Organic matter Raman parameter acquisition method and organic matter type identification method

Abstract

The invention relates to the technical field of oil-gas exploration, and discloses an organic matter Raman parameter acquisition method and an organic matter type identification method. The organic matter Raman parameter acquisition method comprises the following steps: scanning electron microscope imaging, image processing, Raman spectrum acquisition and Raman parameter acquisition. Wherein in the Raman parameter acquisition, fitting is performed on an acquired Raman spectrogram, the ratio D / G of the D peak intensity to the G peak intensity is obtained, and the ratio D / G is the Raman parameter of the organic matter. According to the organic matter type identification method, the Raman parameters of the organic matter are obtained by adopting the organic matter Raman parameter obtaining method; and identifying the type of the organic matter corresponding to the Raman parameter according to the obtained Raman parameter. According to the technical scheme, the types of organic matters with different pore development degrees can be accurately identified and distinguished through Raman spectrum analysis and Raman parameters; and reliable and accurate data can be provided for oil and gas resource evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and in particular to a method for obtaining Raman parameters of organic matter and a method for identifying organic matter types, which can analyze organic matter types with different pore development degrees in shale. Background Art

[0002] Shale gas exploration studies have shown that organic pores are the main pore type in marine shale gas reservoirs in North America and southern China. The characteristics of organic pores in mudstone can provide important theoretical support for the optimization of sweet spots (sections) in shale reservoirs. During the hydrocarbon generation and evolution of organic matter, a large number of nanoscale pores generated inside the organic matter provide storage space and seepage channels for shale oil and gas. The development of organic pores in shale reservoirs in different regions and different layers is extremely different. Studies have shown that the pore structure of organic matter is mainly affected by the type of organic matter. For example, the ability of type I and type II kerogen to develop organic pores is much higher than that of type III kerogen. Therefore, accurate identification of organic matter types with different pore development degrees in shale is the key to further studying the microscopic pore structure of shale.

[0003] In current experimental techniques, the study of organic pores and organic matter types are analyzed separately through single experimental techniques. The main experimental techniques used in the study of organic matter pore structure include argon ion polishing-scanning electron microscopy, focused ion beam scanning electron microscopy, nano-CT, etc. After argon ion polishing, the micropores developed inside the organic matter can be clearly observed through a high-resolution scanning electron microscope, but the type of organic matter is difficult to identify only by its morphology. The type of organic matter in shale is mainly identified by preparing the rock sample into a light sheet and placing it under a polarizing microscope, but the pores in the organic matter are mainly at the micro-nano level. Due to the resolution of the microscope, it is impossible to directly analyze the pore structure of different types of organic matter. Therefore, it is difficult to accurately identify the types of organic matter with different degrees of pore development through only a single experimental technique. Summary of the invention

[0004] The present application provides a method for obtaining Raman parameters of organic matter and a method for identifying the type of organic matter, based on the combination of scanning electron microscopy and Raman spectroscopy, to solve the above-mentioned technical problem that the existing technology is difficult to accurately identify the types of organic matter with different degrees of pore development.

[0005] According to one aspect of the present application, an embodiment provides a method for obtaining Raman parameters of organic matter, comprising the following steps:

[0006] S1. Scanning electron microscope imaging: Use scanning electron microscope to obtain images of pore development characteristics within organic matter particles in shale samples;

[0007] S2. Image processing: processing the image of the organic particles in step S1 to obtain the surface ratio of the pores in the organic particles and achieve quantitative characterization;

[0008] S3. Raman spectrum acquisition: using Raman spectroscopy to acquire Raman spectrum of the organic particles in step S1, and obtain a Raman spectrum graph;

[0009] S4. Obtaining Raman parameters: Fitting the Raman spectrum in step S3 to obtain the ratio D / G of the D peak intensity and the G peak intensity, wherein the ratio D / G is the Raman parameter of the organic matter.

[0010] In one embodiment, in step S1, the scanning electron microscope image acquired by the scanning electron microscope is a high-resolution image, and the resolution is less than 10 nm.

[0011] In one embodiment, in step S3, the scanning electron microscope images of the plurality of organic particles obtained in step S1 are subjected to image segmentation processing to obtain the surface area ratio of the pores in each organic particle.

[0012] In one embodiment, in step S4, after deducting the background from the Raman spectrum in step S3, spectrum fitting is performed.

[0013] In one embodiment, in step S4, fitting the Raman spectrum in step S3 includes the following steps:

[0014] The Lorentzian function was used to fit the D peak and G peak in the Raman spectrum after background subtraction.

[0015] In one embodiment, the method for obtaining Raman parameters of organic matter further includes the following steps:

[0016] S0. Sample polishing: The shale sample is cut into blocks, and the surface is smoothed and then polished to obtain the shale sample.

