Gas-liquid-solid three-phase flow experimental device and method for simulating hydrate decomposition

Abstract

The invention discloses a gas-liquid-solid three-phase flow experimental device and method for simulating hydrate decomposition, and belongs to the technical field of natural gas hydrate exploitation. The device comprises a sample preparation system, a hydrate decomposition pipeline, a temperature control system, a fluid injection system, a measuring system and a data collecting and recording system, a pressure gauge is arranged at the hydrate decomposition pipeline outlet; a hydrate sample prepared by the sample preparation system is fed into the hydrate decomposition pipeline; the temperature control system comprises a plurality of layers of heating and cooling coils and a plurality of temperature sensors; the fluid injection system is connected to the bottom of the hydrate decomposition pipeline; the measuring system comprises a plurality of high-speed cameras, an electrical resistance tomography system and an electromagnetic flowmeter; the data collecting and recording system is connected with the temperature control system, the fluid injection system and the measuring system. The multiphase flow process containing hydrate decomposition can be comprehensively and accurately simulated and studied, and the development requirement of a hydrate efficient exploitation technology is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas hydrate exploitation, and particularly relates to a gas-liquid-solid three-phase flow experimental device and method for simulating hydrate decomposition. Background Art

[0002] As a highly potential strategic resource, the study of the gas-liquid-solid three-phase flow law during the exploitation of natural gas hydrates is of great importance. When exploiting submarine hydrates, such as the mechanical-thermal combined exploitation method and the solid fluidization exploitation method, etc., the mixture of hydrate-bearing sediment particles and seawater during pipeline transportation decomposes hydrates due to pressure reduction and heat transfer, causing the flowing substances in the pipeline to change from a solid-liquid two-phase to a gas-liquid-solid three-phase. Moreover, hydrate decomposition and multiphase flow interact with each other, and the flow field change in the pipeline is extremely complex. Currently, there are many deficiencies in the research on vertical transportation pipelines, such as the lack of a theoretical model for hydrate decomposition under effective convective heat transfer conditions, insufficient understanding of the control factors and evolution characteristics of three-phase flow, and unclear mechanism of the highly correlated gas expansion effect and decomposition equilibrium height. Existing experimental devices and methods are difficult to comprehensively and accurately simulate and study the multiphase flow process of hydrate decomposition, and cannot meet the development needs of efficient hydrate exploitation technology. Summary of the Invention

[0003] To solve the above technical problems, the present invention adopts the following technical solutions:

[0004] A gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition includes: a sample preparation system, a hydrate decomposition pipeline, a temperature control system, a fluid injection system, a measurement system, and a data collection and recording system; the hydrate decomposition pipeline is the reaction site of the entire experimental device; the sample preparation system is used to prepare hydrate samples, and the prepared hydrate samples are sent into the hydrate decomposition pipeline through a pipeline connected to the bottom of the hydrate decomposition pipeline; a pressure gauge is provided at the outlet of the hydrate decomposition pipeline; the temperature control system includes multiple heating and cooling coils and several temperature sensors arranged around the outer wall of the hydrate decomposition pipeline; the fluid injection system is connected to the bottom of the hydrate decomposition pipeline; the measurement system includes several high-speed cameras for photographing the hydrate decomposition pipeline, an electrical resistance tomography system surrounding the vicinity of the outlet of the hydrate decomposition pipeline, and an electromagnetic flowmeter in the middle of the hydrate decomposition pipeline; the data collection and recording system is connected to the temperature control system, the fluid injection system, and the measurement system.

[0005] A gas-liquid-solid three-phase flow experimental method for simulating hydrate decomposition, which is used for the gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition, includes:

[0006] Step 1, sample preparation: Select the silty clay in the submarine hydrate distribution area as the sediment skeleton for hydrate synthesis. Mix the silt with distilled water to form a soil sample with a certain water content. Use a sample preparation system to prepare spherical hydrate particles.

[0007] Step 2, pipeline flow experiment: Pre-stack a certain amount of hydrate-bearing sediment particles at the bottom of the hydrate decomposition pipeline. Use a temperature control system to control the environmental temperature of the hydrate decomposition pipeline below 273.15 K. Use a fluid injection system to inject water with a specific temperature and velocity from the bottom of the hydrate decomposition pipeline to trigger hydrate decomposition. Use a measurement system to measure and record data information. After the hydrate particles start to decompose, use the high-speed camera of the measurement system to record the flow of the gas-liquid-solid three-phase and the decomposition process of the particles in the hydrate decomposition pipeline, and record the flow pattern changes of the gas-liquid-solid three-phase. Use a temperature sensor to collect the temperature information of the flowing water. The data collection and recording system analyzes the influence of the gas generated by hydrate decomposition on the flow pattern in the pipeline and the high expansion of the particles.

