Apparatus and method for testing the rate of gas hydrate dissociation

Abstract

The application provides a testing device and method for gas hydrate decomposition rate. The testing device comprises a sample container, a calibration container, a cooling device, a temperature measuring device, a gas pressure measuring device, a vacuum pump, a high-pressure gas storage device and a thermostat. The sample container, the calibration container, the high-pressure gas storage device and the vacuum pump are connected to the same connecting pipeline via different valves respectively; the sample container, the calibration container and the connecting pipeline form a closed system, and the closed system is located in the thermostat; the temperature measuring device and the gas pressure measuring device are used for measuring the temperature and the pressure of the gas in the connecting pipeline respectively; and the cooling device is used for adjusting the temperature in the sample container. Compared with the prior art, the testing device simulates the real reservoir conditions of the seabed hydrate reservoir, simulates the decomposition rate of the natural gas hydrate under different temperature and pressure conditions for the processes such as heating exploitation and pressure reduction exploitation, and provides important technical support for the selection of exploitation parameters and the optimization design of exploitation schemes.

Description

Technical Field

[0001] This invention relates to the technical field of gas hydrate detection devices, and more particularly to a device and method for testing the decomposition rate of gas hydrates. Background Technology

[0002] Natural gas hydrate, also known as combustible ice, is an ice-like crystalline substance composed of water and natural gas under high pressure and low temperature conditions. It is a vast, clean, unconventional energy resource and one of my country's strategic resources; the State Council has approved it as my country's 173rd mineral resource. Currently, the design of natural gas hydrate extraction schemes primarily focuses on two methods: heated extraction and depressurization extraction. Determining the decomposition rate of natural gas hydrate is fundamental and crucial to the design of extraction schemes. Accurately measuring the decomposition rate of natural gas hydrate under different temperature and pressure conditions is of paramount importance for guiding the extraction of hydrate gas reservoirs. Furthermore, with the deepening of hydrate research, scholars have conducted extensive research on the commercial applications of hydrate in oil and gas storage and transportation, gas separation, and other fields, necessitating a precise understanding of the laws governing and predictive methods for hydrate decomposition rates.

[0003] Current methods for testing the decomposition rate of natural gas hydrates mainly include the constant-volume method and the constant-pressure method. The constant-pressure method is time-consuming, cumbersome, and requires sophisticated testing instruments, while also exhibiting low accuracy. The constant-volume method, on the other hand, uses relatively simple instruments. Based on the gas law, PV = nRT, if the container volume is known, the mass of the decomposed gas can be calculated by measuring the temperature and pressure of the gas under different time conditions, thus solving the problem of the natural gas hydrate decomposition rate. However, in actual plant design and production, numerous valves, conversion joints, and other connecting components make it difficult to accurately measure and calibrate the total volume of the processing container, inevitably introducing systematic errors into the calculation of the mass of the hydrate decomposition gas.

[0004] Currently, Chinese patent CN108181212A discloses a device for measuring the decomposition rate of hydrate-containing spherical soil particles in a pipeline flow system. This device is complex, and the testing process involves sample spherical particle processing and water injection, making the process intricate and demanding on the equipment, thus hindering commercial application. Furthermore, the complex two-phase flow pattern can introduce errors in gas flow rate measurement, affecting the instrument's accuracy. Chinese patent CN105352840A discloses a device and method for determining the decomposition rate of natural gas hydrates using hydrate density. However, due to the instability of natural gas hydrates, their density is difficult to measure accurately. The proposed drainage method for calibrating the density of natural gas hydrate samples is not operationally feasible. Errors in hydrate sample density testing will inevitably introduce systematic errors into subsequent testing and calculation processes, further increasing the difficulty of its widespread application. In July 2006, Tian Long et al. published a novel atmospheric pressure decomposition device for methane hydrate in the *Journal of Wuhan University*. The experimental setup mainly included a reactor, a constant-temperature water bath, temperature and pressure measuring instruments, a flow meter, and a data acquisition system. The core of the device was the high-pressure reactor, with a reported volume of 1 L. This device calculated the amount of gas produced by hydrate decomposition using a constant-volume method. However, the reactor volume calculation involved numerous assumptions and approximations, neglecting the volume occupied by pipelines, valves, and other components, resulting in systematic errors in the measured values. Furthermore, this device only allows for hydrate decomposition testing at atmospheric pressure and cannot determine the decomposition rate under different pressure conditions, limiting its versatility and applicability.

