and development engineering, and particularly relates to a hydrate saturation fine characterization device and method based on time domain reflectometry. BACKGROUND

[0002] Natural gas hydrate is a kind of ice-like substance formed by natural gas (mainly methane) and water under high pressure and low temperature environment. Studies have found that the carbon equivalent of natural gas hydrate is more than twice that of other fossil fuels (such as coal and oil), and natural gas combustion does not produce toxic substances (such as sulfur dioxide and nitrogen oxides). Therefore, natural gas hydrate is considered as a very potential alternative new energy, and its development and utilization have attracted widespread attention worldwide.

[0003] One of the important prerequisites for efficient development and utilization of natural gas hydrate is to fine characterize the hydrate saturation in marine sediments. At present, seismic exploration for detecting acoustic properties and electrical prospecting for detecting electrical properties are popular means for quantifying hydrate saturation in marine sediments. However, although seismic exploration has high resolution, it is not sensitive enough to the type and content of fluid in the sediment pores; unlike this, although electrical prospecting based on resistivity has higher sensitivity to the type and content of fluid in the pores, resistivity is significantly affected by the salinity of pore water and reservoir temperature. Therefore, seismic and electrical prospecting have certain defects in the fine characterization of hydrate saturation in marine sediments. Compared with the above two detection methods, the detection technology based on dielectric properties not only can effectively identify the type of fluid in the sediment pores and directly calculate its content, but also is hardly affected by the salinity of pore water and temperature, thereby providing a new way for the fine characterization of hydrate saturation in marine sediments.

[0004] In recent years, scholars from various countries have carried out a large number of experimental studies through time domain reflectometry based on the detection of dielectric constant, and have explored the relationship between dielectric constant and hydrate saturation in sediment samples, laying a foundation for using dielectric detection data to invert hydrate saturation in marine sediments. For example, Wright et al. (2002) detected the dielectric constant of hydrate-containing sediments at different hydrate saturations based on time domain reflectometry, and established the relationship between hydrate saturation and dielectric constant. Hu Gao-wei et al. (2012) combined time domain reflectometry with the relationship established by Wright et al. (2002) to calculate the hydrate saturation in loose sediments.

[0005] The above studies are all based on the ideal state that hydrates are uniformly distributed in the sediment sample, however, the applicant found that there are spatial differences in the internal pore structure of the sediment sample in the high-pressure reactor, which makes the distribution of methane gas and pore water in the sediment pores uneven, thus leading to uneven distribution of hydrates generated in the sediment pores, and this uneven distribution of hydrates is more significant in actual hydrate-containing sediments. However, the related studies reported so far are all estimating the overall hydrate saturation in the sediment sample, and cannot further explore the distribution of hydrates in the sediment sample, such as the hydrate saturation at different positions in the sediment sample, so the experimental device used in the studies cannot achieve fine characterization of the hydrate saturation in the sediment sample. SUMMARY

[0006] To solve the defect that the prior art cannot achieve fine characterization of the hydrate saturation in hydrate-containing sediments, the present application provides a hydrate saturation fine characterization device and method based on time domain reflectometry, which provides a scientific basis for accurately evaluating the hydrate resource reserves in marine sediments by using dielectric properties, and the scheme is as follows: In one aspect, the present application provides an experimental device for fine characterization of hydrate saturation based on time domain reflectometry, which comprises a device body, the device body comprises a reactor, the device body further comprises a dielectric property testing module connected with the reactor, and a data acquisition and processing module electrically connected with the dielectric property testing module, the dielectric property testing module comprises a time domain reflectometry tester and a time domain reflectometry sensor assembly connected with the time domain reflectometry tester, the time domain reflectometry sensor assembly is vertically penetrated and inserted into the reactor from the bottom of the reactor, the reactor is embedded with a marine sediment sample, the marine sediment sample is virtually divided into multiple layers along the length direction of the reactor, and the time domain reflectometry sensor assembly is composed of one or more groups of time domain reflectometry sensors, each group of time domain reflectometry sensors is composed of time domain reflectometry sensors equal in number to the layers, and the length of each group of time domain reflectometry sensors is different and the top end thereof is located at different layers.

[0007] Further, when the time domain reflectometry sensor assembly is composed of one group of time domain reflectometry sensors, the total number of time domain reflectometry sensors is equal to the number of layers; the reactor is a cylinder, and the multiple time domain reflectometry sensors are arranged in a circumferential uniform distribution in the reactor.

