Sea area granite buried hill rock mineral content calculation method based on CT scanning

Abstract

The invention discloses a sea area granite buried hill rock mineral content calculation method based on CT scanning, and belongs to the technical field of analysis and detection.The sea area granite buried hill rock mineral content calculation method comprises the steps that a granite debris sample is subjected to CT scanning and preprocessing, and a CT gray level image is obtained; measuring and analyzing the granite debris sample, and determining the mass percentage of each mineral in the granite debris sample; according to the density and porosity of each mineral in the granite debris sample, converting the mass percentage of each mineral into a volume percentage; comparing the volume percentage of each mineral with the accumulated pixel value of the gray value of each mineral in the CT gray image, determining the standardized gray threshold of each mineral in the CT gray image, and constructing a mineral content gray threshold table; and determining the mineral content in the granite buried hill rock in the target sea area according to the mineral content gray threshold table. According to the method, the rock mineral content can be calculated with high efficiency and high precision, and the method is more suitable for being applied to reserves evaluation and development work of sea granite buried hill oil and gas reservoirs.

Description

Technical Field

[0001] The present invention belongs to the technical field of analytical testing, and particularly relates to a method for calculating the content of rock minerals in submarine granite buried hills based on CT scanning. Background Art

[0002] With the advancement of the "Deep Sea, Deep Earth" plan, submarine paleo-buried hill oil and gas reservoirs are the key areas for expansion in the current oil and gas industry. However, the strata of submarine paleo-buried hills are mainly composed of granite, and the granite lithology has strong heterogeneity. The rock minerals mainly consist of potassium feldspar, plagioclase, quartz, clay minerals and metal minerals, and it is difficult to accurately calculate the mineral content composition, which restricts the discovery and comprehensive evaluation of submarine paleo-buried hill oil and gas reservoirs.

[0003] At present, there are the following several ways to determine the parameters of the content of rock minerals in submarine granite buried hills:

[0004] Laboratory analysis method: Lower a drilling coring instrument into the well to drill a core sample, and then conduct an X-ray diffraction experiment on the core in the laboratory to obtain the content of mineral components in the rock.

[0005] Element logging calculation method: Measure the element logging data of the granite buried hill formation to obtain the formation element data, construct an oxygen closure model, and then calculate the content of rock mineral components in the formation.

[0006] Logging model calculation method: Based on the rock volume model, establish a logging response equation set through logging data such as neutron, density and resistivity, and solve parameters such as formation mineral components and pores through algorithms such as optimization, so as to obtain the content of granite rock mineral components.

[0007] In the above existing methods, the laboratory analysis method depends on drilling coring operations, and the cost of drilling coring work is expensive, and at the same time the operation cycle is long, which cannot meet the requirements of fine and continuous evaluation of the content of rock minerals in submarine granite buried hills. The element logging calculation and logging model calculation methods depend on the reliability of logging information. Because the fractures in granite buried hills are relatively developed, the wellbore is prone to enlargement during the drilling process, and the wellbore environment is poor, resulting in low reliability of logging information, and the accuracy of calculating granite mineral content by the logging model is low. Summary of the Invention

[0008] Aiming at the above deficiencies in the prior art, the method for calculating the content of rock minerals in submarine granite buried hills based on CT scanning provided by the present invention solves the problem that the existing methods for calculating the content of minerals in submarine granite buried hills are limited by the poor wellbore environment of granite well points, and it is difficult to obtain core and logging information, resulting in low accuracy of calculating the content of rock minerals in granite buried hills.

[0009] To achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows: A method for calculating the rock mineral content of a granite buried hill in the sea area based on CT scanning, comprising the following steps:

[0010] Perform CT scanning and preprocessing on the granite cuttings sample to obtain a CT grayscale image;

[0011] Perform measurement and analysis on the granite cuttings sample to determine the mass percentage of each mineral in the granite cuttings sample;

[0012] According to the density and porosity of each mineral in the granite cuttings sample, convert the mass percentage of each mineral into a volume percentage;

[0013] Compare the volume percentage of each mineral with the cumulative pixel value of the grayscale value of each mineral in the CT grayscale image to determine the standardized grayscale threshold of each mineral in the CT grayscale image, and construct a mineral content grayscale threshold table;

[0014] According to the mineral content grayscale threshold table, determine the mineral content in the granite buried hill rock of the target sea area.

