A method for monitoring the surface creep behavior of solid hydrate structures

Abstract

This invention discloses a method for monitoring the surface creep of solid hydrate structures, relating to the field of natural gas storage and transportation technology. By adding a test proportion of micro-powder to a mother liquor, and after gas is introduced into a reactor, under constant pressure and cooling conditions, the hydrate in the mother liquor grows upwards along the inner wall of the reactor in a solid state. During this growth, the hydrate carries the micro-powder along with it. Therefore, by imaging the micro-powder and using a microscope with magnification to record the upward climbing process of the hydrate on the reactor wall, the position of the micro-powder at different times can be identified based on the images taken at different times. The surface creep of the hydrate structure can be quantitatively studied by observing the changes in the coordinates of a large number of randomly distributed micro-powder particles over time. Furthermore, the flow pattern of liquid water at the hydrate surface can be quantitatively deduced based on the creep pattern.

Description

Technical Field

[0001] This invention relates to the field of natural gas storage and transportation technology, and more specifically, to a method for monitoring the surface creep behavior of solid hydrate structures. Background Technology

[0002] Gas hydrates are compounds formed by water molecules and gas molecules under high pressure and low temperature conditions. Under appropriate low temperature and high pressure conditions, water molecules form cage structures of different shapes and sizes through hydrogen bonding. Different types of gas molecules are trapped in this structure, thus forming gas hydrates [1]. Most of the components of natural gas can form hydrates, including methane, carbon dioxide, hydrogen and other gases with similar molecular sizes. Natural gas hydrates are widely distributed in nature and have huge reserves. They are mainly distributed in marine or freshwater lake sedimentary layers and permafrost layers at depths greater than 300m [2]. Studies suggest that 20.7% of the land area and 90% of the ocean floor meet the temperature and pressure conditions required for the formation of natural gas hydrates. Based on this, it is estimated that the carbon content in global natural gas hydrates is about twice the total carbon reserves in traditional fossil energy (coal, oil, natural gas, oil shale, etc.). To date, at least 116 natural gas hydrate deposits have been discovered globally, including 38 on land (permafrost areas) and 78 in the sea. Abundant methane hydrate deposits are also found in my country. In 2008, physical samples of natural gas hydrates were discovered in the permafrost region of the Qilian Mountains in Qinghai Province; from June to September 2013, high-purity natural gas hydrate samples were drilled in the eastern waters of the Pearl River Estuary Basin along the coast of Guangdong [3-5].

[0003] In order to make scientific use of this energy with huge reserves, researchers at home and abroad have conducted a lot of research on the physical properties of natural gas hydrates in the laboratory. It has been found that under natural conditions, natural gas hydrates are mainly found in various sediments, and pure hydrates existing in the form of large blocks account for less than 6% of all hydrate resources. According to actual survey results, more than 90% of hydrates in real marine environments are found in clay or silty clay with very fine particles, dense internal structure and very low permeability [6]. When hydrates are found in such sediments, they are mainly found in the fracture structure formed inside, thus forming a hydrate structure with a thick layer, layered and vein-like appearance [7]. Due to the very dense particle structure of such sediments and the unique lamellar structure inside, the internal fracture structure will be accompanied by obvious liquid water migration during the formation process [8]. Therefore, thick layered, layered and vein-like hydrates will cause obvious liquid water migration during the formation process [9]. However, there is still no effective tracking method for the migration path of liquid water in solid hydrates.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for monitoring the surface creep of solid hydrate structures in order to track the migration path of liquid water in solid hydrates and analyze the surface creep of solid hydrate structures.

[0006] The formation mechanism of thick, layered, and vein-like hydrates within fractured structures of fine-grained sediments (such as clay, silt, and mud) is a current hot topic and a challenging issue in the international hydrate research field. Existing research confirms that significant liquid water migration occurs during the formation of fractured structures in these sediments; therefore, solid hydrates within the fractures also undergo significant liquid water migration during formation. For the formation mechanism of thick, layered, and vein-like hydrates, without a thorough understanding of the liquid water migration patterns within the solid hydrate structure, it is impossible to conduct in-depth research on the hydrate formation process and its mechanism within these sediments.

