A method for in-situ identification of solid bitumen in shale based on electron microscope-raman spectrum

Abstract

The application discloses a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy, and relates to the field of oil geological detection, which comprises the following steps: obtaining a whole rock optical section, performing in-situ identification operation to obtain a chemical structure spatial distribution map of the solid bitumen block; the in-situ identification operation comprises the following steps: using an optical microscope to identify and mark the solid bitumen; using the photo-electricity combined function of a field emission scanning electron microscope to determine the position of the mark in the electron microscope field of view, and then obtaining a surface morphology characteristic image of the solid bitumen block; based on the image positioning function of a Raman spectrometer, using the area scanning mode of the Raman spectrometer to determine the Raman area scanning image of the solid bitumen block; and superimposing the surface morphology characteristic image and the Raman area scanning image to generate the chemical structure spatial distribution map. The application realizes the matching of the solid bitumen image data obtained by different devices, and is helpful for accurate analysis of the solid bitumen in shale.

Description

Technical Field

[0001] This application relates to the field of petroleum geological exploration, and in particular to a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy. Background Technology

[0002] Organic matter in shale is a major source of oil and natural gas. Among them, solid bitumen, as an important secondary organic matter, contains a wealth of geological information in terms of its optical properties, electrical imaging characteristics, and chemical structure changes. It is of great significance for hydrocarbon generation and evolution in shale reservoirs and the development of organic pores, and is the foundation and key to studying the physical property control mechanism of shale reservoirs.

[0003] Currently, solid bitumen can be identified using only the white light and fluorescence modes of optical microscopy, but its chemical structure cannot be characterized. Scanning electron microscopy (SEM) imaging can clearly observe organic matter in shale, but it cannot reliably identify solid bitumen. Furthermore, chemical structure information is difficult to obtain under an electron microscope alone, requiring transfer to other instruments for chemical structure analysis. The conversion between different instruments makes it difficult to ensure testing at the same location, resulting in mismatches between SEM and Raman spectroscopy data. Summary of the Invention

[0004] The purpose of this application is to provide a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy, which realizes the matching of solid bitumen image data acquired under different devices, and helps to accurately analyze solid bitumen in shale.

[0005] To achieve the above objectives, this application provides the following solution:

[0006] In a first aspect, this application provides a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy, comprising:

[0007] Obtain several whole-rock slides from different evolutionary stages;

[0008] For each whole-rock radiograph, in-situ identification was performed to obtain a spatial distribution map of the chemical structure of each solid bitumen block in the whole-rock radiograph;

[0009] The specific process of the in-situ identification operation is as follows:

[0010] Using an optical microscope, solid bitumen in whole-rock light sections was identified, and each identified solid bitumen block was marked on the whole-rock light section to obtain a marked optical microscopic image of each solid bitumen block;

[0011] The whole rock light section was placed in a field emission scanning electron microscope (SEM). Using the optical-electronic coupling function of the SEM, the positional correspondence between the image under the electron microscope field of view and the marked optical micrograph of each solid bitumen block in the whole rock light section was determined. Thus, the position of the mark of each solid bitumen block in the whole rock light section in the image under the electron microscope field of view was determined.

[0012] Based on the position of the marker of each solid bitumen block in the whole rock light section in the electron microscope field of view, the surface morphology feature image of each solid bitumen block in the whole rock light section is obtained by field emission scanning electron microscopy.

[0013] The whole rock light section was moved under the lens of the Raman spectrometer. Using the image positioning function of the Raman spectrometer, the positional correspondence between the image under the Raman field of view and the surface morphology feature image of each solid bitumen block in the whole rock light section was determined. Then, the Raman surface scan image of each solid bitumen block in the whole rock light section was determined using the surface scan mode of the Raman spectrometer.

[0014] The surface morphology feature images and Raman surface scan images of each solid bitumen block in the whole rock radiograph are overlaid to generate a spatial distribution map of the chemical structure of each solid bitumen block.

