External surface volume correction method and device suitable for measuring porosity of rock sample with rough surface

Abstract

The invention discloses an outer surface volume correction method and device suitable for measuring the porosity of a rock sample with a rough surface. The method comprises the following steps: acquiring and scanning original slice data; obtaining a binary image data volume D skeleton ROI capable of representing rock skeleton components according to the scanned original slice data; obtaining the volume V real of the binary image data volume D real ROI after mean processing according to the D skeleton ROI; according to the binary image data volume D real ROI after averaging processing, the rock sample outer surface development pore volume sum V surface pores are obtained; according to the volume V < actual > and the rock sample outer surface development pore volume sum V < surface pore >, the corrected rock sample outer surface volume V < surface volume > is obtained. According to the invention, a high-precision surface volume measurement result can be provided for low-porosity compact, brittle and fragile rocks, so that the accuracy of a test result of the helium porosity of the rocks is improved.

Description

Technical Field

[0001] The present application relates to the field of volume measurement technology, and in particular to an external volume correction method suitable for porosity measurement of rock samples with rough surfaces and an external volume correction device suitable for porosity measurement of rock samples with rough surfaces. Background Art

[0002] The surface volume of a rock sample is one of the key parameters for measuring and calculating its helium porosity. During cutting, grinding, or natural weathering, a rough, uneven structure often forms on the surface of a rock sample. Some of these recessed spaces on the rock sample's surface are artificially formed by the collapse and loss of rock mineral particles, while others are pores that naturally developed during the rock's burial and diagenetic processes. Ignoring the surface roughness of the rock sample and mistakenly interpreting the recessed spaces left by the collapsed particles as the rock's developed pore volume will cause the measured surface volume to be inflated compared to the actual value, leading to an inflated helium porosity measurement. This impact is particularly significant in low-porosity, dense rocks such as shale.

[0003] How to determine the cause of the concave space on the surface of the rock sample, remove the concave space formed by the missing particles, and retain the real developed pores connected to the surface of the rock sample, is of great significance for accurately measuring the surface volume of the rock sample and correcting the helium porosity measurement value of the rock.

[0004] Current measurements of rock sample surface volume generally do not consider surface roughness. To accurately determine a sample's surface volume, it's often necessary to prepare and use standard rock samples. For example, a plunger sample is prepared and its diameter and height are measured with a vernier caliper to calculate its surface volume. However, even with sophisticated sample preparation techniques like wire cutting, surface particle collapse and loss cannot be avoided. At the microscopic level, surface roughness can still affect helium porosity test results.

[0005] For some brittle rock types (such as shale and coal), or when sampling conditions are limited (such as drilling cuttings or granular samples from fractured rock zones), it is difficult to prepare samples with a regular shape. In such cases, the influence of the rock sample surface roughness on the measured apparent volume and helium porosity is even more significant.

[0006] Commonly used methods for measuring the surface volume of rock samples include using a vernier caliper for regularly shaped rock samples and employing the Archimedean principle, using wax sealing or mercury exclusion methods, for irregularly shaped rock samples. In these existing rock surface volume measurement methods, small depressions artificially created during the sampling and sample preparation processes are interpreted as naturally occurring pores in the rock during measurement. This can lead to an overestimation of the measured helium porosity. This is particularly true for rock types with less pore development and lower porosity, such as shale and coal. Correction is required to account for the effect of surface roughness differences on the surface volume and porosity measurements.

[0007] In summary, the measured surface volume of a rock sample directly affects the accuracy of its helium porosity test results. Existing surface volume measurement techniques, whether for regular or irregular rock samples, fail to correct for the volume of missing microscopic particles on the sample's surface. Summary of the Invention

[0008] The object of the present invention is to provide a surface volume correction method suitable for porosity measurement of rock samples with rough surfaces to solve at least one of the above-mentioned technical problems.

[0009] The present invention provides the following solutions:

[0010] According to one aspect of the present invention, a surface volume correction method for porosity measurement of rock samples with rough surfaces is provided. The surface volume correction method for porosity measurement of rock samples with rough surfaces comprises:

[0011] Acquire raw slice data of each scanned rock sample scanned by CT scanning;

[0012] The three-dimensional data volume is reconstructed for each scanned original slice data to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI ;

[0013] The rock sample solid skeleton binary image data volume D 骨架ROI The outer contour of the image is identified and the space inside the outer contour is processed by averaging, thereby obtaining the binary image data volume D after averaging. 实ROI , and calculate the mean to obtain the binary image data volume D after mean processing 实ROI Volume V 实 ;

[0014] According to the binary image data volume D after mean processing 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 ;

[0015] According to the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V表孔 Get the corrected rock sample surface volume V 外表体积 .

