An experimental simulation device for carbon dioxide sequestration in methane hydrate reservoirs

Abstract

The present invention relates to an experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir, and pertains to the technical field of ocean carbon sequestration. It includes a high-pressure reactor and a low-temperature constant-temperature test chamber. The high-pressure reactor comprises an overlying water layer reactor section, a hydrate layer reactor section, and a lower sediment layer reactor section; an upper cover is installed at the top of the overlying water layer reactor section, and a lower cover is installed at the bottom of the lower sediment layer reactor section; ultrasonic probes are provided in both the overlying water layer reactor section and the hydrate layer reactor section; temperature sensor holes and pressure sensor holes are respectively provided on the upper cover and the lower cover, and a multi-point temperature sensor and a pressure sensor are installed; the high-pressure reactor is placed inside the low-temperature constant-temperature test chamber, and an electric heating rod is provided to change the temperature of the lower sediment layer. While simulating the formation environment of the methane hydrate reservoir formation, the present invention can comprehensively study the diffusion process of CO2 in the sediment layer, the hydrate formation process, and the CO2 sequestration situation.

Description

Technical Field

[0001] The present invention relates to the technical field of marine carbon sequestration, and specifically to an experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir. Background Art

[0002] Facing China's current annual carbon dioxide emissions exceeding 10 Gt, the capacity for geological sequestration of CO2 remains limited. Sequestration can only be achieved in specific geological structures, such as being embedded in impermeable caprock and sandstone layers. For marine carbon sequestration, CO2 hydrates form in the seabed sediments below a water depth of 300 m, thus forming a dense hydrate cap layer. Theoretically, the hydrate cap and gravity trapping can provide dual restrictions on the upward movement of CO2 to the seabed, and it is possible to achieve almost complete isolation of a large amount of CO2 by reaching the deep seabed. Injecting CO2 into a natural gas hydrate reservoir to displace CH4 is considered an economical, safe, and environmentally friendly natural gas extraction method, achieving "killing two birds with one stone", that is, reducing CO2 emissions and obtaining clean energy at low cost, which points out the future research direction for the exploitation and utilization of natural gas hydrates in combination with "carbon peak and carbon neutrality".

[0003] Under the specific ambient temperature and pressure of natural hydrates in nature, CO2 hydrates do not decompose and exist stably, while CH4 hydrates will decompose into methane gas and water. Therefore, the method of displacing CH4 with CO2 to develop hydrate reservoirs is feasible. In order to evaluate the efficiency of CO2 displacing natural gas hydrates and clarify the sequestration mechanism during the process of CO2 displacing natural gas hydrates, relevant experimental simulation equipment needs to be established. Currently, most experimental devices in the laboratory can only simulate this specific lower ambient pressure, but the formation pressure of actual natural gas hydrates generally ranges from 12 to 15 MPa. Secondly, for different natural gas hydrate reservoirs, in addition to formation temperature and formation pressure, the composition, particle size, water content, etc. of their sediments also vary with the increase in formation depth. The properties of sediments not only affect the formation of hydrates, but also during the injection of CO2, its diffusion is interfered by sediments, and there is a lack of various means such as visualization to jointly monitor the formation of hydrates in the formation. In fact, during the marine carbon sequestration process at a water depth greater than 1000 m, the sequestration area consists of the geological environment of the lower sediment layer, hydrate sediment layer, and overlying water layer, and liquid CO2 forms CO2 hydrates during the diffusion process in the sediment layer. Currently, these studies cannot comprehensively obtain the formation of hydrates during the diffusion process of liquid CO2 in the sediment layer, as well as detailed carbon sequestration experimental data such as the influencing factors of carbon sequestration efficiency during the injection process of liquid CO2, which limits the development of marine carbon sequestration technology. Therefore, it is necessary to use a larger-scale simulation experimental device to simulate the marine geological environment. Summary of the Invention

[0004] The object of the present invention is to provide an experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir, which simulates the real marine geological environment, including the lower sediment layer, the hydrate sediment layer and the overlying water layer, and solves the problems that a conventional reactor cannot accurately obtain the formation situation of hydrates during the diffusion process of CO2 in the sediment layer.