[0015] According to the specific embodiments provided in this application, this application has the following technical effects:

[0016] This application provides a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy. First, solid bitumen is identified using an optical microscope, and each identified solid bitumen block is marked on a whole-rock section, thus obtaining a marked optical microscopic image of each solid bitumen block. The whole-rock section is then placed in a field emission scanning electron microscope (FET). Using the FET's photo-electron coupling function, the positional correspondence between the image in the FET field of view and the marked optical microscopic image of each solid bitumen block is determined, thereby determining the position of the mark of each solid bitumen block in the image in the FET field of view. This achieves precise positioning of the solid bitumen blocks in the FET field of view. Then, based on the position of the mark of each solid bitumen block in the image in the FET field of view, the FET is used to... This method acquires surface morphology images of each solid asphalt block, enabling the accurate identification of the blocks and the application of scanning electron microscopy (SEM) to obtain their surface morphology features. The whole-rock section is then moved to the lens of a Raman spectrometer. Utilizing the Raman spectrometer's image positioning function, the positional correspondence of the surface morphology feature images of each solid asphalt block within the Raman field of view is determined. Furthermore, the Raman surface scan image (chemical structure image) of each solid asphalt block is determined using the Raman spectrometer's area scan mode. This also enables the accurate identification of solid asphalt blocks and the acquisition of their chemical structure using Raman spectroscopy. Finally, the surface morphology feature images and Raman surface scan images of each solid asphalt block in the whole-rock section are overlaid to generate a spatial distribution map of the chemical structure of each block. Through this method, this application achieves the matching of solid asphalt image data acquired using different devices, which is of great significance for the accurate analysis of solid asphalt in shale. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy, provided as an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of a full-rock radiograph provided in an embodiment of this application;

[0020] Figure 3 A schematic diagram of an optical micrograph of a whole-rock light section in reflected white light mode provided in an embodiment of this application;

[0021] Figure 4A schematic diagram of an optical micrograph of a whole-rock radiograph in fluorescence mode provided in an embodiment of this application;

[0022] Figure 5 A schematic diagram of a whole-rock radiograph under the field of view of a field emission scanning electron microscope, provided in an embodiment of this application;

[0023] Figure 6 This is a schematic diagram of electron microscopy and Raman 3D visualization observation provided in an embodiment of this application. Detailed Implementation

[0024] This application relates to the application of electron microscopy-Raman spectroscopy in the field of petroleum geology. Addressing the problems of existing technologies, this application provides a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy (also referred to herein as a method for in-situ identification and chemical structure characterization of solid bitumen in shale based on electron microscopy-Raman spectroscopy). Utilizing integrated electron microscopy-Raman spectroscopy, the method describes the electroimaging characteristics of solid bitumen and obtains Raman surface distribution information and related Raman spectral parameters of solid bitumen at the same location to characterize its chemical structure. This overcomes the limitations of existing methods in determining the morphology and molecular structure of solid bitumen under in-situ conditions. This method provides a powerful tool for revealing the relationship between the morphology and chemical properties of solid bitumen and provides direct evidence for determining the hydrocarbon generation process of organic matter.

[0025] In this application, field emission scanning electron microscopy is used to observe the electroimaging characteristics of solid bitumen at the submicron scale, and an electron microscopy-nondestructive high-resolution micro Raman 3D imaging system is used to characterize the internal chemical structure of solid bitumen at different thermal evolution stages. This reveals the characteristics of solid bitumen under in-situ conditions and at the micro- and nano-scale, as well as the transformation law of its chemical structure. The multidimensional results of electron microscopy-Raman imaging are obtained in one go, which helps to reveal the cause of chemical structural heterogeneity at the molecular scale and provides a reference for identifying shale oil geological sweet spots.

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] In one exemplary embodiment, such as Figure 1 As shown, a method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy is provided, including the following steps:

[0029] Step 101: Obtain several whole-rock slides from different evolutionary stages.

[0030] Step 102: Perform in-situ identification for each whole-rock light slice to obtain a spatial distribution map of the chemical structure of each solid bitumen block in the whole-rock light slice.

[0031] The specific process of the in-situ identification operation is as follows:

[0032] Step 102.1: Using an optical microscope, identify the solid bitumen in the whole rock light section, and mark each identified solid bitumen block on the whole rock light section to obtain a marked optical microscopic image corresponding to each solid bitumen block.

