A depressurization and gas collection device for pressure-preserving rock cores and its usage method

Abstract

This invention discloses a depressurization and gas collection device for pressure-maintaining core samples, comprising a support frame, a gas collection cylinder, and a control box. The gas collection cylinder and control box are mounted on the support frame. The control box is equipped with a gas flow meter, a pressure sensor, a flow regulator, a gas-liquid separator, a data acquisition module, a digital display, gas and water pipelines, and related valves and interfaces. The gas and water pipelines are sequentially connected to a first valve, a flow regulator, and then to the first interface of a three-way valve. The second interface of the three-way valve is connected to the inlet of the gas-liquid separator, and the third interface of the three-way valve is connected to the gas collection cylinder via the gas collection cylinder interface. The gas outlet of the gas-liquid separator is connected to a gas discharge interface via a gas flow meter, and a gas collection bag is connected to the gas discharge interface. The data acquisition module is connected to the gas flow meter, pressure sensor, flow regulator, gas-liquid separator, and digital display, respectively. This device can separate the produced gas and produced water, quickly and accurately measure the water and gas produced by the pressure-maintaining core sample, and greatly improve work efficiency.

Description

Technical Field

[0001] This invention relates to the field of pressure-maintaining core technology, and in particular to a pressure-reducing gas collection device for pressure-maintaining cores and its usage method. Background Technology

[0002] Pressure-preserving cores are core samples that retain the pressure level at the sampling site after collection. Pressure-preserving cores containing natural gas hydrates can maintain the original pressure and temperature at the sampling site, prevent hydrate decomposition, preserve the original structure of the internal natural gas hydrates and sediments, and provide in-situ geological and geochemical information about the reservoir.

[0003] Conducting pressure release and gas collection experiments on hydrate-bearing core samples can measure and collect the gas and water produced by the decomposition of hydrates under pressure in the core samples. This provides basic data and samples for calculating hydrate reservoir saturation and analyzing gas composition, and is an important step in the study of hydrate mining and the formation and dynamic evolution of hydrate reservoirs.

[0004] The existing gas and water metering devices for pressurized cores are simple in design, and the gas production measurement relies entirely on syringe extraction, resulting in low metering efficiency and making it difficult to meet the needs of rapid on-site measurement of gas content in long cores. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a depressurization and gas collection device for pressure-preserving rock cores and its usage method.

[0006] This invention is achieved through the following technical solution: a depressurization and gas collection device for pressure-maintaining core samples, connected to a core pressure-maintaining chamber, comprising a support, a gas collection cylinder, and a control box, wherein the gas collection cylinder and the control box are mounted on the support; the control box is equipped with a gas flow meter, a pressure sensor, a flow regulator, a gas-liquid separator, a data acquisition module, a digital display, gas-water pipelines, and related valves and interfaces; the related valves include a first valve, a second valve, a third valve, and a three-way valve, and the related interfaces include a pressure-maintaining chamber interface, a high-pressure water pump interface, a gas collection cylinder interface, a liquid discharge interface, and a gas discharge interface; the end of the gas-water pipeline is a gas-liquid inlet, which is connected to the pressure-maintaining chamber via the pressure-maintaining chamber interface and the high-pressure pipeline; the gas-water pipeline is sequentially connected to the first valve and the flow regulator, and then connected to the first interface of the three-way valve, wherein the three-way valve... The second port of the valve is connected to the inlet of the gas-liquid separator, and the third port of the three-way valve is connected to the gas collection cylinder through the gas collection cylinder port; the pressure sensor is installed on the pipeline between the first valve and the flow regulator, and the high-pressure water pump port connected to the external high-pressure water pump is connected to the pipeline between the first valve and the flow regulator through the second valve; the gas outlet of the gas-liquid separator is connected to the gas discharge port through the gas flow meter, and a gas collection bag is connected to the gas discharge port; a liquid outlet is provided at the bottom of the gas-liquid separator, and the liquid outlet is connected to the liquid discharge port through the third valve; the data acquisition module is connected to the gas flow meter, the pressure sensor, the flow regulator, and the gas-liquid separator respectively, and the digital display is installed on the control box panel and connected to the data acquisition module.