[0015] Further, the method for obtaining the CT scanning grayscale image is as follows:

[0016] Wash and dry the sampled granite cuttings sample;

[0017] Perform CT scanning on the dried granite cuttings sample;

[0018] Perform normalization processing on the CT scanned image to obtain a CT grayscale image.

[0019] Further, perform measurement and analysis on the granite cuttings sample by an X-ray diffraction analyzer, and determine the mass percentage of each mineral in the granite cuttings sample according to the corresponding spectra generated by different minerals.

[0020] Further, the formula for converting the mass percentage of each mineral into a volume percentage is:

[0021] ;

[0022] In the formula, represents the volume percentage of the i-th mineral after normalization, represents the weight of the i-th mineral, represents the mineral density of the i-th mineral, represents the porosity of the i-th mineral, i represents the mineral ordinal number, and n represents the total number of minerals.

[0023] Further, the minerals in the granite include potassium feldspar, plagioclase, quartz, clay minerals and metal minerals.

[0024] Further, when the volume percentage of the mineral is equal to the cumulative pixel value of the mineral gray value in the CT gray image, the gray value is determined as the standardized gray threshold corresponding to the mineral.

[0025] Further, the method for determining the mineral content in the granite buried hill rock in the target sea area is as follows:

[0026] Compare the gray value of the granite buried hill rock in the target sea area in the corresponding CT gray image with the mineral content gray threshold table to determine the mineral type, and accumulate its corresponding gray value to obtain the mineral content.

[0027] Further, in the mineral content gray threshold table:

[0028] The gray value less than 54 is pores; the mineral with a gray value between 54 and 87 is potassium feldspar; the mineral with a gray value between 87 and 109 is plagioclase; the mineral with a gray value between 109 and 95 is quartz; the mineral with a gray value between 195 and 225 is clay mineral; the mineral with a gray value between 225 and 255 is metal mineral.

[0029] Compared with other methods, the rock mineral content calculation method provided by the present invention has the following advantages:

[0030] High prediction result accuracy: The accuracy of the calculation result depends on the abundance of existing cuttings CT scan and X-ray diffraction mineral analysis data in the area. With a large amount of modeling data, the threshold accuracy of the rock mineral CT scan gray map can be improved. Compared with the existing conventional methods, the calculation result accuracy of this method is higher;

[0031] Low cost: The production unit does not need to collect additional geological basic data and does not incur data collection operation costs. Only by processing and mining the existing geological data can the calculation of the percentage content of granite rock minerals be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flowchart of the method for calculating the mineral content of the granite buried hill rock in the sea area based on CT scan provided by the present invention.

[0033] Figure 2 It is a relationship diagram between the gray value and the cumulative pixel value of the granite rock CT image provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0035] Please refer to Figures 1 to 2 , the present invention provides a method for calculating the rock mineral content of submarine granite buried hills based on CT scanning, aiming to accurately calculate the mineral content in granite rocks to suit the application of reserve evaluation and development work of submarine granite buried hill oil and gas reservoirs.

[0036] As Figure 1 shown, the method for calculating the rock mineral content of submarine granite buried hills based on CT scanning in the present invention includes the following steps:

[0037] Perform CT scanning and preprocessing on granite cuttings samples to obtain CT grayscale images;

[0038] Perform measurement and analysis on granite cuttings samples to determine the mass percentage of each mineral in the granite cuttings samples;

[0039] According to the density and porosity of each mineral in the granite cuttings samples, convert the mass percentage of each mineral into volume percentage;

[0040] Compare the volume percentage of each mineral with the cumulative pixel value of the grayscale value of each mineral in the CT grayscale image to determine the standardized grayscale threshold of each mineral in the CT grayscale image, and construct a mineral content grayscale threshold table;

[0041] According to the mineral content grayscale threshold table, determine the mineral content in the submarine granite buried hill rocks of the target sea area.