[0005] To achieve the above object, the present invention provides an experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir, comprising: a high-pressure reactor and a low-temperature constant-temperature test chamber. The high-pressure reactor includes an overlying water layer reactor section, a hydrate layer reactor section and a lower sediment layer reactor section; the overlying water layer reactor section, the hydrate layer reactor section and the lower sediment layer reactor section are connected in sequence; an upper cover is installed at the top of the overlying water layer reactor section, and a lower cover is installed at the bottom of the lower sediment layer reactor section;

[0006] Ultrasonic probes are provided in both the overlying water layer reactor section and the hydrate layer reactor section; temperature sensor holes and pressure sensor holes are respectively provided on the upper cover and the lower cover for installing a multi-point temperature sensor and a pressure sensor; the experimental simulation device is placed inside the low-temperature constant-temperature test chamber, and an electric heating rod is provided in the lower sediment layer reactor section for changing the temperature of the lower sediment layer.

[0007] Further, the overlying water layer reactor section, the hydrate layer reactor section and the lower sediment layer reactor section are connected in sequence by clamps.

[0008] Further, sapphire viewing windows are provided in the overlying water layer reactor section, the hydrate layer reactor section and the lower sediment layer reactor section.

[0009] Further, the upper cover is provided with a water inlet hole and a liquid CO2 outlet hole, and the lower cover is provided with a liquid CO2 injection hole and a safety valve hole.

[0010] Further, the overlying water layer, the hydrate layer and the lower sediment layer of the formation structure of deep-sea shallow carbon sequestration are respectively simulated by using the experimental simulation device; the ultrasonic probe analyzes and detects the CO2 hydrate saturation and the residual amount during the liquid CO2 sequestration process; the multi-point temperature sensor is used to measure the temperature change during the formation process of CO2 hydrates; the pressure sensor is used to monitor the pressure change inside the high-pressure reactor; the high-pressure reactor is placed inside the low-temperature constant-temperature test chamber to maintain the formation temperature at 2-4 °C.

[0011] Further, a temperature measurement point is set every 50 mm for the multi-point temperature sensor to study the local heat release situation during the hydrate formation process.

[0012] Further, each of the upper water layer reactor section, the hydrate layer reactor section, and the lower sediment layer reactor section can be disassembled and used separately, with an applicable pressure of 0 to 20 MPa and an applicable temperature of -10 to 50 °C.

[0013] Further, when applied to the process of ocean carbon sequestration, it includes the following steps:

[0014] S1. Porous media are filled in both the hydrate layer reactor section and the lower sediment layer reactor section. The upper water layer reactor section is filled with water. The pressure in the high-pressure reactor is increased to the formation pressure of 12 to 15 MPa using a water injection pump, and the temperature in the high-pressure reactor is reduced to the formation temperature of 2 to 4 °C using a low-temperature constant temperature test chamber to simulate the ocean environment at a depth of 1200 to 1500 m.

[0015] S2. After the pressure and temperature reach the formation pressure and formation temperature, gaseous CO2 is introduced into the liquid CO2 piston storage tank through a booster pump until the entire liquid CO2 piston storage tank is filled with liquid CO2. Then, the liquid CO2 piston storage tank is used to inject liquid CO2 into the reactor from the bottom of the reactor at a certain rate.

[0016] S3. The formation of CO2 hydrate and the CO2 sequestration rate during the upward diffusion of liquid CO2 from the bottom of the high-pressure reactor are studied through a sapphire viewing window, an ultrasonic device, and a multi-point temperature sensor.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir can simulate the upper water layer, hydrate layer, and lower sediment layer of the deep-sea shallow carbon sequestration formation structure.

[0019] (2) The formation of CO2 hydrate during the diffusion of liquid CO2 in the sediment layer is studied by combining a sapphire viewing window, an ultrasonic device, and a multi-point temperature sensor.

