A method for identifying hydrate phase changes

Abstract

The application discloses a method for identifying hydrate phase change, comprising: acquiring original Raman spectrum graphs of a hydrate to be evaluated in a first wave band range at different time nodes; performing peak type fitting on Raman features of the original Raman spectrum graphs in a second wave band range, and identifying a first fitting peak of intermolecular hydrogen bond Raman spectrum in a bending vibration state and a second fitting peak in a stretching vibration state, wherein the second wave band range is a subset of the first wave band range; calculating the maximum peak intensity and the integral peak area of the first fitting peak, and calculating the maximum peak intensity and the integral peak area of the second fitting peak, and based on this, determining the phase change of the hydrate to be evaluated. The method has strong universality, can be applied to various types of gas hydrates and various application scenarios, is simple to operate, and has high sensitivity.

Description

Technical Field

[0001] This invention relates to the field of petroleum and natural gas gas hydrate crystallization and growth technology, and in particular to a method for identifying phase changes in hydrates. Background Technology

[0002] Natural gas hydrate, also known as combustible ice, is an ice-like crystalline substance composed of water and natural gas under high pressure and low temperature conditions. It is a special type of gas hydrate. Natural gas hydrate is a vast, clean, and unconventional energy resource, and one of my country's strategic resources. It has also been designated as my country's 173rd mineral resource. Deep-sea exploration of natural gas hydrate, especially in-situ, real-time, and continuous exploration, is fundamental and crucial for conducting deep-sea research and studying the distribution and resource assessment of natural gas hydrate.

[0003] Laser Raman spectroscopy is a powerful tool for analyzing and determining the structure of hydrates and monitoring their phase changes in real time in the laboratory. In addition, existing technologies have enabled the on-site detection of natural gas hydrates exposed on the seabed using deep-sea laser Raman spectroscopy probes carried by unmanned submersibles.

[0004] Currently, the laser Raman spectroscopy bands commonly used in the study of gas hydrates mainly consist of the characteristic peaks of carbon-hydrogen bond vibrations in alkanes. This analysis is quite cumbersome. For common hydrocarbons in gas hydrates such as methane, ethane, propane, and butane, their carbon-hydrogen bond vibrations correspond to different Raman spectra, resulting in poor universality of the method. Specific analytical methods need to be developed for each type of hydrocarbon component. In addition, the analysis of carbon-hydrogen bond vibration peaks requires high-precision testing instruments, and deficiencies in testing accuracy can introduce systematic errors into the analytical results.

[0005] Therefore, existing technologies need to provide a universal Raman spectroscopy rapid identification scheme for gas hydrates to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for identifying phase changes in hydrates, characterized by comprising: acquiring the original Raman spectra of the hydrate to be evaluated at different time points within a first waveband; performing peak shape fitting on the Raman features of the original Raman spectra within a second waveband, and identifying a first fitted peak exhibiting bending vibration and a second fitted peak exhibiting stretching vibration in the Raman spectra of intermolecular hydrogen bonds, wherein the second waveband is a subset of the first waveband; calculating the maximum peak intensity and integrated peak area of ​​the first fitted peak, and calculating the maximum peak intensity and integrated peak area of ​​the second fitted peak, thereby determining the phase change of the hydrate to be evaluated.

[0007] Preferably, the step of fitting the Raman features of the Raman spectrum in the second band range and identifying the first fitting peak in the bending vibration state and the second fitting peak in the stretching vibration state of the intermolecular hydrogen bond Raman spectrum includes: fitting the intermolecular hydrogen bond Raman broad band in the original Raman spectrum with three fitting peaks, wherein the three fitting peaks are characteristic peaks in the original Raman spectrum.

[0008] Preferably, the step of calculating the maximum peak intensity and integrated peak area of ​​the first fitted peak, and the maximum peak intensity and integrated peak area of ​​the second fitted peak, and determining the phase change of the hydrate to be evaluated based on this, includes: calculating the ratio of the maximum peak intensity of the second fitted peak to the maximum peak intensity of the first fitted peak at different time points, denoted as the peak intensity ratio; calculating the ratio of the integrated peak area of ​​the second fitted peak to the integrated peak area of ​​the first fitted peak at different time points, denoted as the area ratio; and identifying the phase change of the hydrate to be evaluated at different times based on the peak intensity ratio and / or area ratio.