[0042] The method of the present invention combines CT scanning data of drilling cuttings samples to construct a calculation model for rock mineral content, improving the calculation accuracy of granite rock mineral content.

[0043] The following further illustrates the implementation of the present invention in combination with Examples 1 to 5.

[0044] Example 1:

[0045] In this example, the method for processing granite cuttings samples to obtain corresponding CT grayscale images is mainly described, including:

[0046] Wash and dry the sampled granite cuttings samples;

[0047] Perform CT scanning on the dried granite cuttings samples;

[0048] Perform normalization processing on the CT scanned images to obtain CT grayscale images.

[0049] Specifically, in this embodiment, samples are taken during the drilling process of the granite wellbore to obtain several granite cuttings samples; the obtained cuttings samples are washed with oil and dried, and the cuttings samples are measured by a CT scanner to obtain corresponding CT image data. In order to avoid the interference of image contrast (uneven distribution of image pixel brightness) on subsequent processing, it is necessary to normalize the CT image grayscale (0-255).

[0050] Example 2:

[0051] In this embodiment, the process of determining the mass percentage of each mineral in the cuttings sample through measurement and analysis is elaborated.

[0052] In this embodiment, the granite cuttings sample is measured and analyzed by an X-ray diffraction analyzer, and according to the corresponding spectra generated by different minerals, the mass percentage of each mineral in the granite cuttings sample is determined.

[0053] Specifically, the minerals obtained through measurement and analysis in granite include potassium feldspar, plagioclase, quartz, clay minerals, and metal minerals.

[0054] Example 3:

[0055] This embodiment focuses on the method of converting the mass percentage of each mineral into a volume percentage.

[0056] Since the proportion of grayscale values calculated from the CT grayscale image obtained by CT scanning belongs to the volume percentage, and the mineral content obtained through measurement and analysis belongs to the mass percentage, it is necessary to convert the mass percentage of the cuttings minerals into a volume percentage for subsequent comparison.

[0057] In this embodiment, according to the density and porosity of each mineral, the relative mass content is converted into a volume percentage content and normalized. The conversion formula is:

[0058] ;

[0059] In the formula, represents the volume percentage of the i-th mineral after normalization, %; represents the weight of the i-th mineral, represents the mineral density of the i-th mineral, g / cm 3 ;,[[]]END]] represents the porosity of the i-th mineral, %; i represents the mineral ordinal number, and n represents the total number of minerals.

[0060] Through the above formula, the composition components of granite, potassium feldspar, plagioclase, quartz, clay minerals, and metal minerals, can be converted from mass percentage to volume percentage.

[0061] In this embodiment, during the calculation of rock mineral content, based on the different densities of each mineral, the mineral content is uniformly converted into volume percentage to obtain a unified reference standard for subsequent comparison of volume percentages, thereby quickly determining the mineral content.

[0062] Embodiment 4:

[0063] In this embodiment, the process of constructing the gray threshold table of mineral content is elaborated.

[0064] When the volume percentage of the mineral is equal to the cumulative pixel value of the mineral gray value in the CT gray image, this gray value is determined as the standardized gray threshold corresponding to the mineral.

[0065] In this embodiment, for the above two types of data, the mineral content of the core is used as a scale to measure the pixels, and a unified comparison standard is established, so that the mineral content can be determined through the standardized gray value in the CT gray image.

[0066] Compare the CT gray images corresponding to several sampled granite cuttings samples with the granite mineral volume percentage (content percentage) after percentage conversion, and a relationship diagram of the gray value and cumulative pixel value of the granite CT gray image as shown in Figure 2 can be made. A relationship diagram of the gray value and cumulative pixel value of the CT gray image is made for each cutting sample, and then the relationship diagrams are compared according to the cumulative pixel value of the mineral content percentage gray value of the cutting samples. When the cumulative pixel value of a certain gray value of a certain mineral content (such as quartz) in the granite cuttings is equal, it is considered that the mineral corresponding to this gray value is quartz, and its mineral content is the cumulative pixel value of its gray value, and this gray value is used as the standardized gray threshold of quartz, thereby constructing a gray threshold table of mineral content.