[0008] Further, the multiple time domain reflectometry sensors are uniformly distributed on a circle with a radius of one-half of the inner diameter of the high-pressure reactor and overlapping the fluid passage at the bottom end of the high-pressure reactor.

[0009] Further, when the time domain reflection sensor group is composed of multiple time domain reflection sensor groups, the total number of time domain reflection sensors and the number of layer positions are in a multiple relationship; the reaction kettle is a cylinder, and the multiple time domain reflection sensors are arranged in a circumferential uniform distribution in the reaction kettle from inside to outside.

[0010] Further, the thickness of the layer position can be equally divided or gradually increased from bottom to top.

[0011] Further, the device body further comprises a pore pressure control module and a temperature control module, the pore pressure control module and the temperature control module are connected with the reaction kettle respectively, and the pore pressure control module and the temperature control module are electrically connected with the data acquisition and processing module. The pore pressure control module comprises a methane gas cylinder, a pore water injection pump, a pressure sensor and a vacuum pump connected with each other, so as to adjust and monitor the pore pressure change in the sediment in the reaction kettle in real time. The temperature control module comprises a temperature adjusting device and a temperature sensor connected with each other, so as to adjust and monitor the temperature change of the sediment in the reaction kettle in real time. The data acquisition and processing module can record the data measured by the temperature sensor, the pressure sensor and the time domain reflection sensor in real time, and process and draw images of the measured data.

[0012] On the other hand, the application provides a hydrate saturation fine characterization method based on time domain reflection method, which is applied to the experimental device and comprises the following steps: S1, connecting and installing the experimental device, and checking the sealing property; S2, sample preparation: obtaining sample porosity; S3, experimental measurement: measuring the dielectric constant at different sediment sample thicknesses by multiple time domain reflection sensors; S4, estimation of hydrate saturation in different sediment layer positions: S41, according to the dielectric constant obtained in step S3, the sample porosity is brought into the following formula to calculate the hydrate saturation at different thicknesses of the sediment sample: e =a× e -bSh (1); a= 61.33× φ 2 +18.336× φ +7.2346 (2); b = 3.3499× φ +0.3486 (3); wherein, e is the dielectric constant measured in the experiment,S h For hydrate saturation, φ The porosity of the sample is denoted as ; the thickness of the sediment sample refers to the distance from the top of the time-domain reflectometry sensor to the bottom surface of the marine sediment sample. S42. The hydrate saturation at a certain layer is obtained by subtracting the hydrate saturation at two thicknesses that differ by one layer. S43. Repeat step S42 to obtain the hydrate saturation of each layer.

[0013] Furthermore, step S2 includes: S21. The washed and dried marine sediment simulation medium is loaded into the reactor. The porosity of the sample in the reactor is calculated based on the volume of the sample in the reactor and the mass and density of the marine sediment simulation medium. S22. Vacuum the simulated marine sediment medium in the reactor, inject methane gas into the reactor, inject pore water into the reactor, and lower the temperature of the experimental device. When the temperature and pressure conditions required for hydrate formation are reached, a hydrate-containing sediment sample is formed in the reactor.

[0014] Furthermore, step S3 includes: S31. Record the temperature and pressure changes during the experiment; S32. Inject a predetermined volume and pressure of methane gas into the reactor, inject pore water at a predetermined pressure into the reactor, and set the temperature required for hydrate formation; when the pore pressure controlled by the pore water remains constant, the methane gas in the sediment in the reactor is completely converted into hydrate. S33. Transmit and receive electromagnetic wave signals through a time-domain reflectometry instrument and a time-domain reflectometry sensor, and measure and record dielectric data; S34. Record the temperature and pressure data changes during the test process, and complete the data acquisition and storage.

[0015] Compared with the prior art, the advantages of the present invention are as follows: The experimental device of the present application adopts multiple time domain reflection sensors which are vertically inserted into the reactor from the bottom of the reactor, the marine sediment sample is placed in the reactor, the marine sediment sample is virtually divided into multiple layers along the length direction of the reactor, the number of layers is equal to the number of time domain reflection sensors, the lengths of multiple time domain reflection sensors are different, and the top end of each time domain reflection sensor is located at a different layer, the technical scheme, when the hydrate saturation at a certain layer is obtained by subtracting the hydrate saturation at two thicknesses with a layer difference in thickness, the distribution of hydrates in the sediment sample can be further explored, such as the hydrate saturation at a certain precise layer thickness in the sediment sample, the layer thickness can be accurate to millimeter level, by reducing the length difference between adjacent time domain reflection sensors, the sediment sample layer thickness can be further refined, the hydrate saturation in the sediment sample can be precisely characterized, and the experimental device and the experimental method are simple and practical, and are worth promoting.

