Testing device and method for in-situ monitoring of hydrate by using thermal-electric coupling

Abstract

The invention discloses a test device and method for in-situ monitoring of hydrates by using thermal-electric coupling, and belongs to the technical field of experiments for simulating generation and decomposition of hydrates in laboratories. The device comprises a hydrate synthesis and decomposition system, a temperature control system, a pressure control system, a thermal-electric parameter measurement system, a gas collection system and a data acquisition and user monitoring system, wherein a multi-point temperature sensor, a resistivity measurement probe and a heat conductivity coefficient measurement probe are arranged in a reaction kettle cavity; in-situ and real-time monitoring of multiple physical property parameters such as temperature distribution, resistivity change and heat conductivity coefficient in the whole process of generation and decomposition of the hydrate sample can be realized. According to the invention, thermal-electric coupling monitoring can be realized under high-pressure and low-temperature conditions, and a high-precision means is provided for hydrate formation mechanism research and exploitation processes.

Description

Technical Field

[0001] This invention belongs to the field of experimental technology for simulated laboratory hydrate formation and decomposition. Specifically, it relates to an experimental device and method for in-situ monitoring of hydrates using thermo-electric coupling. Background Technology

[0002] Natural gas hydrates, as a promising future energy source, present both a hot topic and a challenge in their safe and efficient development. The decomposition of hydrates is a complex process involving phase transitions and changes in multiple physical fields, encompassing heat conduction, fluid flow, and formation deformation. Accurately understanding the decomposition front, decomposition rate, and spatial distribution in porous media is crucial for evaluating extraction efficiency and predicting formation stability.

[0003] Currently, most monitoring methods used in laboratory studies of hydrate decomposition processes focus on monitoring single physical fields, making it difficult to comprehensively capture the coordinated evolution of thermophysical and electrical parameters during hydrate decomposition. Hydrate decomposition significantly alters the thermal and electrical conductivity of sediments. However, existing technologies lack effective means for in-situ, synchronous, and coupled monitoring of these two fields, resulting in a insufficient understanding of the decomposition mechanism and hindering the optimization of mining strategies.

[0004] Therefore, it is essential to study a device and method that can integrate multiple thermal and electrical parameters to achieve in-situ fine monitoring of hydrate decomposition processes, enabling coupled monitoring of thermal and electrical fields in laboratory hydrate formation and in-situ decomposition processes, and to quickly obtain hydrate saturation in sediments using existing models. Summary of the Invention

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling, comprising: A hydrate synthesis and decomposition system, comprising a high-pressure resistant reactor body, the cavity of which is used to fill simulated sediment samples; A temperature control system, which is connected to the hydrate synthesis and decomposition system, is used to control the temperature of hydrate synthesis and decomposition within the reactor. A pressure control system, which is connected to the hydrate synthesis and decomposition system, is used to control the initial pressure and decomposition pressure of hydrate synthesis in the reactor. A thermoelectric parameter monitoring system, which is connected to a hydrate synthesis and decomposition system, is used to monitor in situ the changes in resistivity and temperature during the formation and decomposition of hydrates in different layers inside a sediment sample, and to monitor the thermal conductivity of the sediment at different hydrate saturations. A gas collection system, which is connected to a hydrate synthesis and decomposition system, is used to collect methane gas during the hydrate decomposition process; The data acquisition and user monitoring system is connected to the thermo-electric parameter monitoring system and is used to synchronously acquire, process and analyze thermo-electric parameters.

[0006] Furthermore, the hydrate synthesis and decomposition system also includes: an upper end cover of the reactor, a lower end cover of the reactor, and an isolation sleeve; The upper cover of the reactor is located at the upper end of the reactor body and is connected to the reactor body by a clamp. The upper cover of the reactor has three upper cover interfaces, which are respectively used to install a gas injection port, a gas exhaust port, and a pressure sensor. Both the gas injection port and the gas exhaust port are equipped with sand screens. The gas injection port is connected in sequence to a gas injection ball valve, a gas compressor, a pressure reducing valve, and a methane cylinder through a gas injection pipeline. The high-pressure gas in the methane cylinder is slowly discharged through the pressure reducing valve and then continuously pumped into the reactor body by the gas compressor until the set gas injection pressure value is reached to realize the injection of methane gas. The gas injection port is connected to a safety valve through a safety pipeline. The lower end cover of the reactor is located at the lower end of the reactor body and is fixed to the reactor body by bolts. The lower end cover of the reactor is provided with four lower end cover interfaces. The four lower end cover interfaces are respectively used to install a multi-point temperature sensor, a thermal conductivity measuring probe, a resistivity measuring probe and a drain outlet. The drain outlet is equipped with a sandproof mesh. The isolation sleeve is installed inside the reactor body to prevent the hydrate sample from directly contacting the reactor body, the upper end cover, and the lower end cover.

[0007] Furthermore, the temperature control system includes: a circulating water bath cooling jacket, an upper cover of the jacket, a lower cover of the jacket, a circulating water bath inlet, a circulating water bath outlet, and a chiller; The circulating water bath cooling jacket, the upper end cover of the jacket, and the lower end cover of the jacket surround the reactor body to form a cold water chamber. The refrigerator is connected to the water inlet of the circulating water bath through a cooling pipeline to continuously inject a constant low-temperature liquid into the cold water chamber to cool the reactor body. The low-temperature liquid then flows back to the refrigerator through the outlet of the circulating water bath and the pipeline to achieve temperature control of the reactor body.