[0005] Therefore, developing novel and efficient measuring devices and supporting technologies for measuring the decomposition rate of gas hydrates under different temperature and pressure conditions is crucial for the fundamental study of hydrate properties. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a testing device and method for the decomposition rate of gas hydrates. The testing device is based on the constant volume method, has a simple structure, is easy to operate, and provides accurate and reliable test data. The testing method for the decomposition rate of gas hydrates is performed using this testing device, which can test the decomposition rate of natural gas hydrate samples under different temperature and pressure conditions, thereby guiding and optimizing the design of hydrate gas reservoir exploitation schemes.

[0007] The main principle of this invention for determining the decomposition rate of gas hydrates is as follows:

[0008] Assume there exists an independent first closed system with an unknown volume, denoted by V. The initial pressure of the first closed system is P0, and the temperature is maintained at T. A gas hydrate sample is placed in the first closed system. As the cooling liquid nitrogen is depleted, the gas hydrate sample begins to decompose. The system pressure P(t) is recorded at different times with time t. After the gas hydrate has completely decomposed, the pressure of the first closed system remains constant at P1. At this point, since the volume of the first closed system is unknown, the amount of gas hydrate decomposition gas cannot be calculated. If a calibration container with a known volume of V0 and an initial pressure of P0 exists, and this calibration container can be connected to the first closed system, opening the valve between the calibration container and the first closed system creates a second closed system. The decomposition gas diffuses into the calibration container, and the pressure of the second system stabilizes at a lower value P2. The amount of gas hydrate decomposition gas can then be calculated based on the system pressure change.

[0009] (P1-P0)×V=nRT

[0010] (P2-P0)×(V+V0)=nRT

[0011] Where n is the amount of gas produced after the complete decomposition of the gas hydrate.

[0012] Therefore, (P1-P0)×V=(P2-P0)×(V+V0)

[0013]

[0014] For the decomposition of hydrates, since the system pressure P(t) at different times as time t changes is known, the amount of gaseous matter from the decomposition of hydrates at different times can be obtained:

[0015]

[0016] Ultimately, the decomposition rate of natural gas hydrates can be calculated.

[0017] Based on the above principle, the testing device and method for the decomposition rate of gas hydrates proposed in this invention do not require measuring the total volume of pipeline containers. Instead, they only need to calibrate the volume of a calibration container with a fixed shape to complete the calculation of the hydrate decomposition rate.

[0018] This invention provides a testing device for the decomposition rate of gas hydrates, which can measure the decomposition rate of gas hydrates under different temperature and pressure conditions.

[0019] The apparatus for testing the decomposition rate of gaseous hydrates includes a sample container, a calibration container, a cooling device, a temperature measuring device, a gas pressure measuring device, a vacuum pump, a high-pressure gas storage device, and a constant temperature chamber. The sample container, calibration container, vacuum pump, and high-pressure gas storage device are each connected to the same connecting pipe. A first valve is installed between the sample container and the connecting pipe, a second valve between the calibration container and the connecting pipe, a third valve between the vacuum pump and the connecting pipe, and a fourth valve between the high-pressure gas storage device and the connecting pipe. The sample container, calibration container, and connecting pipe form a closed system located within the constant temperature chamber. The vacuum pump is used to discharge the gas from the closed system, and the high-pressure gas storage device stores gas at a set pressure. The temperature measuring device and the gas pressure measuring device are used to measure the temperature and pressure of the gas within the connecting pipe, respectively. The cooling device is used to regulate the temperature inside the sample container.

[0020] This testing device simulates the actual reservoir conditions of seafloor hydrate deposits. For processes such as heated extraction and depressurized extraction, it simulates and tests the decomposition rate of natural gas hydrates under different temperature and pressure conditions by filling the high-pressure gas storage device with high-pressure gas at different set pressures and by changing the set temperature of the constant temperature chamber. This provides important technical support for the selection of extraction parameters and the optimization design of extraction schemes.

[0021] Preferably, the cooling device is a cooling pool containing liquid nitrogen.

[0022] Preferably, the high-pressure gas storage device is a high-pressure gas cylinder, which contains methane or nitrogen.

[0023] Preferably, the temperature measuring device includes a thermocouple temperature sensor; the gas pressure measuring device includes a diffused silicon pressure sensor.

[0024] Preferably, the vacuum pump and the high-pressure gas storage device are located outside the constant temperature chamber, and the constant temperature chamber has a pipeline channel, through which the connecting pipeline between the vacuum pump and the high-pressure gas storage device and the constant temperature chamber passes.

[0025] Preferably, the constant temperature chamber includes an insulated chamber body, an insulated door, a cooling / heating unit, a main control unit, and a temperature sensor; both the insulated chamber body and the insulated door are provided with an insulation layer, the temperature sensor is installed inside the insulated chamber body, the temperature sensor is used to measure the temperature inside the insulated chamber body and transmit the temperature data to the main control unit, the main control unit controls the cooling / heating unit to cool or heat according to the temperature data, so that the temperature inside the insulated chamber body reaches the set temperature.