[0009] Preferably, when the peak intensity ratio is less than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution; when the peak intensity ratio is greater than 1, the phase state of the hydrate to be evaluated is determined to be hydrate phase.

[0010] Preferably, when the area ratio is less than 3 and greater than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution; when the area ratio is greater than 3, the phase state of the hydrate to be evaluated is determined to be hydrate phase.

[0011] Preferably, when the peak intensity ratio is less than 1 and the area ratio is less than 3 but greater than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution; when the peak intensity ratio is greater than 1 and the area ratio is greater than 3, the phase state of the hydrate to be evaluated is determined to be hydrate phase.

[0012] Preferably, the center positions of the three fitted peaks are located at 85 cm⁻¹ of the original Raman spectrum. -1 135cm -1 and 210cm -1 At this location, 85cm -1 The characteristic peak at the position was determined as the first fitted peak and 210cm was used. -1 The fitted peak at the specified position is determined to be the second fitted peak.

[0013] Preferably, the phase change process of hydrates includes, but is not limited to: the synthesis process of gas hydrates in the laboratory, the decomposition process of gas hydrates in the laboratory, the accumulation process of gas hydrates in nature, the in-situ decomposition process of gas hydrates during field development, and the process of hydrate blockage in oil and gas transportation pipelines.

[0014] Preferably, the hydrate to be evaluated is a hydrate of pure gas components or a hydrate of mixed gas components, wherein the components of the hydrate are selected from one or more of methane, ethane, propane, butane, carbon dioxide, hydrogen sulfide and nitrogen.

[0015] Preferably, when acquiring the Raman spectra at different time points, a stable laser with an energy of 5-10 mW and a wavelength of 532 nm or 785 nm is selected, an integration time of 2-5 s is selected, and the number of integrations is 5-15.

[0016] Preferably, the method further includes: performing baseline correction on the original Raman spectrum.

[0017] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0018] This invention proposes a method for rapidly identifying phase changes of hydrates using Raman spectroscopy. This method is highly versatile and applicable to various types of gaseous hydrates, including but not limited to methane, ethane, propane, butane, carbon dioxide, hydrogen sulfide, and nitrogen. It can be applied to hydrates of pure or mixed gases. This method has low precision requirements. By optimizing laser Raman measurement parameters specifically for various gaseous hydrates, it effectively avoids the instability and decomposition of gaseous hydrates caused by excessive laser power while ensuring accuracy. Furthermore, this invention is simple to operate, highly sensitive, and does not require operators with strong professional backgrounds or familiarity with the Raman characteristic peaks of specific gas molecules. It can be widely applied to various scenarios, including indoor experimental research, field exploration, and on-site monitoring in mining operations.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0021] Figure 1This is a step diagram of a method for identifying phase changes of hydrates according to an embodiment of this application.

[0022] Figure 2 This is an example diagram of a Raman spectrum after peak shape fitting in a method for identifying phase changes of hydrates according to an embodiment of this application.

[0023] Figure 3 This is a Raman spectral image of the hydrogen bond stretching vibration during the formation of gas hydrates in a method for identifying phase changes of hydrates according to an embodiment of this application. Detailed Implementation

[0024] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0025] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0026] Natural gas hydrate, also known as combustible ice, is an ice-like crystalline substance composed of water and natural gas under high pressure and low temperature conditions. It is a special type of gas hydrate. Natural gas hydrate is a vast, clean, and unconventional energy resource, and one of my country's strategic resources. It has also been designated as my country's 173rd mineral resource. Deep-sea exploration of natural gas hydrate, especially in-situ, real-time, and continuous exploration, is fundamental and crucial for conducting deep-sea research and studying the distribution and resource assessment of natural gas hydrate.

[0027] Laser Raman spectroscopy is a powerful tool for analyzing and determining the structure of hydrates and monitoring their phase changes in real time in the laboratory. In addition, existing technologies have enabled the on-site detection of natural gas hydrates exposed on the seabed using deep-sea laser Raman spectroscopy probes carried by unmanned submersibles.