[0008] Furthermore, the pressure control system includes: a pressure sensor, an exhaust ball valve, and a back pressure valve. The pressure sensor is installed on the upper end cover interface corresponding to the upper end cover of the reactor. The exhaust port is connected to the exhaust ball valve and the back pressure valve in sequence through an exhaust pipe. The pressure sensor is used to monitor the internal pressure of the reactor body in real time. When it is necessary to adjust the internal pressure of the reactor body, the exhaust ball valve is opened, and the back pressure valve is adjusted to control the internal pressure of the reactor body.

[0009] Furthermore, the thermo-electric parameter measurement system includes: a multi-point temperature sensor, a resistivity measurement probe, and a thermal conductivity measurement probe. The multi-point temperature sensor, the thermal conductivity measurement probe, and the resistivity measurement probe are respectively installed on the corresponding lower end cover interface on the lower end cover of the reactor. The multi-point temperature sensor is used to measure the temperature values ​​at different measurement points inside the reactor.

[0010] Furthermore, the resistivity measurement probe includes a resistivity watertight connector, a mounting limiter, a resistivity probe rod, a connecting wire, and copper electrodes. The mounting limiter is used to fix the resistivity probe rod. Multiple copper electrodes are uniformly installed on the resistivity probe rod along its length and are connected to the resistivity watertight connector via the connecting wire. The thermal conductivity measurement probe includes a thermal conductivity watertight connector, a fixing flange, a thermal conductivity probe rod, a detachable isolation cover, and a thermal conductivity probe. The fixing flange is used to fix the thermal conductivity probe rod. The detachable isolation cover is installed at the head of the thermal conductivity probe rod, and the thermal conductivity probe is installed inside it and connected to the thermal conductivity watertight connector via the connecting wire.

[0011] Furthermore, the gas collection system includes: a gas storage tank ball valve, a gas storage tank, a gas storage tank temperature sensor, a gas storage tank pressure sensor, a vacuum pump ball valve, and a vacuum pump; The exhaust port is connected in sequence to the exhaust ball valve, the back pressure valve, the gas storage tank ball valve, and the gas storage tank via an exhaust pipe. The gas storage tank temperature sensor and the gas storage tank pressure sensor are installed on the gas storage tank. The vacuum pump ball valve is connected between the back pressure valve and the gas storage tank ball valve via a pipe. The vacuum pump and the vacuum pump ball valve are connected via a pipe.

[0012] Furthermore, the data acquisition and user monitoring system includes a data acquisition instrument and a host computer. The data acquisition instrument is electrically connected to the pressure sensor, the multi-point temperature sensor, the resistivity measurement probe, the thermal conductivity measurement probe, the gas storage tank temperature sensor, and the gas storage tank pressure sensor, respectively, and is used to acquire data from each sensor and probe, preprocess, convert, and store the data, and transmit it to the host computer.

