Device and method for measuring surface wettability of hydrate

Abstract

The invention discloses a device and a method for measuring the surface wettability of a hydrate. The testing device comprises a hydrate generating mechanism; a visual cavity pressure control mechanism; a liquid dropping mechanism; an image acquisition mechanism; an analysis processing mechanism; wherein the measuring device further comprises a surrounding liquid phase balance mechanism, the surrounding liquid phase balance mechanism comprises a stirring kettle, a pressure control structure and a second temperature control structure, the pressure control structure can inject the hydrate generation gas into the stirring cavity to control the pressure of the stirring cavity, and the second temperature control structure is used for controlling the temperature of the stirring cavity; the stirring cavity enables the surrounding liquid phase to be saturated by gas generated by the hydrate through stirring, and the saturated surrounding liquid phase can be injected into the visual cavity. According to the invention, the surrounding liquid phase is saturated by the hydrate generation gas, and the efficiency is high, so that the surface of the water drop can be combined with the hydrate generation gas in the saturated surrounding liquid phase to form a stable hydrate film, and the measurement of the surface wettability of the hydrate in the liquid-liquid-solid system is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrate surface wettability research, and in particular to a device and method for measuring hydrate surface wettability. Background Art

[0002] Hydrates, also known as natural gas hydrates, are non-stoichiometric solid crystals that are formed by water molecules connected by hydrogen bonds and encapsulate small gas or liquid molecules (such as methane, carbon dioxide, cyclopentane, etc.). Hydrates need to exist stably under certain low temperature and high pressure conditions. Natural gas hydrates in nature are widely found in deep-sea sediments and polar permafrost, and are a potential energy resource in the future. Currently, active research has been carried out on the exploration and exploitation of natural gas hydrates, hoping to utilize the rich methane resources stored in them. At the same time, due to the high energy density of hydrates, they are also used for the transportation and storage of natural gas, and can store a large amount of natural gas in a relatively small space, reducing transportation and storage costs.

[0003] In recent years, the use of hydrate technology for carbon dioxide capture and storage is a promising means of emission reduction. This process can effectively store greenhouse gas carbon dioxide by injecting carbon dioxide into the seabed to form hydrates, thereby alleviating the problem of global warming. However, the formation of hydrates is a common and thorny problem in the process of oil and gas extraction, transportation and storage. When water in the oil and gas mixture comes into contact with natural gas under low temperature and high pressure, it is very easy to form hydrate solids. These hydrates will be deposited in pipelines and equipment, resulting in obstruction of pipeline flow, and may even cause safety hazards such as blockage and equipment damage. In addition, the formation of hydrates in pipelines is not limited to natural gas transmission pipelines, but may also occur in oil and gas mixed pipelines such as crude oil and condensate containing natural gas. This phenomenon often occurs during the oil and gas gathering and transportation process in cold areas, and is particularly significant during deep-sea oil and gas extraction and transportation, because the deep-sea environment has the low temperature and high pressure conditions required for the formation of hydrates.

[0004] Therefore, as a new research field, the study of hydrates has attracted much attention in the fields of natural gas hydrate exploitation, oil and gas fluid storage and transportation, and mixed gas separation. Among them, the measurement of the contact angle of the hydrate surface can directly characterize the wettability of the hydrate surface. It can not only infer the spreading ability and migration behavior of the fluid in the hydrate-containing interface system during the natural gas hydrate exploitation process, but also predict the interface interaction between the hydrate solid and other interfaces (such as gas, oil, free water, rock, sediment, pipeline surface) during the formation and decomposition process in the ocean or oil and gas transportation pipeline, which is of great significance to the field of hydrate exploitation and flow assurance. At the same time, the measurement of contact angle can also provide microstructural information such as hydrate surface energy and molecular arrangement, which is very important for the study of hydrate formation mechanism and nucleation kinetics. Therefore, the measurement of the contact angle of the hydrate surface can understand the surface properties of the hydrate, which is helpful to design more effective exploitation and transportation methods, greatly reduce the technical difficulties and economic costs in the exploitation process, and reduce the production safety risks caused by hydrate blockage in the oil and gas transportation process.

[0005] However, the measuring device in the prior art is only applicable to the formation of hydrates and the measurement of contact angles in a gas-liquid-solid system under high pressure and low temperature conditions. Summary of the invention

[0006] The purpose of the present invention is to provide a device and method for measuring the wettability of a hydrate surface, so as to solve the technical problem that the measuring devices and methods in the prior art are not applicable to the formation of hydrates in a liquid-liquid-solid system and the measurement of the wettability of the hydrate surface.

[0007] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0008] The present invention provides a device for measuring the wettability of a hydrate surface, comprising: a hydrate generating mechanism, comprising a visual kettle and a first temperature control structure, wherein the visual kettle has a visual cavity inside, a sample stage is installed in the visual cavity, and the first temperature control structure is used to control the temperature of the visual cavity; a visual cavity pressure control mechanism, which is connected to the visual cavity, and the visual cavity pressure control mechanism can inject hydrate generating gas into the visual cavity to control the pressure of the visual cavity; a dripping mechanism, which is connected to the visual cavity, and the output end of the dripping mechanism can generate droplets, and the output end of the dripping mechanism is located above the sample stage; an image acquisition mechanism, which is installed around the visual kettle, and the image acquisition mechanism is used to acquire image data in the visual cavity; an analysis and processing mechanism, which is electrically connected to the image acquisition mechanism , the analysis and processing mechanism is used to analyze and process the image data to obtain the measurement data of the wettability of the hydrate surface; wherein the measuring device also includes a surrounding liquid phase equilibrium mechanism, the surrounding liquid phase equilibrium mechanism includes a stirring kettle, a pressure control structure and a second temperature control structure, the stirring kettle has a stirring chamber inside, the pressure control structure is connected to the stirring chamber, the pressure control structure can inject the hydrate generating gas into the stirring chamber to control the pressure of the stirring chamber, and the second temperature control structure is used to control the temperature of the stirring chamber; the stirring chamber is connected to the visual chamber, the stirring chamber is used to accommodate the surrounding liquid phase and the hydrate generating gas and make the surrounding liquid phase saturated with the hydrate generating gas through stirring and can inject the saturated surrounding liquid phase into the visual chamber.

