Method for acquiring effective pore parameters of shale

Abstract

The invention discloses a method for acquiring effective pore parameters of shale. The method comprises the following steps: S1, acquiring a sample fluorescent slice and an argon ion polishing sample; s2, acquiring a fluorescence image of the sample fluorescence slice in the step S1; s3, obtaining luminous color characteristics of the oil sample of the well section where the sample is located; s4, calculating the percentage ratio of the fluorescent light emitting colors of the effective components in the sample fluorescent slice in the step S2; s5, counting the percentage ratio of organic components to pores; and S6, multiplying the percentage ratio of the fluorescent light emitting colors of the effective components in the step S4 by the percentage ratio of the organic components and the pores in the step S5 to obtain the effective pore parameters of the shale. The method is suitable for the technical field of the shale, and the fluorescent light emitting of different organic components in the fluorescent slice is calibrated through the fluorescence of the crude oil sample, so that the effective pore parameters of the shale can be obtained. The percentage ratio of the effective pores in the shale can be determined, so that the surface porosity data counted by the scanning electron microscope of the argon ion polishing sample is corrected, and the effective pore parameters of the shale are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of mud shale, and in particular relates to a method for obtaining effective pore parameters of mud shale. Background Art

[0002] At present, domestic shale oil and gas production capacity has made continuous breakthroughs. China's shale oil resources are rich and are currently China's most potential, most strategic and most realistic oil replacement resources. Shale reservoir parameters are one of the key issues in shale exploration.

[0003] At present, conventional oil washing is required before testing the physical properties of mud shale. Unlike clastic reservoirs, mud shale contains many types of organic components. The differences in the medium and time of oil washing result in great differences in the test results of mud shale physical properties.

[0004] In recent years, scanning electron microscopy observation based on rock argon ion polishing has become an important method for studying the pore structure of mudstone and obtaining pore parameters. However, due to the strong heterogeneity of pores in mudstone, this method currently has no specific requirements for the number of pore statistics; on the other hand, it cannot distinguish between heavy and light organic components in mudstone, resulting in a large pore surface ratio, which affects the evaluation of mudstone pore performance.

[0005] Therefore, there is currently a lack of a method for obtaining pore parameters based on the classification of organic component types, so as to obtain effective pore parameters of shale. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a method for obtaining effective pore parameters of shale.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for obtaining effective pore parameters of shale comprises the following steps:

[0009] S1 sample collection and processing, obtaining sample fluorescent thin sections and argon ion polished samples;

[0010] S2 obtains a fluorescence image of the sample fluorescence slice in step S1;

[0011] S3 obtains the luminescent color characteristics of the oil sample in the well section where the sample is located as the luminescent color of the effective organic component;

[0012] S4 calibrates the luminescent color of the effective component in step S3 with the luminescent color measurement result of the shale sample in step S2, and calculates the percentage of the fluorescent luminescent color of the effective component in the fluorescent slice of the sample in step S2;

[0013] S5: obtaining backscattered images of multiple fields of view of the argon ion polished sample in step S1, and calculating the percentages of organic components and pores;

[0014] S6: The effective pore parameters of the shale are obtained by multiplying the percentage of the fluorescent luminescent color of the effective component in step S4 by the percentage of the organic component and the pore in step S5.

[0015] Preferably, in step S1, the sample is a shale block sample with a size of 5 cm×5 cm.

[0016] Preferably, in step S1, the vitrinite reflectance of the shale block sample is less than 1.3%.

[0017] Preferably, in step S1, the shale block sample needs to be processed into fluorescent thin sections as soon as possible after the sample is obtained, or sealed and stored for a short period of time at a temperature of -18°C.

[0018] Preferably, in step S1, the sample processing includes: cutting the shale block sample along the direction perpendicular to the bedding, and performing fluorescent thin section preparation and argon ion polishing treatment on two samples with the same cross section after cutting, respectively, to obtain sample fluorescent thin sections and argon ion polished samples.

[0019] Preferably, in step S1, the fluorescent thin slice is observed under a 365nm ultraviolet fluorescence microscope before coverslipping to determine whether there is organic matter such as wool yarn mixed in during the preparation process due to human factors, which in turn affects the analysis results of subsequent fluorescent images. If there is artificial organic matter such as wool yarn, further processing is required.