[0017] In one embodiment, in step S0, the polishing process uses argon ion polishing.

[0018] According to one aspect of the present application, an embodiment provides a method for identifying the type of organic matter, which uses any of the above methods for acquiring Raman parameters of organic matter to obtain Raman parameters of organic matter; based on the obtained Raman parameters, the type of organic matter corresponding to the Raman parameters is identified.

[0019] In one embodiment, identifying the type of organic matter corresponding to the Raman parameters according to the obtained Raman parameters comprises the following steps:

[0020] The Raman parameters are placed into the distribution range diagram of the organic matter type Raman parameters to identify the type of organic matter having the Raman parameters.

[0021] The technical solution of the above-mentioned embodiment of the present application directly obtains the Raman spectra of organic matter with different pore development while analyzing the different degrees of organic matter pore development by combining a scanning electron microscope with a Raman spectrum (equipment); and obtains Raman parameters based on the Raman spectrum. Afterwards, the type of organic matter is accurately identified based on the obtained Raman parameters. By adopting this technical solution, the degree of organic matter pore development in shale can be quantitatively characterized. Specifically, by Raman spectral analysis and Raman parameters, the types of organic matter with different degrees of pore development can be accurately identified and distinguished; reliable and accurate data can be provided for oil and gas resource evaluation.

[0022] In addition, the use of scanning electron microscopy and Raman spectroscopy (equipment) for identification has no requirements on the size and shape of organic matter, has a wider range of applications, and helps to analyze the pore structure of different types of organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a scanning electron microscope image of the pore development of organic matter particles in one embodiment;

[0024] Figure 2 is an image processing diagram of the pores of organic matter particles in an embodiment (blue represents organic matter, and red represents pores);

[0025] Figure 3 is a Raman spectrum of three organic particles in an embodiment;

[0026] Figure 4 The figure is a distribution range diagram of Raman parameters of different organic matter types in an embodiment. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0029] It should be noted that the terms "first", "second" etc. in the present application are used to distinguish similar objects, and need not be used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0030] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be an intermediate element. Moreover, in this application, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element through a third element.

[0031] Embodiment 1

[0032] An embodiment provides a method for obtaining Raman parameters of organic matter, comprising the following steps:

[0033] S0. Sample polishing: Cut the shale sample into blocks, grind the surface and then polish to obtain the shale sample. Specifically, mechanically cut the shale sample into blocks.

[0034] In one embodiment, after the surface of the block sample is ground flat, it is further polished using argon ion polishing.

[0035] S1. Scanning electron microscope imaging: Use a scanning electron microscope to obtain images of the pore development characteristics in the organic matter particles in the shale sample. In the specific implementation, the polished shale sample is placed in a scanning electron microscope to observe the development of the pores in the organic matter particles, thereby obtaining an image.

[0036] In one embodiment, the acquired SEM image is a high-resolution image.

[0037] In one embodiment, since the pores of organic matter in shale are mostly at the nanometer level, the resolution of the acquired scanning electron microscope image / high-resolution image is less than 10 nm.

[0038] S2. Image processing: Process the image of the organic particles in step S1 to obtain the surface ratio of the pores in the organic particles. This step achieves quantitative image characterization through image processing.

[0039] S3. Raman spectrum acquisition: Use Raman spectroscopy (equipment) to collect Raman spectrum of the organic particles in step S1 and obtain a Raman spectrum. One implementation method is to use a scanning electron microscope-Raman spectroscopy system to collect Raman spectrum of the organic particles in step S1 to obtain a Raman spectrum of the measurement point.

[0040] S4. Obtaining Raman parameters: Fitting the Raman spectrum in step S3 to obtain the ratio D / G of the D peak intensity and the G peak intensity, wherein the ratio D / G is the Raman parameter of the organic matter.

[0041] In one embodiment of step S4, after deducting the background from the Raman spectrum in step S3, spectrum fitting is performed.

[0042] Regarding the spectrum fitting in an embodiment of step S4, the following method may be used: a Lorentzian function is used to fit the D peak and the G peak in the Raman spectrum after background subtraction.

[0043] In the above method, since multiple organic particles may be involved, in one embodiment, in step S3, the scanning electron microscope images of the multiple organic particles obtained in step S1 are subjected to image segmentation processing to obtain the surface area ratio of the pores in each organic particle.

[0044] The above technical solution, combined with multiple technologies (scanning electron microscope and Raman spectroscopy (equipment)), can accurately obtain the Raman parameters of organic matter. Furthermore, based on the Raman parameters, the types of organic matter can be identified and distinguished.