[0009] In an embodiment of the present invention, the pressure control structure includes a piston container and a first pumping structure. The inner cavity of the piston container is divided into an upper cavity and a lower cavity by a piston. The upper cavity is used to accommodate the hydrate-generating gas and is connected to the stirring cavity, and the lower cavity is connected to the first pumping structure.

[0010] In an embodiment of the present invention, the stirring chamber is connected to the visual chamber through a first liquid phase injection pipeline, and a liquid phase injection control valve is installed on the first liquid phase injection pipeline.

[0011] In an embodiment of the present invention, the second temperature control structure includes a water bath jacket and a first high and low temperature water bath, wherein the first high and low temperature water bath is used to accommodate a first heat exchange medium and control the temperature of the first heat exchange medium, and the water bath jacket is arranged outside the stirring tank and connected to the first high and low temperature water bath to form a circulation loop of the first heat exchange medium.

[0012] In an embodiment of the present invention, the image acquisition mechanism includes a light source, a microscope and a camera, the camera is installed at the eyepiece end of the microscope and is electrically connected to the analysis and processing mechanism; the side wall of the visual kettle has a first visual window arranged opposite to the light source, a second visual window arranged opposite to the objective end of the microscope and a third visual window for observing the test situation in the visual cavity, the sample stage is installed on the bottom wall of the visual kettle through a lifting structure, the top wall of the visual kettle is provided with a first injection joint, a second injection joint and a third injection joint, the visual cavity pressure control mechanism is connected to the visual cavity through the first injection joint, the dripping mechanism is connected to the visual cavity through the second injection joint, and the surrounding liquid phase balance mechanism is connected to the visual cavity through the third injection joint.

[0013] In an embodiment of the present invention, the first temperature control structure includes a visible water bath, a heat exchange coil, a second high and low temperature water bath and a temperature sensor. The second high and low temperature water bath is used to accommodate a second heat exchange medium and control the temperature of the second heat exchange medium. The heat exchange coil is installed in the visible water bath and connected to the second high and low temperature water bath to form a circulation loop of the second heat exchange medium. The visible water bath accommodates a third heat exchange medium, the visible kettle is immersed in the third heat exchange medium, the temperature sensor extends into the visible cavity, and the lifting structure includes a lifting screw, the upper end of the lifting screw is installed on the bottom wall of the visible kettle and connected to the sample stage, and the lower end of the lifting screw passes through the visible water bath.

[0014] In an embodiment of the present invention, the dripping mechanism includes a third pumping structure and a dripping needle. The dripping needle is installed in the visible cavity and located above the sample stage. The third pumping structure is connected to the dripping needle through a liquid injection pipeline, and a dripping control valve is installed on the liquid injection pipeline.

[0015] In an embodiment of the present invention, the liquid injection pipeline is also connected to a discharge pipeline, and the discharge pipeline is connected between the drip control valve and the drip needle, and a discharge control valve is installed on the discharge pipeline.

[0016] In an embodiment of the present invention, the visible cavity pressure control mechanism includes a gas cylinder and a second pumping structure, the gas cylinder contains hydrate-generating gas, the input end of the second pumping structure is connected to the gas cylinder, the output end of the second pumping structure is connected to the visible cavity through a gas injection pipeline, and a gas injection control valve and a pressure sensor are installed on the gas injection pipeline along its conveying direction.

[0017] The present invention also provides a method for measuring the wettability of a hydrate surface, using the above-mentioned measuring device, and the measuring method comprises the following steps: saturation of surrounding liquid phase: injecting a preset amount of surrounding liquid phase into the stirring chamber, and injecting hydrate-generating gas into the stirring chamber through a pressure control structure, stirring the surrounding liquid phase and the hydrate-generating gas, and controlling the stirring chamber to maintain a preset time at a first preset temperature and a preset pressure through the pressure control structure and the second temperature control structure, so that the surrounding liquid phase is saturated with the hydrate-generating gas; hydrate generation: the output end of the dripping mechanism drops water on the sample table to form water droplets, and then the visible cavity pressure control mechanism injects the hydrate-generating gas into the visible cavity, and the injection of the hydrate-generating gas is stopped after the visible cavity reaches the preset pressure; the surrounding liquid phase after saturation in the stirring chamber is injected into the visible cavity at a preset speed, and the visible cavity pressure control mechanism controls the visible cavity to maintain the preset pressure until the surrounding liquid phase in the visible cavity reaches a preset liquid level; the first temperature control structure controls the visible cavity to be lowered to a second preset temperature to freeze the water drop; the first temperature control structure controls the visual cavity to rise to a third preset temperature, so that the surface of the water drop melts and combines with the hydrate-generating gas to form a first hydrate film; the first temperature control structure controls the visual cavity to continue to rise to a fourth preset temperature to melt the first hydrate film; the first temperature control structure controls the visual cavity to fall to a fifth preset temperature, so that a second hydrate film is formed on the surface of the water drop; drip test: the output end of the drip mechanism forms a test droplet above the sample stage in the visual cavity, so that the test droplet gradually approaches the second hydrate film until the test droplet contacts the second hydrate film and immediately separates the test droplet from the output end of the drip mechanism; wherein the measurement method also includes performing image acquisition and analysis during the drip test: the image acquisition mechanism acquires image data in the visual cavity and transmits the image data to the analysis and processing mechanism, and the analysis and processing mechanism analyzes and processes the image data to obtain measurement data of the wettability of the hydrate surface.

[0018] In an embodiment of the present invention, the preset pressure remains unchanged during the measurement process and is determined according to the hydrate-forming gas used in the experiment, so that the phase equilibrium temperature of the hydrate at the preset pressure is greater than 0°C.