[0020] Preferably, in step S2, the sample fluorescent slice prepared in step S1 is observed under a microscope to obtain a fluorescent image of the sample fluorescent slice.

[0021] Preferably, in step S2, the microscope is an ultraviolet fluorescence microscope with a wavelength of 365 nm.

[0022] Preferably, in step S2, the observation condition is: randomly taking no less than 10 fluorescent images of different viewing areas under a microscope magnification of 100×.

[0023] Preferably, in step S2, the exposure time, saturation, contrast and other parameters of the fluorescent image are kept consistent.

[0024] Preferably, the step S3 specifically comprises obtaining an oil sample from the well section where the sample is located, dropping the sample on a glass slide, covering the sample with a cover slip, and observing the luminescent color characteristics of the crude oil under a fluorescence microscope as the luminescent color of the effective organic component.

[0025] Preferably, in step S4, the percentage of the fluorescent luminescence color of the effective components in the sample fluorescent sheet in step S2 is calculated using image analysis software.

[0026] Preferably, in step S5, obtaining backscattered images of multiple viewing areas of the argon ion polished sample in step S1 specifically includes:

[0027] The argon ion polished sample in step S1 is observed under a scanning electron microscope with a magnification of not less than 10,000 times, and backscattered images of not less than 20 viewing areas are randomly acquired.

[0028] Preferably, in step S5, a multi-point scanning electron microscope energy spectrum test is performed during the observation process to determine whether there are organic components and pores.

[0029] Preferably, in step S5, the grayscale image to be processed is calibrated using the result of the energy spectrum analysis to determine the threshold values ​​of the grayscale of the pores and organic components.

[0030] Preferably, in step S5, all acquired backscattered images are processed by mosaic, and the percentages of organic components and pores are counted in combination with the judgment results of the energy spectrum.

[0031] Preferably, in step S5, the number of pores counted is not less than 4000, and pores with a diameter less than 3 times the pixel diameter are not counted.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] In the present invention, by using an argon ion polished sample scanning electron microscope in conjunction with energy spectrum analysis, the total content of pores and organic components in the mudstone can be accurately obtained. By using the fluorescence of different organic components in the fluorescence thin section of the crude oil sample for fluorescence calibration, the percentage of effective pores in the mudstone can be determined, thereby correcting the surface surface ratio data obtained by the argon ion polished sample scanning electron microscope to obtain the effective pore parameters of the mudstone. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an image of the shale sample in the present invention after argon ion polishing under a backscattering-scanning electron microscope. The black part in the figure is organic matter and pores, and the gray part can be distinguished by means of energy spectrum testing;

[0035] Figure 2 In the present invention, the pores and organic matter parts can be filled with the help of software such as Photoshop;

[0036] Figure 3 is a fluorescence image of the shale sample in the present invention;

[0037] Figure 4 For the present invention Figure 3 Fluorescent photographs of shale after extraction and coloring according to different types of organic matter. DETAILED DESCRIPTION

[0038] The following is combined with Figure 1-4 , further illustrating a specific implementation of a method for obtaining effective pore parameters of shale according to the present invention. The method for obtaining effective pore parameters of shale according to the present invention is not limited to the description of the following embodiments.

[0039] Embodiment 1:

[0040] This embodiment provides a specific implementation method of a method for obtaining effective pore parameters of shale. Figure 1-4 As shown, the following steps are included:

[0041] S1 sample collection and processing, obtaining sample fluorescent thin sections and argon ion polished samples;

[0042] S2 obtains a fluorescence image of the sample fluorescence slice in step S1;

[0043] S3 obtains the luminescent color characteristics of the oil sample in the well section where the sample is located as the luminescent color of the effective organic component;

[0044] S4 calibrates the luminescent color of the effective component in step S3 with the luminescent color measurement result of the shale sample in step S2, and calculates the percentage of the fluorescent luminescent color of the effective component in the fluorescent slice of the sample in step S2;

[0045] S5: obtaining backscattered images of multiple fields of view of the argon ion polished sample in step S1, and calculating the percentages of organic components and pores;

[0046] S6: The effective pore parameters of the shale are obtained by multiplying the percentage of the fluorescent luminescent color of the effective component in step S4 by the percentage of the organic component and the pore in step S5.

[0047] Furthermore, in step S1, the sample is a shale block sample with a size of 5 cm×5 cm.