[0007] The gas collecting cylinder includes an inner sleeve, an outer sleeve, an upper retaining ring, a first plug, and a base. The outer sleeve is a cylindrical structure extending vertically, with its bottom sealed by the first plug. The upper retaining ring is fitted around the upper edge of the outer sleeve. The inner sleeve is inserted into the outer sleeve from top to bottom. The upper end of the inner sleeve has a retaining ring, and the outer periphery of the upper part of the inner sleeve abuts against the inner wall of the upper retaining ring. The retaining ring is supported on the upper side of the upper retaining ring. The inner sleeve is connected to the gas collecting cylinder interface after passing through the first plug via a pipe. The retaining ring has an upper air intake port communicating with the inner sleeve, and the upper air intake port is detachably connected to an external syringe. The upper side wall of the outer sleeve has a detachably connected external syringe. The first plug is installed on the base.

[0008] The inner sleeve is made of transparent PP material and has a volume of 2L. The inner sleeve has graduations on its side wall.

[0009] The outer sleeve is made of transparent PC material, and the base is made of SUS304 material.

[0010] The gas-liquid separator includes a separation tank, a second plug, a separation pipeline, and a pressure cap. The pressure cap protrudes outward on its upper side to form a brim, and the pressure cap is fitted into the upper part of the separation tank, with the brim pressing against the upper edge of the separation tank. The second plug is fitted inside the pressure cap and has an inlet and a gas outlet. The lower end of the inlet is connected to the separation pipeline, and the upper end of the inlet is connected to the gas-water pipeline. The gas outlet is connected to the gas flow meter, and the separation pipeline is located inside the separation tank.

[0011] After being bent, the separation pipeline is placed close to the separation tank along the tangent direction of the tank wall.

[0012] The bracket is equipped with casters at each of the four corners at its bottom.

[0013] The base includes an upper ring, a fixing post, and a lower ring. The first plug is installed on the upper ring. The upper end of the fixing post is fixed to the lower side of the upper ring, and the lower end of the fixing post is fixed to the upper side of the lower ring. There are three fixing posts, and the three fixing posts are at a 120-degree angle to each other. The diameter of the upper ring is smaller than the diameter of the lower ring.

[0014] A method for using a pressure-reducing gas collection device for pressure-maintaining rock cores includes the following steps:

[0015] Step 1: Fill the air-water pipeline with water using the control box valve and pressurize it to the same pressure as the pressure chamber;

[0016] Step 2: Fill the inner sleeve with water using the control box, and then use the syringe connected to the air intake port at the top of the inner sleeve to remove the air from the inner sleeve.

[0017] Step 3: Connect the syringe to the valve on the side wall of the outer sleeve, and remove the excess water from the outer sleeve until the liquid level in the outer sleeve is flush with the valve. This will serve as the initial liquid level.

[0018] Step 4: The water and gas generated from the decomposition of the core in the pressure-holding chamber are controlled by the control box. They enter the inner sleeve through the gas-water pipeline and the internal pipeline of the first plug. The generated gas is collected and measured by a syringe through the upper gas outlet at the top of the inner sleeve. The generated water is extracted and measured by a syringe through the valve on the side wall of the outer sleeve.

[0019] Alternatively, a method for using a depressurization and gas collection device for pressure-maintaining rock cores includes the following steps:

[0020] Step 1: Fill the air-water pipeline with water using the control box valve and pressurize it to the same pressure as the pressure chamber;

[0021] Step 2: Open the first valve through the control box, and use the flow regulator to adjust the pressure in the pressure chamber to begin depressurization and gas release;

[0022] Step 3: The gas and water produced by the decomposition of hydrates enter the gas-liquid separator, and the water production can be directly read from the scale on the gas-liquid separator;

[0023] Step 4: The gas flows through the gas flow meter, and the pressure and gas flow rate are recorded and displayed in real time by the data acquisition module, so as to realize the rapid calculation of gas production in long cores;

[0024] Step 5: After passing through the gas flow meter, the gas flows out from the gas discharge port and enters the gas collection bag, completing the gas collection.