[0019] In an embodiment of the present invention, during the hydrate formation process, the first preset temperature is higher than 0°C and lower than the phase equilibrium temperature of the hydrate at the preset pressure; the second preset temperature is lower than 0°C; the third preset temperature is higher than 0°C and below 2°C; the fourth preset temperature is higher than the phase equilibrium temperature of the hydrate at the preset pressure but not more than 5°C of the phase equilibrium temperature; the fifth preset temperature is equal to the first preset temperature; wherein, the first temperature control structure controls the visible cavity to cool from the fourth preset temperature to the fifth preset temperature at a cooling rate of 1°C / 5min or in a gradient cooling manner so that a second hydrate film is formed on the surface of the water droplet.

[0020] The characteristics and advantages of the present invention are:

[0021] The device and method for measuring the wettability of the hydrate surface of the present invention add a surrounding liquid phase equilibrium mechanism to stir the surrounding liquid phase and the hydrate generating gas at a preset temperature and a preset pressure so that the surrounding liquid phase is saturated with the hydrate generating gas with high efficiency, and then use the visible cavity pressure control mechanism to inject the hydrate generating gas into the visible cavity to control the pressure of the visible cavity, and then inject the saturated surrounding liquid phase into the visible cavity, so that the surface of the water droplet on the sample stage can combine with the hydrate generating gas in the saturated surrounding liquid phase to form a stable hydrate film, thereby realizing the measurement of the wettability of the hydrate surface in the liquid-liquid-solid system.

[0022] The device and method for measuring the wettability of hydrate surfaces of the present invention first control the temperature of the visible cavity to form a first hydrate film on the surface of a water droplet, then control the temperature of the visible cavity to melt the first hydrate film, and then control the temperature of the visible cavity to form a second hydrate film on the surface of the water droplet, thereby ensuring that the second hydrate film is smooth and flat, which is beneficial to improving the accuracy of the measurement result. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is a schematic diagram of the overall structure of the measuring device in the present invention;

[0025] Figure 2 It is an exploded view of the visual kettle in the present invention;

[0026] Figure 3 The image data collected when the test droplet is formed in the present invention;

[0027] Figure 4 The image data collected when the test droplet contacts the second hydrate film on the surface of the water droplet in the present invention;

[0028] Figure 5 This is the image data collected after the test droplet is separated from the dripping mechanism in the present invention.

[0029] In the figure:

[0030] 1. Hydrate generation mechanism; 11. Visual kettle; 111. Kettle body; 112. Base; 113. Upper cover; 114. First injection joint; 115. Second injection joint; 116. Third injection joint; 117. First visual window; 118. Second visual window; 119. Third visual window; 12. First temperature control structure; 121. Visual water bath; 122. Heat exchange coil; 123. Second high and low temperature water bath; 124. Temperature sensor; 125. Stirring structure; 13. Sample table; 14. Lifting structure; 141. Lifting screw;

[0031] 2. Visual cavity pressure control mechanism; 21. Gas cylinder; 22. Second pumping structure; 23. Pressure sensor; 24. Gas phase injection control valve; 25. Output control valve; 26. Input control valve;

[0032] 3. Liquid dripping mechanism; 31. Third pumping structure; 32. Second liquid phase injection pipeline; 321. Liquid dripping control valve; 33. Liquid dripping needle; 34. Discharge control valve;

[0033] 4. Image acquisition mechanism; 41. Light source; 42. Microscope; 43. Camera;

[0034] 5. Analysis and processing organization;

[0035] 6. Surrounding liquid phase balance mechanism; 61. Stirring kettle; 62. Pressure control structure; 621. Piston container; 622. First pumping structure; 623. Pressure control valve; 63. Second temperature control structure; 631. Water bath jacket; 632. First high and low temperature water bath; 64. Liquid phase injection control valve; 65. First liquid phase injection pipeline;

[0036] 7. Test droplets;

[0037] 8. Water drops;

[0038] 9. Second hydrate membrane;

[0039] 10. Surrounding liquid phase after saturation. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Implementation Method 1

[0042] like Figures 1 to 3 As shown, the present invention provides a device for measuring the wettability of a hydrate surface, comprising: a hydrate generating mechanism 1, comprising a visual kettle 11 and a first temperature control structure 12, wherein the visual kettle 11 has a visual cavity inside, a sample stage 13 is installed in the visual cavity, and the first temperature control structure 12 is used to control the temperature of the visual cavity; a visual cavity pressure control mechanism 2, which is connected to the visual cavity, and the visual cavity pressure control mechanism 2 can inject hydrate generating gas into the visual cavity and control the pressure of the visual cavity; a dripping mechanism 3, which is connected to the visual cavity, and the output end of the dripping mechanism 3 can generate droplets, and the output end of the dripping mechanism 3 is located above the sample stage 13; an image acquisition mechanism 4, which is installed around the visual kettle 11, and the image acquisition mechanism 4 is used to acquire image data in the visual cavity; an analysis and processing mechanism 5, which is connected to the visual cavity The image acquisition mechanism 4 is electrically connected, and the analysis and processing mechanism 5 is used to analyze and process the image data to obtain the measurement data of the wettability of the hydrate surface; wherein, the measuring device also includes a surrounding liquid phase balance mechanism 6, the surrounding liquid phase balance mechanism 6 includes a stirring kettle 61, a pressure control structure 62 and a second temperature control structure 63, the stirring kettle 61 has a stirring chamber inside, the pressure control structure 62 is connected to the stirring chamber, the pressure control structure 62 can inject the hydrate generating gas into the stirring chamber and control the pressure of the stirring chamber, and the second temperature control structure 63 is used to control the temperature of the stirring chamber; the stirring chamber is connected to the visual chamber, the stirring chamber is used to accommodate the surrounding liquid phase and the hydrate generating gas and make the surrounding liquid phase saturated with the hydrate generating gas through stirring and can inject the saturated surrounding liquid phase 10 into the visual chamber.