[0007] To address the current challenge of effectively and in real-time tracking the transport of liquid water within solid hydrate structures, this invention is proposed.

[0008] This invention is implemented as follows:

[0009] This invention provides a method for monitoring the surface creep behavior of solid hydrate structures, which specifically includes the following steps:

[0010] In the mother liquor of natural gas hydrate, a test proportion of micro powder was added, and gas was introduced under constant pressure. The solid hydrate was induced to grow upward along the wall of a cubic reactor by cooling the top separately. The upward growth process of the solid hydrate was monitored in real time by microscope and imaged. The pixel coordinates of the micro powder were measured. The change law of pixel coordinates over time was obtained, and the surface creep law of the solid hydrate structure was obtained.

[0011] By adding a test proportion of micro-powder to the mother liquor and then directly introducing gas into the reactor (gas can be introduced directly into the reactor), under the combined effects of constant gas pressure and cooling at the top of the reactor, the hydrates in the mother liquor grow upwards along the inner wall of the reactor in a solid state. During this growth, the hydrates carry the micro-powder along with them. Therefore, by imaging the micro-powder (e.g., continuous imaging) and using a microscope with magnification to record the upward climbing process of the hydrates on the reactor wall, the position of the micro-powder at different times can be identified based on the images. The change in the coordinates of a large number of randomly distributed micro-powder particles over time allows for the quantitative study of the surface creep of the hydrate structure. Furthermore, based on the creep pattern, the flow pattern of liquid water at the hydrate surface can be quantitatively deduced.

[0012] The aforementioned mother liquor refers to: a mixture of fine-particle sediments (such as clay, silt, and mud) and water; or a mixture of fine-particle sediments and treatment solutions (such as SDS); or water; or water with added reaction promoter SDS. For example, the mother liquor is a mixed solution of water with added reaction promoter SDS (sodium dodecyl sulfate).

[0013] The reactor is based on the hydrate formation simulation device described in patent CN201921837858. The top and bottom temperatures of the reactor can be individually controlled. It is cubic in shape and can be used for high-pressure hydrate formation. The reactor can withstand a gas pressure of 10 MPa. During the test of the surface creep law of the hydrate structure, gas is introduced to a certain pressure condition, and the temperature at the top of the reactor is individually controlled to lower the temperature, thus inducing solid hydrates to grow from bottom to top.

[0014] The reactor used in this invention is a cuboid reactor designed and manufactured independently by the inventor, referring to the hydrate formation simulation device described in patent CN201921837858. Its top and bottom temperatures can be independently adjusted, and transparent observation windows are installed on two opposite sides of the reactor for continuous monitoring and filming of the hydrate growth process.

[0015] In a preferred embodiment of the present invention, the aforementioned micropowder is a tracer powder. Micropowder has the advantages of low density and light weight, facilitating upward growth along with the hydrate. Its small volume also allows for uniform distribution, thus better reflecting the growth process of the hydrate structure. The micropowder can thus function as a tracer.

[0016] The aforementioned micro powders are color-developing powders, latex powders, or rubber powders.

[0017] In one alternative embodiment, the chromogenic powder includes, but is not limited to, at least one of clay, silica gel powder, and barium sulfate powder; the chromogenic powder facilitates better identification and observation of the hydrate structure growth process in subsequent imaging.

[0018] In one alternative embodiment, the average particle size of the powder is in the micrometer or nanometer range.

[0019] In one optional embodiment, the average particle size of the microparticles is 0.1-100 μm. The inventors found that if the average particle size of the microparticles is larger than this range, it is difficult for the hydrate to carry the microparticles during growth; if it is smaller than this range, the microparticles are too small, making direct observation with the naked eye and determination of microparticle coordinates during subsequent processing difficult. If the particle size is too small, a high magnification of the microscope is required, and it is also inconvenient for subsequent image capture, imaging, and identification.

[0020] In one alternative embodiment, the average particle size of the micronized powder is 28–56 μm.