[0033] Step 102.2: Place the whole rock light section into a field emission scanning electron microscope (SEM). Using the optical-electronic coupling function of the SEM, determine the positional correspondence between the image under the electron microscope field of view and the marked optical micrograph corresponding to each solid bitumen block in the whole rock light section. Then, determine the position of the mark of each solid bitumen block in the whole rock light section in the image under the electron microscope field of view.

[0034] As an alternative implementation, the same shale sample can be placed in a Zeiss Gemini 500 field emission scanning electron microscope, and the coordinates of the markers can be determined using a photoelectric coupling module to locate the same position. It is important to avoid carbon or gold sputtering on the sample, as this could interfere with the Raman signal.

[0035] Step 102.3: Based on the position of the marker of each solid bitumen block in the whole rock light section in the image under the electron microscope field of view, use field emission scanning electron microscope to obtain the surface morphology feature image of each solid bitumen block in the whole rock light section.

[0036] Step 102.4: Move the whole rock light slide under the lens of the Raman spectrometer, use the image positioning function of the Raman spectrometer to determine the positional correspondence between the image under the Raman field of view and the surface morphology feature image of each solid bitumen block in the whole rock light slide, and then use the surface scanning mode of the Raman spectrometer to determine the Raman surface scan image of each solid bitumen block in the whole rock light slide.

[0037] Before using a Raman spectrometer, a single-crystal silicon wafer (520.7 cm²) is required. -1 The Raman spectrometer was calibrated to ensure a wavenumber error of < ±0.5 cm⁻¹. -1 .

[0038] The area scan mode settings include: a scanning area of ​​10μm×7μm, a step size of 0.5μm, a total of 280 measurement points, a dwell time of 200 ms / pixel, and a laser power density adjusted to <1 mW / μm² using a neutral density filter to avoid carbonization.

[0039] Step 102.5: Overlay the surface morphology feature image (also known as electron microscopy image) and Raman surface scan image (also known as chemical structure map) of each solid bitumen block in the whole rock radiograph to generate a spatial distribution map of the chemical structure of each solid bitumen block.

[0040] As an alternative implementation, electron microscopy images and Raman surface scan images are overlaid using imageJ software to generate spatial distribution maps of chemical structures at different evolution stages.

[0041] As an optional implementation, different whole-rock sections are obtained by slicing different shale samples, and the slicing process for each shale sample is as follows:

[0042] Step 201: Using a diamond cutter, cut a first whole rock block of a predetermined size (e.g., 10 mm × 10 mm × 5 mm) perpendicular to the bedding plane of the shale sample. It is important to avoid damaging the bedding plane.

[0043] Step 202: Vacuum impregnation and curing treatment of the first whole rock block is performed using epoxy resin to obtain the second whole rock block.

[0044] Step 203: Polish the second whole rock block to obtain the third whole rock block.

[0045] Step 204: The third whole-rock block is dried to obtain a whole-rock slide. (See attached image) Figure 2 .

[0046] In this embodiment, shale samples from three evolution stages—low maturity, mature, and high maturity—were selected, so that the Ro values ​​of the shale samples covered the range of 0.7% to 2.0%.

[0047] As an optional implementation, in step 203, the second whole-rock block is polished to obtain the third whole-rock block, specifically including:

[0048] Step 203.1: Polish the second whole rock block step by step using diamond sandpaper of 600#, 1200# and 2000# until the surface roughness of the polished second whole rock block is <0.1μm.

[0049] Step 203.2: Using 0.05μm alumina polishing slurry, polish the second whole rock block again for a preset polishing time (e.g., 30 minutes) to ensure no scratches, and obtain the second whole rock block after repolishing.

[0050] Step 203.3: Place the second whole rock block, after further polishing, into a drying oven for drying to obtain the third whole rock block. The drying temperature and drying time of the drying oven can be set to 60℃ and 24 hours, respectively.

[0051] As an optional implementation, in step 102.1, solid bitumen in the whole-rock slide is identified using an optical microscope, and each identified solid bitumen block is marked on the whole-rock slide, specifically including:

[0052] Step 102.1.1: Using an optical microscope in reflected white light mode, observe and determine the distribution of solid bitumen in the whole rock slide using a 20x oil immersion microscope. A Leica DM4500P microscope can be used as the optical microscope.