[0043] The process of measuring the wettability of the hydrate surface by the measuring device of the present invention is as follows:

[0044] like Figure 1As shown, the surrounding liquid phase is saturated: a preset amount of the surrounding liquid phase is injected into the stirring chamber, and the hydrate-generating gas is injected into the stirring chamber through the pressure control structure 62, the surrounding liquid phase and the hydrate-generating gas are stirred, and at the same time, the stirring chamber is controlled by the pressure control structure 62 and the second temperature control structure 63 to maintain the first preset temperature and the preset pressure for a preset time, so that the surrounding liquid phase is saturated with the hydrate-generating gas. Wherein, the surrounding liquid phase is a liquid hydrocarbon, and the hydrate-generating gas can be methane; in a specific embodiment of the present invention, the preset amount of the surrounding liquid phase is 300ml, and when the stirring chamber is maintained at the first preset temperature and the preset pressure for 2h, it is judged that the surrounding liquid phase is saturated with the hydrate-generating gas.

[0045] like Figure 2 As shown, hydrate generation: the output end of the dripping mechanism 3 drops the water drop 8 on the sample table 13 to form the water drop 8, and then the visible cavity pressure control mechanism 2 injects the hydrate generating gas into the visible cavity until the visible cavity reaches the preset pressure and then stops injecting the hydrate generating gas; the saturated surrounding liquid phase 10 in the stirring cavity is injected into the visible cavity at a preset speed, and at the same time, the visible cavity pressure control mechanism 2 controls the visible cavity to maintain the preset pressure until the surrounding liquid phase in the visible cavity reaches the preset liquid level; the first temperature control structure 12 controls the visible cavity to be lowered to the second preset temperature, so that the water drop 8 freezes; the first temperature control structure 12 controls the visible cavity to be raised to the third preset temperature, so that the surface of the water drop 8 melts and combines with the hydrate generating gas to form a first hydrate film; the first temperature control structure 12 controls the visible cavity to continue to rise until the first hydrate film melts; the first temperature control structure 12 controls the visible cavity to be lowered to the fifth preset temperature, so that the second hydrate film 9 is formed on the surface of the water drop 8. Among them, the first preset temperature is higher than 0°C and lower than the phase equilibrium temperature of the hydrate under the preset pressure; the second preset temperature is lower than 0°C, and in order to make the water droplets freeze quickly, the second preset temperature is preferably -10°C; the third preset temperature is higher than 0°C and below 2°C, preferably 1°C; the fourth preset temperature is higher than the phase equilibrium temperature of the hydrate under the preset pressure but not more than 5°C of the phase equilibrium temperature, preferably 2°C higher than the phase equilibrium temperature; the fifth preset temperature is equal to the first preset temperature; wherein the first temperature control structure controls the visual cavity to decrease from the fourth preset temperature to the fifth preset temperature at a cooling rate of 1°C / 5min or in a gradient cooling manner, so that a second hydrate film is formed on the surface of the water droplet. By first controlling the temperature of the visual cavity to form a first hydrate film on the surface of the water droplet 8, then controlling the temperature of the visual cavity to melt the first hydrate film, and then controlling the cooling rate of the visual cavity to form a second hydrate film 9 on the surface of the water droplet 8, it can ensure that the second hydrate film 9 is smooth and flat, which is conducive to improving the accuracy of the measurement results;

[0046] The preset pressure remains unchanged during the measurement process and is determined according to the hydrate-forming gas used in the experiment, so that the phase equilibrium temperature of the combined hydrate at the preset pressure is greater than 0°C, thereby ensuring that the generated first hydrate film and the second hydrate film are hydrate solids without ice.

[0047] like Figures 3 to 5 As shown, the dripping test: the output end of the dripping mechanism 3 forms a test droplet 7 above the sample stage 13 in the visual cavity, so that the test droplet 7 gradually approaches the second hydrate film 9 until the test droplet 7 contacts the second hydrate film 9 and then immediately separates the test droplet 7 from the output end of the dripping mechanism 3.

[0048] The measurement method further includes performing image acquisition and analysis during the drop test: the image acquisition mechanism 4 acquires image data in the visual cavity and transmits the image data to the analysis and processing mechanism 5, and the analysis and processing mechanism 5 analyzes and processes the image data to obtain measurement data of the wettability of the hydrate surface.

[0049] Specifically, the image acquisition mechanism 4 acquires image data in the visual cavity in real time at a preset acquisition frequency during the drop test, including image data acquired during the formation of the test drop 7, image data acquired during the process when the test drop 7 and the water drop 8 are relatively close to each other until the test drop 7 and the second hydrate film 9 on the surface of the water drop 8 are in contact, and image data acquired after the test drop 7 is separated from the drop mechanism 3. The measurement data of the wettability of the hydrate surface includes the contact angle between the test drop 7 and the second hydrate film 9 after being separated from the output end of the drop mechanism 3. The analysis and processing mechanism 5 obtains the contact angle between the test droplet 7 and the second hydrate film 9 according to the image analysis and processing of the test droplet 7 in contact with the second hydrate film 9 after separation from the dripping mechanism 3. The output end of the dripping mechanism 3 forms a test droplet 7 by injecting a test liquid (including but not limited to water) into the visual cavity, and in the process of forming the test droplet 7 at the output end of the dripping mechanism 3, the analysis and processing mechanism 5 can analyze and process the image data collected by the image acquisition mechanism 4 to obtain the size of the test droplet 7, so as to control the size of the test droplet 7 to meet the requirements and stop the injection of the test liquid in time, so as to avoid the volume of the test droplet 7 being too large and directly contacting the second hydrate membrane 9. In a specific embodiment of the present invention, the volume of the test droplet 7 is not more than 5μL. In addition, before the test, the visual kettle 11 and the sample stage 13 inside it need to be thoroughly cleaned and dried so that there are no residual water droplets 8 in the visual cavity and on the sample stage 13.