[0013] A test method for in-situ monitoring of hydrates using thermo-electric coupling, employing the test apparatus for in-situ monitoring of hydrates using thermo-electric coupling as described above, the method comprising the following steps: The operation steps are as follows: Step 1: Clean the reactor body with deionized water, weigh the corresponding volume of sediment and pore solution, fill it into the reactor evenly in multiple portions, compact it, and simulate seabed sediment samples. Step 2: Apply an appropriate amount of sealing grease to the sealing ring of the upper end cover of the reactor, connect the upper end cover of the reactor to the reactor body, and fix the two with clamps; open the exhaust ball valve, back pressure valve, gas storage tank ball valve, and vacuum pump ball valve in sequence, and use the vacuum pump to evacuate the reactor body and gas storage tank; then close all valves, and finally turn off the vacuum pump; after standing for 20 minutes, check whether the pressure drop is less than 0.001 MPa to ensure that the system has good airtightness; Step 3: Connect the pressure sensor, multi-point temperature sensor, resistivity measurement probe, thermal conductivity measurement probe, gas tank temperature sensor, and gas tank pressure sensor to the data acquisition instrument, and check whether the readings of each sensor are normal through the host computer. Step 4: Turn on the water bath circulation, set the water bath temperature value of the chiller, and make the cold water continuously circulate in the cooling chamber of the circulating water bath cooling jacket through the circulating water bath water inlet and outlet on the side wall of the circulating water bath cooling jacket, thereby stabilizing and maintaining the low temperature environment of the reactor body. Through the circulating cooling process, the internal temperature of the reactor body can be adjusted to the temperature conditions that simulate the actual seabed environment, providing the required initial low temperature state for the formation of hydrates; Step 5: Connect the methane cylinder, pressure reducing valve, and gas compressor in sequence. Connect the methane cylinder to the gas injection port of the upper end cover of the reactor through the injection ball valve. Open the methane cylinder, adjust the pressure reducing valve to make its outlet pressure reach the set value, then open the injection ball valve and start the gas compressor to continuously inject gas into the reactor body through the gas compressor, so that the internal pressure of the reactor body gradually increases to the required hydrate formation pressure condition. After the pressure of the reactor body stabilizes to the set value, close the injection ball valve in sequence, stop the operation of the gas compressor, and close the methane cylinder. Step 6: Under set pressure and temperature conditions, hydrate formation reactions continuously occur in the sediment inside the reactor. During the formation process, multiple temperature sensors record the temperature field distribution in different spaces in real time, pressure sensors record the pressure changes inside the reactor in real time, resistivity measurement probes record the resistivity changes in different layers of the reactor during hydrate formation, and thermal conductivity measurement probes record the thermal conductivity of the reservoir at different hydrate saturation levels in real time. The data acquisition instrument continuously collects and saves the values ​​fed back by each sensor, and packages the data link and uploads it to the host computer. The operator can monitor the changes of various parameters during the hydrate synthesis process in real time through the host computer interface. Step 7: As hydrates are gradually formed, the system will exhibit obvious exothermic characteristics, such as a temperature rise, a pressure drop due to gas consumption, and an increasing trend in the resistivity of the sediment as the hydrate saturation increases. Observe the host computer interface. When the temperature returns to the set temperature and tends to stabilize, the pressure no longer continues to drop, and the resistivity change curve remains in a stable range without significant fluctuations, it can be determined that the system has basically reached thermodynamic equilibrium. At this point, the hydrate formation process ends. Step 8: Connect the exhaust port of the upper end cover of the reactor to the back pressure valve through the exhaust ball valve, and connect the back pressure valve to the gas storage tank through the gas storage tank ball valve. During the hydrate decomposition process, by setting and adjusting the outlet pressure of the back pressure valve, the pressure inside the reactor is changed from the pressure range where the hydrate is stable to its thermodynamic decomposition range. As the pressure inside the reactor decreases, the hydrate begins to decompose and release gas. The gas generated by the hydrate decomposition is collected and stored in real time through the gas storage tank. At the same time, the temperature sensor and pressure sensor of the gas storage tank are used to monitor the temperature and pressure change trends inside the reactor to determine the decomposition status. Step 9: During the hydrate decomposition process, the temperature, pressure, resistivity, and thermal conductivity parameters inside the reactor body are recorded simultaneously, as well as the temperature and pressure change curves of the buffer tank. Since the temperature usually decreases due to endothermic reaction during hydrate decomposition, the resistivity decreases significantly due to the increase of pore water, and the thermal conductivity shows a characteristic change curve with the phase change. When the pressure, temperature, resistivity, and thermal conductivity of the reactor body and the temperature and pressure parameters of the buffer tank gradually stabilize, it is determined that the hydrate has basically completed decomposition. Step 10: Based on the synchronously acquired data on temperature, pressure, thermal conductivity, and resistivity inside the reactor and the temperature and pressure data of the buffer tank, the obtained data are coupled and analyzed by the host computer to determine the spatial distribution, decomposition rate, and saturation changes of hydrates.

[0014] Furthermore, methods such as heat injection, inhibitor injection, temperature increase, or carbon dioxide replacement can also be used to decompose hydrates.

[0015] The beneficial effects of this invention are: (1) This invention can integrate two core physical parameters, namely in-situ thermal conductivity and in-situ resistivity, which have different but complementary response mechanisms to phase change processes, and collect them synchronously and in-situ with pressure field and distributed temperature field. Through coupled analysis of thermal field and electric field, cross-verification and joint interpretation of thermo-electric coupling are realized, which can identify phase changes in the synthesis and decomposition process of hydrate more quickly and accurately, and greatly reduce the risk of misjudging complex decomposition processes.

[0016] (2) The design pressure of this invention is 0-20 MPa, the design temperature is -20 ℃-40 ℃, the reactor volume is about 2.65 L, and the device can be used in different occasions, such as the generation and decomposition process of various hydrates (methane hydrate, THF hydrate, carbon dioxide hydrate), to quickly obtain key parameters such as hydrate resistivity, thermal conductivity, temperature and pressure, to obtain the generation and decomposition law of hydrates, and to determine the generation state and spatial distribution of hydrates.

[0017] (3) This invention can be used for sample reshaping of natural gas hydrate sediments and for coupled monitoring of thermal and electrical fields during the depressurization extraction of natural gas hydrates, to explore the decomposition mechanism of hydrate core samples obtained in situ. At the same time, the device can also be used for hydrate decomposition by methods such as heat injection, inhibitor injection, heating or carbon dioxide replacement.

[0018] (4) This invention integrates a unified solution from precise control of the lower-level machine, multi-channel synchronous acquisition, local secure storage to real-time processing and visualization of the upper-level machine. The platform ensures the synchronization and integrity of massive, multi-source data, and realizes real-time analysis and visualization of data through upper-level machine software, which greatly improves experimental efficiency and data usability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an experimental device for in-situ monitoring of hydrates using thermo-electric coupling according to the present invention; Figure 2 This is a schematic cross-sectional view of the reactor of the hydrate synthesis and decomposition system of the present invention; Figure 3 This is a schematic diagram of the resistivity measurement probe of the present invention; Figure 4 This is a schematic diagram of the thermal conductivity measurement probe of the present invention.