[0025] Compared with existing technologies, the advantages of this invention are as follows: This device can provide two methods of gas volume measurement: manual gas volume measurement using a gas collecting cylinder and automatic gas volume measurement using a gas flow meter; the gas collecting cylinder can accurately measure the gas production during the depressurization stage of hydrate-containing core samples by draining water and collecting gas, and can collect the gas produced by hydrate decomposition without pollution, making it suitable for precise measurement and gas collection of short core samples; by setting up a gas-liquid separator and a gas flow meter, the produced gas and produced water can be separated, and the water and gas produced by the pressurized core samples can be measured quickly and accurately; compared with the method of manually extracting water and gas using a gas collecting cylinder for manual measurement, it can greatly improve work efficiency and meet the needs of rapid measurement and collection of core gas content on site. Attached Figure Description

[0026] Figure 1 This is a structural and principle framework diagram of an embodiment of the present invention;

[0027] Figure 2 This is a front view of an embodiment of the present invention;

[0028] Figure 3 This is a bottom view of an embodiment of the present invention;

[0029] Figure 4 This is a front view of the control box according to an embodiment of the present invention;

[0030] Figure 5 This is a bottom view of the control box according to an embodiment of the present invention;

[0031] Figure 6 This is a side view of the gas collecting cylinder according to an embodiment of the present invention;

[0032] Figure 7 for Figure 6 Sectional view along the middle AA direction;

[0033] Figure 8 This is a perspective view of the gas collecting cylinder according to an embodiment of the present invention;

[0034] Figure 9 This is a bottom view of the first plug according to an embodiment of the present invention;

[0035] Figure 10 for Figure 9 Sectional view along the BB direction;

[0036] Figure 11 This is a side view of the inner sleeve in an embodiment of the present invention;

[0037] Figure 12 This is a top view of the gas-liquid separator according to an embodiment of the present invention;

[0038] Figure 13 for Figure 12 A cross-sectional view along the CC direction.

[0039] The following are the meanings of the reference numerals in the diagram: 1. Support; 2. Gas collecting cylinder; 21. Inner sleeve; 22. Outer sleeve; 23. Base; 24. Upper retaining ring; 25. First plug; 26. Upper gas inlet; 3. Control box; 4. Gas flow meter; 5. Pressure sensor; 6. Flow regulator; 7. Gas-liquid separator; 71. Separation tank; 72. Second plug; 73. Separation pipeline; 74. Pressure cap; 8. Digital display; 9. First valve; 10. Second valve; 11. Third valve; 12. Three-way valve; 13. Pressure holding chamber interface; 14. High-pressure water pump interface; 15. Gas collecting cylinder interface; 16. Liquid discharge interface; 17. Gas discharge interface; 18. Pressure holding chamber; 19. Filter screen. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] Example

[0042] See Figures 1 to 13This is a pressure-reducing gas collection device for pressure-maintaining rock cores, connected to a core pressure-maintaining chamber 18. It includes a support frame 1, a gas collection cylinder 2, and a control box 3, with the gas collection cylinder 2 and control box 3 mounted on the support frame 1. The control box 3 is equipped with a gas flow meter 4, a pressure sensor 5, a flow regulator 6, a gas-liquid separator 7, a data acquisition module, a digital display 8, gas and water pipelines, and related valves and interfaces. The related valves include a first valve 9, a second valve 10, a third valve 11, and a three-way valve 12. Related interfaces include a pressure-maintaining chamber interface 13, a high-pressure water pump interface 14, a gas collection cylinder interface 15, a liquid discharge interface 16, and a gas discharge interface 17. The gas and water pipeline ends at gas and liquid inlets, which are connected to the pressure-maintaining chamber 18 via the pressure-maintaining chamber interface 13 and the high-pressure pipeline. The gas and water pipeline is sequentially connected to the first valve 9, the flow regulator 6, and then to the first interface of the three-way valve 12. The second port of the three-way valve 12 is connected to the inlet of the gas-liquid separator 7, and the third port of the three-way valve 12 is connected to the gas collecting cylinder 2 through the gas collecting cylinder port 15. The pressure sensor 5 is installed on the pipeline between the first valve 9 and the flow regulator 6. The high-pressure water pump port 14, which is connected to the external high-pressure water pump, is connected to the pipeline between the first valve 9 and the flow regulator 6 through the second valve 10. The gas outlet of the gas-liquid separator 7 is connected to the gas discharge port 17 through the gas flow meter 4. The gas discharge port 17 is connected to a gas collecting bag. The bottom of the gas-liquid separator 7 is provided with a liquid outlet, which is connected to the liquid discharge port 16 through the third valve 11. The data acquisition module is connected to the gas flow meter 4, the pressure sensor 5, the flow regulator 6, and the gas-liquid separator 7 respectively. The digital display 8 is installed on the control box 3 panel and connected to the data acquisition module.