[0050] The inventors of the present invention have found that if the wettability of the hydrate surface in the liquid-liquid-solid system is to be measured, the surrounding liquid phase must first be saturated with the hydrate-generating gas at a preset temperature and a preset pressure, so that the surface of the water droplet 8 can combine with the hydrate-generating gas to form a stable hydrate film. If the surrounding liquid phase and the gas phase (i.e., the hydrate-generating gas) are directly introduced into the visual kettle 11, the hydrate film formed by the surface of the water droplet 8 and the hydrate-generating gas will be unstable and strong, or even unable to combine to form a hydrate film, and it will be difficult to achieve the subsequent contact angle measurement between the test droplet 7 and the hydrate film. Moreover, since the mass transfer resistance of the surrounding liquid phase is much greater than the mass transfer resistance of the gas phase, and the surrounding liquid phase with a larger viscosity takes a longer time to be saturated with the gas phase, it generally takes several to dozens of hours or even several days to saturate the surrounding liquid phase with the gas phase, and the general mixing process cannot ensure that the concentration of the hydrate-generating gas in the surrounding liquid phase is stable at the preset concentration.

[0051] Therefore, the device for measuring the wettability of the hydrate surface of the present invention, by adding a surrounding liquid phase equilibrium mechanism 6 to stir the surrounding liquid phase and the hydrate generating gas at a preset temperature and a preset pressure, so that the surrounding liquid phase is saturated with the hydrate generating gas, and the efficiency is high. Then, the hydrate generating gas is injected into the visible cavity by using the visible cavity pressure control mechanism 2 to control the pressure of the visible cavity, and then the saturated surrounding liquid phase 10 is injected into the visible cavity, so that the surface of the water droplet 8 on the sample stage 13 can combine with the hydrate generating gas in the saturated surrounding liquid phase 10 to form a stable hydrate film, thereby realizing the measurement of the wettability of the hydrate surface in the liquid-liquid-solid system.

[0052] like Figure 1 As shown, in an embodiment of the present invention, the pressure control structure 62 includes a piston container 621 and a first pumping structure 622. The inner cavity of the piston container 621 is divided into an upper cavity and a lower cavity by a piston. The upper cavity is used to contain the hydrate-generating gas and is connected to the stirring cavity, and the lower cavity is connected to the first pumping structure 622. The lower cavity of the piston container 621 is pressurized by the first pumping structure 622, so that the hydrate-generating gas in the upper cavity of the piston container 621 is pressed into the stirring cavity, so that the pressure in the stirring cavity can be controlled. Specifically, the first pumping structure 622 includes but is not limited to a hand pump, and a pressure control valve 623 is provided on the connecting pipeline between the first pumping structure 622 and the piston container 621.

[0053] like Figure 1As shown, in an embodiment of the present invention, the second temperature control structure 63 includes a water bath jacket 631 and a first high and low temperature water bath 632, the first high and low temperature water bath 632 is used to accommodate the first heat exchange medium and control the temperature of the first heat exchange medium, the water bath jacket 631 is set outside the stirring tank 61 and connected to the first high and low temperature water bath 632 to form a circulation loop of the first heat exchange medium. Among them, the first heat exchange medium includes but is not limited to water. In addition, the water bath jacket 631 is wrapped with an insulation layer to prevent the water bath jacket 631 from exchanging heat with the outside world. Of course, the second temperature control structure 63 can also use other temperature control methods in the prior art for temperature control.

[0054] like Figure 1 As shown, in the embodiment of the present invention, the stirring chamber is connected to the visual chamber through the first liquid phase injection pipeline 65, and a liquid phase injection control valve 64 is installed on the first liquid phase injection pipeline 65. Before the surrounding liquid phase is saturated with the hydrate generating gas, the liquid phase injection control valve 64 is in a closed state; when the saturated surrounding liquid phase 10 needs to be injected into the visual chamber, the liquid phase injection control valve 64 is opened. In addition, by closing the liquid phase injection control valve 64, the use of the surrounding liquid phase balance mechanism 6 is stopped, so that the hydrate surface wettability measuring device of the present invention can also be applied to the measurement of hydrate surface wettability in a gas-liquid-solid system. The specific measurement process can be the same as that of the prior art, which will not be repeated here.

[0055] like Figure 1 As shown, in the embodiment of the present invention, the first temperature control structure 12 includes a visible water bath 121, a heat exchange coil 122, a second high and low temperature water bath 123 and a temperature sensor 124. The second high and low temperature water bath 123 is used to accommodate a second heat exchange medium and control the temperature of the second heat exchange medium. The heat exchange coil 122 is installed in the visible water bath 121 and connected with the second high and low temperature water bath 123 to form a circulation loop of the second heat exchange medium. The visible water bath 121 contains a third heat exchange medium, and the visible kettle 11 is immersed in the third heat exchange medium. The temperature sensor 124 extends into the visible cavity. The temperature of the second heat exchange medium is adjusted by the second high and low temperature water bath 123 and then input into the heat exchange coil 122, so that the second heat exchange medium and the third heat exchange medium exchange heat, and the temperature of the visible cavity of the visible kettle 11 is controlled by the third heat exchange medium. Among them, the second heat exchange medium includes but is not limited to ethylene glycol aqueous solution, and the first temperature control structure 12 can realize the temperature control of the visible cavity at -30°C to 100°C. The temperature sensor 124 can be a resistive temperature sensor, such as a PT100 resistive temperature sensor, and the accuracy of the temperature sensor 124 is ±0.1°C. The visual water bath 121 can be a tank structure made of colorless transparent organic glass. In addition, the first temperature control structure 12 includes a stirring structure 125 for stirring the third heat exchange medium in the visual water bath 121 to make the temperature distribution of the third heat exchange medium more uniform.