[0026] Preferably, the system further includes a data processing system for collecting and storing temperature and pressure data from the temperature measuring device and the gas pressure measuring device, and for calculating the gas hydrate decomposition rate using the temperature and pressure data.

[0027] The present invention also provides a method for measuring the decomposition rate of gas hydrates, which is measured using the aforementioned gas hydrate decomposition rate testing device and includes the following steps:

[0028] A sample container containing a gas hydrate sample is connected to a connecting pipe, and the temperature inside the sample container is controlled by a cooling device to keep the temperature below the decomposition temperature of the gas hydrate sample.

[0029] Turn on the temperature measuring device and the gas pressure measuring device, and set the set temperature of the constant temperature chamber; with the fourth valve closed and the first valve, the second valve and the third valve open, turn on the vacuum pump to extract the gas in the closed system; when the pressure in the closed system no longer changes, close the third valve.

[0030] Open the fourth valve to allow gas at the set pressure in the high-pressure gas storage device to enter the closed system; once the pressure in the closed system stabilizes, close the fourth valve and record the pressure P0.

[0031] With the first valve open and the third and fourth valves closed, the second valve is closed, and the temperature inside the sample container is controlled by the cooling device to be higher than the decomposition temperature of the gas hydrate sample. The gas hydrate sample decomposes, and the pressure in the sample container and connecting pipe rises. When the temperature and pressure in the sample container and connecting pipe no longer change, the temperature T and pressure P1 in the connecting pipe are recorded at this time.

[0032] Open the second valve to allow the gas hydrate decomposition gas portion to enter the calibration container. Record the pressure P2 after the pressure stabilizes.

[0033] The mass of hydrate decomposition gas at different times can be calculated using the following formula:

[0034]

[0035] Wherein, n(t) - the mass of hydrate decomposition gas at time t;

[0036] Pressure of the closed system at time P(t)-t;

[0037] T - Temperature of the closed system;

[0038] P0 - The pressure of the gas in the sample container, connecting pipe, and calibration container after the gas at the set pressure is introduced;

[0039] The gas pressure in the sample container and connecting pipe after the complete decomposition of P1- gas hydrate;

[0040] The gas pressure in the sample container, connecting pipe and calibrator after complete decomposition of P2- gas hydrate;

[0041] V0 - Volume of the calibration container;

[0042] The instantaneous decomposition rate of hydrates at different times can be calculated using the following formula:

[0043]

[0044] Wherein, r(t)-hydrate decomposition rate in real time;

[0045] dt - the set time interval;

[0046] dn(t) - The change in the amount of gaseous substance resulting from the decomposition of hydrates within dt.

[0047] Preferably, after the testing device is assembled, the airtightness of the testing device is checked by the following steps:

[0048] Open the first, second, and third valves, close the fourth valve, and turn on the vacuum pump to extract gas from the sealed system. Once the pressure in the sealed system stabilizes, close the third valve and turn off the vacuum pump. Open the fourth valve to allow gas from the high-pressure gas storage device to enter the sealed system. Once the pressure in the sealed system stabilizes, close the fourth valve. Let the testing device stand for a predetermined time. If the pressure in the sealed system does not change within the predetermined time, it indicates that the testing device is well-sealed.

[0049] Preferably, the set pressure of the gas in the high-pressure gas storage device is 1MPa to 25MPa.

[0050] This invention allows for the measurement of the decomposition rate of gas hydrates under different pressures by filling a high-pressure gas storage device with high-pressure gas at different set pressures; and the decomposition rate of gas hydrates at different temperatures can be measured by changing the set temperature of the constant temperature chamber.

[0051] This method eliminates the need to measure the total volume of pipeline containers; it only requires calibrating the volume of a fixed-shape calibration container to calculate the hydrate decomposition rate. When the testing device is equipped with a data processing system, the required temperature and pressure parameters are recorded and input into the system. The data acquisition and processing software can then directly calculate the curve of the hydrate decomposition rate over time, reducing tedious calculations.

[0052] The apparatus and method for testing the decomposition rate of gas hydrates provided by this invention are applicable to measuring the decomposition rate of natural gas hydrate samples in sediments obtained from drilling, and can also be used for measuring the decomposition rate of artificially synthesized gas hydrates in the laboratory.