[0016] The experimental method of the present application can directly calculate the hydrate saturation in the sample based on the measured water content, has the advantages of small influence of pore water salinity and temperature, and greatly improves the measurement accuracy of hydrate saturation. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural schematic diagram of the experimental device of the first embodiment of the present application; Figure 2 is a structural schematic diagram of the internal cross-sectional structure of the reactor of the first embodiment of the present application; Figure 3 is a structural schematic diagram of the arrangement mode of the time domain reflection sensor in the reactor of the first embodiment of the present application; Figure 4 is a structural schematic diagram of the arrangement mode of the time domain reflection sensor in the reactor of the second embodiment of the present application.

[0018] In the above figures: A. Reactor; B. Pore pressure control module; C. Temperature control module; D. Data acquisition and processing module; E. Dielectric property testing module; 1. Time domain reflectometer; 2. Refrigeration water bath; 3. Pressure sensor; 4. Temperature sensor; 5. Methane gas cylinder; 6. Valve; 7. Brine injection pump; 8. Vacuum pump; 9. Fluid channel; 10. Permeable stone; 11. Sediment sample layer eight; 12. Sediment sample layer seven; 13. Sediment sample layer six; 14. Sediment 15. Sediment sample layer 5; 16. Sediment sample layer 4; 17. Sediment sample layer 3; 18. Sediment sample layer 2; 19. Sediment sample layer 1; 20. Insulating inner cylinder; 21. Outer shell of the vessel; 22. Dashed line; 23. Time domain reflectance sensor 8; 24. Time domain reflectance sensor 7; 25. Time domain reflectance sensor 6; 26. Time domain reflectance sensor 5; 27. Time domain reflectance sensor 4; 28. Time domain reflectance sensor 3; 29. ​​Time domain reflectance sensor 2; 20. Time domain reflectance sensor 1. Detailed Implementation

[0019] To facilitate understanding of the present invention by those skilled in the art, specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0020] Example 1 like Figures 1 to 3 As shown, this invention proposes an experimental apparatus for fine characterization of hydrate saturation based on time-domain reflectometry. The apparatus includes a reaction vessel A, a pore pressure control module B, a temperature control module C, a dielectric property testing module E, and a data acquisition and processing module D. The reaction vessel A is connected to the pore pressure control module B, the temperature control module C, and the dielectric property testing module E, respectively. The data acquisition and processing module D is electrically connected to the pore pressure control module B, the temperature control module C, and the dielectric property testing module E.

[0021] For handling complex reactions such as marine sediment treatment, the reactor A of this invention is a high-pressure reactor by default. In this embodiment, reactor A is a cylindrical high-pressure reactor, which includes an outer shell 20 and an insulating inner cylinder 19. The insulating inner cylinder 19 is tightly embedded in the outer shell 20 and contains marine sediment samples. Experiments on the formation and decomposition of hydrates can be carried out in it, and the changes in temperature, pore pressure, and dielectric constant during the experiment can be measured.

[0022] The marine sediment sample inside reactor A is virtually divided into multiple layers along the length of reactor A. The thickness of each layer can be evenly divided or gradually increase from bottom to top.

[0023] In this embodiment, eight equally divided layers are used as an example for illustration. From bottom to top, they are layer 1, layer 2, layer 3, layer 4, layer 5, layer 6, layer 7, and layer 8.Figure 2 As shown in the figure, the dotted line 21 is the virtual layering of the sediment, which is for illustration only and does not exist in the actual structure.

[0024] The pore pressure control module B includes a connected methane gas cylinder 5, a pore water injection pump, a pressure sensor 3 and a vacuum pump 88 to adjust and monitor the change of the pore pressure in the sediment in the reactor A in real time.

[0025] The temperature control module C includes a connected temperature adjusting device and a temperature sensor 4 to adjust and monitor the change of the temperature of the sediment in the reactor A in real time. The temperature sensor 4 is inserted into the reactor A to detect the temperature of the sediment in real time, and the temperature adjusting device is used to adjust the temperature of the sediment in the reactor. The temperature adjusting device can adopt the structure of the prior art, for example, the temperature adjusting device includes a refrigerator and a circulating liquid conduit, and the circulating liquid inlet and outlet are arranged inside the reactor, and the circulating liquid inlet and outlet are connected with the thermostat in the refrigerator through the circulating liquid conduit.