[0043] In this embodiment, bracket 1 is used to fix components; control box 3 is used to integrate installation pipelines, components and operation panel; gas collecting cylinder 2 is used to measure and collect gas and water produced by hydrate decomposition in the pressurized core; gas flow meter 4 is used to measure gas production; pressure sensor 5 is used to measure pressure changes; flow regulator 6 adopts a high-precision flow regulator to accurately control pressure changes in the pressurized chamber 18; gas-liquid separator 7 is used to separate gas and water produced by hydrate decomposition in the pressurized core and measure water production; data acquisition module is used to record and display pressure and gas flow in real time; digital display 8 is used to display the pressure in the pressurized chamber 18 in real time and to display flow parameters and other information; pipelines and valves are used to pre-pressurize the device and control pressure changes in the pressurized chamber 18, and provide gas and water flow pipelines. This device can connect to the core pressurized chamber 18, measure the gas and water production of hydrate decomposition in the pressurized core by gradually reducing the pressure and collect pollution-free gas, while recording pressure changes. In this embodiment, the second valve 10 controls the high-pressure water pump to fill the gas-water pipeline or the outer sleeve 22 and inner sleeve 21. The third valve 11 is used to control the liquid from the gas-liquid separator 7 to be discharged outside the device through the liquid discharge port 16. The first valve 9 is used to control the opening and closing of the pressure-holding chamber 18 and the gas-water pipeline. In this embodiment, a filter screen 19 is provided at the connection between the pressure-holding chamber 18 and the high-pressure pipeline, separating the outlet of the high-pressure pipeline from the inside of the pressure-holding chamber 18.

[0044] In this embodiment, the control box 3 consists of a base, an aluminum-plastic cover, front and rear panels, and an internal mounting plate. It integrates an operation panel, a pressure display gauge (digital display 8), a gas flow meter 4, control valves, a flow regulator 6, and gas and water pipelines. This device controls the pressure changes in the pressure chamber 18 via valves and the flow regulator 6, thereby achieving staged decomposition of the hydrate-bearing core. The gas and water produced after decomposition enter the control box 3 through high-pressure pipelines, and different metering methods can be selected via valve control. Using the gas collecting cylinder 2, the gas production during the staged decomposition of the hydrate-bearing core can be accurately measured by draining and collecting gas, and the gas produced by hydrate decomposition can be collected without pollution, suitable for precise metering and gas collection of short cores. Using the gas-liquid separator 7 and the gas flow meter 4, the large amount of gas produced during the core decomposition process can be quickly measured, suitable for rapid decomposition and gas content measurement of long cores.