[0053] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved. Attached Figure Description

[0054] The invention will now be described in more detail based on embodiments that are merely non-limiting and with reference to the accompanying drawings. Wherein:

[0055] Figure 1 This is a schematic diagram of the structure of a testing device for the decomposition rate of gas hydrates provided in an embodiment of the present invention;

[0056] Figure 2 This is a schematic diagram of the main control unit of a constant temperature chamber provided in an embodiment of the present invention;

[0057] Figure 3 This is a schematic diagram of a device for testing the decomposition rate of gas hydrates according to another embodiment of the present invention.

[0058] Explanation of reference numerals in the attached figures:

[0059] 1. Sample container; 2. Cooling pool; 3. Calibration container; 4. Digital pressure acquisition module; 5. Connecting pipe; 6. Vacuum hose; 7. Vacuum pump; 8. High-pressure gas cylinder; 9. First temperature sensor; 10. Pressure sensor; 11. Digital temperature acquisition module; 12. Pressure acquisition and data processing system; 13. Insulated box; 14. Main control unit; 15. Semiconductor cooling chip; 16. Heat sink; 17. Fan; 18. Second temperature sensor; 19. Temperature control layer; 20. Heat-conducting metal layer; 21. Insulation layer; 22. Insulated door; 23. Handle; 24. Insulated glass; 25. Vacuum interlayer; 26. Pipe channel; 27. Data cable channel; 28. Socket group; K1. First valve; K2. Second valve; K3. Third valve; K4. Fourth valve. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Based on the specific embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0061] The terms "first," "second," and similar words used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Words such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well. Terms such as "above," "below," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, this relative positional relationship may also change accordingly.

[0062] In this disclosure, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0063] Example 1:

[0064] like Figure 1 As shown, the testing device for the decomposition rate of gas hydrates includes a sample container 1, a calibration container 3, a connecting pipe 5, a cooling device, a temperature measuring device, a gas pressure measuring device, a vacuum pump 7, a high-pressure gas storage device, and a constant temperature chamber.

[0065] Connecting pipe 5 connects to sample container 1, calibration container 3, vacuum pump 7, and high-pressure gas storage device respectively. In this embodiment, connecting pipe 5 is preferably a stainless steel pressure-bearing pipe capable of withstanding 20MPa gas pressure, as stainless steel pressure-bearing pipes are not easily damaged.

[0066] Sample container 1 is used to contain gas hydrate samples. Sample container 1 can be detachably connected to connecting pipe 5 through vacuum reducer or perforated rubber stopper. A first valve K1 is provided between sample container 1 and connecting pipe 5 to control the opening and closing of the connection channel between sample container 1 and connecting pipe 5. The first valve K1 can be a ball valve.

[0067] The calibration container 3 has a cavity capable of containing gas. It can be connected to the connecting pipe 5 via a vacuum reducer or a perforated rubber stopper. A second valve K2 is installed between the calibration container 3 and the connecting pipe 5 to control the opening and closing of the connection between them; the second valve K2 can be a ball valve. After the calibration container 3 is manufactured, its volume can be measured to obtain its accurate volume.

[0068] The sample container 1, calibration container 3, and connecting pipe 5 form a closed system. This closed system is housed in a constant temperature chamber, through which the overall temperature of the closed system can be controlled.

[0069] The temperature measuring device is used to measure the temperature of the gas inside the connecting pipe 5. It includes a first temperature sensor 9 and a digital display temperature acquisition module 11 connected via a data cable, etc. The first temperature sensor 9 is installed on the connecting pipe 5, and its measuring end extends into the connecting pipe 5 to sense the temperature of the gas inside the connecting pipe 5 and convert it into a usable output signal. The digital display temperature acquisition module 11 is installed outside the constant temperature chamber. The digital display temperature acquisition module 11 is used to automatically acquire the output signal of the first temperature sensor 9 and display the temperature value in real time based on the signal. In some preferred embodiments, the first temperature sensor 9 is a PT100 thermistor with a measurement range of -40℃ to 100℃ and an accuracy of ±0.1℃.

[0070] A gas pressure measuring device is used to measure the pressure of gas within a connecting pipe 5. It includes a pressure sensor 10 and a digital display pressure acquisition module 4 connected via a data cable, etc. The pressure sensor 10 is mounted on the connecting pipe 5, with its measuring end extending into the pipe 5 to sense the gas pressure and convert it into a usable output signal. The digital display pressure acquisition module 4 is located outside the constant temperature chamber and is used to automatically acquire the output signal from the pressure sensor 10 and display the pressure value based on that signal. In some preferred embodiments, the pressure sensor 10 is a high-precision diffused silicon pressure sensor with a range of not less than 30 MPa and a measurement accuracy better than ±0.25% of the range.