[0020] In the diagram: 1-Reaction vessel body; 2-Isolation sleeve; 3-Upper cover of the reaction vessel; 4-Lower cover of the reaction vessel; 5-Clamping hoop; 6-Gas injection port; 7-Exhaust port; 8-Pressure sensor; 9-Sand screen; 10-Multi-point temperature sensor; 11-Resistivity measuring probe; 12-Thermal conductivity measuring probe; 13-Drain outlet; 14-Circulating water bath cooling jacket; 15-Upper cover of the jacket; 16-Lower cover of the jacket; 17-Water injection port of the circulating water bath; 18-Exhaust port of the circulating water bath; 19-Refrigeration unit; 20-Methane cylinder; 21-Pressure reducing valve; 22-Gas compressor; 23- 24-Injection ball valve; 25-Safety valve; 26-Exhaust ball valve; 27-Back pressure valve; 28-Storage tank ball valve; 29-Storage tank temperature sensor; 30-Storage tank pressure sensor; 31-Vacuum pump ball valve; 32-Vacuum pump; 33-Data acquisition instrument; 34-Host computer; 35-Resistivity watertight connector; 36-Installation limiter; 37-Resistivity probe; 38-Connecting wire; 39-Copper electrode; 40-Thermal conductivity watertight connector; 41-Fixed flange; 42-Thermal conductivity probe; 43-Removable isolation cover; 44-Thermal conductivity probe. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0023] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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 limiting this invention.

[0024] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0025] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0026] Example 1

[0027] refer to Figures 1 to 4 An experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling, comprising: A hydrate synthesis and decomposition system, comprising a high-pressure resistant reaction vessel 1, the cavity of which is used to fill simulated sediment samples; Temperature control system, which is connected to hydrate synthesis and decomposition system, is used to control the temperature of hydrate synthesis and decomposition in reactor body 1; The pressure control system is connected to the hydrate synthesis and decomposition system and is used to control the initial pressure and decomposition pressure of hydrate synthesis in the reactor body 1. The thermo-electric parameter monitoring system is connected to the hydrate synthesis and decomposition system to monitor in situ the changes in resistivity and temperature during the formation and decomposition of hydrates in different layers inside the sediment sample, and at the same time monitor the thermal conductivity of the sediment at different hydrate saturation levels. A gas collection system, connected to the hydrate synthesis and decomposition system, is used to collect methane gas during the hydrate decomposition process; The data acquisition and user monitoring system is connected to the thermo-electric parameter monitoring system to synchronously acquire, process, and analyze thermo-electric parameters.

[0028] In this embodiment, the hydrate synthesis and decomposition system further includes: an upper end cover 3 of the reactor, a lower end cover 4 of the reactor, and an isolation sleeve 2; The upper cover 3 of the reactor is located at the upper end of the reactor body 1 and is connected to the reactor body 1 by a clamp 5. The upper cover 3 of the reactor has three upper cover interfaces, which are used to install the gas injection port 6, the exhaust port 7 and the pressure sensor 8 respectively. Both the gas injection port 6 and the exhaust port 7 are equipped with sand screens 9 to prevent mud and sand inside the reactor body from entering the pipeline during decomposition and gas production. The gas injection port 6 is connected to the gas injection ball valve 23, the gas compressor 22, the pressure reducing valve 21 and the methane cylinder 20 in sequence through the gas injection pipeline. The high pressure gas in the methane cylinder 20 is slowly discharged through the pressure reducing valve 21 and then continuously pumped into the reactor body 1 through the gas compressor 22 until the set gas injection pressure value is reached to realize the injection of methane gas. The gas injection port 6 is connected to the safety valve 24 through the safety pipeline for emergency venting when the pressure inside the reactor body is too high or an accident occurs. The lower end cover 4 of the reactor is located at the lower end of the reactor body 1 and is fixed to the reactor body 1 by bolts. The lower end cover 4 of the reactor is provided with four lower end cover interfaces. The four lower end cover interfaces are respectively used to install a multi-point temperature sensor, a thermal conductivity measuring probe 12, a resistivity measuring probe 11 and a drain outlet 13. The drain outlet 13 is equipped with a sand-proof net 9 to prevent mud and sand inside the reactor body from flowing out during drainage. The isolation sleeve 2 is installed inside the reactor body 1 to prevent the hydrate sample from directly contacting the reactor body 1, the upper end cover 3 and the lower end cover 4, so as to avoid interference with the thermo-electric parameter measurement system.

[0029] In this embodiment, the temperature control system includes: a circulating water bath cooling jacket 14, an upper jacket cover 15, a lower jacket cover 16, a circulating water bath inlet 17, a circulating water bath outlet 18, and a chiller 19. The circulating water bath cooling jacket 14, the upper end cover 15 of the jacket, and the lower end cover 16 of the jacket surround the reactor body 1 to form a cold water chamber. The refrigerator 19 is connected to the circulating water bath water inlet 17 through a cooling pipeline to continuously inject a constant low temperature liquid into the cold water chamber to cool the reactor body 1. The low temperature liquid then flows back to the refrigerator 19 through the circulating water bath outlet 18 and the pipeline to achieve temperature control of the reactor body 1.