[0045] The gas collecting cylinder 2 includes an inner sleeve 21, an outer sleeve 22, an upper retaining ring 24, a first plug 25, and a base 23. The outer sleeve 22 is a cylindrical structure that runs vertically through the cylinder, and its bottom is sealed by the first plug 25. The first plug 25 has a connecting pipe (internal pipe) that extends into the inner sleeve 21. The upper retaining ring 24 is fitted onto the upper edge of the outer sleeve 22. The inner sleeve 21 is fitted into the outer sleeve 22 from top to bottom. The upper end of the inner sleeve 21 is provided with a retaining ring. The upper outer circumference of the inner sleeve 21 abuts against the inner wall of the upper retaining ring 24, and the retaining ring is supported on the upper side of the upper retaining ring 24. The inner sleeve 21 is connected to the gas collecting cylinder interface 15 after passing through the first plug 25 via a pipe. The retaining ring is provided with an upper air intake port 26 that communicates with the inner sleeve 21. The upper air intake port 26 is detachably connected to an external syringe. The upper side wall of the outer sleeve 22 is provided with a valve that is detachably connected to the external syringe. The first plug 25 is installed on the base 23. In use, first, control the valve in control box 3 to fill the air-water pipeline with water and pressurize it to the same pressure as the pressure chamber 18. Then, fill the inner sleeve 21 with water and connect a syringe through the upper air intake 26 at the top of the inner sleeve 21 to remove the air, ensuring accurate gas measurement and preventing external gas contamination. A ring groove is formed around the upper outer circumference of the first plug 25, and an O-ring is fitted inside the groove, with the outer circumference of the O-ring pressing against the inner wall of the outer sleeve 22.

[0046] The inner sleeve 21 is made of transparent PP material and has a volume of 2L. The inner sleeve 21 has graduations on its side wall.

[0047] The outer sleeve 22 is made of transparent PC material, and the base 23 is made of SUS304 material.

[0048] The gas-liquid separator 7 includes a separation tank 71, a second plug 72, a separation pipeline 73, and a pressure cap 74. The pressure cap 74 protrudes outward on its upper side to form a brim, and is fitted into the upper part of the separation tank 71, with the brim pressing against the upper edge of the separation tank 71. The second plug 72 is fitted inside the pressure cap 74 and has an inlet and a gas outlet. The separation pipeline 73 is installed at the lower end of the inlet, and the upper end of the inlet is connected to a gas-water pipeline. The gas outlet is connected to a gas flow meter 4, and the separation pipeline 73 is located inside the separation tank 71. In this embodiment, the lower outer periphery of the second plug 72 has an annular groove, and an O-ring is fitted inside the annular groove, with the outer periphery of the O-ring pressing against the inner wall of the separation tank 71.

[0049] After the separation pipeline 73 is bent, it is placed close to the separation tank 71 along the tangential direction of the tank wall.

[0050] The bracket 1 has casters installed at the four corners of its bottom.

[0051] The base 23 includes an upper ring, a fixing post, and a lower ring. The first plug 25 is installed on the upper ring. The upper end of the fixing post is fixed to the lower side of the upper ring, and the lower end of the fixing post is fixed to the upper side of the lower ring. There are three fixing posts, and the three fixing posts form a 120-degree angle between each other. The diameter of the upper ring is smaller than the diameter of the lower ring.

[0052] A method for using a depressurization and gas collection device for pressure-maintaining rock cores, which is a manual metering method, includes the following steps:

[0053] Step 1: Fill the air-water pipeline with water using the control valve in control box 3 and pressurize it to the same pressure as pressure chamber 18;

[0054] Step 2: Fill the inner sleeve 21 with water using the control box 3, and then use the syringe connected to the upper air intake 26 at the top of the inner sleeve 21 to remove the air from the inner sleeve 21.

[0055] Step 3: Connect the syringe to the valve on the side wall of the outer sleeve 22, and remove the excess water inside the outer sleeve 22 until the liquid level in the outer sleeve 22 is flush with the valve. This will serve as the initial liquid level.

[0056] Step 4: The water and gas generated by the decomposition of the pressure-holding core in the pressure-holding chamber 18 are controlled by the control box 3. They enter the inner sleeve through the gas-water pipeline via the internal pipeline of the first plug 25. The generated gas is collected and its production is measured by a syringe through the upper gas outlet 26 at the top of the inner sleeve 21. The generated water is extracted and its production is measured by a syringe through the valve on the side wall of the outer sleeve 22.