[0071] The preferred high-precision diffused silicon pressure sensor and thermocouple temperature sensor effectively improve the accuracy of measuring the temperature and pressure values ​​of gas hydrate decomposition gas, ensure the accuracy of gas hydrate decomposition rate calculation, and have the ability to conduct small-dose gas hydrate sample testing.

[0072] The cooling device is used to regulate the temperature inside sample container 1. By regulating the temperature inside sample container 1, the temperature of the gas hydrate placed inside sample container 1 is kept below or above its decomposition temperature, thereby controlling whether the gas hydrate decomposes or not. In this embodiment, the cooling device is preferably a cooling pool 2, which is filled with liquid nitrogen. Moving the cooling pool 2 filled with liquid nitrogen to the bottom of sample container 1, immersing the bottom of sample container 1 in liquid nitrogen, lowers the temperature inside sample container 1 below the decomposition temperature of the gas hydrate, thus preventing the gas hydrate inside sample container 1 from decomposing. When the cooling pool 2 is removed from the bottom of sample container 1, the temperature inside sample container 1 gradually rises. When the temperature rises above the decomposition temperature of the gas hydrate, the gas hydrate inside sample container 1 begins to decompose.

[0073] Vacuum pump 7 is used to expel gas from the closed system formed by sample container 1, calibration container 3, and connecting pipe 5. The inlet of vacuum pump 7 is connected to connecting pipe 5 via vacuum hose 6. A third valve K3 is installed between vacuum pump 7 and connecting pipe 5 to control the opening and closing of the connection between the vacuum pump 7 and connecting pipe 5; the third valve K3 can be a ball valve. In some preferred embodiments, vacuum pump 7 is a miniature dry pump or a rotary vane vacuum pump 7. To ensure instrument measurement accuracy, the ultimate vacuum of vacuum pump 7 is preferably less than 0.1 mbar (10 Pa).

[0074] A high-pressure gas storage device is used to store gas at a set pressure. The pressure within the closed system formed by the sample container 1, calibration container 3, and connecting pipe 5 is adjusted by introducing the gas at the set pressure. The inlet of the high-pressure gas storage device is connected to the connecting pipe 5 via a pipe. A fourth valve K4 is installed between the high-pressure gas storage device and the connecting pipe 5 to control the opening and closing of the connection between the high-pressure gas storage device and the connecting pipe 5; the fourth valve K4 can be a ball valve. In this embodiment, the high-pressure gas storage device is preferably a high-pressure gas cylinder 8, which contains methane or nitrogen. The high-pressure gas cylinder 8 is also equipped with a valve to control its opening and closing. The high-pressure gas cylinder 8 can provide high-pressure gas up to 25 MPa, enabling the testing device to simulate the pressure conditions of seabed hydrate reservoirs to test the hydrate decomposition rate.

[0075] The incubator can both cool and heat, and has a sealed space that can accommodate the sample container 1, the calibration container 3, and the connecting pipes 5. The incubator includes an insulated chamber body 13, an insulated door 22, a cooling and heating unit, a main control unit 14, and a second temperature sensor 18.

[0076] like Figure 1As shown, the insulated enclosure 13 is equipped with a three-layer plate structure, forming an inner ring cavity, a middle layer, and an outer layer from the inside out. The inner ring cavity is filled with a temperature-controlled solution, such as salt water or automotive antifreeze, forming a temperature-controlled partition 19, which serves to insulate the device and prevent excessive temperature fluctuations from affecting its lifespan and providing safety. The middle layer is assembled with heat-conducting metal blocks to form a heat-conducting metal layer 20, which contacts the semiconductor cooling chip 15 assembled at the bottom of the insulated enclosure 13, facilitating rapid heat transfer. The outer layer is filled with insulation material to form an insulation partition 21, which slows down heat conduction between the inner cavity and the external environment. A socket group 28 is provided on the side of the insulated enclosure 13, which includes a power socket, a network interface, and a communication port. This provides power to meet the internal power needs of the instrument and enables external terminals to collect data and remotely control the device. In addition, the insulated enclosure 13 also has a pipe channel 26 for pipes to pass through and a data cable channel 27 for data cables to pass through.

[0077] The insulated door 22 is composed of two layers of panels, with the inner side filled with insulation material, and a handle 23 is installed on the outer side of the insulated door 22. The insulated door 22 is also provided with an observation window, which is embedded with two layers of heat-insulating glass 24, with a vacuum interlayer 25 between the two layers of heat-insulating glass 24. The conditions inside the constant temperature chamber can be observed through the observation window.

