A method for obtaining shale effective porosity parameters

Abstract

The application discloses a method for obtaining effective pore parameters of shale, and comprises the following steps: S1, obtaining a sample fluorescence slice and an argon ion polishing sample; S2, obtaining a fluorescence image of the sample fluorescence slice in step S1; S3, obtaining the luminescence color characteristics of an oil sample in a well section where the sample is located; S4, calculating the percentage of the fluorescence luminescence color of effective components in the sample fluorescence slice in step S2; S5, counting the percentage of organic components and pores; and S6, multiplying the percentage of the fluorescence luminescence color of the effective components in step S4 and the percentage of the organic components and pores in step S5, so that the effective pore parameters of shale can be obtained. The application is suitable for the technical field of shale, and the fluorescence luminescence of different organic components in the fluorescence slice can be determined by fluorescence calibration of a crude oil sample, the percentage of effective pores in shale can be determined, the surface pore rate data of the argon ion polishing sample scanning electron microscope can be corrected, and the effective pore parameters of shale can be obtained.

Description

Technical Field

[0001] The present 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] China is currently experiencing continuous breakthroughs in shale oil and gas production capacity. China's abundant shale oil resources represent the country's greatest potential, most strategic, and most realistic replacement oil resource. Shale reservoir parameters are a key issue in shale exploration.

[0003] Currently, conventional oil washing is required before testing shale properties. Unlike clastic reservoirs, shale contains a wide variety of organic components. Differences in the medium and timing of oil washing result in significant variations in shale property test results.

[0004] In recent years, scanning electron microscopy (SEM) observation based on argon ion polishing has become an important method for studying shale pore structure and obtaining pore parameters. However, given the high heterogeneity of pores in shale, this method currently has no specific requirements for the number of pores counted. Furthermore, it cannot distinguish between heavy and light organic components in shale, resulting in an excessively high pore porosity, which affects the evaluation of shale porosity.

[0005] Therefore, there is currently a lack of a method for obtaining pore parameters based on the classification of organic component types 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 fluorescence 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 acquiring backscattering images of the multiple visual fields of the argon ion polished sample in step S1, and counting the percentage of the organic components and the pores;

[0014] S6 multiplying the percentage of the fluorescence emission color of the effective components in step S4 by the percentage of the organic components and the pores in step S5, to obtain the effective pore parameter of the shale.

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

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

[0017] Preferably, in step S1, the shale block sample needs to be quickly prepared into a fluorescence thin section after being obtained, or is sealed for short-term storage under the condition of-18℃.

[0018] Preferably, in step S1, the sample treatment includes: cutting the shale block sample along the vertical bedding direction, cutting the two samples with the same section, respectively preparing the fluorescence thin section and the argon ion polishing sample, and obtaining the fluorescence thin section and the argon ion polishing sample.

[0019] Preferably, in step S1, the fluorescence thin section is observed under a 365nm ultraviolet fluorescence microscope before being covered, to determine whether there is organic matter mixed by human factors such as wool during the preparation process, and to further affect the analysis results of the subsequent fluorescence image. If there is human organic matter such as wool, further processing is needed.

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

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

[0022] Preferably, in step S2, the observation condition is that the fluorescence images of different visual fields are randomly taken under the condition of a microscope magnification of 100x, and the number of the images is not less than 10.

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

[0024] Preferably, in step S3, an oil sample of the well section where the sample is located is obtained, dropped on a glass sheet, covered with a cover glass, and the emission color characteristics of the crude oil are observed under a fluorescence microscope as the emission color of the effective organic components.

[0025] Preferably, 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.

[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 it is an organic component 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 mosaicked, and the percentages of organic components and pores are calculated 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, the total content of pores and organic components in mud shale can be accurately obtained by using an argon ion polished sample scanning electron microscope in conjunction with energy spectrum analysis. The fluorescence emission of different organic components in the fluorescent thin section of the crude oil sample can be used to determine the percentage of effective pores in the mud shale, thereby correcting the surface area data statistically obtained by the argon ion polished sample scanning electron microscope to obtain the effective pore parameters of the mud shale. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an image of the shale sample after argon ion polishing under a backscattering-scanning electron microscope. The black part in the figure represents organic matter and pores, and the gray part can be distinguished by 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 Figures 1-4 , further illustrating a specific embodiment of the 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] Example 1:

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

[0041] S1 sample collection and processing, obtaining sample fluorescence 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: acquiring 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 multiplies the percentage of the fluorescent luminescence color of the effective component in step S4 by the percentage of the organic component and the pore in step S5 to obtain the effective pore parameters of the shale.

[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 difficult to observe.

[0049] Furthermore, in step S1, to ensure the authenticity of the fluorescence observation effect of the mudstone sample, the mudstone block sample needs to be prepared into a fluorescent thin section 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 vertical bedding direction, 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 section on fluorescent thin section preparation in the SY / T5913 Rock Sectioning Method. Because fluorescence image analysis will be performed later, the fluorescent thin sections are observed under a 365nm ultraviolet fluorescence microscope before coverslipping to determine whether there is any organic matter, such as lint, that has been introduced during the sectioning process and could affect the subsequent fluorescence image analysis results. If lint or other organic matter is present, 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 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 365 nm.