[0057] Alternatively, a method for using a depressurization and gas collection device for pressure-maintaining core samples, specifically an automatic metering method, includes the following steps:

[0058] Step 1: Fill the air-water pipeline with water using the control valve in control box 3 and pressurize it to the same pressure as pressure chamber 18;

[0059] Step 2: Open the first valve 9 through the control box 3, and use the flow regulator 6 to adjust the pressure inside the pressure chamber 18 to start depressurization and gas release;

[0060] Step 3: The gas and water produced by the decomposition of hydrates enter the gas-liquid separator 7, and the water production can be directly read from the scale on the gas-liquid separator 7;

[0061] Step 4: Gas flows through gas flow meter 4, and the pressure and gas flow rate are recorded and displayed in real time by the data acquisition module to realize the rapid calculation of gas production from long cores;

[0062] Step 5: After passing through the gas flow meter 4, the gas flows out from the gas discharge port 17 and enters the gas collection bag, completing the gas collection.

[0063] In this embodiment, the data acquisition module uses a processor, which is an existing device and therefore requires no detailed analysis. The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of this device, connecting various parts through various interfaces and lines. In this embodiment, the pressure sensor 5, gas flow meter 4, flow regulator 6, and digital display 8 are all existing devices, therefore no detailed structural analysis is required.

[0064] The above detailed description is a specific description of feasible embodiments of the present invention. These embodiments are not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the patent scope of this case.

Claims

1. A pressure relief and gas collection device for a core, connected to a core pressure chamber (18), characterized in that: The utility model provides a kind of gas collection device, including support, gas collecting cylinder and control box, the gas collecting cylinder and control box are installed on the support;The control box is provided with gas flow meter, pressure sensor, flow regulator, gas-liquid separator, data acquisition module, digital display meter, gas-water pipeline and relevant valve and interface;Relevant valve includes first valve, second valve, third valve and tee valve, and relevant interface includes pressure maintaining cabin interface, high-pressure water pump interface, gas collecting cylinder interface, liquid discharge interface and gas discharge interface;The end of the gas-water pipeline is gas-liquid inlet, and gas-liquid inlet is connected with the pressure maintaining cabin by pressure maintaining cabin interface and high-pressure pipeline;The gas-water pipeline is sequentially connected with first valve, flow regulator and then connected with the tee valve first interface, the tee valve second interface is connected with the inlet of gas-liquid separator, and the tee valve third interface is connected with the gas collecting cylinder by gas collecting cylinder interface;The pressure sensor is installed on the pipeline between the first valve and the flow regulator, and the high-pressure water pump interface connected with external high-pressure water pump is connected with the pipeline between the first valve and the flow regulator by second valve;The gas outlet of the gas-liquid separator is connected with gas discharge interface by the gas flow meter, and the gas discharge interface is externally connected with gas bag;The bottom of the gas-liquid separator is provided with liquid outlet, and the liquid outlet is connected with liquid discharge interface by third valve;The data acquisition module is connected with the gas flow meter, pressure sensor, flow regulator, gas-liquid separator respectively, and the digital display meter is installed on the control box panel and connected with the data acquisition module.

2. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 1, characterized in that: The gas collecting cylinder includes inner sleeve, outer sleeve, upper stop ring, first plug and base;The outer sleeve is a cylinder structure that penetrates from top to bottom, and its bottom is closed by the first plug, and the upper sleeve of the outer sleeve is sleeved with the upper stop ring;The inner sleeve is sleeved into the outer sleeve from top to bottom, the upper end of the inner sleeve is provided with a stop ring, the upper part of the outer circumference of the inner sleeve abuts against the inner wall surface of the upper stop ring, and the stop ring is supported on the upper surface of the upper stop ring;The inner sleeve is connected with the gas collecting cylinder interface through the first plug by pipeline, and the stop ring is provided with an upper gas outlet that is communicated with the inner sleeve and is detachably connected with an external syringe;The sidewall above the outer sleeve is provided with a valve that is detachably connected with an external syringe;The first plug is installed on the base.

3. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 2, characterized in that: The inner sleeve is a sleeve made of transparent pp material, and the volume of the inner sleeve is 2L, and the sidewall is provided with a scale.

4. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 2, characterized in that: The outer sleeve is a sleeve made of transparent PC material, and the base is made of SUS304 material.

5. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 1, characterized in that: The gas-liquid separator includes separation tank, second plug, separation pipeline and pressure cap;The pressure cap is outwardly protruded on the upper side to form a brim, the pressure cap is embedded on the upper part of the separation tank, and the brim presses the upper edge of the separation tank;The second plug is sleeved in the pressure cap, the second plug is provided with an inlet and a gas outlet, the inlet is installed with a separation pipeline at lower end, the inlet is connected with the gas-water pipeline at upper end, the gas outlet is connected with the gas flow meter, and the separation pipeline is located in the separation tank.

6. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 5, characterized in that: The separation pipeline is close to the tank wall of the separation tank along the tangential direction after being bent.

7. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 1, characterized in that: Four universal wheels are arranged at four corners of the bottom of the support.

8. The pressure-maintaining and pressure-reducing gas collecting device for core according to claim 2, characterized in that: The base comprises an upper circular ring, fixing columns and a lower circular ring, the first plug is installed on the upper circular ring, upper ends of the fixing columns are fixed to the lower side of the upper circular ring, lower ends of the fixing columns are fixed to the upper side of the lower circular ring, three fixing columns are arranged, and the fixing columns are mutually arranged at a degree angle.

9. The method of claim 2, wherein the method further comprises: The method comprises the following steps: Step one: fill the gas-water pipeline with water through the valve controlled by the operation box, and pressurize to the same pressure as the pressure maintaining cabin; Step two: fill the inner sleeve with water through the operation box, and remove the air in the inner sleeve through the upper gas outlet at the top of the inner sleeve and a syringe; Step three: connect the syringe to the valve on the sidewall of the outer sleeve, remove the excess water in the outer sleeve, and make the liquid level of the outer sleeve flush with the valve as the initial liquid level; Step four: the water and gas generated by the decomposition of the pressure-maintained core in the pressure-maintaining cabin are controlled by the operation box, enter the inner sleeve through the first plug, the generated gas is collected and measured by the syringe through the upper gas outlet at the top of the inner sleeve, and the generated water is extracted and measured by the syringe through the valve on the sidewall of the outer sleeve.

10. The method of claim 1, wherein the method further comprises: The method comprises the following steps: Step one: fill the gas-water pipeline with water through the valve controlled by the operation box, and pressurize to the same pressure as the pressure maintaining cabin; Step two: open the first valve through the operation box, and adjust the pressure in the pressure-maintaining cabin by using the flow regulator to start the pressure reduction and gas release; Step three: the gas and water generated by the decomposition of the hydrate enter the gas-liquid separator, and the water yield can be directly read through the scale on the gas-liquid separator; Step four: the gas flows through the gas flow meter, and the pressure and gas flow are recorded and displayed in real time through the data acquisition module, so that the long core gas yield is quickly calculated; Step five: after the gas passes through the gas flow meter, the gas flows out from the gas discharge interface, enters the gas collection bag, and the gas collection is completed. The method comprises the following steps: Step one: fill the gas-water pipeline with water through the valve controlled by the operation box, and pressurize to the same pressure as the pressure maintaining cabin; Step two: open the first valve through the operation box, and adjust the pressure in the pressure-maintaining cabin by using the flow regulator to start the pressure reduction and gas release; Step three: the gas and water generated by the decomposition of the hydrate enter the gas-liquid separator, and the water yield can be directly read through the scale on the gas-liquid separator; Step four: the gas flows through the gas flow meter, and the pressure and gas flow are recorded and displayed in real time through the data acquisition module, so that the long core gas yield is quickly calculated; Step five: after the gas passes through the gas flow meter, the gas flows out from the gas discharge interface, enters the gas collection bag, and the gas collection is completed.

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