[0026] The dielectric property testing module E includes a time domain reflectometry tester 1 and a set of time domain reflectometry sensors connected with the time domain reflectometry tester 1. The number of the time domain reflectometry sensors in the set of time domain reflectometry sensors is the same as the number of the divided layers, and the plurality of time domain reflectometry sensors are arranged in a circumferential distribution in the reactor A. In this way, the dielectric constant at different positions can be measured. The number of the time domain reflectometry sensors in each group is determined according to the number of the intended layers, and the length of the time domain reflectometry sensors is determined according to the height of the reactor A.

[0027] In this embodiment, as shown in the figure, Figure 2 The set of time domain reflectometry sensors includes 8 time domain reflectometry sensors, and the length of the 8 sensors is different. The 8 sensors vertically penetrate into the reactor A from the bottom of the reactor A, and the length in the reactor A is 30 mm, 80 mm, 130 mm, 180 mm, 230 mm, 280 mm, 330 mm and 380 mm respectively. In order to facilitate the distinction, the time domain reflectometry sensors with the above lengths are named as time domain reflectometry sensor one 29, time domain reflectometry sensor two 28, time domain reflectometry sensor three 27, time domain reflectometry sensor four 26, time domain reflectometry sensor five 25, time domain reflectometry sensor six 24, time domain reflectometry sensor seven 23 and time domain reflectometry sensor eight 22.

[0028] Specifically, the length of the time domain reflectometry sensor one 29 in the reactor A is 30 mm, and the sensor can detect the dielectric constant of the marine sediment sample with a thickness of 30 mm. The length of the time domain reflectometry sensor two 28 in the reactor A is 80 mm, and the sensor can detect the dielectric constant of the marine sediment sample with a thickness of 80 mm. Similarly, the time domain reflectometry sensors can detect the dielectric constant of the marine sediment sample with other thicknesses.

[0029] The data acquisition and processing module D can record the data measured by the temperature sensor 4, the pressure sensor 3 and the time domain reflection sensor in real time, and process and draw images of the measured data.

[0030] Specifically, the fluid passage 9 is arranged at the center of the top end and the bottom end of the reactor A, so that the pore water and the methane gas are injected into the sediment in the reactor A from the fluid passage 9. The gas-permeable and water-permeable stone 10 is arranged at the top end and the bottom end of the reactor A, so that the pore water and the methane gas are uniformly dispersed into the sediment.

[0031] This embodiment is particularly suitable for the case that the size of the reactor A is small, especially the case that the inner diameter of the reactor A is small.

[0032] In order to avoid mutual interference between adjacent time domain reflection sensors during the measurement process, and to expand the detection range of the time domain reflection sensors as much as possible to obtain better test results, referring to Figure 3 The eight time domain reflection sensors are uniformly distributed on a circle whose center overlaps with the fluid passage 9 at the bottom end of the reactor A, but the radius is half of the inner diameter of the reactor A.

[0033] Embodiment Two Compared with the first embodiment, the difference is that the time domain reflection sensors are multiple groups. The dielectric property testing module E includes the time domain reflection tester 1 and multiple groups of time domain reflection sensors connected to the time domain reflection tester 1. The total number of time domain reflection sensors and the number of layers are in a multiple relationship. The multiple groups of time domain reflection sensors are arranged in a circumferential uniform distribution in the reactor A from inside to outside.

[0034] This embodiment is particularly suitable for the case that the size of the reactor A is large, especially the case that the inner diameter of the reactor A is large.

[0035] Referring to Figure 4 In this embodiment, there are two groups of time domain reflection sensors, each group of time domain reflection sensors includes 8 time domain reflection sensors, of course, other numbers are also possible, and the 8 sensors have different lengths, vertically penetrating into the reactor from the bottom of the reactor A, and the lengths in the reactor are 30 mm, 80 mm, 130 mm, 180 mm, 230 mm, 280 mm, 330 mm and 380 mm, respectively.

[0036] In order to finely detect the hydrate saturation at different positions of the sediment sample in the reactor as much as possible, so as to obtain a more fine characterization effect, referring to Figure 4One group (i.e. 8) of time domain reflectometry sensors are evenly distributed on a circle with the center overlapping the fluid passage 9 at the bottom end of the reactor A and a radius of one fourth of the inner diameter of the reactor A, and another group (i.e. 8) of time domain reflectometry sensors are evenly distributed on a circle with the center overlapping the fluid passage 9 at the bottom end of the reactor A and a radius of three fourths of the inner diameter of the reactor A.