[0016] Optionally, the three-dimensional data volume is reconstructed for each scanned original slice data to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI include:

[0017] The grayscale range of the rock solid skeleton is determined by using the Otsu algorithm, and on this basis, the three-dimensional image data volume of the rock sample solid part is segmented and extracted to obtain the binary image data volume D that can characterize the rock skeleton components. 骨架ROI .

[0018] Optionally, the binary image data volume D after mean processing 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 include:

[0019] According to the binary image data volume D after the mean processing 实ROI Obtain a concave data volume D with multiple discrete units that can represent the concave space volume on the rock sample surface 凹-multiROI ;

[0020] According to the concave data volume D with multiple discrete units that can characterize the concave space volume of the rock sample surface 凹-multiROI Obtain the naturally developed pores D on the outer surface of the rock 表孔-multiROI ;

[0021] According to the pores D that develop naturally on the outer surface of each rock 表孔-multiROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 .

[0022] Optionally, the binary image data volume D processed according to the mean value 实ROI Obtain a data volume D with multiple discrete units that can represent the concave spatial volume of the rock sample surface 凹-multiROI include:

[0023] The binary image data volume D after mean processing 实ROI Perform image morphological closing operation to obtain a binary image data volume D with a relatively smooth appearance 基准面ROI ;

[0024] The binary image data volume D with a relatively smooth appearance 基准面ROI The outer surface of the rock is taken as the reference surface, the outer surface is the convex part of the rock surface, and the inner surface is the concave part of the rock surface. 基准面ROI -D 实ROI Obtain the difference space data volume D 差值ROI ;

[0025] For the difference space data volume D 差值ROI Perform voxel connectivity analysis and resolve it into multiple discrete unit difference data volumes D 差值-multiROI ;

[0026] And for each discrete unit difference data volume D 差值-multiROI The voxel size is measured, and the data information with insufficient spatial resolution to represent the credible pore space is removed. The difference data volume D of the remaining discrete units is 差值-multiROI As the concave data volume D 凹-multiROI .

[0027] Optionally, the concave data volume D having multiple discrete units capable of characterizing the concave spatial volume of the rock sample surface is 凹-multiROI Obtain the naturally developed pores D on the outer surface of the rock 表孔-multiROI include:

[0028] Obtaining a standard image data volume;

[0029] Obtain a binary image data volume D according to the standard image data volume 孔 ;

[0030] For binary image data volume D 孔 According to the results of pore voxel connectivity analysis, binary image data volume D of multiple discrete units is obtained. 孔-multiROI ;

[0031] Extract binary image data volume D 孔-multiROI The pore data volume connected to the outer surface is used to obtain discrete binary image data volume units and the noise units with smaller voxels are removed to obtain the outer pore binary image data volume D 外孔-multiROI ;

[0032] According to each outer hole binary image data volume D 外孔-multiROI Obtain characteristic parameters and standards for determining the origin of pores;

[0033] According to the characteristic parameters and standards for distinguishing the origin of pores, the concave data volume D 凹-multiROI The individual discrete units in the rock are screened to obtain the naturally developed pores D on the rock surface. 表孔-multiROI .

[0034] Optionally, the pores D naturally developed on the outer surface of each rock 表孔-multiROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 include:

[0035] Calculate and count the naturally developed pores D on the outer surface of each rock 表孔-multiROI The volume of the unit space is summed up to obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 .

[0036] Optionally, the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 include:

[0037] Get volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔之和 As the corrected rock sample surface volume V 外表体积 .

[0038] Optionally, the surface volume correction method applicable to porosity measurement of rock samples with rough surfaces further comprises:

[0039] Obtain helium porosity of test rock samples.

[0040] Optionally, obtaining the helium porosity of the test rock sample includes:

[0041] Obtain pressure change information and known volume information obtained during the helium porosity test experiment;

[0042] According to the gas equation, calculate the skeleton volume V of the rock sample being tested solid ;

[0043] According to the skeleton volume V of the rock sample being tested solid , the corrected rock sample surface volume V 外表体积 Obtain helium porosity of test rock samples.