[0028] Currently, the laser Raman spectroscopy bands commonly used in the study of gas hydrates mainly consist of the characteristic peaks of carbon-hydrogen bond vibrations in alkanes. This analysis is quite cumbersome. For common hydrocarbons in gas hydrates such as methane, ethane, propane, and butane, their carbon-hydrogen bond vibrations correspond to different Raman spectra, resulting in poor universality of the method. Specific analytical methods need to be developed for each type of hydrocarbon component. In addition, the analysis of carbon-hydrogen bond vibration peaks requires high-precision testing instruments, and deficiencies in testing accuracy can introduce systematic errors into the analytical results.

[0029] Therefore, to address one or more of the aforementioned technical problems, this application proposes a method for identifying phase changes in hydrates. Whether used for determining phase transition points in indoor gas hydrate formation experiments or for in-situ detection of gas hydrates in extreme environments using Raman spectroscopy, this method is based on gas hydrate identification. It develops novel and universal rapid Raman spectroscopy identification schemes for different types of gas hydrates and / or those containing different gas components. This provides significant guidance for determining the time points of phase changes in gas hydrates and for studying the microscopic occurrence processes of gas hydrates in nature.

[0030] Figure 1 This diagram illustrates the steps of a method for identifying phase changes in hydrates according to an embodiment of this application. Figure 1 As shown, the method for identifying phase changes of hydrates (hereinafter referred to as the "phase change identification method") according to the embodiments of the present invention includes the following steps: Step S110: Obtain the original Raman spectra of the hydrate to be evaluated at different time points in the first band range; Step S120: Perform peak shape fitting on the Raman features of the original Raman spectra obtained in Step S110 in the second band range, and identify the first fitting peak in the bending vibration state and the second fitting peak in the stretching vibration state of the intermolecular hydrogen bond Raman spectrum, wherein the second band range is a subset of the first band range; Finally, Step S130: Calculate the maximum peak intensity and integrated peak area of ​​the first fitting peak obtained in Step S120, and calculate the maximum peak intensity and integrated peak area of ​​the second fitting peak obtained in Step S120. Then, determine the phase change of the hydrate to be evaluated based on the maximum peak intensity and integrated peak area of ​​the first fitting peak and the maximum peak intensity and integrated peak area of ​​the second fitting peak.

[0031] It should be noted that the hydrate to be evaluated in the embodiments of the present invention is a hydrate of pure gas components or a hydrate of mixed gas components. The components of the hydrate to be evaluated are selected from one or more of methane, ethane, propane, butane, carbon dioxide, hydrogen sulfide, and nitrogen. Furthermore, in the embodiments of the present invention, the phase change process of the hydrate to be evaluated includes, but is not limited to: the synthesis process of gaseous hydrates in the laboratory, the decomposition process of gaseous hydrates in the laboratory, the accumulation process of gaseous hydrates in nature, the in-situ decomposition process of gaseous hydrates during field development, and the process of hydrate blockage in oil and gas transportation pipelines.

[0032] Further, in step S110, it is necessary to obtain the (dynamic) original Raman spectra of the hydrate to be evaluated at different time points during the phase change process. The wavelength range of the original Raman spectra is the first wavelength range. In this embodiment of the invention, the first wavelength range is 20–1000 cm⁻¹. -1 .

[0033] To determine the phase change process of gas hydrates, appropriate instrument parameters are needed to measure the phase changes of the hydrate under evaluation at different time points from 20 to 1000 cm⁻¹. -1 Raman spectra within a specific wavelength range. Specifically, when continuously conducting Raman spectroscopy tests on the phase change process of the hydrate under evaluation and obtaining dynamic raw Raman spectra (raw Raman spectra at different times), a stable laser with energy of 5–10 mW at a wavelength of 532 nm or 785 nm is selected, an integration time of 2–5 s is used, and the number of integrations is 5–15. Therefore, this invention can ensure the quality of the obtained raw Raman spectra as much as possible while avoiding laser-induced hydrate decomposition.