[0037] Example Three The application also proposes an experimental method for fine characterization of hydrate saturation based on the time domain reflectometry method, which comprises the following steps: Step 1, connect the reactor A, the pore pressure control module B, the temperature control module C, the dielectric property test module E and the data acquisition and processing module D of the experimental device, prepare the items needed for the experiment, including marine sediment simulation medium (quartz sand), time domain reflectometry sensors, temperature sensor 4, pressure sensor 3, pore water, methane gas cylinder 5, etc.

[0038] Step 2, check the sealing of the experimental device: Install the time domain reflectometry sensors, temperature sensor 4 and pressure sensor 3 on the reactor A, inject nitrogen gas with a certain pressure into the reactor A, then block the fluid passage 9 at the top and bottom center of the reactor A with valves 66, observe the pressure change monitored by the pressure sensor 3, and after a period of time, the pressure does not change, indicating that the sealing condition of the experimental device is good.

[0039] Step 3, sample preparation: (1) Put the washed and dried quartz sand into the high-pressure reactor A, and calculate the porosity of the sample in the reactor A according to the volume of the sample in the reactor A and the mass and density of the quartz sand loaded.

[0040] (2) Prepare a hydrate-containing sediment sample: first, vacuum the quartz sand in the reactor A, then inject methane gas into the reactor A, then inject pore water into the reactor A, reduce the temperature of the experimental device, and when the temperature and pressure conditions required for hydrate formation are reached, a hydrate-containing sediment sample will be formed in the reactor A.

[0041] Step 4, experimental measurement: (1) Connect the data acquisition and processing module D, start measurement, and record the temperature and pressure changes during the experiment.

[0042] (2) Injecting methane gas with a predetermined volume and pressure into the reactor A, operating the pore pressure control module B and the temperature control module C, injecting pore water with a predetermined pressure into the reactor A, and setting the temperature required for hydrate formation; when the temperature and pressure required for hydrate formation are adjusted, the pore pressure controlled by the pore water is constant, indicating that the methane gas in the sediment in the reactor A is completely converted into hydrate, at which time the sediment pores only contain pore water and natural gas hydrate.

[0043] (3) Operating the dielectric property testing module E, transmitting and receiving electromagnetic wave signals by the time domain reflectometry tester 1 and the time domain reflectometry sensor, starting to measure and record the dielectric data.

[0044] (4) Recording the temperature and pressure data changes during the test, completing data acquisition and storage.

[0045] Step 5, Estimation of hydrate saturation in different sediment horizons: (1) According to the dielectric constant measured by the multiple time domain reflectometry sensors in step 4, the hydrate saturation at different thicknesses of the sediment sample is calculated respectively by using the following formula, in which the different thicknesses include 30 mm, 80 mm, 130 mm, 180 mm, 230 mm, 280 mm, 330 mm and 380 mm in this embodiment: e =a× e -bSh (1) a= 61.33× φ 2 +18.336× φ +7.2346 (2) b= 3.3499× φ +0.3486 (3) wherein, e is the dielectric constant measured in the experiment, S h is the hydrate saturation, φ is the porosity of the sample.

[0046] (2) The hydrate saturation at a certain horizon is obtained by subtracting the hydrate saturation at two thicknesses with a difference of one horizon. The thickness of the sediment sample refers to the distance from the top end of the time domain reflectometry sensor to the bottom surface of the marine sediment sample.

[0047] For example, the hydrate saturation of horizon eight is calculated by subtracting the hydrate saturation detected by the time domain reflectometry sensor 23 from the hydrate saturation detected by the time domain reflectometry sensor 22.

[0048] (3) By analogy, repeating the above steps, the hydrate saturation of any layer with precise thickness in the sediment sample can be calculated; and finally the fine characterization of hydrate saturation in different layers of the sediment sample is achieved.

[0049] The above-described embodiments of the present application are not intended to limit the scope of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall fall within the scope of the claims of the present application.

Claims

1. An experimental apparatus for fine characterization of hydrate saturation based on time-domain reflectometry, comprising an apparatus body, wherein the apparatus body includes a reaction vessel, characterized in that, The device body also includes a dielectric property testing module connected to the reactor and a data acquisition and processing module electrically connected to the dielectric property testing module. The dielectric property testing module includes a time-domain reflectometry instrument and a time-domain reflectometry sensor assembly connected to the time-domain reflectometry instrument. The time-domain reflectometry sensor assembly is vertically inserted into the reactor from the bottom. The reactor contains a marine sediment sample, which is virtually divided into multiple layers along the length of the reactor. The time-domain reflectometry sensor assembly consists of one or more time-domain reflectometry sensors. Each time-domain reflectometry sensor assembly consists of time-domain reflectometry sensors equal to the number of layers, and each time-domain reflectometry sensor assembly has a different length and its top is located at a different layer.