[0078] The cooling and heating unit is located at the bottom of the constant temperature chamber. The unit includes a thermoelectric cooler 15, a heat sink 16, and a fan 17, assembled sequentially from the inside out (with the constant temperature chamber as a reference). The thermoelectric cooler 15 is environmentally friendly, with a temperature control range of -30℃ to 80℃. The heat sink 16 includes heat dissipation fins and cooling fins respectively located at the cold and hot ends of the thermoelectric cooler 15; a fan cover is provided on the insulation chamber 13 corresponding to the position of the fan 17.

[0079] The second temperature sensor 18 is installed inside the insulation box 13. The second temperature sensor 18 is used to measure the temperature inside the insulation box 13 and transmit the temperature data to the main control unit 14.

[0080] The main control unit 14 includes a microcontroller and an operation panel, which functions as the temperature control actuator for the entire constant temperature chamber, regulating cooling and heating. Its circuit working principle is (see...). Figure 2 The electrical signal generated by the second temperature sensor 18 is sent to the microcontroller's acquisition module to obtain the sampled temperature value. The microcontroller performs PID calculations and controls the pulse width modulation (PWM) based on the calculation results. The PWM output is sent to the power regulation circuit, which adjusts the voltage applied to the thermoelectric cooler 15 to achieve power regulation. The set temperature can be input through the operation panel, and the power of the thermoelectric cooler is adjusted by the microcontroller to ensure that the temperature inside the insulation box 13 reaches the set temperature.

[0081] Example 2:

[0082] Based on the gas hydrate content testing device provided in Example 1, a data processing system is added. This system collects and stores temperature and pressure data from the temperature and pressure measuring devices, and calculates the gas hydrate decomposition rate using these data. In one specific embodiment, the data processing system includes a data acquisition module and a data processing module. The data acquisition module collects temperature and pressure data from the temperature and pressure measuring devices and transmits this data to the data processing module. The data processing module includes a storage and processing chip and acquisition and processing software. This software, programmed in VB, can convert the output of measurement parameters, including temperature and pressure, into the gas hydrate decomposition rate. By setting up the data processing system, the gas hydrate decomposition rate can be directly obtained, reducing tedious calculations.

[0083] In some implementations, the digital pressure acquisition module can also be integrated with the data processing system to form a pressure acquisition and data processing system 12 (see...). Figure 3 ).

[0084] Example 3:

[0085] The present invention also provides a method for measuring the decomposition rate of gas hydrates. This method is based on the constant volume method for quantitative measurement of the decomposition rate of gas hydrates. The decomposition rate of gas hydrates is calculated by using the temperature and pressure parameters of the gas produced by the decomposition of gas hydrates under vacuum conditions.

[0086] The following describes the operational steps of measuring the gas hydrate content using the gas hydrate content testing device provided in Example 1:

[0087] (1) Check the airtightness of the device

[0088] When the testing device follows Figure 1 After assembly, open the first valve K1, the second valve K2, and the third valve K3, and close the fourth valve K4. Turn on the vacuum pump 7 to extract the gas from the closed system formed by the sample container 1, the calibration container 3, and the connecting pipe 5. Once the pressure in the closed system stabilizes, close the third valve K3 and turn off the vacuum pump 7. Open the fourth valve K4 and the high-pressure gas cylinder 8 to introduce 10 MPa of gas into the closed system. Once the pressure in the closed system stabilizes, close the fourth valve K4. Let the test device stand for 24 hours. If the pressure in the closed system does not change within 24 hours, it indicates that the test device is well sealed. Otherwise, it is necessary to re-inspect all connections of the pipeline and repeat the airtightness check until the airtightness of the device meets the requirements.

[0089] (2) Calibration device

[0090] During the fabrication of the testing device, the volume V0 of the calibrator must be accurately calibrated.

[0091] (3) Monitoring of the decomposition process of gas hydrates:

[0092] Liquid nitrogen is placed in cooling pool 2. The bottom of sample container 1 containing the gas hydrate sample is immersed in cooling pool 2 to place it in liquid nitrogen environment, so that the temperature of the gas hydrate sample is lower than its decomposition temperature, at which point the gas hydrate does not decompose; then sample container 1 is connected to connecting pipe 5.

[0093] Turn on the digital display temperature acquisition module 11 and the digital display pressure acquisition module 4, and set the set temperature of the constant temperature chamber; while keeping the fourth valve K4 closed and the second valve K2 and the third valve K3 normally open, slightly open the first valve K1, turn on the vacuum pump 7 to extract the gas in the closed system, and after the pressure of the closed system drops significantly, fully open the first valve K1 until the pressure in the closed system no longer changes, and then close the third valve K3;

[0094] Open the fourth valve K4, open the high-pressure gas cylinder 8, and introduce methane gas at the set pressure value into the closed system. When the pressure in the closed system stabilizes, close the fourth valve K4, close the high-pressure gas cylinder 8, and record the pressure P0.