[0030] In this embodiment, the pressure control system includes: a pressure sensor 8, an exhaust ball valve 25, and a back pressure valve 26. The pressure sensor 8 is installed on the corresponding upper end cover interface on the upper end cover 3 of the reactor. The exhaust port 7 is connected to the exhaust ball valve 25 and the back pressure valve 26 in sequence through the exhaust pipe. The pressure sensor 8 is used to monitor the internal pressure of the reactor body 1 in real time. When it is necessary to adjust the internal pressure of the reactor body 1, the exhaust ball valve 25 is opened and the back pressure valve 26 is adjusted to control the internal pressure of the reactor body 1.

[0031] In this embodiment, the thermoelectric parameter measurement system includes: a multi-point temperature sensor 10, a resistivity measurement probe 11, and a thermal conductivity measurement probe 12. The multi-point temperature sensor, the thermal conductivity measurement probe 12, and the resistivity measurement probe 11 are respectively installed on the corresponding lower end cover interface on the lower end cover 4 of the reactor. The multi-point temperature sensor 10 is used to measure the temperature values ​​at different measurement points inside the reactor body 1.

[0032] In this embodiment, the resistivity measuring probe 11 includes a resistivity watertight connector 35, a mounting limiter 36, a resistivity probe 37, a connecting wire 38, and copper electrodes 39. The mounting limiter 36 is used to fix the resistivity probe 37. Multiple copper electrodes 39 are uniformly installed on the resistivity probe 37 along its length and are connected to the resistivity watertight connector 35 through the connecting wire 38. The thermal conductivity measuring probe 12 includes a thermal conductivity watertight connector 40, a fixing flange 41, a thermal conductivity probe 42, a detachable isolation cover 43, and a thermal conductivity probe 44. The fixing flange 41 is used to fix the thermal conductivity probe 42. The head of the thermal conductivity probe 42 is equipped with a detachable isolation cover 43, and the thermal conductivity probe 44 is installed inside and connected to the thermal conductivity watertight connector 40 through the connecting wire 38.

[0033] In this embodiment, the gas collection system includes: a gas storage tank ball valve 27, a gas storage tank 28, a gas storage tank temperature sensor 29, a gas storage tank pressure sensor 30, a vacuum pump ball valve 31, and a vacuum pump 32; The exhaust port 7 is connected in sequence to the exhaust ball valve 25, the back pressure valve 26, the gas storage tank ball valve 27 and the gas storage tank 28 through the exhaust pipe. The gas storage tank temperature sensor 29 and the gas storage tank pressure sensor 30 are installed on the gas storage tank 28. The vacuum pump ball valve 31 is connected between the back pressure valve 26 and the gas storage tank ball valve 27 through the pipe. The vacuum pump 32 is connected to the vacuum pump ball valve 31 through the pipe. Before conducting the experiment, open the exhaust ball valve 25, back pressure valve 26, gas storage tank ball valve 27, and vacuum pump ball valve 31. Use vacuum pump 32 to evacuate each chamber in the system to a vacuum state. Then close the exhaust ball valve 25, back pressure valve 26, gas storage tank ball valve 27, and vacuum pump ball valve 31, and turn off vacuum pump 32. After the hydrate inside the reactor body 1 decomposes and produces gas, open the gas storage tank ball valve 27. The methane gas produced by the hydrate decomposition will enter the gas storage tank 28. The gas production amount and rate of hydrate decomposition are calculated by the gas storage tank temperature sensor 29 and the gas storage tank pressure sensor 30.

[0034] In this embodiment, the data acquisition and user monitoring system includes a data acquisition unit 33 and a host computer 34. The data acquisition unit 33 is electrically connected to the pressure sensor 8, the multi-point temperature sensor 10, the resistivity measurement probe 11, the thermal conductivity measurement probe 12, the gas storage tank temperature sensor 29, and the gas storage tank pressure sensor 30, respectively. It is used to collect data from each sensor and probe, preprocess, convert, and store the data, and transmit it to the host computer 34. The operator can monitor various key values ​​through the host computer and understand the equipment operation status.