[0021] In a preferred embodiment of the present invention, the gas is carbon dioxide or methane;

[0022] In one alternative implementation, constant pressure refers to a constant pressure of less than 10 MPa.

[0023] In a preferred embodiment of the invention, the temperature at the top of the reactor is individually cooled to 0-10°C. The temperature range can be adaptively adjusted depending on whether a solid hydrate structure is formed, for example, by adjusting the temperature inside the reactor according to the magnitude of the constant pressure, such as adjusting it to 1-15°C.

[0024] In a preferred embodiment of the present invention, the microscope is a digital microscope. In other embodiments, the microscope is equipped with a high-speed imaging device, which can quickly capture images or record videos of the growth process of solid hydrate structures.

[0025] The main reason for using a digital microscope to monitor the growth process of hydrates is that it allows for magnified observation of microparticles embedded in the solid hydrate structure, which facilitates accurate measurement of the pixel coordinates of the microparticles during subsequent image processing.

[0026] The digital microscope is a 10× to 200× digital microscope; in an optional embodiment, the digital microscope is a 100× digital microscope.

[0027] In a preferred embodiment of the invention, the imaging refers to continuous imaging over a continuous time period of 0–100 seconds. This continuous imaging device allows for real-time monitoring of the hydrate growth process. In other embodiments, a high-speed camera can also be used for rapid imaging.

[0028] In one alternative implementation, imaging refers to continuous imaging over a continuous time period of 0 to 10 seconds.

[0029] In one alternative implementation, imaging refers to continuous imaging within a continuous time period of 0 to 6 seconds.

[0030] In a preferred embodiment of the present invention, ImageJ software is used to count the positions of silicone powder in the image and measure the specific pixel coordinates.

[0031] In a preferred embodiment of the present invention, Origin or Excel plotting software is used to plot the variation of pixel coordinates over time.

[0032] In a preferred embodiment of the present invention, by comparing and analyzing the changes in the position of silica powder embedded in the solid hydrate structure over time, the surface creep law of the solid hydrate structure and the flow law of liquid water on the surface of the hydrate structure are obtained.

[0033] In a preferred embodiment of the present invention, the above-mentioned test ratio is 0.5-20 wt%. Insufficient addition will lead to data omissions; the above-mentioned addition ratio provides better test results.

[0034] The present invention has the following beneficial effects:

[0035] This invention involves adding a test proportion of micro-powder to a mother liquor. After gas is introduced into a reactor, under constant gas pressure and cooling at the top of the reactor, the hydrates in the mother liquor grow upwards along the inner wall of the reactor in a solid state. During this growth, the hydrates carry the micro-powder along with them. Therefore, by imaging the micro-powder (e.g., continuous imaging) and recording the upward climbing process of the hydrates on the reactor wall using a microscope with magnification, the positions of the micro-powders at different times can be identified. The surface creep of the hydrate structure can be quantitatively studied by observing the changes in the coordinates of a large number of randomly distributed micro-powder particles over time. Furthermore, the flow pattern of liquid water at the hydrate surface can be quantitatively deduced based on the creep pattern. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is an exterior photo of a cubic high-pressure hydrate formation reactor with individually adjustable top and bottom temperatures.

[0038] Figure 2 The images show the process of solid hydrates climbing along the reactor and the monitoring process under a digital microscope at 100× magnification.

[0039] Figure 3 The tracking ball and its pixel coordinates at the 0-second timing point recorded by a 100× digital microscope (measured using ImageJ software);

[0040] Figure 4 The tracking ball and its pixel coordinates at a 1-second timing point recorded by a 100× digital microscope (measured using ImageJ software);

[0041] Figure 5 Tracking ball and its pixel coordinates at a 2-second timing point recorded by a 100× digital microscope (measured using ImageJ software);

[0042] Figure 6 The variation of the pixel coordinates of the tracking ball embedded in the solid hydrate during the continuous time period from 0 to 6 seconds is shown (plotted using Origin software). Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0044] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0045] Example 1

[0046] This embodiment provides a method for monitoring the surface creep behavior of solid hydrate structures, including the following steps:

[0047] (1) In this embodiment, the mother liquor is a mixed solution of water and reaction promoter SDS (sodium dodecyl sulfate), with SDS accounting for 0.5% by mass. Silica gel powder particles with an average particle size of 28–56 μm are incorporated into the hydrate formation mother liquor at a mass ratio of 1 wt%.