[0095] With the first valve K1 open and the third valve K3 and the fourth valve K4 closed, close the second valve K2 and remove the cooling pool 2 at the bottom of the sample container 1. The temperature inside the sample container 1 will gradually rise. When the temperature of the gas hydrate sample is higher than the decomposition temperature, the gas hydrate will decompose, and the pressure in the sample container 1 and the connecting pipe 5 will rise. When the pressure value remains unchanged for 2 hours, it indicates that the gas hydrate sample has completely decomposed. Record the temperature T and pressure P1 in the connecting pipe 5 at this time.

[0096] Open the second valve K2 to allow the gas hydrate decomposition gas portion to enter the calibration container 3. Record the pressure P2 after the pressure stabilizes.

[0097] (4) Calculation of the decomposition rate of gas hydrates

[0098] According to the gas law, we can obtain:

[0099] (P1-P0)×V=nRT

[0100] (P2-P0)×(V+V0)=nRT

[0101] Among them, the amount of gas produced after the complete decomposition of n-gas hydrate;

[0102] T - Temperature of the closed system;

[0103] P0 - The pressure of the gas in the sample container 1, connecting pipe 5, and calibration container 3 after the gas at the set pressure is introduced;

[0104] The gas pressure in both sample container 1 and connecting pipe 5 after complete decomposition of P1-gas hydrate;

[0105] The gas pressure of the three parts of the sample container 1, connecting pipe 5 and calibrator after complete decomposition of P2- gas hydrate;

[0106] V - The volume of the sample container 1 and the connecting pipe 5;

[0107] V0 - Volume of calibration container 3;

[0108] Therefore, (P1-P0)×V=(P2-P0)×(V+V0)

[0109]

[0110] For the decomposition of hydrates, since the system pressure P(t) at different times as time t changes is known, the amount of gaseous matter from the decomposition of hydrates at different times can be obtained:

[0111]

[0112] Wherein, n(t) - t represents the real-time decomposition rate of the hydrate.

[0113] Pressure of the closed system at time P(t)-t;

[0114] Through data fitting and differential processing, the instantaneous numerical value of the hydrate decomposition rate r(t) at different times can be calculated by the following formula:

[0115]

[0116] Wherein, r(t)-hydrate decomposition rate in real time;

[0117] dt - Sets a very small time interval, such as 1 to 10 seconds;

[0118] dn(t) - The change in the amount of gaseous substance resulting from the decomposition of hydrates over time dt.

[0119] During the monitoring of the decomposition process of gas hydrates, the decomposition rate of gas hydrates under different pressures can be measured by filling the high-pressure gas cylinder 8 with high-pressure gas at different set pressures; the decomposition rate of gas hydrates at different temperatures can be measured by changing the set temperature of the constant temperature chamber.

[0120] The step of checking the airtightness of the apparatus in the above steps is not a necessary step for every measurement of gas hydrate decomposition gas. It is usually necessary to re-check the airtightness of the apparatus after assembly or after replacing consumables such as vacuum hoses 6 and valves.

[0121] Once the volume of calibration container 3 in the testing device is calibrated, it generally does not need to be recalibrated unless the original calibration container 3 is damaged or replaced.

[0122] During the monitoring of the gas hydrate decomposition process, the temperature inside the connecting pipe 5 is approximately the set temperature inside the constant temperature chamber, i.e., approximately constant temperature.

[0123] During the vacuuming process, the first valve K1 is slightly opened for a period of time before being fully opened, which can reduce the decomposition of gas hydrates during the vacuuming process.

[0124] This method eliminates the need to measure the total volume of the pipeline container; it only requires calibrating the volume of a fixed-shape calibration container 3 to calculate the hydrate decomposition rate. When the testing device is equipped with a data processing system, the required temperature and pressure parameters are recorded and input into the system. The data acquisition and processing software can then directly calculate the curve of the hydrate decomposition rate over time, reducing tedious calculations.

[0125] Finally, it should be noted that the above embodiments and examples are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments and examples, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments or examples, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments or examples of the present invention.