[0035] Example 2

[0036] This embodiment provides an experimental method for in-situ monitoring of hydrates using thermo-electric coupling, which is used to achieve in-situ decomposition of natural gas hydrate core samples, rapidly obtain key parameters such as hydrate resistivity, thermal conductivity, and temperature distribution, and explore the decomposition mechanism of the in-situ obtained hydrate core samples. The method employs an experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling as described in Embodiment 1 above, and includes the following steps: The operation steps are as follows: Step 1: Clean the reactor body 1 with deionized water, weigh the corresponding volume of sediment and pore solution, fill it into the reactor evenly in multiple portions, compact it, and simulate the seabed sediment sample. Step 2: Apply an appropriate amount of sealing grease to the sealing ring of the upper cover 3 of the reactor, connect the upper cover 3 of the reactor to the reactor body 1, and fix the two with clamps 5; open the exhaust ball valve 25, back pressure valve 26, gas storage tank ball valve 27, and vacuum pump ball valve 31 in sequence, and use vacuum pump 32 to evacuate the reactor body 1 and gas storage tank 28; then close all valves, and finally turn off vacuum pump 32; after standing for 20 minutes, check whether the pressure drop is less than 0.001 MPa to ensure that the system has good airtightness; Step 3: Connect the pressure sensor 8, multi-point temperature sensor 10, resistivity measurement probe 11, thermal conductivity measurement probe 12, gas tank temperature sensor 29, and gas tank pressure sensor 30 to the data acquisition instrument 33, and check whether the readings of each sensor are normal through the host computer 34. Step 4: Turn on the water bath circulation, set the water bath temperature value of the chiller 19, and make the cold water continuously circulate in the cooling chamber of the circulating water bath cooling jacket 14 through the circulating water bath inlet 17 and the circulating water bath outlet 18 on the side wall of the circulating water bath cooling jacket 14, thereby stably maintaining the low temperature environment of the reactor body 1. Through the circulating cooling process, the internal temperature of the reactor body 1 can be adjusted to the temperature conditions that simulate the actual seabed environment, providing the required initial low temperature state for the formation of hydrates; Step 5: Connect the methane cylinder 20, pressure reducing valve 21, and gas compressor 22 in sequence, and connect the methane cylinder 20 to the gas injection port 6 of the upper end cover 3 of the reactor through the injection ball valve 23. Open the methane cylinder 20, adjust the pressure reducing valve 21 to make its outlet pressure reach the set value, then open the injection ball valve 23 and start the gas compressor 22 to continuously inject gas into the reactor body 1 through the gas compressor 22, so that the internal pressure of the reactor body 1 gradually increases to the required hydrate formation pressure condition. After the pressure of the reactor body 1 stabilizes to the set value, close the injection ball valve 23 in sequence, stop the operation of the gas compressor 22 and close the methane cylinder 20. Step 6: Under set pressure and temperature conditions, hydrate formation reactions continuously occur in the sediment inside reactor 1. During the formation process, multiple temperature sensors record the temperature field distribution in different spaces in real time, pressure sensor 8 records the pressure changes inside the reactor in real time, resistivity measurement probe 11 records the resistivity changes in different layers of the reactor 1 during hydrate formation in real time, and thermal conductivity measurement probe 12 records the thermal conductivity of the reservoir at different hydrate saturation levels in real time. Data acquisition instrument 33 continuously collects and saves the values ​​fed back by each sensor, and packages and uploads the data chain to host computer 34. The operator can monitor the changes of various parameters during the hydrate synthesis process in real time through the interface of host computer 34. Step 7: As hydrates are gradually formed, the system will exhibit obvious exothermic characteristics, such as a temperature rise, a pressure drop due to gas consumption, and an increasing trend in the resistivity of the sediment as the hydrate saturation increases. Observe the host computer interface 34. When the temperature returns to the set temperature and tends to stabilize, the pressure no longer continues to drop, and the resistivity change curve remains in the stable range without significant fluctuations, it can be determined that the system has basically reached thermodynamic equilibrium. At this point, the hydrate formation process ends. Step 8: Connect the exhaust port 7 of the upper end cover 3 of the reactor vessel to the back pressure valve 26 through the exhaust ball valve 25, and connect the back pressure valve 26 to the gas storage tank 28 through the gas storage tank ball valve 27. During the hydrate decomposition process, by setting and adjusting the outlet pressure of the back pressure valve 26, the pressure inside the reactor vessel 1 is changed from the pressure range where the hydrate is stable to its thermodynamic decomposition range. As the pressure inside the reactor vessel 1 decreases, the hydrate begins to decompose and release gas. The gas generated by the hydrate decomposition is collected and stored in real time through the gas storage tank 28. At the same time, the temperature sensor 29 and the pressure sensor 30 of the gas storage tank are used to monitor the temperature and pressure change trends inside the reactor vessel 1 to determine the decomposition status. Step 9: During the hydrate decomposition process, the temperature, pressure, resistivity, and thermal conductivity parameters inside the reactor body 1 are recorded simultaneously, as well as the temperature and pressure change curves of the buffer tank. Since the temperature usually decreases due to endothermic effect during the hydrate decomposition process, the resistivity decreases significantly due to the increase of pore water, and the thermal conductivity shows a characteristic change curve with the phase change. When the pressure, temperature, resistivity, thermal conductivity of the reactor body 1 and the temperature and pressure parameters of the buffer tank gradually stabilize, it is determined that the hydrate has basically completed the decomposition. Step 10: Based on the synchronously acquired data of temperature, pressure, thermal conductivity and resistivity in the reactor and temperature and pressure data in the buffer tank, the data obtained are coupled and analyzed by the host computer 34 to determine the changes in hydrate spatial distribution, decomposition rate and saturation. In this embodiment, methods such as heat injection, inhibitor injection, temperature increase, or carbon dioxide replacement can also be used to decompose hydrates.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. An experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling, characterized in that, include: A hydrate synthesis and decomposition system, comprising a high-pressure resistant reactor body, the cavity of which is used to fill simulated sediment samples; A temperature control system, which is connected to the hydrate synthesis and decomposition system, is used to control the temperature of hydrate synthesis and decomposition within the reactor. A pressure control system, which is connected to the hydrate synthesis and decomposition system, is used to control the initial pressure and decomposition pressure of hydrate synthesis in the reactor. A thermoelectric parameter monitoring system, which is connected to a hydrate synthesis and decomposition system, is used to monitor in situ the changes in resistivity and temperature during the formation and decomposition of hydrates in different layers inside a sediment sample, and to monitor the thermal conductivity of the sediment at different hydrate saturations. A gas collection system, which is connected to a hydrate synthesis and decomposition system, is used to collect methane gas during the hydrate decomposition process; The data acquisition and user monitoring system is connected to the thermo-electric parameter monitoring system and is used to synchronously acquire, process and analyze thermo-electric parameters.

2. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 1, characterized in that, The hydrate synthesis and decomposition system also includes: an upper end cover of the reactor, a lower end cover of the reactor, and an isolation sleeve; The upper cover of the reactor is located at the upper end of the reactor body and is connected to the reactor body by a clamp. The upper cover of the reactor has three upper cover interfaces, which are respectively used to install a gas injection port, a gas exhaust port, and a pressure sensor. Both the gas injection port and the gas exhaust port are equipped with sand screens. The gas injection port is connected in sequence to a gas injection ball valve, a gas compressor, a pressure reducing valve, and a methane cylinder through a gas injection pipeline. The high-pressure gas in the methane cylinder is slowly discharged through the pressure reducing valve and then continuously pumped into the reactor body by the gas compressor until the set gas injection pressure value is reached to realize the injection of methane gas. The gas injection port is connected to a safety valve through a safety pipeline. The lower end cover of the reactor is located at the lower end of the reactor body and is fixed to the reactor body by bolts. The lower end cover of the reactor is provided with four lower end cover interfaces. The four lower end cover interfaces are respectively used to install a multi-point temperature sensor, a thermal conductivity measuring probe, a resistivity measuring probe and a drain outlet. The drain outlet is equipped with a sandproof mesh. The isolation sleeve is installed inside the reactor body to prevent the hydrate sample from directly contacting the reactor body, the upper end cover, and the lower end cover.

3. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 1, characterized in that, The temperature control system includes: a circulating water bath cooling jacket, an upper end cover of the jacket, a lower end cover of the jacket, a circulating water bath inlet, a circulating water bath outlet, and a chiller; The circulating water bath cooling jacket, the upper end cover of the jacket, and the lower end cover of the jacket surround the reactor body to form a cold water chamber. The refrigerator is connected to the water inlet of the circulating water bath through a cooling pipeline to continuously inject a constant low-temperature liquid into the cold water chamber to cool the reactor body. The low-temperature liquid then flows back to the refrigerator through the outlet of the circulating water bath and the pipeline to achieve temperature control of the reactor body.

4. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 2, characterized in that, The pressure control system includes a pressure sensor, an exhaust ball valve, and a back pressure valve. The pressure sensor is installed on the upper end cover interface corresponding to the upper end cover of the reactor. The exhaust port is connected to the exhaust ball valve and the back pressure valve in sequence through an exhaust pipe. The pressure sensor is used to monitor the internal pressure of the reactor body in real time. When it is necessary to adjust the internal pressure of the reactor body, the exhaust ball valve is opened, and the back pressure valve is adjusted to control the internal pressure of the reactor body.

5. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 2, characterized in that, The thermo-electric parameter measurement system includes: a multi-point temperature sensor, a resistivity measurement probe, and a thermal conductivity measurement probe. The multi-point temperature sensor, the thermal conductivity measurement probe, and the resistivity measurement probe are respectively installed on the corresponding interfaces of the lower end cover of the reactor. The multi-point temperature sensor is used to measure the temperature values ​​at different measurement points inside the reactor.

6. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 5, characterized in that, The resistivity measurement probe includes a resistivity watertight connector, a mounting limiter, a resistivity probe rod, a connecting wire, and copper electrodes. The mounting limiter is used to fix the resistivity probe rod. Multiple copper electrodes are evenly installed on the resistivity probe rod along its length and are connected to the resistivity watertight connector via the connecting wire. The thermal conductivity measurement probe includes a thermal conductivity watertight connector, a fixing flange, a thermal conductivity probe rod, a detachable isolation cover, and a thermal conductivity probe. The fixing flange is used to fix the thermal conductivity probe rod. The detachable isolation cover is installed at the head of the thermal conductivity probe rod, and the thermal conductivity probe is installed inside it and connected to the thermal conductivity watertight connector via the connecting wire.

7. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 5, characterized in that, The gas collection system includes: a gas storage tank ball valve, a gas storage tank, a gas storage tank temperature sensor, a gas storage tank pressure sensor, a vacuum pump ball valve, and a vacuum pump; The exhaust port is connected in sequence to the exhaust ball valve, the back pressure valve, the gas storage tank ball valve, and the gas storage tank via an exhaust pipe. The gas storage tank temperature sensor and the gas storage tank pressure sensor are installed on the gas storage tank. The vacuum pump ball valve is connected between the back pressure valve and the gas storage tank ball valve via a pipe. The vacuum pump and the vacuum pump ball valve are connected via a pipe.

8. The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling according to claim 7, characterized in that, The data acquisition and user monitoring system includes a data acquisition instrument and a host computer. The data acquisition instrument is electrically connected to the pressure sensor, the multi-point temperature sensor, the resistivity measurement probe, the thermal conductivity measurement probe, the gas storage tank temperature sensor, and the gas storage tank pressure sensor, respectively. It is used to collect data from each sensor and probe, preprocess, convert, and store the data, and transmit it to the host computer.