2. The experimental apparatus according to claim 1, characterized in that, When the time-domain reflectometry sensor assembly consists of a set of time-domain reflectometry sensors, the total number of time-domain reflectometry sensors is equal to the number of layers; the reactor is a cylinder, and multiple time-domain reflectometry sensors are arranged circumferentially within the reactor.

3. The experimental apparatus according to claim 2, characterized in that, The multiple time-domain reflectometry sensors are evenly distributed on a circle whose center overlaps with the fluid channel at the bottom of the high-pressure reactor, but whose radius is half the inner diameter of the reactor.

4. The experimental apparatus according to claim 1, characterized in that, When the time-domain reflectometry sensor group consists of multiple time-domain reflectometry sensors, the total number of time-domain reflectometry sensors is proportional to the number of layers; the reactor is a cylinder, and multiple time-domain reflectometry sensors are arranged circumferentially and evenly from the inside to the outside inside the reactor.

5. The experimental apparatus according to claim 1, characterized in that, The thickness of the layers is either evenly divided or gradually increases from bottom to top.

6. The experimental apparatus according to claim 1, characterized in that, The device body also includes a pore pressure control module and a temperature control module, which are respectively connected to the reaction vessel and electrically connected to the data acquisition and processing module. The pore pressure control module includes a connected methane gas cylinder, a pore water injection pump, a pressure sensor, and a vacuum pump to regulate and monitor changes in pore pressure in the sediment within the reactor in real time. The temperature control module includes a connected temperature regulating device and a temperature sensor to regulate and monitor the temperature changes of the deposits inside the reactor in real time. The data acquisition and processing module can record the data measured by the temperature sensor, pressure sensor and time domain reflectance sensor in real time, and process the measurement data to draw images.

7. An experimental method for fine characterization of hydrate saturation based on time-domain reflectometry, applied to the experimental apparatus described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Connect and install the experimental apparatus, and check its sealing. S2. Sample preparation: Obtaining sample porosity; S3. Experimental Measurement: The dielectric constant at different thicknesses of sediment samples was measured using multiple time-domain reflectometry sensors. S4. Estimation of hydrate saturation in different sedimentary layers: S41. Using the dielectric constant and sample porosity obtained in step S3, calculate the hydrate saturation at different thicknesses of the sediment sample using the following formula: ε =a× e -bSh （1）； a= 61.33× φ 2 +18.336× φ +7.2346 （2）； b = 3.3499× φ +0.3486 （3）； in, ε The dielectric constant is the one measured experimentally. S h For hydrate saturation, φ The porosity of the sample is denoted as ; the thickness of the sediment sample refers to the distance from the top of the time-domain reflectometry sensor to the bottom surface of the marine sediment sample. S42. The hydrate saturation at a certain layer is obtained by subtracting the hydrate saturation at two thicknesses that differ by one layer. S43. Repeat step S42 to obtain the hydrate saturation of each layer.

8. The experimental method according to claim 7, characterized in that, Step S2 includes: S21. The washed and dried marine sediment simulation medium is loaded into the reactor. The porosity of the sample in the reactor is calculated based on the volume of the sample in the reactor and the mass and density of the marine sediment simulation medium. S22. Vacuum the simulated marine sediment medium in the reactor, inject methane gas into the reactor, inject pore water into the reactor, and lower the temperature of the experimental device. When the temperature and pressure conditions required for hydrate formation are reached, a hydrate-containing sediment sample is formed in the reactor.

9. The experimental method according to claim 7, characterized in that, Step S3 includes: S31. Record the temperature and pressure changes during the experiment; S32. Inject a predetermined volume and pressure of methane gas into the reactor, inject pore water at a predetermined pressure into the reactor, and set the temperature required for hydrate formation; when the pore pressure controlled by the pore water remains constant, the methane gas in the sediment in the reactor is completely converted into hydrate. S33. Transmit and receive electromagnetic wave signals through a time-domain reflectometry instrument and a time-domain reflectometry sensor, and measure and record dielectric data; S34. Record the temperature and pressure data changes during the test process, and complete the data acquisition and storage.

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