Multifunctional testing device and method for hydrate exploitation and CO2 multiphase storage

Abstract

The invention discloses a multifunctional testing device and method for hydrate exploitation and CO2 multiphase sealing, the device comprises an experiment kettle for testing reaction, the experiment kettle is respectively connected with a confining pressure system, a vacuumizing system, a gas injection system, a CO2 injection system, a supercritical CO2 injection system, a liquid injection system and a permeation and diffusion characteristic testing system. The device is high in measurement precision, reliable in performance and high in practicability, can meet the requirements of methane hydrate layered mining simulation and carbon dioxide multi-phase storage multifunctional testing under the coupling effect of different working conditions of real simulation ocean working conditions, and can provide important technical support for commercial development of methane hydrate reservoirs and realization of efficient carbon dioxide storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrate development, and particularly relates to a multifunctional testing device and method for hydrate exploitation and CO2 multiphase state storage. BACKGROUND

[0002] Natural gas hydrate is a new type of clean energy with great potential in the 21st century, and it has rich resources, huge reserves and broad development prospects. However, hydrate deposits are unevenly distributed, mainly in deep sea areas and permafrost regions, making development difficult. In the process of hydrate test mining, the depressurization method is often selected for its simple operation, easy to realize large-scale development, and low development cost, but it is limited by low gas production rate, limited range of suitable reservoirs, and other shortcomings, and cannot be widely applied. At present, the global climate change problem caused by CO2 emission is a great challenge facing the world today, and under the current energy transformation and "double carbon" target, permanent storage of CO2 in the underground is a promising solution to reduce CO2 emission. Compared with simply storing CO2, using CO2 to replace natural gas hydrate not only can extract CH4, but also can store CO2, which can achieve the exploitation of natural gas hydrate, carbon storage and reservoir stability, and meet the dual needs of energy exploitation and carbon storage.

[0003] However, the research on the mechanism of CO2 replacing CH4 is still in the initial stage of theoretical interpretation, and there are still deficiencies in the qualitative understanding of the replacement mechanism and the quantitative evaluation method of the replacement efficiency. The migration, solidification and permeation rules of each phase of CO2 in the hydrate reservoir of porous media, as well as the key influencing factors and influencing rules of CO2 storage rate and methane recovery rate are still not well understood. There is less systematic research on the migration, development and storage rules of liquid CO2 in the reservoir under the coupling of different particle size combination reservoirs, different methane hydrate saturations, different temperatures, different pressures, different depressurization amplitudes, different vertical depressurization points, different CO2 injection positions, different CO2 injection modes (continuous injection, intermittent injection, cyclic injection (CO2 injection and water injection cycle), etc.), different CO2 injection phases (gaseous, liquid, supercritical state), different CO2 injection rates, etc. And the existing experimental device only supports liquid and gaseous CO2 injection, without considering the injection of supercritical CO2; without carrying out layered exploitation simulation of CO2 replacing CH4 hydrate reservoir; and without fully exploring the variation rules of methane recovery rate, CO2 solidification and storage rules under the coupling of the above different working conditions.

[0004] Therefore, a hydrate exploitation and CO2 multi-phase state storage multifunctional testing device and method are considered to be developed, which integrates real simulation of actual reservoir conditions, in-situ generation of methane hydrate, depressurization of methane hydrate under different working conditions, replacement of methane hydrate by CO2 under different working conditions, diffusion and penetration of CO2 in the methane hydrate layer, and research on the synergistic mechanism of CO2 three-phase mode storage, so as to truly simulate actual marine reservoir working conditions, clarify the diffusion and penetration of CO2 in the hydrate reservoir, clarify the key influencing factors and laws of CO2 storage rate and methane recovery rate, and reveal the replacement-storage synergistic mechanism of CO2 three-phase mode, thereby providing important equipment for deep-sea hydrate commercial development and important technical support for CO2 replacement method for exploiting natural gas hydrate and CO2 multi-phase state storage testing. SUMMARY

[0005] The purpose of the present application is to provide a hydrate exploitation and CO2 multi-phase state storage multifunctional testing device and method to simulate the multifunctional testing of methane hydrate depressurization exploitation and CO2 multi-phase state storage under marine working conditions, and to truly simulate actual reservoir conditions, generate methane hydrate reservoir in-situ, and carry out research on the synergistic laws of methane hydrate depressurization and CO2 replacement under different particle size combinations and shale content simulated reservoirs, different methane hydrate saturations, different temperatures, different pressures, different depressurization amplitudes, different vertical depressurization points, different CO2 injection positions, different CO2 injection modes (continuous injection, intermittent injection, cyclic injection (CO2 injection and water injection cycle), etc.), different CO2 injection phases (gas, liquid, supercritical state), different CO2 injection rates, and the diffusion and penetration of different phase CO2 in the methane hydrate layer, and the synergistic mechanism of CO2 three-phase mode (liquid, gas, supercritical state) injection, so as to clarify the diffusion and penetration of CO2 in the hydrate reservoir, clarify the key influencing factors and laws of CO2 storage rate and methane recovery rate, and provide important data support for the CO2 replacement hydrate exploitation method and CO2 multi-phase state storage testing.

[0006] The present application is implemented by using the following technical scheme: a hydrate exploitation and CO2 multi-phase state storage multifunctional testing device, comprising: An experimental kettle for testing reactions; A confining pressure system for providing pressure to the experimental kettle to simulate actual reservoir pressure; A vacuum pumping system for vacuumizing the experimental kettle; A gas injection system for injecting methane gas into the experimental kettle; A CO2 injection system for injecting required CO2 into the experimental kettle, which can selectively inject gaseous or liquid CO2 by selecting different injection pipelines; The supercritical CO2 injection system is used for converting CO2 in the gas cylinder into supercritical CO2 and injecting into the experimental kettle. The liquid injection system is used for injecting required chemical agents and experimental liquids into the experimental kettle. The permeation and diffusion characteristic test system is used for determining the permeation and diffusion characteristics of CO2 in the hydrate reservoir under different particle size combinations, different shale content, different temperatures, different pressures, different hydrate synthesis stages, different hydrate saturations, and different hydrate saturations after different depressurization amplitudes and time lengths.

[0007] Further, the high and low temperature experiment box for adjusting the temperature of the experimental kettle is further included, and a visual window is arranged on the high and low temperature experiment box, which is used for adjusting and controlling the temperature of the experimental kettle in the test process.

[0008] Further, the experimental kettle is connected with a sound wave detector, a bridge instrument, a CT scanner, a gas chromatograph, a methane sensor and a high-definition camera, and the sound wave detector, the bridge instrument, the CT scanner, the gas chromatograph, the methane sensor and the high-definition camera are further connected with the data acquisition and control system.

[0009] Further, a plurality of temperature sensors, pressure sensors and resistivity detectors are further arranged on the experimental kettle, wherein the temperature sensors and the pressure detectors are all cluster type probes used for detecting data in different depth radius ranges.

[0010] Further, the confining pressure system includes an oil tank, an oil pump and a second pressure sensor, the oil tank is connected with the oil pump, and the oil pump is connected with the experimental kettle through a pipeline provided with a plurality of injection valves.

[0011] Further, the gas injection system includes a methane gas cylinder, a first gas flow meter, a piston container and a gas booster pump, the methane gas cylinder is connected with the first gas flow meter, the piston container and the gas booster pump, and the gas booster pump is connected with the experimental kettle through the piston container.

[0012] Further, the CO2 injection system includes a gas phase CO2 injection system subsystem and a liquid phase CO2 injection subsystem, the gas phase CO2 injection system subsystem includes a second CO2 gas cylinder and a first gas flow meter, the second CO2 gas cylinder is connected with the first gas flow meter, a piston container and a gas booster pump, and the gas booster pump is connected with the experimental kettle through the piston container, and the liquid phase CO2 injection subsystem includes a high-pressure metering pump, and the high-pressure metering pump is connected with the experimental kettle through a pipeline.