[0034] To ensure the accuracy of peak shape fitting of the original Raman spectrum, this embodiment of the invention requires baseline correction of the original Raman spectrum after obtaining it, and then proceeds to step S120 after baseline correction is completed.

[0035] In step S120, the Raman characteristics of the original Raman spectrum obtained in step S110 need to be fitted in the second band range. In this embodiment of the invention, the second band range is 60–300 cm⁻¹. -1 .

[0036] In a preferred embodiment, step S120 uses three fitting peaks to perform peak shape fitting on the broad Raman band of intermolecular hydrogen bonds in the original Raman spectrum. The three fitting peaks used as the peak shape fitting standard are three characteristic peaks from the original Raman spectrum.

[0037] Furthermore, the peak centers of the three fitted peaks are located at 85 cm⁻¹ of the original Raman spectrum. -1 135cm -1 and 210cm -1 Location. Among them, 85cm -1 The characteristic peak at position 210cm was determined as the first fitting peak, and the 210cm peak was used as the first fitting peak. -1 The fitted peak at the given location was determined to be the second fitted peak.

[0038] Specifically, in step S120, the original Raman spectrum is first baseline corrected, and then the Lorentz line function is used to correct the baseline of the spectrum from 60 to 300 cm⁻¹. -1 The Raman characteristic broad bands between them, with the peak center position at 85 cm⁻¹ respectively. -1 135cm -1 and 210cm -1Three nearby characteristic peaks were used to fit the broad Raman band of intermolecular hydrogen bonds. Additionally, the peak shape fitting results for the three original Raman spectra corresponding to the three fitted peaks were obtained (see...). Figure 2 After obtaining the three gray curves in the image, the fitting results of the three peaks are compared with the original Raman spectrum to obtain the first fitting peak used to characterize the bending vibration state of the Raman spectrum of intermolecular hydrogen bonds and the second fitting peak used to characterize the stretching vibration state of the Raman spectrum of intermolecular hydrogen bonds.

[0039] Figure 2 This is an example diagram of a Raman spectrum after peak shape fitting in a method for identifying phase changes of hydrates according to an embodiment of this application. Figure 2 This paper presents the original Raman spectrum at a certain time point during the phase change of the hydrate under evaluation, and the fitting results of three peaks formed after fitting the original Raman spectrum to the broad band of the corresponding Raman shift using three characteristic peaks. Figure 2 As shown, after peak shape fitting, 85cm was used -1 The fitted peak corresponds to the bending vibration of intermolecular hydrogen bonds (O…O…O), and 210 cm⁻¹ -1 The fitted peak corresponds to the stretching vibration of intermolecular hydrogen bonds (O…O).

[0040] After obtaining the first and second fitting peaks, proceed to step S130. In practical applications, because the hydrogen bonds of water molecules in liquid water are constantly in a dynamic process of formation and breakage, the stretching vibration intensity of unstable hydrogen bond structures is relatively weak, and bending vibrations dominate. However, in hydrated phases, a stable hydrogen bond network is formed between water molecules, resulting in intermolecular hydrogen bonds reaching a maximum strength of 210 cm⁻¹. -1 The intensity of the nearby stretching bands increases.

[0041] Based on the above principles, in step S130 of this embodiment of the invention, on the one hand, the ratio of the maximum peak intensity of the second fitted peak to the maximum peak intensity of the first fitted peak is calculated under different time node spectra, and recorded as the peak intensity ratio; simultaneously, the ratio of the integrated peak area of ​​the second fitted peak to the integrated peak area of ​​the first fitted peak is calculated under different time node spectra, and recorded as the area ratio. Finally, based on the peak intensity ratio and / or area ratio under the same time node spectrum, the real-time phase state of the hydrate to be evaluated under different time nodes is identified, thereby identifying the phase state change of the current hydrate.

[0042] In other words, embodiments of the present invention can comprehensively determine the phase state of gas hydrates by using both the maximum peak intensity ratio (peak intensity ratio) and the integrated peak area ratio (area ratio), or a single indicator can be used to roughly identify the phase state of hydrates. Combining the two determination indicators can improve the accuracy of identifying changes in the phase state of hydrates.