[0056] like Figure 1 As shown, in the embodiment of the present invention, the dripping mechanism 3 includes a third pumping structure 31 and a dripping needle 33, the dripping needle 33 is installed in the visual cavity and located above the sample stage 13, the third pumping structure 31 is connected to the dripping needle 33 through the second liquid phase injection pipeline 32, and the second liquid phase injection pipeline 32 is installed with a dripping control valve 321. In addition, the second liquid phase injection pipeline 32 is also provided with a discharge pipeline, and the discharge pipeline is connected between the dripping control valve 321 and the dripping needle 33, and a discharge control valve 34 is installed on the discharge pipeline. First, open the discharge control valve 34 and close the drip control valve 321, and then inject the hydrate-generating gas into the visible cavity through the visible cavity pressure control mechanism 2 until all the air in the visible cavity is discharged from the discharge pipeline, then close the discharge control valve 34 and continue to inject the hydrate-generating gas into the visible cavity until the visible cavity reaches a preset pressure, and then after the saturated surrounding liquid phase 10 is injected into the visible cavity, open the drip control valve 321, and use the third pumping structure 31 to pump water from the drip needle 33 to form a water drop 8 and drip onto the sample table 13; during the drip test, open the drip control valve 321, and use the third pumping structure 31 to pump the test liquid from the drip needle 33 to form a test drop 7, but do not drip first and do not contact the water drop 8. Among them, the third pumping structure 31 can use a hand pump or other liquid pumps in the prior art. The material of the dripping needle 33 can be selected according to the interfacial tension between the test droplet 7 and the surrounding liquid phase, such as a dripping needle 33 made of 316L stainless steel and a dripping needle 33 made of polytetrafluoroethylene, to ensure that the test droplet 7 can smoothly detach from the dripping needle 33 and transfer to the hydrate membrane.

[0057] like Figure 1 As shown, in the embodiment of the present invention, the visible cavity pressure control mechanism 2 includes a gas cylinder 21 and a second pumping structure 22, the gas cylinder 21 stores hydrate-generating gas, the input end of the second pumping structure 22 is connected to the gas cylinder 21, the output end of the second pumping structure 22 is connected to the visible cavity through a gas phase injection pipeline, and a gas phase injection control valve 24 and a pressure sensor 23 are installed on the gas phase injection pipeline along its conveying direction. After the gas phase injection control valve 24 is opened, the second pumping structure 22 pumps the hydrate-generating gas into the visible cavity according to the pressure detection signal of the pressure sensor 23. In addition, an output control valve 25 and an input control valve 26 are provided on the connecting pipeline between the input end of the second pumping structure 22 and the gas cylinder 21; the output control valve 25 is arranged near the output end of the gas cylinder 21 to control the outflow of the hydrate-generating gas in the gas cylinder 21; the input control valve 26 is arranged near the input end of the second pumping structure 22 to control the hydrate-generating gas to flow into the second pumping structure 22. The second pumping structure 22 may adopt a high-precision plunger pump or other air pumps in the prior art.

[0058] like Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the image acquisition mechanism 4 includes a light source 41, a microscope 42 and a camera 43, the camera 43 is installed at the eyepiece end of the microscope 42 and is electrically connected to the analysis and processing mechanism 5; the side wall of the visual kettle 11 has a first visual window 117 arranged opposite to the light source 41, a second visual window 118 arranged opposite to the objective end of the microscope 42 and a third visual window 119 for observing the test situation in the visual cavity, the sample stage 13 is installed on the bottom wall of the visual kettle 11 through the lifting structure 14, the top wall of the visual kettle 11 is provided with a first injection joint 114, a second injection joint 115 and a third injection joint 116, the visual cavity pressure control mechanism 2 is connected to the visual cavity through the first injection joint 114, the dripping mechanism 3 is connected to the visual cavity through the second injection joint 115, and the surrounding liquid phase balance mechanism 6 is connected to the visual cavity through the third injection joint 116. During the drip test, the test droplet 7 is first fixed, and the sample stage 13 is driven up by the lifting structure 14, so that the water droplet 8 on the sample stage 13 gradually approaches the test droplet 7, until the second hydrate film 9 on the surface of the water droplet 8 contacts the test droplet 7, and then the sample stage 13 is driven down by the lifting structure 14 to separate the test droplet 7 from the output end of the drip mechanism 3.

[0059] Specifically, the sample stage 13 can be provided with a groove for accommodating the water droplet 8, and the size of the groove can be set as required, such as a circular groove with a diameter of 2 mm, 4 mm, 6 mm, 8 mm, 10 mm or other sizes. The lifting structure 14 includes a lifting screw 141, the upper end of which is mounted on the bottom wall of the visual kettle 11 and connected to the sample stage 13, and the lower end of the lifting screw 141 passes through the visual water bath 121. By operating the lower end of the lifting screw 141 to rotate the lifting screw 141, the lifting screw 141 drives the sample stage 13 to move up and down. The first visual window 117, the second visual window 118 and the third visual window 119 can all be sapphire visual windows. The visual kettle 11 includes a kettle body 111 constituting its side wall, a base 112 constituting its bottom wall, and an upper cover 113 constituting its top wall. The base 112 is sealed and installed at the bottom opening of the kettle body 111 through multiple fasteners, and the upper cover 113 is sealed and installed at the top opening of the kettle body 111 through multiple fasteners. The drip needle 33 is installed at the lower end of the second injection joint 115, and the upper end of the second injection joint 115 is connected to the second liquid phase injection pipeline 32. The side wall of the visual kettle 11 is generally a four-sided structure enclosed by a square, and the first visual window 117 and the second visual window 118 are located on two oppositely arranged wall surfaces. The camera 43 can use a CCD online camera 43. The analysis and processing mechanism 5 is a computer installed with corresponding analysis and processing software.

[0060] Implementation Method 2

[0061] Combination Figures 1 to 5 As shown, the present invention also provides a method for measuring the wettability of a hydrate surface, which adopts the measuring device in the first embodiment. Therefore, the implementation of the measuring method can refer to the implementation of the measuring device in the first embodiment, which will not be repeated here.