[0013] Further, the supercritical CO2 injection system comprises a CO2 gas cylinder, a supercritical CO2 generator, a buffer accumulator, a phase state monitoring unit, and a supercritical adjustment system. The supercritical CO2 generator is connected to the buffer accumulator, the phase state monitoring unit, and the supercritical adjustment system through pipelines and an experimental kettle.

[0014] Further, the permeation and diffusion characteristic test system comprises a third pressure sensor, a high-pressure gas injection pump, a CO2 gas container, and a third gas flow meter. The CO2 gas container is connected to the third pressure sensor, the high-pressure gas injection pump, and the third gas flow meter through pipelines and an experimental kettle.

[0015] A hydrate exploitation and CO2 multi-phase state storage multifunctional test method is realized based on the above-mentioned hydrate exploitation and CO2 multi-phase state storage multifunctional test device, and the method comprises the following test contents. Pressure reduction exploitation of methane hydrates and CO2 injection and storage law test; Pressure reduction exploitation of methane hydrates after CO2 injection in hydrate layers; CO2 injection permeation characteristic test in methane hydrate layers.

[0016] The pressure reduction exploitation of methane hydrates and CO2 injection and storage law test comprises the following sub-steps: S1: simulation of reservoir preparation and loading process; S2: connection of data acquisition and control system; S3: experimental kettle cooling process; S4: experimental kettle confining pressure loading process; S5: experimental kettle methane gas injection process; S6: in-situ methane hydrate generation stage; S7: pressure reduction exploitation of methane hydrates process; S8: experimental kettle multi-phase CO2 injection process; S9: CO2 displacement of methane hydrates process; S10: data processing and analysis process.

[0017] The pressure reduction exploitation of methane hydrates after CO2 injection in hydrate layers test comprises the following sub-steps: S1: simulation of reservoir preparation and loading process; S2: connection of data acquisition and control system; S3: experimental kettle cooling process; S4: experimental kettle confining pressure loading process; S5: experimental kettle methane gas injection process; S6: in-situ methane hydrate generation stage; S7: experimental kettle multi-phase CO2 injection process; S8: CO2 replacement of methane hydrate process; S9: depressurization exploitation of methane hydrate process; S10: data processing and analysis process.

[0018] The CO2 replacement of methane hydrate layer permeability test comprises the following sub-steps: S1: simulation reservoir preparation and loading process; S2: connection of data acquisition and control system; S3: experimental kettle cooling process; S4: experimental kettle confining pressure loading process; S5: experimental kettle methane gas injection process; S6: in-situ generation stage of methane hydrate; S7: reservoir dynamic permeability test and different phase CO2 diffusion and permeability test process; S8: data processing and analysis process.

[0019] The present application has the beneficial effects that: The experimental device has a layered test capability, can simulate the hydrate layer and the underlying layer, and can simulate the actual reservoir conditions according to the target reservoir physical property characteristic data; in the in-situ generation stage of the hydrate, the real-time measured acoustic wave and resistivity data are compared and analyzed with the logging data of the actual target reservoir, and the simulation reservoir and the underlying layer matched with the actual reservoir are prepared.

[0020] The present application is equipped with an acoustic wave detector, a bridge instrument and a CT scanner, can reveal the distribution rule of the hydrate reservoir in-situ generation stage, the depressurization decomposition stage and the CO2 replacement of methane hydrate stage, the diffusion and permeability rule of CO2 in the methane hydrate layer and the real-time spatial distribution characteristics by measuring the acoustic wave and resistivity data combined with the test results of the CT scanner.

[0021] The temperature and pressure sensor probe equipped in the present application is loaded with multiple cluster probes, can detect the data in different depth radius range by arranging different arrays for multi-point synchronous monitoring, can realize internal measurement point data correction and dynamic tracking of CO2 hydrate formation and methane hydrate decomposition front, and can analyze the three-dimensional field dynamic evolution rule.

[0022] The present application is equipped with a methane sensor and a gas chromatograph, can detect the methane concentration change, component composition and content in the experimental kettle in real time; and can calculate the carbon dioxide concentration change, carbon dioxide consumption, carbon dioxide storage, methane replacement amount, methane replacement rate, methane recovery rate and carbon dioxide storage rate in the experimental kettle.

[0023] The present application is equipped with three high-definition camera probes, can observe the hydrate reaction in each layer of the kettle in real time.

[0024] The application has gaseous CO2, liquid CO2 and supercritical CO2 multi-mode injection functions, and discloses a (liquid / gas / supercritical state) CO2 three-phase mode injection synergistic mechanism.

[0025] The application has high measurement precision, reliable performance and strong practicability, and can meet the needs of real simulation of different working conditions of marine working conditions, coupling of methane hydrate layered mining simulation and multi-phase state sealing of carbon dioxide, and can provide important technical support for commercial development of methane hydrate reservoirs and realization of multi-phase state efficient sealing of carbon dioxide. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0027] Figure 1 It is a structure schematic diagram of an experimental kettle of the application and a process flow chart; Figure 2 It is a structure schematic diagram of a high-low temperature test box; Figure 3 It is a structure schematic diagram of an end cover of an experimental kettle body of the application; Figure 4 It is a structure schematic diagram of an experimental kettle wall temperature, pressure and resistivity sensor arrangement of the application; Figure 5 It is a structure schematic diagram of a layered partition plate of the application; Figure 6 It is a structure schematic diagram of a sand prevention filter screen of the application; Figure 7 It is a structure schematic diagram of a cluster type temperature and pressure sensor probe of the application; In the figure: 1-methane gas cylinder, 2-first pressure reducing valve, 3-methane injection valve, 4-first gas flow meter, 5-piston container, 6-gas booster pump, 7-nitrogen gas cylinder, 8-first vent valve, 9-first injection valve, 10-first vacuum valve, 11-first pressure sensor, 12-second vacuum valve, 13-vacuum pump, 14-liquid injection valve, 15-high-pressure liquid injection pump, 16-liquid container, 17-first CO2 gas cylinder, 18-second pressure reducing valve, 19-first CO2 injection valve, 20-supercritical CO2 generator, 21-buffer accumulator, 22-phase state monitoring unit, 23-supercritical adjustment system, 24-supercritical CO2 injection valve, 25-regular CO2 injection valve, 26-high-pressure metering pump, 27-second CO2 injection valve, 28-third pressure reducing valve, 29-second CO2 gas cylinder, 30-computer, 31-data acquisition and control system, 32-second vent valve, 33-second injection valve, 34-third injection valve, 35-fourth injection valve, 36-methane sensor, 37-oil tank, 38-first check valve, 39-gas chromatograph, 40-discharge valve, 41-second gas flow meter, 42-pressure reducing valve, 43-heating jacket, 44-fifth pressure reducing valve, 45-first sampling outlet valve, 46-acoustic wave detector, 47-second sampling outlet valve, 48-locking nut, 49-bridge instrument, 50-second check valve, 51-high-pressure oil filling pump, 52-attendant valve, 53-second pressure sensor, 54-analog oil pipe, 55-first sand prevention screen assembly, 56-second sand prevention screen assembly, 57-rubber sleeve, 58-titanium alloy partition plate with sealing ring, 59-high-definition camera, 60-resistance sensor, 61-temperature sensor, 62-CT scanner, 63-pressure sensor, 64-third pressure sensor, 65-first gas injection valve, 66-high-pressure gas injection pump, 67-fifth injection valve, 68-CO2 gas container, 69-locking bolt at lower end of kettle body, 70-third gas flow meter, 71-locking bolt at upper end of kettle body, 72-outer wall of experimental kettle, 73-perfluoroether rubber (FFKM) O-ring, 74-injection pipe sealing ring, 75-sealing ring of injection pipe in underlying layer, 76-check valve sealing ring, 77-check valve, 78-through hole of analog oil pipe, 79-wall of analog oil pipe, 80-sand prevention screen, 81-sensor probe, 82-sensor probe rod, 83-first injection port, 84-second injection port, 85-third injection port, 86-first sampling outlet, 87-second sampling outlet, 88-first interface of acoustic wave detector, 89-second interface of acoustic wave detector, 90-port of locking bolt of kettle cover, 91-port of hanging buckle of kettle cover, 92-high-low temperature test box, 93-visual window, 94-fourth pressure sensor, 95-experimental kettle, 96-simulated hydrate reservoir, 97-simulated underlying layer. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0029] It should be noted that similar reference numerals and letters refer to like items in the accompanying drawings, and thus, once an item is defined in one drawing, it is not necessary to further define and explain it in subsequent drawings.