[0043] Specifically, calculate 85cm respectively. -1 and 210cm -1 The maximum peak intensity I of the two fitted peaks at the position max,i and the integral peak area A i Where i = 1 represents 85cm -1 The first fitted peak, i=2 represents 210cm. -1 The second fitted peak. Then, the relative ratio of the maximum peak intensity I is calculated. max,2 / I max,1 The calculation result is recorded as the peak intensity ratio. At the same time, the relative ratio of the integral peak area A2 / A1 is calculated, and the calculation result is recorded as the area ratio.

[0044] In the first embodiment, when using the peak intensity ratio as an indicator for evaluating hydrate phase changes, the evaluation criterion applicable in the current example is: when the peak intensity ratio at the current time point is less than 1 (i.e., I...). max,2 / I max,1 If the value is less than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution; if the peak intensity ratio at the current time point is greater than 1 (i.e., I...), then... max,2 / I max,1 If the value is greater than 1, the phase state of the hydrate to be evaluated is determined to be the hydrate phase.

[0045] In the second embodiment, when using the area ratio as an identification index for evaluating the phase change of hydrates, the evaluation criteria applicable in the current example are as follows: when the area ratio at the current time point is less than 3 and greater than 1 (i.e., the A2 / A1 value is distributed between 1 and 3), the phase of the hydrate to be evaluated is determined to be liquid water or aqueous solution; when the area ratio at the current time point is greater than 3 (i.e., the A2 / A1 value is greater than 3), the phase of the hydrate to be evaluated is determined to be hydrate phase.

[0046] In the third embodiment, when both the area ratio and the peak ratio are used as identification indicators for evaluating hydrate phase changes, the evaluation criteria applicable in the current example are: when the peak intensity ratio is less than 1 and the area ratio is less than 3 but greater than 1 at the current time point (i.e., I...). max,2 / I max,1 If the value is less than 1, and the A2 / A1 value is between 1 and 3, the phase of the hydrate to be evaluated is determined to be liquid water or aqueous solution; when the peak intensity ratio is greater than 1 and the area ratio is greater than 3 at the current time point (i.e., I...), the phase of the hydrate to be evaluated is determined to be liquid water or aqueous solution. max,2 / I max,1 If the value is greater than 1 and the A2 / A1 value is greater than 3, the phase state of the hydrate to be evaluated is determined to be the hydrate phase.

[0047] Thus, embodiments of the present invention observe the spectra at different times during the hydrate formation process. max,2 / I max,1 The real-time numerical changes of A2 / A1 are used to dynamically identify phase changes in gas hydrates. Specifically, when the peak intensity ratio of the evaluated hydrate changes from less than 1 to greater than 1, and / or the area ratio changes from less than 3 to greater than 3, the transition from liquid to hydrate phase of the hydrate under evaluation can be determined, and the timing of the transition is recorded. Similarly, when the peak intensity ratio of the evaluated hydrate changes from greater than 1 to less than 1, and / or the area ratio changes from greater than 3 to less than 3, the transition from hydrate phase to liquid phase of the hydrate under evaluation can be determined, and the timing of the transition is recorded.

[0048] The following detailed description of the specific process of the hydrate phase change identification method described in the embodiments of the present invention will be provided through several specific examples.

[0049] Example 1

[0050] This embodiment 1 provides a method for identifying phase changes in the synthesis process of gas hydrates in the laboratory, specifically including the following steps:

[0051] First, inject pure water or aqueous solution into the pressure-resistant sealed container, turn on the vacuum pump and continuously evacuate the vacuum for at least one minute each time, until the vacuum pressure value remains unchanged after two consecutive evacuations.

[0052] The second step involves introducing gas components, including but not limited to methane, ethane, propane, butane, carbon dioxide, hydrogen sulfide, and nitrogen, according to the type of target gas hydrate. The system temperature and pressure conditions are controlled above the hydrate stable phase equilibrium curve. Then, the inlet and outlet valves of the pressure-resistant sealed container are closed, and hydrates are generated under constant volume conditions. The temperature and pressure changes inside the pressure-resistant sealed container are monitored in real time.