Claims

1. A method for measuring the decomposition rate of gas hydrates, characterized in that, The gas hydrate decomposition rate is measured using a testing device comprising a sample container, a calibration container, a cooling device, a temperature measuring device, a gas pressure measuring device, a vacuum pump, a high-pressure gas storage device, and a constant temperature chamber. The sample container, calibration container, vacuum pump, and high-pressure gas storage device are each connected to the same connecting pipe. A first valve is installed between the sample container and the connecting pipe; a second valve is installed between the calibration container and the connecting pipe; a third valve is installed between the vacuum pump and the connecting pipe; and a fourth valve is installed between the high-pressure gas storage device and the connecting pipe. The sample container, calibration container, and connecting pipe form a closed system located within the constant temperature chamber. The vacuum pump is used to expel gas from the closed system, and the high-pressure gas storage device stores gas at a set pressure. The temperature measuring device and the gas pressure measuring device are used to measure the temperature and pressure of the gas within the connecting pipe, respectively. The cooling device is used to regulate the temperature within the sample container. The measurement method includes the following steps: A sample container containing a gas hydrate sample is connected to a connecting pipe, and the temperature inside the sample container is controlled by a cooling device to keep the temperature below the decomposition temperature of the gas hydrate sample. Turn on the temperature measuring device and the gas pressure measuring device, and set the set temperature of the constant temperature chamber; with the fourth valve closed and the first valve, the second valve and the third valve open, turn on the vacuum pump to extract the gas in the closed system; when the pressure in the closed system no longer changes, close the third valve. Open the fourth valve to allow gas at the set pressure in the high-pressure gas storage device to enter the closed system; once the pressure in the closed system stabilizes, close the fourth valve and record the pressure P0. With the first valve open and the third and fourth valves closed, the second valve is closed, and the temperature inside the sample container is controlled by the cooling device to be higher than the decomposition temperature of the gas hydrate sample. The gas hydrate sample decomposes, and the pressure in the sample container and connecting pipe rises. When the temperature and pressure in the sample container and connecting pipe no longer change, the temperature T and pressure P1 in the connecting pipe are recorded at this time. Open the second valve to allow the gas hydrate decomposition gas portion to enter the calibration container. Record the pressure P2 after the pressure stabilizes. The mass of hydrate decomposition gas at different times can be calculated using the following formula: Wherein, n(t) represents the mass of hydrate decomposition gas at time t; Pressure of the closed system at time P(t)-t; T - Temperature of the closed system; P0 - The pressure of the gas in the sample container, connecting pipe, and calibration container after the gas at the set pressure is introduced; The gas pressure in the sample container and connecting pipe after the complete decomposition of P1- gas hydrate; The gas pressure in the sample container, connecting pipe, and calibration container after complete decomposition of P2- gas hydrate; V0 - Volume of the calibration container; The instantaneous decomposition rate of hydrates at different times can be calculated using the following formula: Wherein, r(t)-hydrate decomposition rate in real time; dt - the set time interval; dn(t) - The change in the amount of gaseous substance resulting from the decomposition of hydrates within dt.

2. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The cooling device is a cooling pool, which contains liquid nitrogen.

3. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The high-pressure gas storage device is a high-pressure gas cylinder, which contains methane or nitrogen.

4. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The temperature measuring device includes a thermocouple temperature sensor; the gas pressure measuring device includes a diffused silicon pressure sensor.

5. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The vacuum pump and the high-pressure gas storage device are located outside the constant temperature chamber. The constant temperature chamber has a pipeline channel, and the connecting pipeline between the vacuum pump and the high-pressure gas storage device and the constant temperature chamber passes through the pipeline channel.

6. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The constant temperature chamber includes an insulated chamber body, an insulated door, a cooling and heating unit, a main control unit, and a temperature sensor. Both the insulated chamber body and the insulated door are provided with an insulation layer. The temperature sensor is located inside the insulated chamber body and is used to measure the temperature inside the insulated chamber body and transmit the temperature data to the main control unit. The main control unit controls the cooling and heating unit to cool or heat the chamber body according to the temperature data, so that the temperature inside the insulated chamber body reaches the set temperature.

7. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The testing apparatus also includes a data processing system, which is used to collect and store temperature data and pressure data from the temperature measuring device and the gas pressure measuring device, and to calculate the decomposition rate of gas hydrates using the temperature data and the pressure data.

8. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, After the testing device is assembled, its airtightness is checked by the following steps: Open the first, second, and third valves, close the fourth valve, and turn on the vacuum pump to extract gas from the sealed system. Once the pressure in the sealed system stabilizes, close the third valve and turn off the vacuum pump. Open the fourth valve to allow gas from the high-pressure gas storage device to enter the sealed system. Once the pressure in the sealed system stabilizes, close the fourth valve. Let the testing device stand for a predetermined time. If the pressure in the sealed system does not change within the predetermined time, it indicates that the testing device is well-sealed.

9. The method for measuring the decomposition rate of gas hydrates according to claim 1, characterized in that, The set pressure of the gas in the high-pressure gas storage device is 1 MPa ~ 25 MPa.

Images