[0048] Furthermore, in step S1, the vitrinite reflectance of the shale block sample is less than 1.3%. When the vitrinite reflectance is greater than 1.3%, the fluorescence intensity of the organic component is affected and is difficult to observe.

[0049] Furthermore, in step S1, in order to ensure the authenticity of the fluorescence observation effect of the shale sample, the shale block sample needs to be prepared into fluorescent thin sections as soon as possible after the sample is obtained, or sealed and stored for a short period of time at a temperature of -18°C.

[0050] Furthermore, in step S1, the sample processing includes: cutting the shale block sample along the direction perpendicular to the bedding, and performing fluorescent thin section preparation and argon ion polishing on two samples with the same cross section after cutting, respectively, to obtain sample fluorescent thin sections and argon ion polished samples.

[0051] Furthermore, in step S1, the preparation of fluorescent thin sections refers to the preparation of fluorescent thin sections in "SY / T5913 Rock Sectioning Method". Because fluorescent image analysis is required later, the fluorescent thin sections are observed under a 365nm ultraviolet fluorescence microscope before coverslipping to determine whether there is organic matter such as wool yarn mixed in during the sectioning process, which will affect the analysis results of subsequent fluorescent images. If there is artificial organic matter such as wool yarn, further processing is required.

[0052] Furthermore, in step S2, the sample fluorescent slice prepared in step S1 is observed under a microscope to obtain a fluorescent image of the sample fluorescent slice. Different types of organic components emit light with obvious differences in color under fluorescent excitation (the identification of fluorescent colors of different organic components is a prior art).

[0053] Furthermore, in step S2, the microscope is an ultraviolet fluorescence microscope with a wavelength of 365nm.

[0054] Furthermore, in step S2, in order to avoid the influence of heterogeneous distribution of organic components in the shale sample, the observation conditions are: randomly taking no less than 10 fluorescence images of different viewing areas under the condition of a microscope magnification of 100×.

[0055] Furthermore, in step S2, the exposure time, saturation, contrast and other parameters of the fluorescence image are kept consistent.

[0056] Furthermore, the organic components in shale are widely distributed from light to heavy organic components, where the light component content represents the effective pore content. The main difficulty currently exists is to distinguish between heavy organic components and light organic components.

[0057] Different types of organic components in shale emit different luminescent colors under ultraviolet light excitation. The properties of the organic components in shale can be determined by the luminescent color and brightness of the fluorescence.

[0058] The color of fluorescence reflects the characteristics of organic components, and the brightness of fluorescence reflects the content of organic components. Generally, the color of organic components can be blue-white, yellow-white, orange, brown, etc.

[0059] Furthermore, step S3 specifically includes obtaining an oil sample from the well section where the sample is located, dropping the sample on a glass slide, covering the sample with a cover slip, and observing the luminescent color characteristics of the crude oil under a fluorescence microscope as the luminescent color of the effective organic component.

[0060] Furthermore, the current determination of effective components in shale mainly relies on the shale pyrolysis parameter S1 as the identification standard for the content of effective components, which has large errors and many influencing factors. The oil samples in the same layer of shale samples are directly produced from the shale in the same layer, and have the natural advantage of calibrating effective components.

[0061] Furthermore, in step S4, the percentage of the fluorescent luminescence color of the effective components in the sample fluorescent sheet in step S2 is calculated using image analysis software.

[0062] Further, in step S5, backscattered images of multiple viewing areas of the argon ion polished sample in step S1 are obtained, specifically including:

[0063] The argon ion polished sample in step S1 is observed under a scanning electron microscope with a magnification of not less than 10,000 times, and backscattered images of not less than 20 viewing areas are randomly acquired.

[0064] Furthermore, in step S5, the brightness of the backscattered image is often related to the density of the observed object. Pores and organic components have a smaller density than rock minerals, and the image grayscale color is darker. During the observation process, a multi-point scanning electron microscope energy spectrum test is performed to determine whether it is an organic component and pores.

[0065] Furthermore, in step S5, currently in the process of processing the backscattered grayscale image, there is subjectivity in the identification of organic components. During the test, the organic components can be effectively identified by calibration of multi-point energy spectrum analysis. The grayscale image to be processed is calibrated using the results of the energy spectrum analysis to determine the threshold of the image grayscale of pores and organic components.