[0053] The third step involves using a frequency-stabilized laser source with a wavelength of 532 nm or 785 nm, a laser energy of 5–10 mW, and an integration time of 2–5 seconds to continuously perform Raman spectroscopy measurements on the hydrate formation process. The number of integrations is 5–15, and the spectral range covers 20–1000 cm⁻¹. -1 .

[0054] The fourth step is to perform baseline correction on the Raman spectrum, using the Lorentz line function to correct the baseline of the 60–300 cm⁻¹ spectrum. -1 Peak shape fitting is performed on the broad Raman characteristic bands between them. Preferably, refer to the appendix. Figure 2 As shown, three fitting peaks were used to fit the broad Raman band of intermolecular hydrogen bonds, with the peak center positions controlled at 85 cm⁻¹. -1 135cm-1 and 210cm -1 Nearby, including 85cm -1 The fitted peak corresponds to the intermolecular hydrogen bond bending vibration, while 210 cm⁻¹ -1 The fitting peak corresponds to the stretching vibration of intermolecular hydrogen bonds.

[0055] Step 5, calculate 85cm -1 and 210cm -1 The two fitted peaks at the location have the maximum peak intensity Imax,i and the integral peak area Ai, where i = 1 represents 85cm. -1 The fitted peak, i=2 represents 210cm -1 The fitted peaks were analyzed, and the relative ratios of maximum peak intensity (Imax,2 / Imax,1) and integrated peak area (A2 / A1) were calculated. For liquid water or aqueous solutions, Imax,2 / Imax,1 is less than 1, and A2 / A1 ranges from 1 to 3. For hydrates, Imax,2 / Imax,1 is greater than 1, and A2 / A1 is greater than 3. Therefore, by observing the trends of Imax,2 / Imax,1 and A2 / A1 at different times during hydrate formation, a transition from liquid to hydrate phase can be determined when the relative ratio of maximum peak intensity (Imax,2 / Imax,1) changes from less than 1 to greater than 1, or when the relative ratio of integrated peak area (A2 / A1) changes from between 1 and 3 to greater than 3.

[0056] Example 2

[0057] This embodiment 2 provides a Raman imaging scanning method for the formation of gas hydrates using hydrogen bond stretching vibrations, which can determine the spatial heterogeneity of hydrate phase changes. The method specifically includes the following steps:

[0058] The first step is to inject pure water or aqueous solution into a pressure-resistant reactor with a sapphire window, evacuate the reactor, and then introduce the gas of the target component. The temperature and pressure conditions of the system are controlled above the equilibrium curve of the stable phase of the hydrate, and the hydrate is generated under constant volume conditions.

[0059] The second step involves using a frequency-stabilized laser source with a wavelength of 532 nm or 785 nm, a laser energy of 5–10 mW, and an integration time of 2–5 seconds to conduct Raman spectral imaging scans of the hydrate formation process. Based on the target scanning area, an appropriate scanning step size and number of scanning points are selected, covering a spectral range of 20–1000 cm⁻¹. -1 .

[0060] The third step is to use the peak center at 210cm. -1 Using the intensity of nearby Raman characteristic peaks as an indicator, a Raman spectral image was plotted. (See attached reference.) Figure 3 ( Figure 3 This is a Raman spectral image of the hydrogen bond stretching vibration during the formation of gas hydrates in the method for identifying phase changes of hydrates according to an embodiment of this application. The Raman imaging results show the Raman spectral intensity as the brightness of the color patch at the scanning point corresponds to the intensity of the Raman spectrum, with brighter areas representing 210 cm⁻¹. -1 The stronger Raman characteristic peaks in the vicinity indicate that the stretching vibrations of intermolecular hydrogen bonds dominate, and the more stable the hydrate phase structure, the earlier the phase change occurs in the region. Figure 3 The darker part in the text represents 210cm. -1 The Raman characteristic peaks in the vicinity are relatively weak, and the stretching vibrations of intermolecular hydrogen bonds are weak, corresponding to regions where phase changes occur slowly. Thus, the spatial heterogeneity of phase changes in hydrates can be determined.