9. A test method for in-situ monitoring of hydrates using thermo-electric coupling, characterized in that, The experimental apparatus for in-situ monitoring of hydrates using thermo-electric coupling as described in any one of claims 1 to 8, the method comprising the following steps: The operation steps are as follows: Step 1: Clean the reactor body with deionized water, weigh the corresponding volume of sediment and pore solution, fill it into the reactor evenly in multiple portions, compact it, and simulate seabed sediment samples. Step 2: Apply an appropriate amount of sealing grease to the sealing ring of the upper end cover of the reactor, connect the upper end cover of the reactor to the reactor body, and fix the two with clamps; open the exhaust ball valve, back pressure valve, gas storage tank ball valve, and vacuum pump ball valve in sequence, and use the vacuum pump to evacuate the reactor body and gas storage tank; then close all valves, and finally turn off the vacuum pump; after standing for 20 minutes, check whether the pressure drop is less than 0.001 MPa to ensure that the system has good airtightness; Step 3: Connect the pressure sensor, multi-point temperature sensor, resistivity measurement probe, thermal conductivity measurement probe, gas tank temperature sensor, and gas tank pressure sensor to the data acquisition instrument, and check whether the readings of each sensor are normal through the host computer. Step 4: Turn on the water bath circulation, set the water bath temperature value of the chiller, and make the cold water continuously circulate in the cooling chamber of the circulating water bath cooling jacket through the circulating water bath water inlet and outlet on the side wall of the circulating water bath cooling jacket, thereby stabilizing and maintaining the low temperature environment of the reactor body. Through the circulating cooling process, the internal temperature of the reactor body can be adjusted to the temperature conditions that simulate the actual seabed environment, providing the required initial low temperature state for the formation of hydrates; Step 5: Connect the methane cylinder, pressure reducing valve, and gas compressor in sequence. Connect the methane cylinder to the gas injection port of the upper end cover of the reactor through the injection ball valve. Open the methane cylinder, adjust the pressure reducing valve to make its outlet pressure reach the set value, then open the injection ball valve and start the gas compressor to continuously inject gas into the reactor body through the gas compressor, so that the internal pressure of the reactor body gradually increases to the required hydrate formation pressure condition. After the pressure of the reactor body stabilizes to the set value, close the injection ball valve in sequence, stop the operation of the gas compressor, and close the methane cylinder. Step 6: Under set pressure and temperature conditions, hydrate formation reactions continuously occur in the sediment inside the reactor. During the formation process, multiple temperature sensors record the temperature field distribution in different spaces in real time, pressure sensors record the pressure changes inside the reactor in real time, resistivity measurement probes record the resistivity changes in different layers of the reactor during hydrate formation, and thermal conductivity measurement probes record the thermal conductivity of the reservoir at different hydrate saturation levels in real time. The data acquisition instrument continuously collects and saves the values ​​fed back by each sensor, and packages the data link and uploads it to the host computer. The operator can monitor the changes of various parameters during the hydrate synthesis process in real time through the host computer interface. Step 7: As hydrates are gradually formed, the system will exhibit obvious exothermic characteristics, such as a temperature rise, a pressure drop due to gas consumption, and an increasing trend in the resistivity of the sediment as the hydrate saturation increases. Observe the host computer interface. When the temperature returns to the set temperature and tends to stabilize, the pressure no longer continues to drop, and the resistivity change curve remains in a stable range without significant fluctuations, it can be determined that the system has basically reached thermodynamic equilibrium. At this point, the hydrate formation process ends. Step 8: Connect the exhaust port of the upper end cover of the reactor to the back pressure valve through the exhaust ball valve, and connect the back pressure valve to the gas storage tank through the gas storage tank ball valve. During the hydrate decomposition process, by setting and adjusting the outlet pressure of the back pressure valve, the pressure inside the reactor is changed from the pressure range where the hydrate is stable to its thermodynamic decomposition range. As the pressure inside the reactor decreases, the hydrate begins to decompose and release gas. The gas generated by the hydrate decomposition is collected and stored in real time through the gas storage tank. At the same time, the temperature sensor and pressure sensor of the gas storage tank are used to monitor the temperature and pressure change trends inside the reactor to determine the decomposition status. Step 9: During the hydrate decomposition process, the temperature, pressure, resistivity, and thermal conductivity parameters inside the reactor body are recorded simultaneously, as well as the temperature and pressure change curves of the buffer tank. Since the temperature usually decreases due to endothermic reaction during hydrate decomposition, the resistivity decreases significantly due to the increase of pore water, and the thermal conductivity shows a characteristic change curve with the phase change. When the pressure, temperature, resistivity, and thermal conductivity of the reactor body and the temperature and pressure parameters of the buffer tank gradually stabilize, it is determined that the hydrate has basically completed decomposition. Step 10: Based on the synchronously acquired data on temperature, pressure, thermal conductivity, and resistivity inside the reactor and the temperature and pressure data of the buffer tank, the obtained data are coupled and analyzed by the host computer to determine the spatial distribution, decomposition rate, and saturation changes of hydrates.

10. The experimental method for in-situ monitoring of hydrates using thermo-electric coupling according to claim 9, characterized in that, Other methods for decomposing hydrates include heat injection, injection of inhibitors, heating, or carbon dioxide replacement.

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