[0053] Step 102.1.2: Based on the distribution of solid bitumen in the whole-rock slide, the (optical) morphological characteristics of the solid bitumen in the whole-rock slide are determined using a 50x oil immersion lens. See [link to relevant documentation]. Figure 3 .

[0054] Record the optical characteristics and morphology (such as stripes and granules) of typical solid bitumen under a 50x oil immersion lens.

[0055] Step 102.1.3: Switch the optical microscope to fluorescence mode to determine the fluorescence color of solid bitumen in the whole-rock slide. See [link to relevant documentation]. Figure 4 .

[0056] In fluorescence mode, the excitation wavelength is 450-490 nm, and the fluorescence color of solid asphalt is recorded.

[0057] Step 102.1.4: Based on the morphological characteristics and fluorescence color of solid bitumen in the whole rock slide, use a microhardness tester to mark the location of each solid bitumen block on the surface of the whole rock slide.

[0058] As an optional implementation method, cross marks (accuracy ±2μm) can be inscribed on the sample surface using a microhardness tester to record the coordinates of typical solid asphalt. Each sample should have at least 10 marked locations. One mark can be made for each asphalt block.

[0059] As an optional implementation, in step 102.3, based on the position of the marker of each solid bitumen block in the whole-rock light section in the image under the electron microscope field of view, a surface morphology feature image of each solid bitumen block in the whole-rock light section is obtained using a field emission scanning electron microscope, specifically including:

[0060] Step 102.3.1: For each solid bitumen block in the whole rock radiograph, based on the position of the solid bitumen block's mark in the image under electron microscopy, first determine the dark gray solid bitumen portion in the image under low voltage SEM and backscattered electron mode.

[0061] Step 102.3.2: Based on the dark gray solid bitumen portion in the electron microscope image, use high-magnification secondary electron mode to acquire the surface morphology feature image of each solid bitumen block in the whole-rock light section. See [link to relevant documentation]. Figure 5 and Figure 6 .

[0062] In this embodiment, to prevent issues due to poor sample conductivity, low-voltage SEM (10 keV) and backscattered electron (BSE) modes are preferred for observing the whole-rock radiograph to distinguish between dark gray solid bitumen and bright white minerals. The surface morphology of the solid bitumen is then observed and recorded in high-magnification secondary electron (SE) mode.

[0063] Regarding the identification characteristics of solid asphalt at different evolution stages: in the low maturity stage, solid asphalt often exhibits the characteristics of precursor kerogen; in the mature stage, solid asphalt fills the pores and exists in the mineral pores after cementation; in the high maturity stage, it replaces the primary organic matter to form a continuous organic matter network, on which sponge-like pores develop.

[0064] As an optional implementation, the in-situ identification operation further includes:

[0065] Step 102.6: Use the spot scan mode of the Raman spectrometer to acquire the spectral data of each solid bitumen block in each whole rock radiograph.

[0066] The spot scan mode uses a 473nm laser (8mW power, 1μm spot diameter), with a total of 3 scans (10s each), achieving a spectral resolution of 2cm. -1 Repeat the measurement three times to ensure that the relative standard deviation (RSD) is less than 5%.

[0067] The area scan mode selects a typical solid bitumen from the whole rock radiograph for scanning, while the spot scan mode scans different areas of a solid bitumen in the sample.

[0068] Figure 6 A schematic diagram of electron microscopy and Raman 3D visualization observation is shown; Figure 6 In the middle, the sample is a whole-rock radiograph. denoted by ; h represents Planck's constant, which serves as the bridge connecting the frequency and energy of a photon and is a fundamental constant in quantum mechanics; v 0 represents the frequency of the incident light, which is the natural frequency of the incident laser; h( v 0± v ) represents the frequency change caused by the energy exchanged between light and matter; hν0 represents the incident photon energy, representing the energy carried by a single photon in the incident laser; XYZ offset refers to the spatial distance the sample stage moves from under the electron gun of the scanning electron microscope to under the Raman objective (movement occurs along the X, Y, and Z axes).

[0069] Step 102.7: Use the Gauss-Lorentz peak fitting technique to fit the spectral data of each solid bitumen block in each whole rock slice to obtain the spectral curve of each solid bitumen block in each shale sample.