[0061] This invention discloses a method for rapidly identifying phase changes of hydrates using Raman spectroscopy. This method is highly versatile and applicable to various types of gaseous hydrates, including but not limited to methane, ethane, propane, butane, carbon dioxide, hydrogen sulfide, and nitrogen. It can be applied to hydrates of pure or mixed gases. This method has low precision requirements. By optimizing laser Raman measurement parameters specifically for various gaseous hydrates, it effectively avoids the instability and decomposition of gaseous hydrates caused by excessive laser power while ensuring accuracy. Furthermore, this invention is simple to operate, highly sensitive, and does not require operators with strong professional backgrounds or familiarity with the Raman characteristic peaks of specific gas molecules. It can be widely applied to various scenarios, including indoor experimental research, field exploration, and on-site monitoring in mining operations.

[0062] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0063] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0064] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0065] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for identifying phase changes in hydrates, characterized in that, include: Obtain the original Raman spectra of the hydrate to be evaluated at different time points within the first wavelength range, which is 20–1000 cm⁻¹. -1 ; Using the center position at 85cm respectively -1 135cm -1 and 210cm -1 Three characteristic peaks were used to fit the broad Raman band of intermolecular hydrogen bonds in the second band of the original Raman spectrum. The fitting results of the three peaks were compared with the original Raman spectrum to obtain a first fitting peak characterizing the bending vibration state of the intermolecular hydrogen bond Raman spectrum and a second fitting peak characterizing the stretching vibration state of the intermolecular hydrogen bond Raman spectrum. The second band range is a subset of the first band range, and the second band range is 60~300 cm⁻¹. -1 ; Calculate the maximum peak intensity and integrated peak area of ​​the first fitted peak, and calculate the maximum peak intensity and integrated peak area of ​​the second fitted peak. Based on this, determine the phase change of the hydrate to be evaluated, including: At different time points, the ratio of the maximum peak intensity of the second fitted peak to the maximum peak intensity of the first fitted peak is calculated and denoted as the peak intensity ratio. At different time points, the ratio of the integral peak area of ​​the second fitted peak to the integral peak area of ​​the first fitted peak is calculated and denoted as the area ratio. Based on the peak intensity ratio and / or area ratio at the same time point, the phase changes of the hydrate to be evaluated at different times are identified.

2. The method according to claim 1, characterized in that, When the peak intensity ratio is less than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution; When the peak intensity ratio is greater than 1, the phase state of the hydrate to be evaluated is determined to be the hydrate phase.

3. The method according to claim 1, characterized in that, When the area ratio is less than 3 and greater than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution; When the area ratio is greater than 3, the phase of the hydrate to be evaluated is determined to be the hydrate phase.

4. The method according to claim 1, characterized in that, When the peak intensity ratio is less than 1 and the area ratio is less than 3 but greater than 1, the phase state of the hydrate to be evaluated is determined to be liquid water or aqueous solution. When the peak intensity ratio is greater than 1 and the area ratio is greater than 3, the phase of the hydrate to be evaluated is determined to be the hydrate phase.

5. The method according to claim 1, characterized in that, 85cm -1 The characteristic peak at the position was determined as the first fitted peak, and the 210cm peak was... -1 The fitted peak at the specified position is determined to be the second fitted peak.

6. The method according to any one of claims 1 to 5, characterized in that, The phase change process of hydrates includes, but is not limited to: the synthesis process of gas hydrates in the laboratory, the decomposition process of gas hydrates in the laboratory, the accumulation process of gas hydrates in nature, the in-situ decomposition process of gas hydrates in field development, and the formation process of hydrate blockage in oil and gas transportation pipelines.

7. The method according to any one of claims 1 to 5, characterized in that, The hydrate to be evaluated is a hydrate of pure gas components or a hydrate of mixed gas components, wherein the components of the hydrate are selected from one or more of methane, ethane, propane, butane, carbon dioxide, hydrogen sulfide and nitrogen.

8. The method according to any one of claims 1 to 5, characterized in that, When acquiring the Raman spectra at different time points, a stable laser with an energy of 5~10mW and a wavelength of 532nm or 785nm is selected, an integration time of 2~5s is selected, and the number of integrations is 5~15.

9. The method according to any one of claims 1 to 5, characterized in that, The method further includes: baseline correction of the original Raman spectrum.

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