[0008] The present invention has the following beneficial effects:

[0009] The sample preparation system of the present invention selects the silty clay in the submarine hydrate distribution area as the sediment skeleton for hydrate synthesis, and prepares it into spherical particles through a specific method of the sample preparation system, simulating a more realistic hydrate sample. The hydrate synthesis is carried out in the autoclave of the special sample preparation system, and the temperature, pressure and synthesis time are all precisely controlled. After synthesis, the particles also need to be stabilized to ensure the quality and stability of the experimental samples, laying a foundation for the accuracy of subsequent experiments.

[0010] The measurement system of the present invention is composed of a variety of advanced measurement devices. Among them, the high-speed cameras are installed at two angles, the front and the side, with a shooting frame rate of over 5000 frames per second, which can clearly capture the instantaneous details such as the decomposition process of the particles, the flow pattern changes and the bed expansion in all directions. The electrical resistance tomography system surrounds the measurement part at the bottom of the hydrate decomposition pipeline, and can monitor the gas production change and the local phase holdup downstream of the particle distribution range in the pipeline in real time, with an accuracy within ±5%. The temperature sensors are evenly distributed along the axial direction of the pipeline and can accurately collect the temperature information of the flow. These devices cooperate with each other to monitor the experimental process from different dimensions, and can provide comprehensive and accurate data, which is helpful for in-depth study of the multiphase flow law.

[0011] The overall system coordination, the close connection and collaborative work among systems are important improvements of the present invention. The sample preparation system provides experimental samples for the hydrate decomposition pipeline, the temperature control system ensures the stability of the environmental temperature inside the pipeline and provides accurate temperature conditions for the experiment, the fluid injection system simulates the seawater environment and controls the hydrate decomposition, the measurement system monitors the experimental data in real time, and the data collection and recording system collects and analyzes the data of the measurement system. The above collaborative work mode can comprehensively and accurately simulate and study the multiphase flow process of hydrate decomposition, meet the development needs of high-efficiency hydrate exploitation technology, enable the experimental process to be precisely controlled and comprehensively monitored, and improve the accuracy and reliability of the experiment. Brief Description of the Drawings

[0012] Figure 1 It is a schematic diagram of the gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition of the present invention;

[0013] Figure 2 It is a schematic diagram of the sample preparation system of the present invention. Detailed Embodiments

[0014] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition of the present invention includes: a hydrate decomposition pipeline, a sample preparation system, a temperature control system, a fluid injection system, a measurement system and a data collection and recording system.

[0016] The hydrate decomposition pipeline is made of high-strength transparent material, which is convenient for observing the flow phenomena of the gas-liquid-solid three-phase inside the pipeline. Its inner diameter is 5 cm, which can ensure that the hydrate particles have enough flow and reaction space inside the pipeline, and can withstand a certain pressure to ensure the safety of the experiment. The length is designed according to the experimental requirements. A pressure gauge is set at the outlet of the hydrate decomposition pipeline to measure the pressure inside the hydrate decomposition pipeline. The hydrate decomposition pipeline is the reaction site of the entire experimental device, and other systems work around it.

[0017] The sample preparation system includes a temperature control box, a high-pressure autoclave, a pressure sensor, a gas booster system and a gas tank, as Figure 2As shown. The autoclave is the core component for preparing samples and is set in a temperature-controlled box. A pressure sensor is connected to the autoclave to measure the gas pressure inside the autoclave. The gas tank is connected to the autoclave through a gas pressurization system. The silty clay in the seabed hydrate distribution area is selected as the sediment skeleton for hydrate synthesis. The silty clay and distilled water are mixed in a specific proportion to form a soil sample with a certain water content, and then prepared into spherical particles with a diameter ranging from 5mm to 12mm through a silica gel spherical mold. Hydrate synthesis is carried out in an autoclave. The temperature of the autoclave is controlled at 270K-278K and the pressure is controlled at 1MPa-10MPa through a temperature-controlled box. The synthesis time is 48-72 hours. After the synthesis, the temperature of the temperature-controlled box is lowered to 240K and maintained for 3-4 hours before the spherical particles are taken out to stabilize the hydrate state. The prepared particles are placed in the hydrate decomposition pipeline through a special sealing interface at the bottom of the hydrate decomposition pipeline for experiment, and the initial position of the particles in the hydrate decomposition pipeline is ensured to be stable (stacked to a certain height).