[0020] (3) The residual amount of liquid CO2 in the upper water layer is monitored using a sapphire viewing window and an ultrasonic device, so as to accurately calculate the CO2 sequestration rate and sequestration rate. Description of the Drawings

[0021] Figure 1 is a schematic structural diagram of the present invention;

[0022] Figure 2 is a top view of the upper cover of the present invention;

[0023] Figure 3 is a top view of the lower cover of the present invention;

[0024] Figure 4 is a schematic distribution diagram of the multi-point temperature sensor of the present invention;

[0025] Figure 5 It is a flow chart of an experimental device for simulating shallow carbon sequestration in the deep sea.

[0026] Among them, in the figure: 1 - overlying water layer reactor section, 2 - hydrate layer reactor section, 3 - lower sediment layer reactor section, 4 - ultrasonic probe, 5 - clamp, 6 - low-temperature constant-temperature test chamber, 7 - sapphire viewing window, 8 - electric heating rod, 9 - upper cover, 10 - lower cover, 11 - liquid CO2 outlet hole, 12 - pressure sensor hole, 13 - temperature sensor hole, 14 - water inlet hole, 15 - safety valve hole, 16 - liquid CO2 injection hole, 101 - experimental simulation device for sequestering carbon dioxide in methane hydrate reservoir, 102 - gas cylinder pressure reducer, 103 - CO2 gas cylinder, 104 - horizontal valve, 105 - gas booster pump, 106 - liquid storage tank, 107 - injection pump, 108 - pressure sensor, 109 - single-point temperature sensor, 110 - liquid CO2 piston storage tank, 111 - multi-point temperature sensor, 112 - gas storage tank, 113 - pulse transmitter, 114 - oscilloscope, 115 - data collector, 116 - computer. Specific embodiments

[0027] To achieve the above purposes and effects, the technical means and structure adopted by the present invention will be described in detail in combination with the drawings for the preferred embodiments of the present invention to explain its features and functions.

[0028] As Figures 1-4 shown, the present invention provides an experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir, including: a high-pressure reactor and a low-temperature constant-temperature test chamber 6, the high-pressure reactor includes an overlying water layer reactor section 1, a hydrate layer reactor section 2 and a lower sediment layer reactor section 3; the overlying water layer reactor section 1, the hydrate layer reactor section 2 and the lower sediment layer reactor section 3 are connected in sequence; an upper cover 9 is installed at the top of the overlying water layer reactor section 1, and a lower cover 10 is installed at the bottom of the lower sediment layer reactor section 3;

[0029] Both the overlying water layer reactor section 1 and the hydrate layer reactor section 2 are provided with ultrasonic probes 4; the upper cover 9 and the lower cover 10 are respectively provided with a temperature sensor hole 13 and a pressure sensor hole 12 for installing a multi-point temperature sensor 111 and a pressure sensor 108; the high-pressure reactor is placed inside a low-temperature constant-temperature test chamber 6 with a temperature control accuracy of ±0.05 °C, which can accurately control the formation temperature at 2 - 4 °C, and an electric heating rod 8 is provided in the lower sediment layer reactor section 3 for changing the temperature of the lower sediment layer. The longitudinal wave and transverse wave of the ultrasonic device are used to monitor the formation of hydrates according to the different sound velocities presented by hydrates with different saturations; since the sound velocity of liquid CO2 is relatively small, the residual amount during the liquid CO2 sequestration process can be monitored according to the degree of sound velocity attenuation.

[0030] In this embodiment, the overlying water layer reactor section 1, the hydrate layer reactor section 2, and the lower sediment layer reactor section 3 are sequentially connected by a clamp 5.

[0031] In this embodiment, the overlying water layer reactor section 1, the hydrate layer reactor section 2, and the lower sediment layer reactor section 3 are all provided with sapphire viewing windows 7 to observe the formation inside the reactor. The length of the sapphire viewing window 7 is close to the length of each reactor section, so as to facilitate observing the formation of hydrates during the diffusion process of liquid CO2 from the lower sediment layer to the overlying water layer.

[0032] In this embodiment, the upper cover 9 is provided with a water inlet hole 14 and a liquid CO2 outlet hole 11, and the lower cover 10 is provided with a liquid CO2 injection hole 16 and a safety valve hole 15.