[0062] The measurement method of the present invention comprises the following steps: saturation of surrounding liquid phase: injecting a preset amount of surrounding liquid phase into the stirring chamber, and injecting hydrate-generating gas into the stirring chamber through the pressure control structure 62, stirring the surrounding liquid phase and the hydrate-generating gas, and controlling the stirring chamber to maintain a preset time at a first preset temperature and a preset pressure through the pressure control structure 62 and the second temperature control structure 63, so that the surrounding liquid phase is saturated with the hydrate-generating gas; hydrate generation: the output end of the dripping mechanism 3 drops a water droplet 8 on the sample table 13 to form a water droplet 8, and then the visible chamber pressure control mechanism 2 injects the hydrate-generating gas into the visible chamber until the visible chamber reaches a preset pressure and then stops injecting the hydrate-generating gas; injecting the saturated surrounding liquid phase 10 in the stirring chamber into the visible chamber at a preset speed, and at the same time, the visible chamber pressure control mechanism 2 controls the visible chamber to maintain a preset pressure until the surrounding liquid phase in the visible chamber reaches a preset liquid level; the first temperature control structure 12 controls the visible chamber to drop to a second preset temperature, so that the water droplets 8 are 8 freezes; the first temperature control structure 12 controls the visible cavity to rise to a third preset temperature, so that the surface of the water droplet 8 melts and combines with the hydrate-generating gas to form a first hydrate film; the first temperature control structure 12 controls the visible cavity to continue to rise to a fourth preset temperature, so that the first hydrate film melts; the first temperature control structure 12 controls the visible cavity to lower to a fifth preset temperature, so that a second hydrate film 9 is formed on the surface of the water droplet 8; drip test: the output end of the drip mechanism 3 forms a test droplet 7 above the sample stage 13 in the visible cavity, so that the test droplet 7 and the second hydrate film 9 gradually approach each other, until the test droplet 7 contacts the second hydrate film 9 and immediately separates the test droplet 7 from the output end of the drip mechanism 3; wherein the measurement method also includes image acquisition and analysis during the drip test: the image acquisition mechanism 4 acquires image data in the visible cavity and transmits the image data to the analysis and processing mechanism 5, and the analysis and processing mechanism 5 analyzes and processes the image data to obtain measurement data of the wettability of the hydrate surface.

[0063] The preset pressure remains unchanged during the measurement process and is determined according to the hydrate-forming gas used in the experiment, so that the phase equilibrium temperature of the combined hydrate at the preset pressure is greater than 0° C., thereby ensuring that the generated first hydrate film and the second hydrate film are hydrate solids without ice.

[0064] In an embodiment of the present invention, during the process of hydrate formation, the first preset temperature is higher than 0°C and lower than the phase equilibrium temperature of the hydrate under a preset pressure; the second preset temperature is lower than 0°C, and in order to make the water droplets freeze quickly, the second preset temperature is preferably -10°C; the third preset temperature is higher than 0°C and below 2°C, preferably 1°C; the fourth preset temperature is higher than the phase equilibrium temperature of the hydrate under the preset pressure but not more than 5°C of the phase equilibrium temperature, preferably 2°C higher than the phase equilibrium temperature; the fifth preset temperature is equal to the first preset temperature; wherein the first temperature control structure 12 controls the visible cavity to cool from the fourth preset temperature to the fifth preset temperature at a cooling rate of 1°C / 5min or in a gradient cooling manner, so that a second hydrate film 9 is formed on the surface of the water droplet 8.

[0065] The above are only several embodiments of the present invention. Those skilled in the art may make various changes or modifications to the embodiments of the present invention based on the contents disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. A device for measuring the wettability of a hydrate surface, characterized in that: include: The hydrate generation mechanism comprises a visual kettle and a first temperature control structure, wherein the visual kettle has a visual cavity inside, a sample stage is installed in the visual cavity, and the first temperature control structure is used to control the temperature of the visual cavity; A visible cavity pressure control mechanism is in communication with the visible cavity, and the visible cavity pressure control mechanism can inject hydrate-generating gas into the visible cavity to control the pressure of the visible cavity; A liquid dripping mechanism, which is in communication with the visual cavity, wherein an output end of the liquid dripping mechanism can generate liquid droplets, and the output end of the liquid dripping mechanism is located above the sample stage; An image acquisition mechanism is installed around the visual kettle, and is used to acquire image data in the visual cavity; An analysis and processing mechanism, electrically connected to the image acquisition mechanism, and configured to analyze and process the image data to obtain measurement data of the wettability of the hydrate surface; In which, the measuring device also includes a surrounding liquid phase balance mechanism, which includes a stirring kettle, a pressure control structure and a second temperature control structure. The stirring kettle has a stirring chamber inside, and the pressure control structure is connected to the stirring chamber. The pressure control structure can inject the hydrate-generating gas into the stirring chamber to control the pressure of the stirring chamber. The second temperature control structure is used to control the temperature of the stirring chamber. The stirring chamber is connected to the visible chamber. The stirring chamber is used to accommodate the surrounding liquid phase and the hydrate-generating gas and saturate the surrounding liquid phase with the hydrate-generating gas through stirring, and the saturated surrounding liquid phase can be injected into the visible chamber.

2. The measuring device according to claim 1, characterized in that The pressure control structure includes a piston container and a first pumping structure. The inner cavity of the piston container is divided into an upper cavity and a lower cavity by a piston. The upper cavity is used to contain the hydrate-generating gas and is connected to the stirring cavity, and the lower cavity is connected to the first pumping structure.

3. The measuring device according to claim 1, characterized in that The stirring chamber is connected to the visual chamber through a first liquid phase injection pipeline, and a liquid phase injection control valve is installed on the first liquid phase injection pipeline.