[0066] Furthermore, in step S5, all acquired backscattered images are processed by mosaic, and the percentages of organic components and pores are calculated in combination with the judgment results of the energy spectrum.

[0067] Furthermore, in step S5, in order to ensure the accuracy of the number of pore statistics, the number of pores counted is not less than 4000, and pores with a pore diameter less than 3 times the pixel diameter are not counted.

[0068] Example 2

[0069] A method for obtaining effective pore parameters of shale comprises the following steps:

[0070] S1: Sample pretreatment and fluorescent thin section preparation: Collect blocky shale samples with a sample size of 4.6 cm × 3.6 cm. Cut the samples along the vertical bedding direction, and perform fluorescent thin section preparation and argon ion polishing on two samples with the same cut surface.

[0071] S2: The fluorescent slice prepared in step S1 is observed under a 365nm ultraviolet fluorescence microscope. 20 fluorescent images of the sample fluorescent slice are randomly obtained at a microscope magnification of 100× and are processed into a puzzle.

[0072] The fluorescence characteristics of the organic components of this sample are mainly bright yellow and yellowish brown.

[0073] Two fluorescent colors were extracted through the software. A total of 52,122 samples were extracted through bright yellow fluorescence, accounting for 4.71%; a total of 83,198 samples were extracted through yellowish-brown fluorescence, accounting for 4.85%.

[0074] S3: Get the oil sample from the well section where the sample is taken, drop it on a glass slide, and cover it with a cover glass. Observe the luminescent color characteristics of the crude oil under a fluorescence microscope, and mainly emit yellow fluorescence as the luminescent color of the effective organic component.

[0075] S4: Calibrate the luminescent color of the effective component in step S3 with the luminescent color measurement result of the shale sample in step S2. The percentage of the fluorescent luminescent color of the effective component in the sample in step S2 is 49.3%.

[0076] S5: Observe the argon ion polished sample obtained in step S1 under a scanning electron microscope with a magnification of 10,000 times. Randomly obtain backscattered images of no less than 26 fields of view. A total of 6,805 pores were counted, of which pores with diameters less than 3 times the length of the pixel point diameter were not counted. The total surface area ratio was 5.17%.

[0077] S6: Multiply the percentage of the fluorescent color of the effective components in step S4 by the percentage of the organic components and pores in step S5 to obtain the effective surface area ratio of the shale, which is 2.55%.

[0078] Example 3

[0079] A method for obtaining effective pore parameters of shale comprises the following steps:

[0080] S1: Sample pretreatment and fluorescent thin section preparation: Collect blocky shale samples with a sample size of 5.3 cm × 5.6 cm. Cut the samples along the vertical bedding direction, and perform fluorescent thin section preparation and argon ion polishing on two samples with the same cut surface.

[0081] S2: The fluorescent slice prepared in step S1 is observed under a 365nm ultraviolet fluorescence microscope. 34 fluorescent images of the sample fluorescent slice are randomly obtained at a microscope magnification of 100× and are processed into a puzzle.

[0082] The fluorescence characteristics of the organic components of this sample are mainly bright yellow and yellowish brown.

[0083] Two fluorescent colors were extracted through the software. A total of 63,454 samples were extracted through bright yellow fluorescence, accounting for 5.23%; a total of 96,785 samples were extracted through yellowish-brown fluorescence, accounting for 6.24%.

[0084] S3: Get the oil sample from the well section where the sample is taken, drop it on a glass slide, and cover it with a cover glass. Observe the luminescent color characteristics of the crude oil under a fluorescence microscope, and mainly emit yellow fluorescence as the luminescent color of the effective organic component.

[0085] S4: Calibrate the luminescent color of the effective component in step S3 with the luminescent color measurement result of the shale sample in step S2. The percentage of the fluorescent luminescent color of the effective component in the sample in step S2 is 54.40%.

[0086] S5: Observe the argon ion polished sample obtained in step S1 under a scanning electron microscope with a magnification of 10,000 times. Randomly obtain backscattered images of no less than 26 fields of view. A total of 6,805 pores were counted, of which pores with diameters less than 3 times the length of the pixel point diameter were not counted. The total face rate was 6.38%.

[0087] S5: By multiplying the percentage of the fluorescent color of the effective component of S4 by the percentage of the organic component content and pores of S5, we can obtain the effective surface area of ​​​​the shale, which is 3.47%.