[0048] (2) Methane was introduced to a constant pressure (8.5 MPa) using the reactor described in patent CN201921837858. Figure 1 As shown, the top of the reactor was cooled to 0.5℃, while the bottom temperature was kept stable at 12℃, which induced the natural gas hydrate to grow upwards along the four walls of the reactor.

[0049] (3) The reactor can be designed as a cubic structure with transparent observation windows on both sides. A digital microscope with 100× magnification is installed outside the windows. The digital microscope monitors and records the upward creeping growth process of the solid hydrate structure in real time. The pre-incorporated silica powder particles can creep and grow along with the solid hydrate structure and can be clearly identified at 100× magnification (see reference). Figure 2 (As shown in A in the diagram);

[0050] (4) Take photos of any moment from the video data recorded by the microscope and observe the distribution pattern of silica powder particles embedded in the solid hydrate structure.

[0051] (5) Use ImageJ software to count the positions of the silicone balls in the captured photos and measure their specific pixel coordinates; capture photos continuously within a certain time period that meets the requirements and measure the pixel coordinates of the silicone balls;

[0052] Figure 3 Image of a silicone sphere and its pixel coordinates at 0 seconds, recorded using a 100× digital microscope (measured with ImageJ software). Figure 4 Image of a silicone sphere and its pixel coordinates at a 1-second timing point recorded by a 100× digital microscope (measured using ImageJ software). Figure 5 Image of a silicone sphere and its pixel coordinates at a 2-second timing point recorded by a 100× digital microscope (measured using ImageJ software). Figures 3-5 This involves the specific determination of the coordinate values ​​of the silicone ball within a continuous 3-second time period.

[0053] (6) Use Origin or Excel plotting software to plot the pixel coordinates over time; the positional changes of all silicone spheres embedded in the solid hydrate were measured within a continuous 7-second time period from 0 to 6 seconds, referring to... Figure 6 As shown (drawn using Origin software).

[0054] (7) By comparing and analyzing the changes in the position of the silica gel balls embedded in the solid hydrate structure over time, the surface creep law of the solid hydrate structure and the flow law of liquid water on the surface of the hydrate structure can be obtained.

[0055] Example 2

[0056] This embodiment provides a method for monitoring the surface creep behavior of solid hydrate structures, including the following steps:

[0057] (1) In this embodiment, the mother liquor is pure water. In the mother liquor for the formation of hydrate, silica powder particles with an average particle size of 28 to 56 μm are added at a mass ratio of 1 wt%, and yellow clay is added at a mass ratio of 0.5%. The yellow clay is mainly used to dye the white hydrate brown to facilitate the identification and observation of silica spheres.

[0058] (2) Methane was introduced to a constant pressure of 8.5 MPa, using the reactor described in patent CN201921837858. Figure 1 As shown, the reactor can withstand a gas pressure of 10 MPa, and the temperatures at its top and bottom can be independently controlled. By cooling the top of the reactor to 0.5°C and maintaining the bottom temperature at 12°C, the natural gas hydrate is induced to grow from bottom to top along the four walls of the reactor.

[0059] (3) The reactor can be designed as a cubic structure with transparent observation windows on both sides. A digital microscope with 100× magnification is installed outside the windows. The digital microscope monitors and records the upward creeping growth process of the solid hydrate structure in real time. The pre-incorporated silica powder particles can creep and grow along with the solid hydrate structure and can be clearly identified at 100× magnification (see reference). Figure 2 (as shown in B in the image);

[0060] (4) Take photos from 0-6s in the video data recorded by the microscope and observe the distribution pattern of silica powder particles embedded in the solid hydrate structure.