[0030] The embodiments of the present application will be described below in detail with reference to the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] Referring to Figures 1 to 7 , the hydrate exploitation and CO2 multiphase state storage multifunctional test device can simulate the multifunctional test of methane hydrate exploitation and CO2 multiphase state storage under marine working conditions, and truly simulate actual reservoir conditions; in-situ generated methane hydrate reservoir; the synergistic law research of methane hydrate depressurization and CO2 replacement of methane hydrate under different particle size combinations, simulated reservoirs with different shale contents, different methane hydrate saturations, different temperatures, different pressures, different depressurization amplitudes, different vertical depressurization points, different CO2 injection positions, different CO2 injection modes (continuous injection, intermittent injection, cyclic injection (CO2 injection and water injection cycle) and the like), different CO2 injection phases (gaseous, liquid, supercritical state) and different CO2 injection rates and the like working conditions; the research of the diffusion and permeation law of different phase CO2 in the methane hydrate layer; the research of the synergistic mechanism of CO2 three-phase mode (liquid, gaseous, supercritical state) injection.

[0032] The device comprises an experimental kettle 95 for testing reaction; a confining pressure system for providing confining pressure to the experimental kettle; a vacuumizing system for vacuumizing the experimental kettle; a gas injection system for injecting methane gas into the experimental kettle 95; a CO2 injection system for injecting gas phase and liquid phase CO2 into the experimental kettle 95; a supercritical CO2 injection system for injecting supercritical CO2 into the experimental kettle 95; a liquid injection system for injecting various chemicals and experimental liquids into the experimental kettle 95; a permeation and diffusion characteristic testing system for injecting CO2 into the experimental kettle 95 to test the dynamic permeability of the reservoir with different hydrate synthesis stages, different hydrate saturations, different depressurization amplitudes and time lengths, and the permeation and diffusion rules of each phase CO2 in the hydrate reservoir; and a high and low temperature experimental box 92 for adjusting and controlling the temperature of the experimental kettle 95 during the experimental test, and a data acquisition and control system 31.

[0033] The experimental kettle 95 is made of titanium alloy to avoid corrosion by supercritical CO2. The experimental kettle 95 is divided into a hydrate reservoir 96 and an underlying layer 97 by a partition 58 with a sealing ring. The experimental kettle 95 is externally provided with a methane sensor 36, a gas chromatograph 39, a bridge instrument 49, and a CT scanner 62, and is internally provided with a rubber sleeve 57. An acoustic wave detector 46 is externally connected to the top of the experimental kettle. The gas chromatograph 39, the acoustic wave detector 46, the bridge instrument 49, and the CT scanner 62 are connected to a terminal to the data acquisition and control system 31. Three high-definition cameras 59 for observing the inside of the experimental kettle are connected to the outer wall of the experimental kettle, as well as six array-distributed resistivity sensors 60, six temperature sensors 61, and six pressure sensors 63. The specific distribution of the sensors is shown in Figure 4 The experimental kettle 95 is externally provided with a second pressure sensor 53, an oil tank 37, a first one-way valve 38, a high-pressure oil filling pump 51, a servo valve 52, a third pressure sensor 64, a third gas flow meter 70, a high-pressure gas injection pump 66, and a gas container 68. The rubber sleeve 57 is provided with a perfluoroether rubber (FFKM) O-shaped sealing ring 73. The left side of the experimental kettle 95 is provided with the second pressure sensor 53, the oil tank 37, the first one-way valve 38, the high-pressure oil filling pump 51, and the servo valve 52, which have the function of oil filling and confining pressure increase. The lower end of the experimental kettle 95 is connected to the third pressure sensor 64, the third gas flow meter 70, the high-pressure gas injection pump 66, and the gas container 68, which have the function of testing the gas permeation and diffusion characteristics in the hydrate layer. The values of the fourth pressure sensor 94 and the second gas flow meter 41 at the outlet of the experimental kettle 95 are compared, and the dynamic permeability of the hydrate reservoir under different conditions, in different stages, and with different saturations can be obtained by using Darcy's formula.

[0034] In this embodiment, the confining pressure system, its power is provided by the high-pressure oil pump 51, open one-way valve 38, close the second one-way valve 50, open the servo valve 52, so that the oil tank 37 oil through the pressurized processing, injection into the experimental kettle 95 and rubber sleeve 57, load to the experimental required pressure, can be observed by the second pressure sensor 53, read the pump oil pressure. When the pressure loading process is completed, close the one-way valve 38 and servo valve 52, open the second one-way valve 50, the oil through the transparent pipeline into the oil tank 37, while the oil tank 37 with the liquid level gauge, can be used for real-time monitoring of the oil tank 37 liquid level.

[0035] In this embodiment, the vacuum system, adjust the first vacuum valve 10, the second vacuum valve 12 and the first gas injection valve 9, open the vacuum pipeline, run the vacuum pump 13, the experimental kettle 95 air through the first vent valve 8 discharged outside the kettle, and observe the number of one-way valve 11 read the pressure in the pipeline, until the vacuum degree is -0.09MPa after stopping the vacuum operation.

[0036] In this embodiment, the gas injection system, by methane gas cylinder 1 provides methane gas source, injection of methane gas pipeline through the pressure regulating valve 2, through the methane injection valve 3, the first gas flow meter 4, the experimental required quantitative methane gas injection into the piston container 5 cache, and the gas booster pump 6 pressure processing, and through the adjustment of the second injection valve 33, the third injection valve 34, the fourth injection valve 35 different injection valve door will be methane gas through different vertical depth simulation oil pipe 54 into different burial depth reservoir. In addition, the gas booster pump 6 is provided with a pressure relief valve 8, to ensure that there is no pressure in the gas booster pump 6 in the non-working state.

[0037] In this embodiment, the CO2 injection system, divided into gas phase CO2 injection system subsystem and liquid phase CO2 injection system subsystem, wherein the gas phase CO2 injection system subsystem by the second CO2 cylinder 29 provides carbon dioxide gas source, through the pressure regulating valve 28, through the CO2 second injection valve 27, the first gas flow meter 4, the experimental required quantitative carbon dioxide gas injection into the piston container 5 cache, and the gas booster pump 6 pressure processing, and through the adjustment of the second injection valve 33, the third injection valve 34, the fourth injection valve 35 different injection valve door will be carbon dioxide gas through different vertical depth simulation oil pipe 54 into different burial depth hydrate reservoir and underlying layer. The liquid phase CO2 injection system subsystem includes a high-pressure metering pump 26, by adjusting the pressure of the high-pressure metering pump 26 so that the gas phase CO2 in the pump cache tank is converted to liquid phase CO2 and metered, through the conventional CO2 injection valve 25, adjust the second injection valve 33, the third injection valve 34, the fourth injection valve 35 different injection valve door will be required for the experiment CO2 through different vertical depth simulation oil pipe 54 into the experimental kettle 95 into different burial depth hydrate reservoir and underlying layer.