[0088] It should be noted that in Examples 1-3, the processing, color extraction, and calculation of the argon ion polishing scanning electron microscope images and fluorescent images are processed using professional software and do not fall within the scope of protection of the present invention.

[0089] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for obtaining effective pore parameters of shale, characterized in that: The following steps are involved: S1 sample collection and processing, obtaining sample fluorescent thin sections and argon ion polished samples; S2 obtains a fluorescence image of the sample fluorescence slice in step S1; S3 obtains the luminescent color characteristics of the oil sample in the well section where the sample is located as the luminescent color of the effective organic component; S4 calibrates the luminescent color of the effective component in step S3 with the luminescent color measurement result of the shale sample in step S2, and calculates the percentage of the fluorescent luminescent color of the effective component in the fluorescent slice of the sample in step S2; S5: obtaining backscattered images of multiple fields of view of the argon ion polished sample in step S1, and calculating the percentages of organic components and pores; S6: The effective pore parameters of the shale are obtained by multiplying the percentage of the fluorescent luminescent color of the effective component in step S4 by the percentage of the organic component and the pore in step S5.

2. A method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In the step S1, the sample is a shale block sample with a size of 5 cm×5 cm.

3. A method for obtaining effective pore parameters of shale according to claim 2, characterized in that: In the step S1, the vitrinite reflectance of the shale block sample is less than 1.3%.

4. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In the step S1, the shale block sample needs to be processed into fluorescent thin sections as soon as possible after the sample is obtained, or sealed and stored for a short period of time at a temperature of -18°C.

5. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In step S1, the sample processing includes: cutting the shale block sample along the vertical bedding direction, and performing fluorescent thin section preparation and argon ion polishing on two samples with the same cut surface after cutting, respectively, to obtain sample fluorescent thin sections and argon ion polished samples.

6. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In step S1, the fluorescent thin slices are observed under a 365nm ultraviolet fluorescence microscope before coverslipping to determine whether there are organic matters such as wool yarn mixed in during the preparation process due to human factors, which may affect the analysis results of subsequent fluorescent images. If there are artificial organic matters such as wool yarn, further processing is required.

7. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In the step S2, the sample fluorescent slice prepared in the step S1 is observed under a microscope to obtain a fluorescent image of the sample fluorescent slice.

8. The method for obtaining effective pore parameters of shale according to claim 7, characterized in that: In step S2, the microscope is an ultraviolet fluorescence microscope with a wavelength of 365nm.

9. The method for obtaining effective pore parameters of shale according to claim 7, characterized in that: In step S2, the observation condition is: randomly taking no less than 10 fluorescent images of different viewing areas under the condition of a microscope magnification of 100×.

10. The method for obtaining effective pore parameters of shale according to claim 9, characterized in that: In step S2, the exposure time, saturation, contrast and other parameters of the fluorescent image are kept consistent.

11. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: The step S3 specifically includes obtaining an oil sample from the well section where the sample is located, dropping the sample on a glass slide, covering the sample with a cover glass, and observing the luminescent color characteristics of the crude oil under a fluorescence microscope as the luminescent color of the effective organic component.

12. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In step S4, the percentage of the fluorescent color of the effective components in the sample fluorescent sheet in step S2 is calculated using image analysis software.

13. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In the step S5, obtaining backscattered images of multiple viewing areas of the argon ion polished sample in step S1 specifically includes: The argon ion polished sample in step S1 is observed under a scanning electron microscope with a magnification of not less than 10,000 times, and backscattered images of not less than 20 viewing areas are randomly acquired.

14. A method for obtaining effective pore parameters of shale according to claim 13, characterized in that: In the step S5, a multi-point scanning electron microscope energy spectrum test is performed during the observation process to determine whether it is an organic component and pores.

15. The method for obtaining effective pore parameters of shale according to claim 13, characterized in that: In the step S5, the grayscale image to be processed is calibrated using the result of the energy spectrum analysis to determine the threshold values ​​of the grayscale of the pores and organic components.

16. A method for obtaining effective pore parameters of shale according to claim 15, characterized in that: In the step S5, all acquired backscattered images are processed by mosaic, and the percentages of organic components and pores are counted in combination with the judgment results of the energy spectrum.

17. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: In the step S5, the number of pores counted is not less than 4000, and pores with a diameter less than 3 times the pixel diameter are not counted.

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