[0018] like Figure 1 As shown, the temperature control system includes multiple layers of heating and cooling coils and several temperature sensors arranged around the outer wall of the hydrate decomposition pipeline to accurately control the ambient temperature in the pipeline. The multiple layers of heating and cooling coils are tightly wrapped around the outer wall of the hydrate decomposition pipeline. This wrapping arrangement can ensure that all parts of the pipeline can be evenly heated or cooled. The temperature sensors are evenly distributed along the axial direction of the pipeline, and the number is reasonably set according to the pipeline length and the experimental accuracy requirements. Generally, one is installed every 10-20cm, and the control accuracy is ±0.1K. The temperature sensor monitors the temperature changes in the hydrate decomposition pipeline in real time and feeds back the temperature data to the data collection and recording system. The data collection and recording system adjusts the working state of the heating and cooling coils based on these feedback data. When the temperature sensor detects that the temperature in the pipeline is lower than the set value, the control system will start the heating coil to increase the pipeline temperature; conversely, if the temperature is higher than the set value, the cooling coil is controlled to start working and reduce the temperature. In this way, through the coordinated work of the temperature sensor and the heating and cooling coils, the temperature in the pipeline can be accurately controlled to ensure the stability and accuracy of the temperature during the experiment, and avoid the influence of temperature fluctuations on the experimental results.

[0019] The fluid injection system includes a water pump, a liquid flowmeter, a water tank, and a refrigeration device, which are connected to the bottom of the hydrate decomposition pipeline. The refrigeration device is in direct contact with the water in the water tank. The water tank is connected to the water pump and then, via a liquid flowmeter, to the bottom of the hydrate decomposition pipeline. The temperature of the injected water flow can be controlled within the range of 263.15K - 293.15K by the refrigeration device, the salinity of the water can be controlled within the range of 0% - 15% by dissolving different masses of salts in the water, and the flow rate of the water flow can be controlled within the range of 0.02m / s - 1m / s by the coordinated use of the water pump and the liquid flowmeter. By adjusting the flow rate and temperature of the water flow, both the seawater environment can be simulated and the starting time and rate of hydrate decomposition can be controlled to meet the requirements of different experimental conditions.

[0020] The measurement system includes a high-speed camera, an electrical resistance tomography system, and an electromagnetic flowmeter.

[0021] High-speed camera: Multiple high-speed cameras can be set up. For example, they can be set at two angles, the front and the side, of the hydrate decomposition pipeline (more high-speed cameras can also be set at other angles). It can comprehensively capture the decomposition process of particles, the change of flow patterns, and the bed expansion. The shooting frame rate is set above 5000 frames per second, which can clearly capture the internal flow and reaction details of the hydrate decomposition pipeline, providing intuitive image data for subsequent analysis.

[0022] The electrical resistance tomography system surrounds the downstream measurement part near the outlet of the hydrate decomposition pipeline, and is used to measure the gas production change and local phase holdup downstream of the particle distribution range in the pipeline, and to monitor the dynamic distribution of the gas-liquid-solid three-phase in real time. Its measurement accuracy is within ±5%, which can accurately reflect the phase state change of the gas-liquid-solid three-phase flow inside the hydrate decomposition pipeline.

[0023] Electromagnetic flowmeter: It is set at the middle position of the hydrate decomposition pipeline and is used to accurately measure the water flow rate injected into the hydrate decomposition pipeline. The measurable flow rate range is 4m 3 / h - 100m 3 / h, and the response time is less than 5ms. By monitoring the water flow rate, the experimental conditions can be accurately controlled, and the influence of different water flow velocities on hydrate decomposition and gas-liquid-solid three-phase flow can be simulated, providing key flow rate data support for the experiment.

[0024] The data collection and recording system is connected to the above-mentioned temperature control system, fluid injection system, and measurement system. It uses a high-speed data acquisition card and professional data processing software to collect, store, and process experimental data in real time, realizing the visual display and analysis of data, and facilitating the quick acquisition and analysis of experimental results. The data collection and recording system is a computer system.

[0025] The experimental method for simulating gas-liquid-solid three-phase flow during hydrate decomposition of the present invention includes:

[0026] Step 1: Sample preparation. Select silty clay from the submarine hydrate distribution area as the sediment skeleton for hydrate synthesis, and mix silt with distilled water to prepare a soil sample with a certain water content. Use a sample preparation system to prepare spherical hydrate particles. The synthesis temperature is controlled at 270K - 278K, the synthesis pressure is controlled at 1MPa - 10MPa, and the synthesis process lasts for 48h - 72h. Before taking out the prepared hydrate particles from the autoclave, first lower the temperature of the temperature control box to 240K and keep it for 3h - 4h.