[0044] The present application also provides an external volume correction device suitable for measuring the porosity of a rock sample with a rough surface, the external volume correction device suitable for measuring the porosity of a rock sample with a rough surface comprising:

[0045] A scanning original slice data acquisition module, wherein the scanning original slice data acquisition module is used to acquire each scanning original slice data of the rock sample scanned by CT scanning;

[0046] D 骨架ROI Get module, the D 骨架ROI The acquisition module is used to reconstruct the three-dimensional data volume of each scanned original slice data to obtain the binary image data volume D that can characterize the rock skeleton components. 骨架ROI ;

[0047] Volume acquisition module, the volume acquisition module is used to obtain the rock sample solid skeleton binary image data volume D 骨架ROI The outer contour of the image is identified and the space inside the outer contour is processed by averaging, thereby obtaining the binary image data volume D after averaging. 实ROI, and calculate the binary image data volume D after mean processing 实ROI Volume V 实 ;

[0048] The module for obtaining the total volume of the pores on the outer surface is used to obtain the total volume of the pores on the outer surface according to the binary image data volume D after mean processing. 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 ;

[0049] The corrected rock sample surface volume acquisition module is used to obtain the corrected rock sample surface volume according to the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 .

[0050] Based on CT three-dimensional scanning technology, this paper establishes an external volume correction method suitable for measuring and calculating the porosity of rock samples with rough surfaces. This method utilizes three-dimensional image processing technology to establish a method for identifying the causes of surface depressions on rock samples. This method corrects for the volume of missing particles caused by sample preparation within the rock sample's external volume. This method enables convenient, rapid, and non-destructive measurement and calculation of the external volume of regular or irregular rock samples. It can provide highly accurate external volume measurements for low-porosity, dense, brittle, and fragile rocks, thereby improving the accuracy of rock helium porosity test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a flow chart of an external volume correction method for porosity measurement of rock samples with rough surfaces in one embodiment of the present application.

[0052] Figure 2 is a schematic structural diagram of a rock sample with a rough surface in an embodiment of the present application; wherein,

[0053] 2a is a three-dimensional rendering of the image data volume of a rock sample with a rough surface; 2b is a two-dimensional slice rendering of the image data volume of a rock sample with a rough surface reconstructed by CT scanning; 2c is a binary image data volume D corresponding to 2b that represents the rock skeleton. 骨架ROI Two-dimensional slice effect diagram; 2d is the binary image data volume D after mean processing corresponding to 2c 实ROI Two-dimensional slice effect diagram; 2e is the binary image data volume D after the closing operation corresponding to 2d 基准面ROI Two-dimensional slice effect diagram; 2f is the binary image data volume D after the subtraction operation of 2e and 2d. 差值ROI Two-dimensional slice effect diagram; 2g is the binary image data volume D after connectivity analysis and noise processing corresponding to 2f 凹-multiROITwo-dimensional slice effect diagram; 2h is the binary image data volume D corresponding to 2g after screening naturally developed pores according to the established standards 表孔-multiROI Two-dimensional slice effect diagram; 2i is the binary image data volume D corresponding to 2a, which represents the naturally developed pores on the surface 表孔-multiROI Three-dimensional rendering.

[0054] Figure 3 It is the binary image data volume D in one embodiment of the present application. 孔 Schematic diagram; 3a is in Figure 2 The data volume shown in a is sampled in a regular cylindrical shape to obtain data volume D 孔 , which is used to establish the discrimination standard of naturally developed pores on the surface; 3b is the binary image data volume D corresponding to 3a that represents the developed pores 孔 3D rendering; 3c is the data volume D of the pores connected to the outer surface of the cylinder corresponding to 3b 外孔-multiROI Three-dimensional pore effect diagram; 3d is the statistical calculation data volume D 外孔-multiROI Frequency distribution histogram of pore structure parameters (pore volume / surface area). DETAILED DESCRIPTION

[0055] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0056] like Figure 1 The surface volume correction method shown for porosity measurements of rock samples with rough surfaces includes:

[0057] Obtain raw slice data for each rock sample scanned by CT scanning. Specifically, the rock sample is fixed to a CT scanning holder and scanned. The scanning imaging resolution should be able to image larger pores within the rock. Block samples can be directly fixed, and granular samples can be placed in a container made of low-density material (such as resin). The container's surface volume must be known and large enough to fit in the helium porosimeter and CT scanner (the surface volume can be measured in advance with helium).

[0058] The three-dimensional data volume is reconstructed for each scanned original slice data to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI ;

[0059] The rock sample solid skeleton binary image data volume D 骨架ROI The outer contour of the image is identified and the space inside the outer contour is processed by averaging, thereby obtaining the binary image data volume D after averaging.实ROI , and calculate the binary image data volume D after mean processing 实ROI Volume V 实 ;

[0060] According to the binary image data volume D after mean processing 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 ;

[0061] According to the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 .