[0038] In the embodiment, the supercritical CO2 system is used for injection. The supercritical CO2 has high diffusivity and strong solubility, high wave efficiency, and deep penetration characteristics, and can achieve high CH4 recovery rate, high stability of CO2 storage, low energy consumption ratio, and wide application range. The system mainly comprises a first CO2 cylinder 17, a supercritical CO2 generator 20, a buffer accumulator 21, a phase state monitoring unit 22, and a supercritical adjustment system 23. The CO2 gas in the first CO2 cylinder 17 is adjusted in pressure by a second pressure reducing valve 18, injected into the supercritical CO2 generator 20 through a first CO2 injection valve 19, prepared into supercritical CO2, and output to the buffer accumulator 21 for temporary storage. The temperature and pressure of the supercritical CO2 transported in the pipeline are monitored by the phase state monitoring unit 22. If the state of the supercritical CO2 is found to change, the supercritical adjustment system 23 is automatically adjusted to maintain the supercritical state of CO2 (with a temperature control accuracy of ±0.1°C and a pressure control accuracy of ±0.1MPa). The supercritical CO2 is injected into different buried depth hydrate reservoirs and underlying layers through different vertical depth simulation oil pipes 54 by adjusting different injection valves, such as a second injection valve 33, a third injection valve 34, and a fourth injection valve 35.

[0039] In the embodiment, a liquid injection system is used. The system mainly comprises a high-pressure liquid injection pump 15 and a liquid container 16. The liquid injection pipeline is directly connected to the experimental kettle 95 by adjusting the liquid injection valve 14. The required quantitative chemical reagents and experimental liquids in the liquid container 16 are pressurized by the high-pressure liquid injection pump 15 and directly injected into the experimental kettle.

[0040] In the embodiment, a permeation and diffusion characteristic test system is used. The system mainly comprises a third pressure sensor 64, a high-pressure gas injection pump 66, a CO2 gas container 68, and a third gas flow meter 70. The CO2 gas in the CO2 gas container 68 is pressurized by the high-pressure gas injection pump 66, injected into the experimental kettle 95, and reacted with the hydrate reservoir. The hydrate reservoir is detected every 2-3 hours by a CT scanner 62. The real-time spatial distribution characteristics of the hydrate reservoir are explored by using a sound wave detector 46 and a bridge instrument 49 to monitor the sound wave and resistivity data in real time. The pressure readings of the third pressure sensor 64 and the flow data of the third gas flow meter 70 are compared with the values of a fourth pressure sensor 94 and a second gas flow meter 41 at the outlet of the experimental kettle 95. The dynamic permeability of the reservoir under different particle size combinations, different shale content reservoirs, different temperatures, different pressures, and other working conditions, different hydrate synthesis stages, different hydrate saturations, and different hydrate saturations after mining through different pressure reduction amplitudes and time lengths is obtained by using the Darcy formula. The permeation and diffusion characteristics of the hydrate reservoir, the dynamic permeability of the hydrate reservoir, and the CO2 diffusion and permeation rules in the hydrate reservoir are obtained. The gas components and contents at the outlet of the experimental kettle 95 are analyzed by a gas chromatograph, and the gas permeation and diffusion characteristics in the hydrate layer are determined.

[0041] The hydrate exploitation and CO2 multi-phase state storage multifunctional test method is realized based on the hydrate exploitation and CO2 multi-phase state storage multifunctional test device, and includes the following test contents and steps: Content one: testing of CO2 storage rules after depressurization exploitation of methane hydrate S1: simulation of reservoir preparation and loading process According to the experiment needs, combined with the characteristics of the South China Sea marine hydrate reservoir, the sand required for simulating the reservoir and the underlying layer is configured according to the actual reservoir composition, particle size combination and shale content, combined with the reservoir basic physical property data, the experimental water matching the parameters such as the target reservoir salinity and pH value is prepared, the quantitative water amount is weighed according to the calculation of different initial methane hydrate saturations (8%~50%), and the sand sample is mixed uniformly to prepare the shale fine sand for standby; the experimental kettle 95 is loaded and sealed, the titanium alloy partition plate 58 with a sealing ring is added and fixed, the one-way valve 77 is installed to ensure that the underlying layer fluid can pass through in one direction when the pressure difference between the upper and lower layers is greater than 1 MPa, the resistivity sensor 60, the temperature sensor 61 and the pressure sensor 63 are installed, and the perfluoroether rubber (FFKM) O-shaped sealing ring 73 with a nano silica grafted layer (thickness 200 nm) is installed between the experimental kettle wall 72 and the rubber sleeve 57. The upper end cover of the experimental kettle is closed, the locking nut 48 and the kettle body upper end locking bolt 71 are tightened, the assembly installation is completed, and no gap is ensured.

[0042] S2: connection of data acquisition and control system The data acquisition and control system 31 is opened, and the programs in the computer 30 are run to connect the resistivity sensor 60, the temperature sensor 61, the pressure sensor 63, the gas flow meter 41 and the gas flow meter 70 of all peripherals to the terminal of the data acquisition and control system 31, connect the bridge instrument 49, the acoustic wave detector 46, the methane sensor 36 and the gas chromatograph 39, and detect and control whether the data (temperature, pressure, resistivity, longitudinal wave, transverse wave and methane concentration) is normally displayed.

[0043] S3: experimental kettle cooling process The experimental kettle 95 is placed in the high and low temperature test box, the preset temperature is set in the data acquisition and control system 31, the refrigeration operation of the experimental kettle 95 is performed, the kettle temperature data is observed, after the refrigeration is completed, the bubble water is evenly applied to each connection port outside the kettle body, whether the air tightness of each port outside the device is good is checked, and the next stage is performed if the air tightness is good.

[0044] S4: experimental kettle confining pressure loading process Open the one-way valve 38 of the pressurized upper pipeline, the servo valve 52, select the confining pressure, press the "filling oil" button on the control cabinet, and the high-pressure oil filling pump 51 provides power. Through the servo valve 52, the oil is injected into the experimental kettle and the rubber sleeve 57, and the transparent hose at the oil tank 37 is observed. When there is no intermittent flow of oil in the transparent tube and no bubbles, the experimental kettle is filled with oil, the exhaust is completed, and the oil filling button is pressed again. To prevent the pressure difference between the inside and outside of the rubber sleeve 57 in the experimental kettle from being too large, the actual experimental kettle filling and gas injection process are alternately performed, and the internal and external pressure difference is maintained to reach the required effective confining pressure (not more than 3 MPa).

[0045] S5: Experimental kettle methane gas injection process Before gas injection, adjust the first vacuum valve 10, the second vacuum valve 12, and the first gas injection valve 9, open the vacuum pipeline, run the vacuum pump 13, and perform vacuum treatment. The air in the experimental kettle 95 is discharged outside the kettle through the first vent valve 8, and the pressure in the pipeline is observed by the first pressure sensor 11. Stop the vacuum operation until the vacuum degree is-0.09 MPa. Inject the required amount of methane gas into the experimental kettle 95, and measure the amount of injected methane gas through the first gas flow meter 4; stop injecting methane gas when the pressure reaches the required experimental pressure, and observe whether the pressure in the reaction kettle can remain unchanged for 2 hours to further check the gas tightness of the device; after good gas tightness, prepare the hydrate according to the "quantitative water, excess gas" method.

[0046] In addition, the liquid container 16 outlet valve can be opened through the liquid injection system, the liquid injection valve 14 is adjusted, and the liquid injection pipeline is pressurized by the high-pressure liquid injection pump 15. The required amount of chemical reagent and experimental liquid is directly injected into the experimental kettle 95.