[0045] Among them, the scanning electron microscope and Raman spectroscopy system can collect the morphology, composition and structure information of the same micro-area of ​​the sample in situ, so as to conduct a comprehensive analysis of the sample micro-area, avoid errors caused by factors such as sample movement and test environment changes, and ensure the accuracy and precision of the experimental results. Using the scanning electron microscope and Raman spectroscopy system, while analyzing the degree of organic matter pore development, the Raman spectra of organic matter with different pore development can be directly obtained, and the type of organic matter can be accurately identified using Raman spectrum parameters.

[0046] The method for obtaining Raman parameters of organic matter of the present invention, according to the characteristics of the scanning electron microscope and Raman spectroscopy combined system, first uses a scanning electron microscope to obtain the characteristic image of the pore development of organic matter in the shale sample after argon ion polishing, and obtains the surface ratio parameters of the organic pores through image processing technology; then uses Raman spectroscopy to perform in-situ analysis on the organic matter to obtain the Raman spectrum of the organic matter; after spectrum fitting, the ratio D / G of the Raman parameter D peak intensity and G peak intensity is obtained. Finally, by comparing the distribution range of Raman parameters of different organic matter types, the types of organic matter with different degrees of pore development are identified. The above technical scheme is a method for obtaining Raman parameters of organic matter based on the scanning electron microscope-Raman spectroscopy combined technology, which further forms a method for identifying the types of organic matter with different degrees of pore development in shale (see Example 2 for details).

[0047] Embodiment 2

[0048] An embodiment provides a method for identifying the type of organic matter, using the method for obtaining Raman parameters of organic matter as described in the first embodiment above to obtain Raman parameters of organic matter; based on the obtained Raman parameters, the type of organic matter corresponding to the Raman parameters is identified.

[0049] Among them, regarding the identification of the type of organic matter corresponding to the Raman parameter based on the obtained Raman parameter, one implementation method is: putting the Raman parameter into a distribution range diagram of the organic matter type Raman parameter to identify the type of organic matter having the Raman parameter.

[0050] The method for identifying the type of organic matter of the present invention uses scanning electron microscopy and Raman spectroscopy to form a set of methods for in-situ analysis of organic pore development and organic matter types. The degree of organic pore development in shale can be quantitatively characterized by scanning electron microscopy and image processing technology; the types of organic matter with different degrees of pore development can be accurately identified and distinguished by Raman spectroscopy analysis and Raman parameters; reliable and accurate data can be provided for oil and gas resource evaluation.

[0051] Embodiment 3

[0052] An embodiment provides a method for identifying organic matter types with different pore development degrees in shale using scanning electron microscopy and Raman spectroscopy, which can provide reliable and accurate data parameters for oil and gas resource evaluation.

[0053] In general, the present invention first uses a scanning electron microscope to obtain the characteristic image of the pore development of organic matter in the shale sample after argon ion polishing, and obtains the surface ratio parameters of the organic pores through image processing technology. Then, Raman spectroscopy is used to perform in-situ analysis on the organic matter to obtain the Raman spectrum of the organic matter, and the ratio D / G of the Raman parameter D peak intensity and G peak intensity is obtained after fitting the spectrum. The ratio D / G is the Raman parameter of the organic matter. Finally, based on the obtained Raman parameters, the distribution range of Raman parameters of different organic matter types is compared to identify the types of organic matter with different pore development degrees.

[0054] Embodiment 4

[0055] Please refer to Figure 1-Figure 4 An embodiment provides a method for identifying organic matter types, which is described below through an application case to facilitate further understanding of its technical solution.

[0056] The following is a detailed explanation of this technical solution using the Longmaxi Formation black shale sample in the Pingqiao area of ​​the Sichuan Basin as an example. The main steps are as follows:

[0057] (1) Sample polishing

[0058] The organic matter in the shale samples from the Pingqiao area mainly develops nanoscale pores, and the samples need to be polished by argon ions during scanning electron microscopy imaging.

[0059] (2) Scanning electron microscope imaging

[0060] The polished shale samples were placed in a scanning electron microscope to observe the development of pores in organic matter particles and obtain scanning electron microscope images of organic matter pores. The pore diameter of organic matter in shale in Pingqiao area is in the range of 10nm to 100nm, and a scanning electron microscope image with a resolution of 6nm was used. After a large number of observations in the early stage, scanning electron microscope images of three organic matter particles with large differences in pore development in the samples were obtained.

[0061] (3) Image processing

[0062] The scanning electron microscope images of the three organic particles in step (2) are subjected to image segmentation processing to obtain the surface area ratio of the pores in each organic particle. Figure 1 This is a scanning electron microscope image of the pore development of organic matter particles, in which image segmentation was performed. Figure 2 This is an image processing diagram of the pores of organic matter particles (blue is organic matter and red is pores).