[0070] As an optional implementation, the obtained spectral data is first processed using Project software to remove fluorescence background and smooth it in real time (Savitzky-Golay, window width 9). Then, Gaussian-Lorentz peak fitting technique is used to achieve visualization and analysis of the spectral curves.

[0071] Step 102.8: Based on the spectral curve of each solid bitumen block in each whole-rock radiograph, determine the spectral parameters of each solid bitumen block in each shale sample. The spectral parameters include: D peak position, G peak position, peak spacing, full width at half maximum (FWHM) of the D peak, FWHM of the G peak, and intensity ratio.

[0072] Step 102.9: Based on the spectral parameters and spatial distribution maps of the chemical structure of each solid bitumen block in several whole-rock radiographs at different evolution stages, determine the evolution information (evolutionary law) of the chemical structure of solid bitumen.

[0073] In this embodiment, the evolution of the chemical structure of solid asphalt is determined by the changes in the position of peak D (WD), peak G (WG), peak spacing (RBS=WG-WD), half width at half maximum (FWHM-D) of peak D, half width at half maximum (FWHM-G) of peak G, and strength ratio (ID / IG) during the low maturity, mature, and high maturity stages.

[0074] To help those skilled in the art understand the technical solution of this application, further explanation is provided below.

[0075] The method for in-situ identification of solid bitumen in shale and characterization of its chemical structure based on electron microscopy-Raman spectroscopy provided in this application includes: sample pretreatment, effective identification of solid bitumen under electron microscopy, three-dimensional visualization observation of Raman spectroscopy, and characterization of the chemical structure of solid bitumen.

[0076] Sample pretreatment: Shale samples from different thermal evolution stages (hereinafter referred to as samples) were selected. Whole-rock sections were prepared perpendicular to the sample plane and polished to ensure a smooth surface. The dried sections were then placed under both reflected white light and fluorescence modes. The overall distribution of micro-components and the structure, morphology, color, and intensity of reflected and fluorescence light were observed using 20x and 50x objectives, respectively. Typical locations of solid bitumen (such as micro-components surrounding brightly colored minerals) were marked as points for subsequent in-situ electron microscopy-Raman spectroscopy testing.

[0077] Effective identification of solid bitumen under electron microscopy: The photo-electron coupled function of scanning electron microscope is used to locate the solid bitumen marked under the optical microscope. When further observation is needed, the magnification is gradually increased. After magnification, the main focus is on the external morphology, hardness, brightness, color, protrusion, and contact relationship with surrounding minerals of the solid bitumen. The typical identification marks of solid bitumen under different thermal evolution stages under scanning electron microscopy are observed and summarized.

[0078] The application of the optical-electronic coupled-array function in scanning electron microscopy (SEM) to locate solid bitumen marked under an optical microscope involves the following steps: After viewing the large field-of-view (OF) images (optical microscopy images) of the whole rock section under reflected light and fluorescence, mark the locations of typical solid bitumen. Place the same whole rock section into the SEM sample chamber, evacuate the vacuum, and adjust the working distance, astigmatism, and objective lens alignment to ensure the obtained scanning image remains clear. Open the Raman-localization function in the toolbar of the SEM software (the large field-of-view image from the optical microscope needs to be imported into the software system beforehand). Locate and correspond the large field-of-view image of the same sample under reflected light with the field of view observed under the SEM (using the obvious bright-colored minerals or the concave and convex positions of irregular samples). The specific operation is as follows: First, select the aforementioned characteristic minerals or positions in the large field-of-view image (optical microscope), left-click, and then find the corresponding characteristic minerals or positions in the field of view under the SEM. Selecting at least two sets of corresponding points can determine the correspondence between the entire large field-of-view image of the optical microscope and the field of view (image) of the SEM. After matching, when you double-click a feature position on the large field of view image of the optical microscope, the field of view of the electron microscope will automatically jump. You can observe whether the image scanned by the electron microscope after the jump is consistent with that of the optical microscope to judge the effect of optical-electronic coupling.