[0047] S6: In-situ generation of methane hydrate By measuring the longitudinal wave, transverse wave, and resistivity data in real time during the in-situ generation of hydrate, observing the changes of each parameter, and judging the generation of hydrate, the generation and spatial distribution of hydrate are detected every 2-3 hours by setting the acoustic wave detector 46 and the CT scanner 62, and the bridge instrument 49 is monitored in real time to reveal the generation rule and distribution characteristics of hydrate. If the pressure in the experimental kettle changes significantly (decreases more), open the methane gas cylinder 1, the first pressure reducing valve 2, the methane gas injection valve 3, and the piston container 5, and measure the amount of methane gas through the first gas flow meter 4. Adjust the gas booster pump 6 for pressurization, and supplement the injection of a certain amount of methane gas into the experimental kettle 95 to supplement the pressure to the preset experimental pressure. When the methane gas continues to be supplemented, after 5 hours, the temperature, pressure, resistivity, and acoustic wave parameter data in the kettle no longer change significantly, and it is considered that the water in the kettle has been used to generate methane hydrate, and the in-situ generation of methane hydrate is completed.

[0048] By measuring the hydrate generated in situ, the acoustic wave, resistivity data of the reservoir and underlying layer are compared with the actual field P-wave, S-wave, resistivity logging data. If the P-wave, S-wave, resistivity logging data are in good agreement, it means that the prepared simulation reservoir and underlying layer in the laboratory have high matching with the real reservoir (meet the experimental requirements).

[0049] S7: Pressure reduction exploitation of methane hydrate process When pressure reduction exploitation is carried out, through investigation and calculation of the phase equilibrium conditions of methane hydrate under corresponding working conditions, by controlling the temperature unchanged, by adjusting the data acquisition and control system 31 and opening the pressure regulating valve 42, the outlet pressure is precisely controlled, the methane hydrate reservoir under different temperature and pressure conditions is exploited by different pressure reduction amplitude and different pressure reduction time. The first outlet valve 45 and the second outlet valve 47 are selectively opened to exploit the hydrate reservoir under different vertical point conditions, then the discharge valve 40 is opened, and the power switch of the heating and insulation sleeve 43 is opened to heat the outlet pipeline, so as to avoid the blockage of the pipeline by undecomposed hydrate particles. When the pressure in the experimental kettle reaches the preset pressure reduction amplitude, the data acquisition and control system 31 is adjusted and the pressure regulating valve 42 is closed, and the pressure reduction exploitation is ended. The gas production is counted by the second flow meter 41, and the change of methane concentration is read by the methane sensor 36, and the gas component and content are analyzed by the gas chromatograph 39.

[0050] When the temperature and pressure conditions in the experimental kettle 95 are higher than the phase equilibrium conditions of methane hydrate under corresponding working conditions, and the methane hydrate does not decompose, the data acquisition and control system 31 is adjusted and the pressure regulating valve 42 is opened to precisely control the outlet pressure, the first outlet valve 45 and the second outlet valve 47 are selectively opened, then the discharge valve 40 is opened, and the power switch of the heating and insulation sleeve 43 is opened to heat the outlet pipeline, so as to avoid pipeline blockage, and the free gas in the experimental kettle is exhausted, which provides a prerequisite for the next step of CO2 injection process to study the synergistic mechanism of different abundance methane hydrate reservoirs replacing methane hydrate with CO2.

[0051] S8: CO2 injection process of experimental kettle in multiple phases This experiment considers two cases of methane hydrate simulation reservoir decomposition and non-decomposition to carry out CO2 injection process, and explores the influence of different abundance methane hydrate reservoirs on the synergistic mechanism of CO2 replacing methane hydrate.

[0052] (1) CO2 injection process in gaseous state Opening the second CO2 cylinder 29 to provide a carbon dioxide gas source, regulating the pressure through the third pressure reducing valve 28, opening the CO2 second injection valve 27, injecting a required amount of carbon dioxide gas into the piston container 5 for storage, measuring the amount of gaseous CO2 injected using the first gas flow meter 4, and adjusting the gas booster pump 6 for CO2 gas pressure boosting, adjusting different CO2 injection rates, and different CO2 injection mode cycles (continuous injection, cyclic injection, intermittent injection, etc.), then opening the first injection valve 9, selectively adjusting the second injection valve 33, the third injection valve 34, and the fourth injection valve 35 to select different CO2 injection positions to inject CO2 gas into different buried hydrate reservoirs 96 or underlying layers 97 through different vertical depth simulation oil pipes 54 for displacement reaction.

[0053] (2) Liquid CO2 injection process Opening the second CO2 cylinder 29, regulating the pressure through the third pressure reducing valve 28, opening the CO2 second injection valve 27, injecting a required amount of CO2 gas into the high-pressure metering pump 26, converting the gaseous CO2 in the pump to liquid CO2 by adjusting the pressure of the high-pressure metering pump 26, and measuring the liquid CO2, adjusting different CO2 injection rates, and different CO2 injection mode cycles (continuous injection, cyclic injection, intermittent injection, etc.), opening the conventional CO2 injection valve 25, selectively adjusting the second injection valve 33, the third injection valve 34, and the fourth injection valve 35 to select different CO2 injection positions to inject the required liquid CO2 into the experimental kettle 95 through different vertical depth simulation oil pipes 54 for reaction in different buried hydrate reservoirs 96 and underlying layers 97.

[0054] (3) Supercritical CO2 injection process Opening a CO2 cylinder 17, CO2 gas is regulated by a second pressure reducing valve 18, and injected into a supercritical CO2 generator 20 through a CO2 first injection valve 19. In the supercritical CO2 generator 20, the conventional CO2 gas is converted into supercritical CO2 by adjusting temperature and pressure, and output to a buffer accumulator 21 for temporary storage. A phase state monitoring unit 22 is used to monitor the temperature and pressure of the supercritical CO2 in the pipeline. If the state of the supercritical CO2 changes, the supercritical adjustment system 23 is automatically adjusted to maintain the supercritical state of CO2 (with a temperature control accuracy of ±0.1°C and a pressure control accuracy of ±0.1MPa). Different CO2 injection rates, different CO2 injection cycle periods, and multiple CO2 injection modes (continuous injection, intermittent injection, and cyclic injection (CO2 injection and water injection cycle)) are adjusted. The supercritical CO2 is injected into different buried depth hydrate reservoirs 96 and underlying layers 97 through different vertical depth simulation oil pipes 54 by selecting different CO2 injection positions through selective adjustment of a second gas injection valve 33, a third gas injection valve 34, and a fourth gas injection valve 35.

[0055] In addition, the device not only considers the separate injection of CO2 in three phases (liquid, gas, and supercritical state), but also considers the mixed injection process of gaseous CO2, liquid CO2, and supercritical CO2 in different phases, i.e., continuous or intermittent mixed injection of gaseous CO2, liquid CO2, and supercritical CO2, to further explore the synergistic mechanism of CO2 three-phase mode (liquid, gas, and supercritical state) injection.

[0056] S9: CO2 displacement of methane hydrate process By observing and analyzing the changes in temperature, pressure, resistivity, longitudinal wave, transverse wave, and other parameters, the changes in each parameter are observed to determine the formation of hydrates; the acoustic wave detector 46 and the CT scanner 62 are set to detect the formation and spatial distribution of hydrates every 2-3 hours, and the bridge instrument 49 is used for real-time monitoring to reveal the formation rules and distribution characteristics of hydrates. It is determined that the replacement process of CO2 replacing methane hydrates continues (the replacement reaction is an exothermic process, the temperature rises, and the pressure decreases), and after the replacement reaction no longer occurs through the observation of the data acquisition and control system 31, the pressure is reduced for mining, the pressure of the outlet is precisely controlled by adjusting the data acquisition and control system 31 and opening the pressure regulating valve 42, and methane hydrate reservoirs under different temperature and pressure conditions are mined through different pressure reduction amplitudes and different pressure reduction times. The first outlet valve 45 and the second outlet valve 47 are selectively opened to mine hydrate reservoirs under different vertical point conditions, then the discharge valve 40 is opened, and the power switch of the heating and insulation sleeve 43 is turned on to heat the outlet pipeline to prevent un-decomposed hydrate particles from blocking the pipeline. When the pressure in the experimental kettle reaches the preset pressure reduction amplitude, the data acquisition and control system 31 is adjusted and the pressure regulating valve 42 is closed to end the pressure reduction mining. The amount of CO2 replacing methane gas is measured by the second gas flow 41 and the methane sensor 36, and the change in the methane concentration is read by the methane sensor 36 and analyzed by the gas chromatograph 39 to analyze the composition and content of the produced gas, and the experiment is ended.