[0062] In this embodiment, the three-dimensional data volume is reconstructed for each scanned original slice data to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI include:

[0063] The grayscale range of the rock solid skeleton is determined by using the Otsu algorithm, and on this basis, the three-dimensional image data volume of the rock sample solid part is segmented and extracted to obtain the binary image data volume D that can characterize the rock skeleton components. 骨架ROI Specifically, the original scanned slice data is reconstructed into a three-dimensional data volume, and the reconstructed data volume is imported into the visualization software platform. The grayscale range of the rock solid skeleton part is determined by using the Otsu algorithm, and on this basis, the three-dimensional image data volume of the solid part of the rock sample is segmented and extracted to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI ;

[0064] In this embodiment, the binary image data volume D after the mean processing 实ROI Obtaining the total volume of pores developed on the outer surface of the rock sample (V surface pores) includes:

[0065] According to the binary image data volume D after the mean processing 实ROI Obtain a concave data volume D with multiple discrete units that can represent the concave space volume on the rock sample surface 凹-multiROI ;

[0066] According to the concave data volume D with multiple discrete units that can characterize the concave space volume of the rock sample surface 凹-multiROI Obtain the naturally developed pores D on the outer surface of the rock 表孔-multiROI ;

[0067] According to the pores D that develop naturally on the outer surface of each rock 表孔-multiROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 .

[0068] In this embodiment, the binary image data volume D after the mean processing 实ROI Obtain a concave data volume D with multiple discrete units that can represent the concave space volume on the rock sample surface 凹-multiROI include:

[0069] The binary image data volume D after mean processing 实ROI Perform image morphological closing operation to obtain a binary image data volume D with a relatively smooth appearance 基准面ROI ;

[0070] The binary image data volume D with a relatively smooth appearance 基准面ROI The outer surface of the rock is taken as the reference surface, the outer surface is the convex part of the rock surface, and the inner surface is the concave part of the rock surface. 基准面ROI -D 实ROI Obtain the difference space data volume D 差值ROI ;

[0071] For the difference space data volume D 差值ROI Perform voxel connectivity analysis and resolve it into a difference data volume D with multiple discrete units 差值-multiROI ;

[0072] And for each discrete unit difference data volume D 差值-multiROI The voxel size is measured, and the data information with insufficient spatial resolution to represent the credible pore space is removed. The difference data volume D of the remaining discrete units is 差值-multiROI As the concave data volume D 凹-multiROI .

[0073] Specifically, the binary image data volume D 实ROI The target data volume is subjected to image morphological closing operation (closing operation is a basic operation in morphological processing, which consists of two steps: expansion and corrosion. In CT image processing, closing operation is often used to fill small holes in the image, connect adjacent objects, and smooth the edges of objects) to obtain a binary image data volume D with a relatively smooth appearance. 基准面ROI , the outer surface of the data body is used as the reference surface, the outer surface is the convex part of the rock surface, and the inner surface is the concave part of the rock surface. On this basis, the above two data bodies are subjected to spatial subtraction operation, that is, D 基准面ROI -D 实ROI Obtain the difference space data volume D 差值ROI The data volume is analyzed for voxel connectivity and parsed into multiple discrete unit difference data volumes D 差值-multiROI, and the voxel size of each unit data volume is measured. On this basis, the data information with insufficient spatial resolution to represent the credible pore space is removed, such as the data volume unit with less than 4 voxels, to obtain the concave data volume D with multiple discrete units that can represent the concave space volume of the rock sample surface. 凹-multiROI ;

[0074] In this embodiment, the concave data volume D having multiple discrete units capable of characterizing the concave spatial volume of the rock sample surface is 凹-multiROI Obtain the naturally developed pores D on the outer surface of the rock 表孔-multiROI include:

[0075] Obtaining a standard image data volume;

[0076] Obtain a binary image data volume D according to the standard image data volume 孔 ;

[0077] For binary image data volume D 孔 According to the results of pore voxel connectivity analysis, binary image data volume D of multiple discrete units is obtained. 孔-multiROI ;

[0078] Extract each binary image data volume D 孔-multiROI中 The pore data volume connected to the outer surface is used to obtain discrete binary image data volume units and remove the noise units with smaller voxels to obtain the outer pore binary image data volume D 外孔-multiROI ;

[0079] According to each outer hole binary image data volume D 外孔-multiROI Obtain characteristic parameters and standards for determining the origin of pores;

[0080] According to the characteristic parameters and standards for distinguishing the origin of pores, the concave data volume D of each discrete unit is 凹 -multi ROI Screening is performed to obtain the naturally developed pores D on the outer surface of the rock. 表孔-multiROI .