4. The measuring device according to claim 1, characterized in that The second temperature control structure includes a water bath jacket and a first high and low temperature water bath box. The first high and low temperature water bath box is used to accommodate a first heat exchange medium and control the temperature of the first heat exchange medium. The water bath jacket is arranged outside the stirring tank and connected to the first high and low temperature water bath box to form a circulation loop of the first heat exchange medium.

5. The measuring device according to claim 1, characterized in that The image acquisition mechanism includes a light source, a microscope and a camera, wherein the camera is installed at the eyepiece end of the microscope and is electrically connected to the analysis and processing mechanism; The side wall of the visual kettle has a first visual window arranged opposite to the light source, a second visual window arranged opposite to the objective end of the microscope, and a third visual window for observing the test situation in the visual cavity. The sample stage is installed on the bottom wall of the visual kettle through a lifting structure. The top wall of the visual kettle is provided with a first injection joint, a second injection joint and a third injection joint. The visual cavity pressure control mechanism is connected to the visual cavity through the first injection joint, the dripping mechanism is connected to the visual cavity through the second injection joint, and the surrounding liquid phase balance mechanism is connected to the visual cavity through the third injection joint.

6. The measuring device according to claim 5, characterized in that The first temperature control structure includes a visible water bath, a heat exchange coil, a second high and low temperature water bath and a temperature sensor. The second high and low temperature water bath is used to accommodate a second heat exchange medium and control the temperature of the second heat exchange medium. The heat exchange coil is installed in the visible water bath and connected to the second high and low temperature water bath to form a circulation loop of the second heat exchange medium. The visible water bath accommodates a third heat exchange medium. The visible kettle is immersed in the third heat exchange medium. The temperature sensor extends into the visible cavity. The lifting structure includes a lifting screw. The upper end of the lifting screw is installed on the bottom wall of the visible kettle and connected to the sample stage. The lower end of the lifting screw passes through the visible water bath.

7. The measuring device according to claim 1, characterized in that The dripping mechanism includes a third pumping structure and a dripping needle. The dripping needle is installed in the visual cavity and located above the sample stage. The third pumping structure is connected to the dripping needle through a second liquid phase injection pipeline, and a dripping control valve is installed on the second liquid phase injection pipeline.

8. The measuring device according to claim 7, characterized in that The second liquid phase injection pipeline is connected to a discharge pipeline, and the discharge pipeline is connected between the dripping control valve and the dripping needle, and a discharge control valve is installed on the discharge pipeline.

9. The measuring device according to claim 1, characterized in that The visible cavity pressure control mechanism includes a gas cylinder and a second pumping structure, wherein the gas cylinder contains hydrate-generating gas, the input end of the second pumping structure is connected to the gas cylinder, the output end of the second pumping structure is connected to the visible cavity through a gas injection pipeline, and a gas injection control valve and a pressure sensor are installed on the gas injection pipeline along its conveying direction.

10. A method for measuring the wettability of a hydrate surface, characterized in that: Using the measuring device according to any one of claims 1 to 9, the measuring method comprises the following steps: Saturation of surrounding liquid phase: injecting a preset amount of surrounding liquid phase into the stirring chamber, and injecting hydrate-generating gas into the stirring chamber through the pressure control structure, stirring the surrounding liquid phase and the hydrate-generating gas, and controlling the stirring chamber to maintain a preset time at a first preset temperature and a preset pressure through the pressure control structure and the second temperature control structure, so that the surrounding liquid phase is saturated with the hydrate-generating gas; Hydrate formation: the output end of the dripping mechanism drops water on the sample table to form water droplets, and then the visible cavity pressure control mechanism injects the hydrate generating gas into the visible cavity until the visible cavity reaches the preset pressure and then stops injecting the hydrate generating gas; the surrounding liquid phase saturated in the stirring cavity is injected into the visible cavity at a preset speed, and at the same time, the visible cavity pressure control mechanism controls the visible cavity to maintain the preset pressure until the surrounding liquid phase in the visible cavity reaches the preset liquid level; the first temperature control structure controls the visible cavity to drop to the second preset temperature to freeze the water droplets; the first temperature control structure controls the visible cavity to rise to the third preset temperature to melt the surface of the water droplets and combine with the hydrate generating gas to form a first hydrate film; the first temperature control structure controls the visible cavity to continue to rise to the fourth preset temperature to melt the first hydrate film; the first temperature control structure controls the visible cavity to drop to the fifth preset temperature to form a second hydrate film on the surface of the water droplets; Drop test: the output end of the drop mechanism forms a test drop above the sample stage in the visual cavity, so that the test drop gradually approaches the second hydrate film until the test drop contacts the second hydrate film, and then the test drop is separated from the output end of the drop mechanism immediately; Among them, the measurement method also includes performing image acquisition and analysis during the drop test: an image acquisition mechanism acquires image data in the visual cavity and transmits the image data to an analysis and processing mechanism, and the analysis and processing mechanism analyzes and processes the image data to obtain measurement data of the wettability of the hydrate surface.

11. The method for measuring the wettability of a hydrate surface according to claim 10, characterized in that: The preset pressure remains unchanged during the measurement process and is determined according to the hydrate-forming gas used in the experiment, so that the phase equilibrium temperature of the hydrate at the preset pressure is greater than 0°C.

12. The method for measuring the wettability of a hydrate surface according to claim 10, characterized in that: During the hydrate generation process, the first preset temperature is higher than 0°C and lower than the phase equilibrium temperature of the hydrate at the preset pressure; the second preset temperature is lower than 0°C; the third preset temperature is higher than 0°C and lower than 2°C; the fourth preset temperature is higher than the phase equilibrium temperature of the hydrate at the preset pressure but not higher than 5°C of the phase equilibrium temperature; the fifth preset temperature is equal to the first preset temperature; The first temperature control structure controls the visible cavity to cool from the fourth preset temperature to the fifth preset temperature at a cooling rate of 1°C / 5min or in a gradient cooling manner so that a second hydrate film is formed on the surface of the water droplet.

Images