[0057] S10: Data processing and analysis process In the hydrate in-situ generation stage, by comparing and analyzing the acoustic wave and resistivity data of the in-situ generated hydrate simulation reservoir and underlying layer with the actual longitudinal wave, transverse wave, and resistivity logging data, a simulation reservoir and underlying layer with high matching performance to the real reservoir are prepared, and the basic physical parameters such as porosity of the simulation reservoir and underlying layer are determined in combination with the basic data of the target reservoir.

[0058] The CH4 concentration change, CO2 concentration change, experimental temperature, pressure change data, gas production amount, and component data under different particle size combinations, different shale content reservoirs, different methane hydrate saturations, different temperatures, different pressures, different pressure reduction amplitudes, different vertical pressure reduction points, different CO2 injection positions, different CO2 injection modes (continuous injection, intermittent injection, cyclic injection (CO2 injection and water injection cycle), etc.), different CO2 injection phases (gaseous, liquid, supercritical), different CO2 injection rates, and other working conditions during the experiment are calculated to calculate the CO2 replacement methane gas amount, replacement rate, CH4 recovery rate, CO2 solidification amount, CO2 storage amount, and CO2 storage rate under different working conditions.

[0059] The specific testing method and process of parameters such as CH4 replacement rate, CH4 recovery rate, CO2 storage rate and CO2 storage amount are shown as follows: Methane hydrate synthesis stage: The amount of methane gas Q0 at standard conditions for synthesizing hydrate is measured by using a gas flow meter 4, and the amount of water Q used for the experiment is additionally measured. 水 The hydrate reservoir with different initial saturations is synthesized by controlling the amount of water used; The amount of methane hydrate synthesized is calculated according to the volume ratio of 1 unit of natural gas hydrate = 164 units of methane gas + 0.8 units of water, combined with the calculated amount of methane gas and the amount of water used, and the experimental temperature and pressure conditions.

[0060] Pressure reduction and decomposition stage: 1) When methane hydrate does not decompose The pressure is reduced to the phase equilibrium pressure corresponding to the temperature by adjusting the data acquisition and control system 31, the free gas in the experimental kettle is emptied, and the amount of free gas Q is measured by using a second gas flow meter 41. 游离 The composition and content of the produced gas are analyzed by using a gas chromatograph 39. This provides a prerequisite for studying the mechanism of CO2 replacing methane hydrate in different abundance methane hydrate reservoirs.

[0061] 2) When methane hydrate decomposes The pressure in the kettle is reduced to the target pressure of the experiment by adjusting the data acquisition and control system 31. When the pressure in the kettle is reduced to the phase equilibrium pressure of methane hydrate, the amount of free gas Q is measured by using a second gas flow meter 41. Q 1When the pressure is reduced to the phase equilibrium pressure corresponding to the working condition, the amount of escaped methane gas Q2 is started to be measured.

[0062] CO2 injection stage: According to the experimental requirements, the amount of CO2 injected at standard conditions is Q （二氧化碳，1） converted into the amount of gaseous, liquid or supercritical CO2 at the corresponding temperature and pressure conditions of the experiment Q （二氧化碳，2） and measured by using a flow meter.

[0063] CO2 replacement of methane hydrate stage: After the replacement is completed, the second extraction is carried out for measuring the amount of methane replacement. The pressure in the kettle is reduced to the phase equilibrium pressure of methane hydrate by using the data acquisition and control system 31, the extraction valve and pipeline of the experimental kettle 95 are opened, and the amount of extracted gas at standard conditions Q3 is measured by using a second gas flow meter 41. Q 3, and the composition and content of the produced gas are analyzed by using a gas chromatograph 39, combined with the methane sensor 36 for monitoring the percentage of methane concentration C in the experimental kettle 95. 甲烷 , the percentage of carbon dioxide concentration C is calculated二氧化碳 , the amount of CO2 replacing methane gas Q 4, the amount of CO2 gas escaping Q 5, (wherein the percentage of methane concentration C 甲烷 + the percentage of carbon dioxide concentration C 二氧化碳 = 1).

[0064] The CH4 replacement rate, CH4 recovery rate, CO2 storage rate and CO2 storage amount are calculated, and the formulas are as follows: CH4 replacement rate: (1) When the methane hydrate does not decompose: the amount of CO2 replacing methane gas is the CH4 recovery amount: replacement rate replacement rate E 置换 = recovery rate ER; (2) When the methane hydrate decomposes: replacement rate CH4 recovery rate (excluding free gas): (1) When the methane hydrate does not decompose: the amount of CO2 replacing methane gas is the CH4 recovery amount: ; (2) When the methane hydrate decomposes: recovery rate .

[0065] CO2 storage rate: ; .

[0066] CO2 storage amount: .

[0067] CO2 solidification amount: 1 unit of carbon dioxide hydrate = 1 unit of carbon dioxide gas + 6 units of water: .

[0068] Content two: test of depressurization production of methane hydrate after CO2 injection in the hydrate layer The S1~S6 process is as described in the test content one: CO2 storage rule test after depressurization production of methane hydrate, and the S1~S6 process is not repeated here.

[0069] S7: multi-phase CO2 injection process in the experimental kettle (1) gaseous CO2 injection process Opening the second CO2 cylinder 29 to provide CO2 gas source, through the third pressure reducing valve 28 to adjust the pressure, opening the CO2 second injection valve 27, the required amount of CO2 gas injection into the piston container 5 for storage, using the first gas flow meter 4 to measure the amount of gaseous CO2 injection, and adjusting the gas booster pump 6 to pressurize the CO2 gas, adjusting the different CO2 injection rate, and the different CO2 injection cycle and (continuous injection, cyclic injection, intermittent injection, etc.) multiple different CO2 injection mode, then open the first injection valve 9, selectively adjust the second injection valve 33, the third injection valve 34, the fourth injection valve 35 to select different CO2 injection position to inject CO2 gas into different buried depth hydrate reservoir 96 or underlying layer 97 through different vertical depth simulation oil pipe 54 for displacement reaction.

[0070] (2) Liquid CO2 injection process Opening the second CO2 cylinder 29, through the third pressure reducing valve 28 to adjust the pressure, opening the CO2 second injection valve 27, the required amount of CO2 gas injection into the high pressure metering pump 26, through adjusting the pressure of the high pressure metering pump 26 to make the gaseous CO2 in the pump storage into liquid CO2 and measure the liquid CO2, then adjust the different CO2 injection rate, and the different CO2 injection cycle and (continuous injection, cyclic injection, intermittent injection, etc.) multiple different CO2 injection mode, open the conventional CO2 injection valve 25, selectively adjust the second injection valve 33, the third injection valve 34, the fourth injection valve 35 to select different CO2 injection position to inject the required CO2 into the experimental kettle 95 through different vertical depth simulation oil pipe 54 for reaction in different buried depth hydrate reservoir 96 and underlying layer 97.