[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: at least 10 fluorescence images of different viewing areas are randomly taken under 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 in distinguishing heavy organic components from light organic components.

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

[0058] The color of fluorescence reflects the characteristics of the organic component, and the brightness of the fluorescence reflects the content of the organic component. Generally, the color of the fluorescence of organic components can be seen as 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 it 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 relies primarily on the shale pyrolysis parameter S1 as a criterion for determining the content of effective components, which has large errors and multiple influencing factors. Oil samples from the same interval as shale samples are directly produced from the same shale layer and have a natural advantage in calibrating effective components.

[0061] Furthermore, 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.

[0062] Furthermore, 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 object being observed. Pores and organic components are less dense than rock minerals, resulting in darker grayscale images. During the observation process, a multi-point SEM energy spectrum test is performed to determine whether the objects are organic components and pores.

[0065] Furthermore, in step S5, while the current processing of backscattered grayscale images can be subjective in identifying organic components, multi-point energy spectrum analysis can be used to calibrate the grayscale image to be processed, determining the grayscale thresholds for pores and organic components.

[0066] Furthermore, in step S5, all acquired backscattered images are mosaicked and combined with the judgment result of the energy spectrum to calculate the percentage of organic components and pores.

[0067] Furthermore, in step S5, to ensure the accuracy of the number of pore statistics, 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.

[0068] Example 2

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

[0070] S1: Sample pretreatment and fluorescence thin section preparation: A massive shale sample (4.6 cm × 3.6 cm) was collected. The sample was cut perpendicular to the bedding plane. Two samples with the same cross section were subjected to fluorescence thin section preparation and argon ion polishing, respectively.

[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 mosaic pattern.

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

[0073] Two fluorescent colors were extracted using software. A total of 52,122 samples were extracted using bright yellow fluorescence, accounting for 4.71%; a total of 83,198 samples were extracted using 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, cover it with a cover glass, and observe the luminescent color characteristics of the crude oil under a fluorescence microscope. The main luminescent color is bright yellow, which is 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 at a magnification of 10,000x. Randomly acquire backscattered images from at least 26 viewing zones. A total of 6,805 pores were counted. Pores with diameters less than three times the pixel diameter were not counted. The total porosity was 5.17%.

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

[0078] Example 3

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

[0080] S1: Sample pretreatment and fluorescence thin section preparation: A massive shale sample (5.3 cm × 5.6 cm) was collected. The sample was cut perpendicular to the bedding plane. Two samples with the same cross section were subjected to fluorescence thin section preparation and argon ion polishing, respectively.

[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 mosaic pattern.

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

[0083] Two fluorescence colors are extracted by software, 63454 samples are co-extracted by bright yellow fluorescence, accounting for 5.23%; 96785 samples are co-extracted by yellow-brown fluorescence, accounting for 6.24%.

[0084] S3: Obtain the oil sample in the well section where the sample is located, drop it on a glass sheet, and cover it with a cover glass. Observe the luminescent color characteristics of the crude oil under a fluorescence microscope, mainly bright yellow fluorescence, as the luminescent color of effective organic components.

[0085] S4: Calibrate the luminescent color of the effective components in step S3 with the luminescent color determination results of the shale sample in step S2. The percentage of the fluorescence luminescent color of the effective components 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 instrument with a magnification of 10000 times. Randomly obtain backscattered images of not less than 26 fields of view. A total of 6805 pores are counted, of which pores with a diameter less than 3 times the pixel length are not counted. The total face porosity is 6.38%.

[0087] S5: Multiply the percentage of the fluorescence luminescent color of the effective components in S4 with the percentage of the organic component content and the pore in S5, and the effective face porosity of the shale is 3.47%.

[0088] It should be noted that in Examples 1-3, the processing and color extraction, calculation of argon ion polishing scanning electron microscope images and fluorescence images are processed by professional software, which is not within the protection scope of the present application.

[0089] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the protection scope of the present application.

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 fluorescence 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: acquiring 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 multiplies the percentage of the fluorescent luminescence color of the effective component in step S4 by the percentage of the organic component and the pore in step S5 to obtain the effective pore parameters of the shale.

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

3. The method for obtaining effective pore parameters of shale according to claim 2, characterized in that: In 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 step S1, 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.

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 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.

7. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: 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.

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 365 nm.

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 at least 10 fluorescent images of different viewing areas under 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 fluorescence 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 onto 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.

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 step S5, obtaining backscattered images of multiple viewing zones 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. The method for obtaining effective pore parameters of shale according to claim 13, characterized in that: In step S5, a multi-point scanning electron microscope energy spectrum test is performed during the observation process to determine whether the components are organic components and pores.

15. The method for obtaining effective pore parameters of shale according to claim 13, characterized in that: 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.

16. The method for obtaining effective pore parameters of shale according to claim 15, characterized in that: In step S5, all acquired backscattered images are mosaicked, and the percentages of organic components and pores are calculated based on the determination results of the energy spectrum.

17. The method for obtaining effective pore parameters of shale according to claim 1, characterized in that: 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.

Images