[0067] In the gray threshold table of mineral content:

[0068] The gray value less than 54 is pores; the mineral with a gray value between 54 and 87 is potassium feldspar; the mineral with a gray value between 87 and 109 is plagioclase; the mineral with a gray value between 109 and 95 is quartz; the mineral with a gray value between 195 and 225 is clay mineral; the mineral with a gray value between 225 and 255 is metal mineral.

[0069] Embodiment 5:

[0070] In this embodiment, the method for determining the mineral content in the granite buried hill rock of the target sea area according to the gray threshold table of mineral content is elaborated; specifically:

[0071] Compare the gray value of the granite buried hill rock in the corresponding CT gray image with the gray threshold table of mineral content to determine the mineral type, and accumulate its corresponding gray value to obtain the mineral content.

[0072] Through the above method, the calculation results of the percentage content of granite rock minerals are determined and stored for the user to evaluate the reservoir reserves and formulate the development implementation plan.

[0073] The calculation of the percentage content of granite rock minerals in the submarine granite buried hill formation provided by the present invention is based on the CT scan data of drilling cuttings, and provides a quick and reliable method for calculating the percentage content of granite rock minerals for oil and gas production units.

[0074] In the present invention, specific embodiments are used to elaborate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

[0075] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principle of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention according to the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A method for calculating the mineral content of granite buried hill rocks in the sea based on CT scanning, characterized in that: The following steps are involved: The granite rock cuttings samples were CT scanned and preprocessed to obtain CT grayscale images; Measure and analyze the granite rock chip samples to determine the mass percentage of each mineral in the granite rock chip samples; According to the density and porosity of each mineral in the granite rock chip sample, the mass percentage of each mineral is converted into volume percentage; The volume percentage of each mineral is compared with the cumulative pixel value of each mineral gray value in the CT gray image, the standardized gray threshold of each mineral in the CT gray image is determined, and a mineral content gray threshold table is constructed; According to the mineral content grayscale threshold table, the mineral content in the granite buried hill rock in the target sea area is determined.

2. The method according to claim 1, characterized in that The method to obtain the CT scan grayscale image is: The sampled granite cuttings were oil washed and dried; CT scanning of the dried granite rock cuttings samples; The CT scanned image is normalized to obtain a CT grayscale image.

3. The method according to claim 1, characterized in that The granite rock chip samples were measured and analyzed by an X-ray diffraction analysis instrument, and the mass percentage of each mineral in the granite rock chip samples was determined based on the corresponding spectra produced by different minerals.

4. The method according to claim 1, characterized in that The formula for converting the mass percentage of each mineral into volume percentage is: ； In the formula, represents the normalized volume percentage of the ith mineral, represents the weight of the i-th mineral, represents the mineral density of the i-th mineral, It represents the porosity of the i-th mineral, i represents the mineral number, and n represents the total number of minerals.

5. The method according to claim 1, characterized in that The minerals in the granite include potassium feldspar, plagioclase, quartz, clay minerals and metal minerals.

6. The method according to claim 1, characterized in that When the volume percentage of the mineral is equal to the cumulative pixel value of the mineral grayscale value in the CT grayscale image, the grayscale value is determined to be the standardized grayscale threshold corresponding to the mineral.

7. The method according to claim 1, characterized in that The method for determining the mineral content in the granite buried hill rock in the target sea area is: The grayscale value of the granite buried hill rock in the target sea area in the corresponding CT grayscale image is compared with the mineral content grayscale threshold table to determine the mineral type, and the corresponding grayscale value is accumulated to obtain the mineral content.

8. The method according to claim 1, characterized in that In the mineral content grayscale threshold table: Grayscale values ​​less than 54 are pores; minerals with grayscale values ​​between 54 and 87 are potassium feldspar; minerals with grayscale values ​​between 87 and 109 are plagioclase; minerals with grayscale values ​​between 109 and 95 are quartz; minerals with grayscale values ​​between 195 and 225 are clay minerals; and minerals with grayscale values ​​between 225 and 255 are metallic minerals.

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