[0071] (3) Supercritical CO2 injection process Opening the first CO2 cylinder 17, making CO2 gas through the second pressure reducing valve 18 to adjust the pressure, through the CO2 first injection valve 19 into the supercritical CO2 generator 20, preparing the conventional CO2 gas into supercritical CO2 by adjusting the temperature and pressure in the supercritical CO2 generator 20 and outputting to the buffer accumulator 21 for temporary storage, using the phase state monitoring unit 22 in the supercritical CO2 injection pipeline to monitor the temperature and pressure of the supercritical CO2 in the pipeline, if the state of the supercritical CO2 is found to change, automatically adjusting the supercritical adjustment system 23 to maintain the CO2 in the supercritical state, (wherein the temperature control accuracy is ±0.1°C, and the pressure control accuracy is ±0.1MPa), and adjusting the different CO2 injection rate, and the different CO2 injection cycle and (continuous injection, cyclic injection, intermittent injection, etc.) multiple different CO2 injection mode, and selecting different CO2 injection position by selectively adjusting the second injection valve 33, the third injection valve 34, the fourth injection valve 35 to inject supercritical CO2 into different buried depth hydrate reservoir 96 and underlying layer 97 through different vertical depth simulation oil pipe 54 for reaction.

[0072] In addition, the device not only considers the injection of CO2 in three phases (liquid, gas, and supercritical state) alone, but also considers the mixed injection process of gaseous CO2 injection, liquid CO2 injection, and supercritical CO2 injection, i.e., the segmented mixed injection of gaseous CO2, liquid CO2, and supercritical CO2, and further explores the synergistic mechanism of CO2 three-phase mode (liquid, gas, and supercritical state) injection.

[0073] S8: CO2 displacement of methane hydrate process By observing and analyzing the changes in temperature, pressure, resistivity, longitudinal wave, and transverse wave parameters, the changes in each parameter are observed to determine the generation of hydrates; the sound wave detector 46 and the CT scanner 62 detect the generation and spatial distribution of hydrates every 2-3 hours, and the bridge instrument 49 monitors in real time to reveal the generation law and distribution characteristics of hydrates. It is determined that the CO2 displacement of methane hydrate displacement process continues (the displacement reaction is an exothermic process, the temperature rises, and the pressure decreases), and after the displacement reaction no longer occurs, the pressure is reduced for mining through the observation data acquisition and control system 31.

[0074] S9: depressurization mining of methane hydrate process When depressurization mining is performed, the phase equilibrium conditions of methane hydrates under corresponding working conditions are investigated and calculated, the temperature is controlled to be constant, the data acquisition and control system 31 is adjusted, and the pressure regulating valve 42 is opened to accurately control the outlet pressure, so that the methane hydrate reservoir under different temperature and pressure conditions is mined through different depressurization amplitudes and different depressurization times. The first outlet valve 45 and the second outlet valve 47 are selectively opened to mine the hydrate reservoir under different vertical point conditions, then the discharge valve 40 is opened, and the power switch of the heating and heat preservation sleeve 43 is turned on to heat the outlet pipeline to avoid the blockage of the pipeline by undecomposed hydrate particles. The fourth pressure sensor 94 and the data acquisition and control system 31 are observed when the pressure in the experimental kettle reaches the preset depressurization amplitude, the data acquisition and control system 31 is adjusted, and the pressure regulating valve 42 is closed to end the depressurization mining. The second flow meter 41 is used to count the produced gas, and the methane sensor 36 is used to read the methane concentration change, and the gas chromatograph 39 is used to analyze the gas composition and content.

[0075] S10: data processing and analysis process In the hydrate in-situ generation stage, the acoustic wave and resistivity data of the in-situ generated hydrate simulation reservoir and underlying layer are compared and analyzed with the actual longitudinal wave, transverse wave, and resistivity logging data, a simulation reservoir and underlying layer with high matching performance to the real reservoir are prepared, and the basic physical parameters such as porosity of the simulation reservoir and underlying layer are determined in combination with the basic data of the target reservoir.

[0076] The statistical experimental process includes different particle size combinations of reservoirs, different methane hydrate saturations, different temperatures, different pressures, different pressure reduction amplitudes, different vertical pressure reduction points, different CO2 injection positions, different CO2 injection modes (continuous injection, intermittent injection, cyclic injection (CO2 injection and water injection cycle), etc.), different CO2 injection phases (gaseous, liquid, supercritical state), different CO2 injection rates, and the like. The data of CH4 concentration change, CO2 concentration change, experimental temperature, pressure change data, gas output and components under different working conditions are calculated to calculate the CO2 displacement methane gas volume, CH4 displacement rate, CH4 recovery rate, CO2 solidification amount, CO2 storage amount, CO2 storage rate under different working conditions.

[0077] The specific test method and process of CH4 displacement rate, CH4 recovery rate, CO2 storage rate and CO2 storage amount and the like are as follows: Methane hydrate synthesis stage: The first gas flow meter 4 is used to measure the methane gas volume under standard conditions for synthesizing hydrates Q 6, and the water quantity for quantitative experiments is additionally weighed Q 水 The hydrate reservoirs with different initial saturations are synthesized by controlling the amount of water used. The calculated methane gas volume and water quantity are combined with the experimental temperature and pressure conditions to calculate the amount of methane hydrate synthesized according to the volume ratio of 1 unit of natural gas hydrate = 164 units of methane gas + 0.8 units of water.

[0078] After the hydrate is generated in situ, the pressure in the kettle is reduced to the methane hydrate phase equilibrium pressure by using the data acquisition and control system 31, the production valve and pipeline of the experimental kettle 95 are opened, and the second gas flow meter 41 is used to measure the amount of unreacted free gas under standard conditions Q 游离 .

[0079] CO2 injection stage: The CO2 injection amount under standard conditions is calculated according to the experimental requirements Q （二氧化碳，3） The amount of gaseous, liquid, supercritical state CO2 under the corresponding temperature and pressure conditions of the experiment is converted Q （二氧化碳，4） And the flow meter is used for measurement.

[0080] CO2 displacement methane hydrate stage: By observing and analyzing the changes in temperature, pressure, resistivity, longitudinal wave, transverse wave and other parameters, observing the changes in each parameter, and judging the formation of hydrate; setting the acoustic wave detector 46 and the CT scanner 62 to detect the hydrate formation and spatial distribution every 2-3 hours, and the bridge instrument 49 to monitor in real time, the hydrate formation rule and distribution characteristics are revealed. It is determined that the CO2 displacement of methane hydrate displacement process continues (the displacement reaction is an exothermic process, the temperature rises, and the pressure decreases). When the displacement is completed, the data acquisition and control system 31 is used to reduce the pressure in the kettle to the methane hydrate phase equilibrium pressure, open the production valve and pipeline of the experimental kettle 95, and use the second gas flow meter 41 to measure the production gas volume at standard conditions Q 7, and use the gas chromatograph 39 to analyze the composition and content of the produced gas, combined with the methane sensor 36 to monitor the methane concentration percentage C 甲烷 in the experimental kettle 95, calculate the carbon dioxide concentration percentage C 二氧化碳 , obtain the CO2 displacement methane gas volume Q 8, CO2 escape gas volume Q 9, (wherein, the methane concentration percentage C 甲烷 + the carbon dioxide concentration percentage C 二氧化碳 =1).

[0081] Pressure reduction and decomposition stage: According to the pressure reduction amplitude required by the experimental conditions, adjust the data acquisition and control system 31 to reduce the pressure in the kettle to the corresponding experimental pressure, when the pressure is reduced below the phase equilibrium pressure, and use the gas chromatograph 39 to analyze the composition and content of the produced gas, combined with the methane sensor 36 to monitor, and use the second gas flow meter 41 to measure the produced gas volume Q 10 , determine the methane gas volume of pressure reduction and decomposition Q 11 .

[0082] Calculate the CH4 displacement rate, CH4 recovery rate, CO2 storage rate and CO2 storage volume, the formulas are as follows: CH4 displacement rate: displacement rate CH4 recovery rate (excluding free gas): .

[0083] CO2 storage rate: ; .

[0084] CO2 storage volume: .

[0085] CO2 solidification amount: 1 unit of carbon dioxide hydrate = 1 unit of carbon dioxide gas + 6 units of water .

[0086] Content three: CO2 injection permeation characteristics test of methane hydrate layer S1~S6 process is as described in test content one: CO2 injection and storage law test after depressurized production of methane hydrate, which is not repeated here.