[0033] In this embodiment, the experimental simulation device is used to simulate the overlying water layer, the hydrate layer, and the lower sediment layer of the deep-sea shallow carbon sequestration formation structure respectively; the ultrasonic probe 4 analyzes and detects the CO2 hydrate saturation and the residual amount during the liquid CO2 sequestration process; the multi-point temperature sensor 111 is used to measure the temperature change during the CO2 hydrate formation process; the pressure sensor 108 is used to monitor the pressure change inside the high-pressure reactor; the high-pressure reactor is placed inside the low-temperature constant-temperature test chamber 6 to maintain the formation temperature at 2 - 4 °C.

[0034] In this embodiment, a temperature measurement point is set every 50 mm for the multi-point temperature sensor 111 to study the local heat release during the hydrate formation process.

[0035] In this embodiment, each of the overlying water layer reactor section 1, the hydrate layer reactor section 2, and the lower sediment layer reactor section 3 can be disassembled and used separately, with an applicable pressure of 0 - 20 MPa and an applicable temperature of -10 - 50 °C.

[0036] An experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir is applied in the process of ocean carbon sequestration, as Figure 5As shown in the figure, the specific process of carbon sequestration is as follows:

[0037] Porous media are filled into the lower sediment layer reactor section and the hydrate layer reactor section of the experimental simulation device 101 for sequestering carbon dioxide in the methane hydrate reservoir. The overlying water layer reactor section is filled with water. The pressure in the reactor is increased to the formation pressure of 12 - 15 MPa using the liquid injection pump 107, and the temperature in the reactor is reduced to the formation temperature of 2 - 4 °C using the low-temperature constant-temperature test chamber, simulating the marine environment at a water depth of 1200 - 1500 m. The water inlet end of the liquid injection pump 107 is connected to the liquid storage tank 106 through a horizontal valve. After the pressure and temperature reach the formation pressure and formation temperature, the pressure reducing valve 102 of the CO2 gas cylinder 103 is opened. The CO2 gas cylinder 103 is connected to the gas booster pump 105 through the horizontal valve 104, and the gaseous CO2 is introduced into the liquid CO2 piston storage tank 110 through the gas booster pump 105 until the entire storage tank is filled with liquid CO2. Then, the liquid CO2 piston storage tank 110 is used to inject the liquid CO2 into the high-pressure reactor at a certain rate from the bottom of the experimental simulation device 101 for sequestering carbon dioxide in the methane hydrate reservoir. During the hydrate synthesis process, the formation of hydrates in the reactor is observed through the sapphire viewing window of the experimental simulation device 101 for sequestering carbon dioxide in the methane hydrate reservoir, and the hydrate nucleation time and the growth rate of hydrates are recorded; the ultrasonic device is used to analyze and detect the CO2 hydrate saturation and the residual amount during the liquid CO2 sequestration process, and the ultrasonic frequency is adjusted through the pulse transmitter 113 and the arrival time of the first wave of the ultrasonic wave passing through the sediment layer is recorded by the oscilloscope 114; the pressure sensor 108 and the single-point temperature sensor 109 are used to record the pressure and temperature changes in the liquid CO2 piston storage tank 110 and the gas storage tank 112; the pressure sensor 108 and the multi-point temperature sensor 111 are used to record the pressure and temperature changes during the formation of CO2 hydrates in the experimental simulation device 101 for sequestering carbon dioxide in the methane hydrate reservoir; an electric heating rod is installed in the lower sediment layer of the experimental simulation device 101 for sequestering carbon dioxide in the methane hydrate reservoir to change the formation temperature; the data collector 115 and the computer 116 are used to record the temperature and pressure changes during the hydrate formation process in the carbon sequestration process, and then the CO2 sequestration situation is calculated and analyzed.

[0038] The present invention can simulate the overlying water layer, hydrate layer, and lower sediment layer of the deep-sea shallow carbon sequestration formation structure. The sapphire viewing window, ultrasonic device, and multi-point temperature sensor are used to jointly study the formation of CO2 hydrates during the diffusion process of liquid CO2 in the sediment layer. The sapphire viewing window and ultrasonic device are used to monitor the residual amount of liquid CO2 in the overlying water layer, so as to accurately calculate the CO2 sequestration rate and sequestration rate.