[0027] Step 2: Pipeline flow experiment. First, stack a certain amount (the particle stacking height is 10cm - 50 cm, and the initial volume fraction is 0.5 - 0.6) of hydrate-bearing sediment particles at the bottom of the hydrate decomposition pipeline. Use a temperature control system to keep the environmental temperature of the hydrate decomposition pipeline below 273.15 K to prevent premature decomposition of the hydrate.

[0028] Use a fluid injection system to inject water with a specific temperature (263.15 K - 293.15 K) and velocity (0.02 m / s - 0.10 m / s) from the bottom of the hydrate decomposition pipeline to trigger hydrate decomposition. Use a measurement system to measure and record the temperature, velocity, particle diameter, initial stacking height, and initial volume fraction information of the water flow. After the hydrate particles start to decompose, use the high-speed camera of the measurement system to record the flow of the gas-liquid-solid three-phase and the decomposition process of the particles in the hydrate decomposition pipeline, and record the flow pattern changes of the gas-liquid-solid three-phase; use a temperature sensor to collect the temperature information of the flowing water; the data collection and recording system analyzes the impact of the gas generated by hydrate decomposition on the flow pattern in the pipeline and the height expansion of the particles.

[0029] The present invention focuses on the indoor gas-liquid-solid three-phase flow experiment for simulating the exploitation of natural gas hydrates, aiming to solve the deficiencies existing in the prior art in studying the multiphase flow process of hydrate decomposition. Compared with traditional experimental devices, the present invention can simulate and study related processes more accurately and comprehensively, providing strong support for the development of efficient natural gas hydrate exploitation technologies.

[0030] The sample preparation system of the present invention selects silty clay from the submarine hydrate distribution area as the sediment skeleton for hydrate synthesis, and prepares it into spherical particles through the sample preparation system, simulating a more realistic hydrate sample. The hydrate synthesis is carried out in the autoclave of the sample preparation system, and the temperature, pressure, and synthesis time are precisely controlled. After synthesis, the particles need to undergo stabilization treatment to ensure the quality and stability of the experimental samples, laying a foundation for the accuracy of subsequent experiments.

[0031] The measurement system of the present invention consists of a variety of advanced measurement devices. Among them, high-speed cameras are installed at two angles, the front and the side, which can clearly capture in all directions the instantaneous details such as the decomposition process of particles, the change of flow patterns, and the bed expansion. The electrical resistance tomography system surrounds the bottom of the hydrate decomposition pipeline, which can monitor in real time the gas production change and the local phase holdup downstream of the particle distribution range in the pipeline. The temperature sensors are evenly distributed along the axial direction of the pipeline, which can accurately collect the temperature information during the flow. These devices cooperate with each other to monitor the experimental process from different dimensions, providing comprehensive and accurate data, which helps to deeply study the multiphase flow law.

[0032] The various systems of the present invention are closely connected and work in coordination: the sample preparation system provides experimental samples for the hydrate decomposition pipeline, the temperature control system ensures the stability of the environmental temperature in the pipeline, providing accurate temperature conditions for the experiment, the fluid injection system simulates the seawater environment and controls the hydrate decomposition, the measurement system monitors the experimental data in real time, and the data collection and recording system collects and analyzes the data of the measurement system. The above collaborative working mode can comprehensively and accurately simulate and study the multiphase flow process of hydrate decomposition, meeting the development needs of efficient hydrate exploitation technology.

Claims

1. A gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition, characterized in that: include: The invention comprises a sample preparation system, a hydrate decomposition pipeline, a temperature control system, a fluid injection system, a measurement system and a data collection and recording system; the hydrate decomposition pipeline is the reaction site of the entire experimental device; the sample preparation system is used to prepare hydrate-containing samples, and the prepared hydrate samples are sent into the hydrate decomposition pipeline through a pipeline connected to the bottom of the hydrate decomposition pipeline; a pressure gauge is arranged at the outlet of the hydrate decomposition pipeline; the temperature control system comprises a multi-layer heating and cooling coil and a plurality of temperature sensors arranged around the outer wall of the hydrate decomposition pipeline; the fluid injection system is connected to the bottom of the hydrate decomposition pipeline; the measurement system comprises a plurality of high-speed cameras for photographing the hydrate decomposition pipeline, a resistance tomography system surrounding the outlet of the hydrate decomposition pipeline, and an electromagnetic flowmeter in the middle of the hydrate decomposition pipeline; the data collection and recording system is connected to the temperature control system, the fluid injection system and the measurement system.

2. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 1, characterized in that: The hydrate decomposition pipeline is made of high-strength transparent material.

3. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 1, characterized in that: The sample preparation system includes a temperature control box, an autoclave, a pressure sensor, a gas pressurization system and a gas tank. The autoclave is the core component for preparing the sample and is arranged in the temperature control box; the autoclave is externally connected to a pressure sensor for measuring the gas pressure inside the autoclave; the gas tank is connected to the autoclave through the gas pressurization system.

4. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 3, characterized in that: Silty clay from the seabed hydrate distribution area was selected as the sediment skeleton for hydrate synthesis. The silty clay and distilled water were mixed in a specific proportion to form a soil sample with a certain water content, and then prepared into spherical particles using a silica gel spherical mold. The prepared spherical particles were placed in an autoclave, and the temperature of the autoclave was controlled at 270K-278K and the pressure was controlled at 1MPa-10MPa through a temperature control box, and the synthesis time was 48-72 hours. Before the synthesized spherical particles were taken out, the temperature of the temperature control box was lowered to 240K and maintained for 3-4 hours to stabilize the hydrate state. The prepared particles were placed into the hydrate decomposition pipeline through a special sealing interface at the bottom of the hydrate decomposition pipeline for experiment.

5. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 1, characterized in that: The multi-layer heating and cooling coils are tightly wrapped around the outer wall of the hydrate decomposition pipeline to ensure that all parts of the pipeline are evenly heated or cooled; a number of temperature sensors are evenly distributed along the axial direction of the pipeline, and the temperature sensors monitor the temperature changes in the hydrate decomposition pipeline in real time and feed back the temperature data to the data collection and recording system; the data collection and recording system adjusts the working status of the heating and cooling coils according to the feedback data.

6. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 1, characterized in that: The fluid injection system includes a water pump, a liquid flow meter, a water tank and a refrigeration device connected to the bottom of the hydrate decomposition pipeline; the refrigeration device is in contact with water in the water tank, and the water tank is connected to the water pump and then connected to the bottom of the hydrate decomposition pipeline via the liquid flow meter; by adjusting the flow rate and temperature of the water flow, the seawater environment is simulated, the starting time and rate of hydrate decomposition are controlled, and the requirements of different experimental working conditions are met.

7. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 1, characterized in that: High-speed cameras are installed at the front and side angles of the hydrate decomposition pipeline to capture the decomposition process of particles, flow pattern changes and bed expansion in all directions; the electrical resistance tomography system is placed around the downstream measurement position near the outlet of the hydrate decomposition pipeline to measure the changes in gas production and local phase content downstream of the particle distribution range in the pipeline, and to monitor the distribution dynamics of the gas-liquid-solid three-phase in real time; the electromagnetic flowmeter is set in the middle of the hydrate decomposition pipeline to accurately measure the water flow rate injected into the hydrate decomposition pipeline. By monitoring the water flow rate, the experimental conditions are accurately controlled to simulate the effects of different water flow velocities on hydrate decomposition and gas-liquid-solid three-phase flow.

8. The gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition according to claim 1, characterized in that: The data collection and recording system is a computer system.

9. A gas-liquid-solid three-phase flow experimental method for simulating hydrate decomposition, used in a gas-liquid-solid three-phase flow experimental device for simulating hydrate decomposition as claimed in any one of claims 1 to 8, characterized in that: include: Step 1, sample preparation: select silty clay from the seabed hydrate distribution area as the sediment skeleton for hydrate synthesis, mix the silty clay with distilled water to form a soil sample with a certain water content; use a sample preparation system to prepare hydrate-containing spherical particles; Step 2, pipeline flow experiment; a certain amount of hydrate-containing sediment particles are deposited at the bottom of the hydrate decomposition pipeline in advance, and the ambient temperature of the hydrate decomposition pipeline is controlled to be below 273.15 K using a temperature control system; a water flow with a specific temperature and velocity is injected from the bottom of the hydrate decomposition pipeline using a fluid injection system to induce hydrate decomposition, and the data information is measured and recorded using a measurement system; after the hydrate-containing particles begin to decompose, the flow of the gas-liquid-solid three-phase in the hydrate decomposition pipeline and the decomposition process of the particles are recorded using a high-speed camera of the measurement system, and the flow pattern changes of the gas-liquid-solid three-phase are recorded; a temperature sensor is used to collect the temperature information of the flowing water; the data collection and recording system analyzes the influence of the gas generated by hydrate decomposition on the flow pattern in the pipeline and the height expansion of the particles.

10. The gas-liquid-solid three-phase flow experimental method for simulating hydrate decomposition according to claim 9, characterized in that: The data information includes: water flow temperature, velocity, particle diameter, initial stacking height, and initial volume fraction.

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