[0087] S7: reservoir dynamic permeability test and different phase CO2 diffusion and permeation law test process Open the CO2 gas container 68 outlet end switch to release CO2 gas, observe the injection pressure reading of the third pressure sensor 64, and use the third gas flow meter 70 to measure the value, then use the high-pressure gas pump 66 to pressurize the CO2 gas, pump it into the hydrate reservoir 96 in the experimental kettle 95 for reaction, at the same time, open the CT scanner 62 to detect the hydrate reservoir 96 every 2~3 hours, use the acoustic wave detector 46 and the bridge instrument 49 to monitor the acoustic wave and resistivity data in real time, show the real-time spatial distribution of the hydrate reservoir 96 and the CO2 diffusion characteristics, and combine the macroscopic observation of the hydrate distribution and change characteristics in the hydrate reservoir by the high-definition camera on the left side of the experimental kettle outer wall 72, when the reaction is completed, selectively open the first outlet valve 45 and the second outlet valve 47, then open the discharge valve 40, and turn on the power switch of the heating insulation sleeve 43 to heat the outlet pipeline to avoid blocking the pipeline by undecomposed hydrate particles, and compare the pressure reading of the third pressure sensor 64, the measurement value of the third gas flow meter 70, and the values of the fourth pressure sensor 94 and the second gas flow meter 41 at the outlet end of the experimental kettle 95, use Darcy's formula to obtain the dynamic permeability of the hydrate reservoir under different working conditions, at different stages, and with different saturations, and use the acoustic wave detector 46 and the bridge instrument 49 to monitor the acoustic wave and resistivity data in real time, combine the CT scanner 62 measurement data and the gas chromatograph analysis of the gas composition and content at the outlet end of the experimental kettle 95, and further determine the CO2 permeation and diffusion characteristics in the hydrate layer.

[0088] Use Darcy's formula to calculate the dynamic permeability K of hydrates with different saturations (real-time changing values), which is as follows: ; K : permeability, unit m² or D (Darcy); : volumetric flow rate, unit m³ / s or cm³ / s; : cross-sectional area, unit m² or cm²; Pressure difference, in Pa or atm; Fluid viscosity, in Pa·s or mPa·s; : Seepage length, in meters or centimeters.

[0089] S8: Data Processing and Analysis Process The temperature, pressure, acoustic wave, and resistivity parameters during the testing process were statistically analyzed and processed under various operating conditions, including different particle size combinations, different clay content reservoirs, different temperatures, different pressures, different hydrate synthesis stages, different hydrate saturations, and reservoirs with different hydrate saturations after different pressure reductions and mining durations. Based on flow rate, temperature, and pressure data, the dynamic permeability K of the reservoir under different operating conditions was calculated in real time. Furthermore, based on the concentration change data measured by the methane sensor 36 and the gas composition and content data analyzed by the gas chromatograph 39 at the extraction end of the experimental vessel 95, combined with data from the CT scanner 62, the real-time changes in CO2 diffusion and permeation of each phase within the hydrate reservoir were monitored, thereby revealing the gas permeation and diffusion characteristics within the hydrate layer.

[0090] It should be noted that the terms "connection" and "setting" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "connection" or "setting" may explicitly or implicitly include one or more of that feature. Furthermore, the terms "connection" and "setting," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Moreover, for the foregoing embodiments, for the sake of simplicity, they are all described as a series of actions; however, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Secondly, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to this application.

[0091] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the invention should be within the protection scope of the appended claims.

Claims

1. A multifunctional testing device for hydrate extraction and CO2 multiphase storage, characterized in that, include: Experimental vessel (95), used for testing reactions; A confining pressure system is used to provide pressure to the experimental vessel (95) to simulate the actual reservoir pressure; A vacuum system is used to vacuum the experimental vessel (95); The gas injection system is used to inject methane gas into the experimental vessel (95); The CO2 injection system is used to inject a quantitative amount of CO2 required for the experiment into the experimental vessel (95), and to selectively inject gaseous or liquid CO2 by selecting different injection lines; The supercritical CO2 injection system is used to convert CO2 in the gas cylinder into supercritical CO2 and inject it into the experimental vessel (95); The liquid injection system is used to inject the required chemical reagents and experimental liquids into the experimental vessel (95); The permeability and diffusion characteristic testing system is used to determine the dynamic permeability of reservoirs with different particle size combinations, different clay content, different temperatures, different pressures, different hydrate synthesis stages, different hydrate saturations, and after different depressurization amplitudes and mining durations, as well as the permeability and diffusion characteristics of CO2 diffusion and permeation patterns in hydrate reservoirs with different hydrate saturations.

2. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, It also includes a high and low temperature test chamber (92) for adjusting the temperature of the test vessel. The high and low temperature test chamber (92) is provided with a viewing window (93) for adjusting and controlling the temperature of the test vessel (95) during the test process.

3. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, The experimental vessel (95) is externally connected to an acoustic wave detector (46), a bridge instrument (49), a CT scanner (62), a gas chromatograph (39), a methane sensor (36), and a high-definition camera (59). The acoustic wave detector (46), bridge instrument (49), CT scanner (62), gas chromatograph (39), methane sensor (36), and high-definition camera (59) are also connected to a data acquisition and control system (31).

4. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 3, characterized in that, The experimental vessel (95) is also equipped with multiple temperature sensors (61), pressure sensors (63) and resistivity detectors (60). The temperature sensors (61) and pressure detectors (63) are both clustered probes used to detect data within different depth radius ranges.

5. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, The confining pressure system includes an oil tank (37), an oil pump (51), and a second pressure sensor (53). The oil tank (37) is connected to the oil pump (51), and the oil pump (51) is connected to the experimental vessel (95) through a pipeline with multiple injection valves.

6. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, The gas injection system includes a methane cylinder (1), a first gas flow meter (4), a piston container (5), and a gas booster pump (6). The methane cylinder (1) is connected to the first gas flow meter (4), the piston container (5), and the gas booster pump (6). The gas booster pump (6) is connected to the experimental vessel (95) through the piston container (5).

7. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, The CO2 injection system includes a gas phase CO2 injection subsystem and a liquid phase CO2 injection subsystem. The gas phase CO2 injection subsystem includes a second CO2 cylinder (29) and a first gas flow meter (4). The second CO2 cylinder (29) is connected to the first gas flow meter (4), a piston container (5), and a gas booster pump (6). The gas booster pump (5) is connected to the experimental vessel (95) through the piston container (6). The liquid phase CO2 injection subsystem includes a high-pressure metering pump (26). The high-pressure metering pump (26) is connected to the experimental vessel (95) through a pipeline.

8. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, The supercritical CO2 injection system includes a CO2 cylinder (17), a supercritical CO2 generator (20), a buffer accumulator (21), a phase monitoring unit (22), and a supercritical regulation system (23). The supercritical CO2 generator (20), the buffer accumulator (21), the phase monitoring unit (22), and the supercritical regulation system (23) are connected to the experimental vessel (95) through pipelines.

9. The multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in claim 1, characterized in that, The permeation and diffusion characteristic testing system includes a pressure sensor (64), a high-pressure gas injection pump (66), a CO2 gas container (68), and a gas flow meter (70). The CO2 gas container (68), pressure sensor (64), high-pressure gas injection pump (66), and gas flow meter (70) are connected to the experimental vessel (95) via pipelines.

10. A multifunctional testing method for hydrate extraction and CO2 multiphase storage, implemented based on the multifunctional testing device for hydrate extraction and CO2 multiphase storage as described in any one of claims 1 to 9, characterized in that, The test content includes the following: Test on the CO2 sequestration mechanism after depressurization mining of methane hydrate; Tests of depressurization extraction of methane hydrates after CO2 injection into hydrate layers; CO2 permeation characteristics test of methane hydrate layer.

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