[0079] Three-dimensional visualization of Raman spectroscopy: Within the vacuum chamber of a scanning electron microscope, a precision scanning stage automatically transfers the whole-rock section from one measurement position to another. After repositioning, a point-to-surface combined approach is used to further analyze the internal chemical structure of solid asphalt. Before using the Raman spectrometer, wavenumber calibration is performed using silicon wafer standards. The laser power is 8mW for surface scanning, and the scanning range is 95-4000 cm⁻¹. -1 The residence time was 200 ms / pixel, and the scanning area was 10 μm × 7 μm. The surface distribution information of the Raman spectrum was obtained. Then, spectra were acquired on individual particles (each particle corresponding to a solid bitumen block), and a wavelength of 473 nm was selected for sample testing (spot scan).

[0080] The first measurement location refers to the location under an electron microscope, primarily used to obtain the morphology and pore development characteristics of solid bitumen. The second location is the measurement location under Raman spectroscopy. Effective chemical structure information is difficult to obtain under an electron microscope alone; therefore, it is necessary to transfer the measurement to Raman spectroscopy for chemical structure analysis. When the whole-rock light section is switched to the Raman spectroscopy lens, the electron microscope image of each solid bitumen block is imported into the Raman spectrometer's accompanying software system. Using the software system's automatic positioning function, the positional correspondence between the Raman image and the electron microscope image of each solid bitumen block in the whole-rock light section can be established.

[0081] Chemical structure characterization of solid asphalt: By overlaying scanning electron microscopy (SEM) images and Raman spectroscopy (RaMAN) images, the heterogeneity of the chemical structure exhibited by solid asphalt within individual particles, between adjacent particles, and at different stages of thermal evolution can be analyzed. Furthermore, the orderliness of the aromatic structure of solid asphalt is reflected by calculating its Raman spectral parameters, mainly including: peak position (WD and WG), peak spacing (RBS=WGWD), vibrational frequency intensity of half-width at half-maximum (FWHM-G and FWHM-D), and peak intensity ratio (ID / IG). A single solid asphalt particle represents a solid asphalt block.

[0082] Heterogeneity analysis refers to the analysis of the heterogeneity of solid asphalt by observing the superimposed electron microscopy and Raman images and utilizing the color differences in the images due to different spectral characteristics.

[0083] This application has the following beneficial effects:

[0084] (1) Compared with traditional methods, this method can realize in-situ simultaneous testing of solid asphalt morphology observation (SEM) and chemical structure analysis (Raman), avoiding data misalignment caused by sample transfer, improving the accuracy of solid asphalt identification and providing analytical precision.

[0085] (2) Combining scanning electron microscopy-Raman spectroscopy, this method can obtain the surface morphology and chemical structure information of in-situ solid asphalt based on sample pretreatment, acquire the differences in chemical structure inside and between solid asphalt particles, analyze the order of aromatic structure (parameters such as D peak, G peak, ID / IG, etc.) and surface heterogeneity of solid asphalt at different thermal evolution stages, and reveal the variation law of its chemical structure with maturity, providing a new method for the study of the heterogeneity of shale organic matter. That is, this application combines scanning electron microscopy-Raman spectroscopy to achieve accurate characterization of solid asphalt from morphology to molecular structure.

[0086] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0087] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy, characterized in that, The method comprises the following steps: obtaining a plurality of whole rock light slices of different evolution stages; for each whole rock light slice, performing in-situ identification to obtain a chemical structure spatial distribution map of each solid bitumen block in the whole rock light slice; the specific process of the in-situ identification operation is as follows: using an optical microscope, identifying the solid bitumen in the whole rock light slice, and marking each solid bitumen block identified on the whole rock light slice to obtain a labeled optical micrograph corresponding to each solid bitumen block; placing the whole rock light slice into a field emission scanning electron microscope, and using the photo-electricity combined function of the field emission scanning electron microscope to determine the position correspondence between the image under the electron microscope view and the labeled optical micrograph corresponding to each solid bitumen block in the whole rock light slice, and then determine the position of the mark of each solid bitumen block in the whole rock light slice in the image under the electron microscope view; according to the position of the mark of each solid bitumen block in the whole rock light slice in the image under the electron microscope view, using the field emission scanning electron microscope to obtain the surface topography feature image of each solid bitumen block in the whole rock light slice; moving the whole rock light slice to the lens of a Raman spectrometer, using the image positioning function of the Raman spectrometer to determine the position correspondence between the image under the Raman view and the surface topography feature image of each solid bitumen block in the whole rock light slice, and then using the area scanning mode of the Raman spectrometer to determine the Raman area scanning image of each solid bitumen block in the whole rock light slice; superimposing the surface topography feature image and the Raman area scanning image of each solid bitumen block in the whole rock light slice to generate a chemical structure spatial distribution map of each solid bitumen block; the in-situ identification operation further comprises the following steps: using the point scanning mode of the Raman spectrometer to obtain the spectral data of each solid bitumen block in each whole rock light slice; using Gaussian-Lorentz peak fitting technology to fit the spectral data of each solid bitumen block in each whole rock light slice to obtain the spectral curve of each solid bitumen block in each whole rock light slice; based on the spectral curve of each solid bitumen block in each shale sample, determining the spectral parameters of each solid bitumen block in each whole rock light slice; based on the spectral parameters and the chemical structure spatial distribution map of each solid bitumen block in the plurality of whole rock light slices of different evolution stages, determining the evolution information of the chemical structure of solid bitumen.

2. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, Different whole rock light slices are obtained by slicing different shale samples, and the slicing process of each shale sample is as follows: using a diamond cutting machine, cutting a first whole rock block body of a predetermined size in a direction perpendicular to the bedding plane of the shale sample; using epoxy resin to perform vacuum impregnation and curing treatment on the first whole rock block body to obtain a second whole rock block body; polishing the second whole rock block body to obtain a third whole rock block body; drying the third whole rock block body to obtain a whole rock light slice.

3. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 2, characterized in that, The polishing operation on the second whole rock block body to obtain the third whole rock block body comprises the following steps: using 600#, 1200# and 2000# diamond sandpaper to polish the second whole rock block body step by step until the surface roughness of the polished second whole rock block body is less than 0.1 μm; The second full rock block after polishing is polished again by using 0.05 μm alumina polishing liquid for a preset polishing time, to obtain a third full rock block after polishing again. The third full rock block after polishing again is placed in a drying box for drying treatment, to obtain a fourth full rock block.

4. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, The solid bitumen in the full rock slice is identified by using an optical microscope, and each solid bitumen block identified on the full rock slice is marked, specifically including: The distribution of the solid bitumen in the full rock slice is determined by using a 20 times oil lens under a reflected white light mode by using the optical microscope; Based on the distribution of the solid bitumen in the full rock slice, the morphological characteristics of the solid bitumen in the full rock slice are determined by using a 50 times oil lens; The optical microscope is switched to a fluorescence mode to determine the fluorescence color of the solid bitumen in the full rock slice; Based on the morphological characteristics and the fluorescence color of the solid bitumen in the full rock slice, a microhardness tester is used to mark each solid bitumen block on the surface of the full rock slice.

5. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, According to the position of the mark of each solid bitumen block in the image under the field emission scanning electron microscope, the surface topography characteristic image of each solid bitumen block in the full rock slice is obtained by using the field emission scanning electron microscope, specifically including: For each solid bitumen block in the full rock slice, according to the position of the mark of the solid bitumen block in the image under the field emission scanning electron microscope, the dark gray solid bitumen part in the image under the field emission scanning electron microscope is determined under a low voltage SEM and a backscattered electron mode; According to the dark gray solid bitumen part in the image under the field emission scanning electron microscope, the surface topography characteristic image of each solid bitumen block in the full rock slice is obtained by using a high magnification secondary electron mode.

6. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, The spectral parameters include a D peak position, a G peak position, a peak interval, a D peak half-height width, a G peak half-height width, and an intensity ratio.

7. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, The Raman spectrometer has a wave number error < ± 0.5 cm -1 .

8. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, In the area scan mode, the parameter settings of the Raman spectrometer include: the scan area is 10 μm x 7 μm, the step length is 0.5 μm, the total number of measuring points is 280, the laser power density is <1 mW / μm, and the residence time is 200 ms / pixel. 2 , the residence time is 200 ms / pixel.

9. The method for in-situ identification of solid bitumen in shale based on electron microscopy-Raman spectroscopy according to claim 1, characterized in that, In the point scanning mode, the parameter settings of the Raman spectrometer include: laser wavelength of 473 nm, laser power of 8 mW, spot diameter of 1 μm, spectral resolution of 2 cm -1 .

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