[0039] As described above, it is only a preferred embodiment of the present invention, and does not impose any limitation on the technical scope of the present invention. Therefore, any minor modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir, characterized in that It is realized by an experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir, and its application in the process of ocean carbon sequestration includes the following steps: S1. Porous media are filled in both the hydrate layer reactor section and the lower sediment layer reactor section. The overlying water layer reactor section is filled with water. The pressure in the high-pressure reactor is increased to the formation pressure of 12 - 15 MPa by using a water injection pump, and the temperature in the high-pressure reactor is reduced to the formation temperature of 2 - 4 °C by using a low-temperature constant-temperature test chamber to simulate the ocean environment at a depth of 1200 - 1500 m. S2. After the pressure and temperature reach the formation pressure and formation temperature, the gas CO2 is introduced into the liquid CO2 piston storage tank through a booster pump until the entire liquid CO2 piston storage tank is filled with liquid CO2. Then, the liquid CO2 is injected into the reactor from the bottom of the reactor at a certain rate by using the liquid CO2 piston storage tank. S3. The formation of CO2 hydrate and the CO2 sequestration rate during the upward diffusion of liquid CO2 from the bottom of the high-pressure reactor are studied through sapphire visual windows, ultrasonic devices, and multi-point temperature sensors. The experimental simulation device for sequestering carbon dioxide in a methane hydrate reservoir includes: a high-pressure reactor and a low-temperature constant-temperature test chamber. The high-pressure reactor includes an overlying water layer reactor section, a hydrate layer reactor section, and a lower sediment layer reactor section; the overlying water layer reactor section, the hydrate layer reactor section, and the lower sediment layer reactor section are connected in sequence; an upper cover is installed at the top of the overlying water layer reactor section, and a lower cover is installed at the bottom of the lower sediment layer reactor section. Ultrasonic probes are provided in both the overlying water layer reactor section and the hydrate layer reactor section; temperature sensor holes and pressure sensor holes are respectively provided on the upper cover and the lower cover for installing multi-point temperature sensors and pressure sensors; the high-pressure reactor is placed inside the low-temperature constant-temperature test chamber, and an electric heating rod is provided in the lower sediment layer reactor section to change the temperature of the lower sediment layer.

2. The experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir according to claim 1, characterized in that The overlying water layer reactor section, the hydrate layer reactor section, and the lower sediment layer reactor section are sequentially connected by clamps.

3. The experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir according to claim 1 or 2, wherein Sapphire visual windows are provided in both the overlying water layer reactor section, the hydrate layer reactor section, and the lower sediment layer reactor section.

4. The experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir according to claim 1, wherein The upper cover is provided with a water inlet hole and a liquid CO2 outlet hole, and the lower cover is provided with a liquid CO2 injection hole and a safety valve hole.

5. The experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir according to claim 1, wherein The experimental simulation device is used to simulate the overlying water layer, hydrate layer, and lower sediment layer of the deep-sea shallow carbon sequestration formation structure respectively; the ultrasonic probe analyzes and detects the CO2 hydrate saturation and the residual amount during the liquid CO2 sequestration process; the multi-point temperature sensor is used to measure the temperature change during the formation of CO2 hydrate; the pressure sensor is used to monitor the pressure change in the high-pressure reactor; the high-pressure reactor is placed inside the low-temperature constant-temperature test chamber to maintain the formation temperature of 2 - 4 °C.

6. The experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir according to claim 5, wherein, A temperature measurement point is set every 50 mm for the multi-point temperature sensor to study the local heat release during the formation of hydrate.

7. The experimental simulation method for sequestering carbon dioxide in a methane hydrate reservoir according to claim 1, wherein Each of the overlying water layer reactor section, the hydrate layer reactor section, and the lower sediment layer reactor section can be disassembled and used separately, with an applicable pressure of 0 - 20 MPa and an applicable temperature of -10 - 50 °C.

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