[0063] (4) Raman spectrum acquisition

[0064] The Raman spectra of the three organic particles in step (2) are collected using a scanning electron microscope-Raman spectroscopy system to obtain a Raman spectrum of the organic matter.

[0065] (5) Raman parameter acquisition

[0066] The background of the Raman spectrum in step (4) is subtracted, and then the D peak and the G peak in the Raman spectrum after the background is subtracted are fitted respectively using the Lorentzian formula to obtain the ratio D / G of the D peak intensity to the G peak intensity, which is the Raman parameters of the three organic matters. Figure 3 These are the Raman spectra of three organic particles.

[0067] (6) Identification of organic matter types

[0068] The Raman parameters of the three organic matters in step (5) are placed in the distribution range chart of Raman parameters of different organic matter types to identify the type of the organic matter, as shown in the table below. Figure 4 This is the distribution range of Raman parameters for different types of organic matter.

[0069] Face ratio, Raman parameters and types of organic matter

[0070]

[0071] The experimental instrument is the RISE scanning electron microscope-Raman spectroscopy online system of TESCAN. Raman spectroscopy uses 532nm laser, 100× objective lens, laser power of 8mW, spatial resolution of 360nm, and spectral resolution of 1cm -1 , scanning range 95~4000cm -1 , Raman spectrum parameters are calculated by the spectrum analysis software provided by the instrument.

[0072] Through existing organic petrology detection means, it is detected that the organic matter type at the measurement point of the sample used in this embodiment is consistent with that in the embodiment. This application case verifies that the feasibility of the technical solution of the present invention is high.

[0073] Furthermore, the technical solution of the present invention illustrates that the types of organic matter with different pore development degrees in shale can be accurately identified by combining scanning electron microscopy with Raman spectroscopy. While analyzing the pore development degrees of different organic matter, the Raman spectra of organic matter with different pore development can be directly obtained, and the type of organic matter can be accurately identified using Raman spectrum parameters. In addition, the use of scanning electron microscopy and Raman spectroscopy for identification has no requirements on the size and morphology of organic matter, has a wider range of applications, and is helpful for analyzing the pore structure of different organic matter types.

[0074] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for obtaining Raman parameters of organic matter, characterized in that: The following steps are involved: S1. Scanning electron microscope imaging: Use scanning electron microscope to obtain images of pore development characteristics within organic matter particles in shale samples; S2. Image processing: processing the image of the organic particles in step S1 to obtain the surface ratio of the pores in the organic particles and achieve quantitative characterization; S3. Raman spectrum acquisition: using Raman spectroscopy to acquire Raman spectrum of the organic particles in step S1, and obtain a Raman spectrum graph; S4. Obtaining Raman parameters: Fitting the Raman spectrum in step S3 to obtain the ratio D / G of the D peak intensity and the G peak intensity, wherein the ratio D / G is the Raman parameter of the organic matter.

2. The method for obtaining Raman parameters of organic matter according to claim 1, characterized in that: In step S1, the scanning electron microscope image acquired by the scanning electron microscope is a high-resolution image, and the resolution is less than 10 nm.

3. The method for obtaining Raman parameters of organic matter according to claim 1, characterized in that: In step S3, the scanning electron microscope images of the plurality of organic particles obtained in step S1 are subjected to image segmentation processing to obtain the surface area ratio of the pores in each organic particle.

4. The method for obtaining Raman parameters of organic matter according to claim 1, characterized in that: In step S4, after the background is subtracted from the Raman spectrum in step S3, spectrum fitting is performed.

5. The method for obtaining Raman parameters of organic matter according to claim 1, characterized in that: In step S4, fitting the Raman spectrum in step S3 includes the following steps: The Lorentzian function was used to fit the D peak and G peak in the Raman spectrum after background subtraction.

6. A method for obtaining Raman parameters of organic matter according to any one of claims 1 to 5, characterized in that: The following steps are also included: S0. Sample polishing: The shale sample is cut into blocks, and the surface is smoothed and then polished to obtain the shale sample.

7. The method for obtaining Raman parameters of organic matter according to claim 6, characterized in that: In step S0, the polishing process adopts argon ion polishing.

8. A method for identifying organic matter types, characterized in that: The Raman parameters of the organic matter are obtained by using the method for obtaining the Raman parameters of the organic matter as described in any one of claims 1 to 7; and the type of the organic matter corresponding to the Raman parameters is identified according to the obtained Raman parameters.

9. The method for identifying the type of organic matter according to claim 8, characterized in that: The step of identifying the type of organic matter corresponding to the Raman parameters according to the obtained Raman parameters comprises the following steps: The Raman parameters are placed into the distribution range diagram of the organic matter type Raman parameters to identify the type of organic matter having the Raman parameters.

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