[0061] (5) Use ImageJ software to count the positions of the silicone balls in the captured photos and measure the specific pixel coordinates; capture photos continuously within 0-6 seconds and measure the pixel coordinates of the silicone balls;

[0062] (6) Use Origin or Excel plotting software to plot the change of pixel coordinates over time;

[0063] (7) By comparing and analyzing the changes in the position of the silica gel balls embedded in the solid hydrate structure over time, the surface creep law of the solid hydrate structure and the flow law of liquid water on the surface of the hydrate structure can be obtained.

[0064] Example 3

[0065] Compared with Example 2, the difference is that step (1) is different, while the rest of the steps are the same.

[0066] Step (1) includes: adding silica gel powder particles with an average particle size of 28-56 μm at a mass ratio of 10 wt% to the mother liquor for hydrate formation, and adding yellow clay at a mass ratio of 0.5%. The yellow clay is mainly used to dye the white hydrate brown to facilitate the identification and observation of the silica gel spheres. In this embodiment, the mother liquor is a mixed solution of water and reaction promoter SDS (sodium dodecyl sulfate), and the mass ratio of SDS in the mother liquor is 0.5%.

[0067] Solid hydrates exhibit slow surface creep and strong water absorption during their growth, but currently, there is no quantitative method to study this process in depth. The advantages of the method for studying the creeping behavior of hydrates provided in this invention are as follows: Before hydrate formation, silica gel powder particles with an average particle size of micrometers can be incorporated into the mother liquor at a certain mass ratio. As the hydrate climbs along the reactor wall, it carries the microparticles with it. At this time, a microscope with magnification is used to record the microparticles embedded in the solid hydrate structure, and the pixel coordinates of the microparticles are quantitatively measured using ImageJ image quantification software. By observing the coordinate changes of a large number of randomly distributed microparticles, the surface creeping behavior of the hydrate structure can be quantitatively studied. Furthermore, based on the creeping behavior, the flow pattern of liquid water at the hydrate surface can be quantitatively deduced.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0069] References:

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Claims

1. A method for monitoring the surface peristalsis of a solid hydrate structure, characterized by, It comprises the following steps: In the mother liquor of natural gas hydrate, a test proportion of micro powder is added, the gas is filled, and under the condition of constant pressure, the method of separately cooling the top is used to induce the upward climbing growth of solid hydrate along the wall of the cubic reactor, the upward climbing growth process of solid hydrate is monitored and imaged in real time through a microscope, the pixel coordinates of the micro powder are measured, the change rule of the pixel coordinates with time is obtained, and then the surface creep rule of the solid hydrate structure is obtained; the average particle size of the micro powder is 0.1-100µm. The test proportion is 0.5-20wt%; the micro powder is color developing powder, latex powder or rubber powder, and the color developing powder is selected from at least one of clay, silica gel powder and barium sulfate powder.

2. The method of claim 1, wherein the solid hydrate structure surface peristalsis regularity is monitored by: The average particle size of the micro powder is 28-56µm.

3. The method of claim 1, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The gas is carbon dioxide or methane.

4. The method of claim 3, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The constant pressure refers to a constant pressure less than 10MPa.

5. The method of claim 1, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The top is cooled to a temperature of 0-10℃.

6. The method of claim 1, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The microscope is a digital microscope. The digital microscope is a 10×-200×digital microscope.

7. The method of claim 6, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The digital microscope is a 100×digital microscope.

8. The method of claim 6, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The imaging is continuous imaging within a continuous time period of 0-100s.

9. The method of claim 8, wherein the solid hydrate structure surface peristalsis regularity is monitored by a method comprising: The imaging is continuous imaging within a continuous time period of 0-10s.

10. The method of claim 8, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, The imaging is continuous imaging within a continuous time period of 0-6s.

11. The method of claim 8, wherein the solid hydrate structure surface peristalsis regularity monitoring method is characterized by, By comparing and analyzing the position change rule of the silica gel powder embedded in the solid hydrate structure with time, the surface creep rule of the solid hydrate structure and the flow rule of liquid water on the hydrate structure surface are obtained.

Images