[0081] In this embodiment, the pores D that are naturally developed on the outer surface of each rock are 表孔-multiROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 include:

[0082] Calculate the volume of each unit space and sum it up to obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 .

[0083] Specifically, first, a standard shape image (i.e., a regular geometric image, such as a cylinder, etc.) is used to resample the image data volume within the three-dimensional rock sample data volume to obtain an image data volume with a regular shape that is not disturbed by the actual rock surface and is smaller in volume than the original analysis data volume. This is used to establish the discrimination standard, and the grayscale threshold of the pore component is determined and image segmentation and extraction are performed to obtain a binary image data volume D. 孔 , and further calculate the binary image data volume D of multiple discrete units based on the pore voxel connectivity analysis results 孔-multiROI , extract the pore data volume unit connected to the outer surface to obtain the discrete binary image data volume unit and remove the noise unit with smaller voxels to obtain the new binary image data volume D 外孔-multiROI , analyze its structural characteristics, calculate the pore volume / surface area parameter value of each data unit, and statistically analyze to determine the distribution range of the pore volume / surface area characteristic parameters of the real pores in the rock sample, and use them as the characteristic parameters and standards for judging the origin of pores. On this basis, the concave data volume D is 凹-multiROI The pore volume / surface area parameters are calculated, and the cause of the depression is determined based on the established characteristic parameter standards. Units outside the standard range are removed, and the units that meet the standards are retained as naturally developed pores on the outer surface of the rock. 表孔-multiROI Calculate the volume of each unit space and sum it up to obtain the total volume of pores on the outer surface of the rock sample V 表 hole;

[0084] In this embodiment, the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 include:

[0085] Get volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔之和 As the corrected rock sample surface volume V 外表体积 .

[0086] In this embodiment, the surface volume correction method applicable to porosity measurement of rock samples with rough surfaces further includes:

[0087] Obtain helium porosity of test rock samples.

[0088] In this embodiment, obtaining the helium porosity of the test rock sample includes:

[0089] Obtain pressure change information and known volume information obtained during the helium porosity test experiment (the known volume information is the volume of the reference chamber in the helium porosity test instrument, based on the measured pressure after the valve between the reference chamber and the sample chamber is closed and opened, as well as the volume of the reference chamber);

[0090] According to the gas equation, calculate the skeleton volume V of the rock sample being tested solid ;

[0091] According to the skeleton volume V of the rock sample being tested solid , the corrected rock sample surface volume V 外表体积 Obtain the helium porosity of the test rock sample. The helium porosity of the test rock sample is Ф=(V 外表体积 -V solid ) / V 外表体积 *100%.

[0092] The following combination Figure 2 as well as Figure 3 The present application will be further elaborated. It will be understood that this example does not constitute any limitation to the present application.

[0093] Select appropriate resolution to scan and image the entire rock sample. Perform three-dimensional reconstruction on the original scanned projection image to obtain the three-dimensional data volume of the rock sample. In this example, the rock sample is a cylinder ( Figure 2 a), the cross section of the cylinder is perpendicular to the natural sedimentary bedding direction of the rock ( Figure 2 b).

[0094] Select appropriate grayscale threshold to segment the image, identify the skeleton of the rock sample and obtain the data volume D 骨架ROI In this example, the grayscale threshold of the rock sample skeleton is calculated using the Otsu method. Figure 2 b and Figure 2 c shows a slice of rock perpendicular to the bedding direction and the binary image of the rock sample skeleton corresponding to the slice after identification and segmentation;

[0095] For the skeleton data volume D 骨架ROI The internal pore space is filled with images to obtain the corresponding solid data volume D 实ROI The specific method used in this example is to perform a cross-sectional analysis of the binary image data volume D along the cross-sectional direction perpendicular to the bedding direction. 骨架ROI The outer contour of each slice is identified and its interior is filled with 1. Figure 2 d shows the Figure 2 c slice corresponding to D 实ROI Image processing results;

[0096] The reference surface data volume of the rock sample's outer surface is calculated and obtained. In this example, the image morphology closing operation function is used in the image processing software. An appropriate structure element size is selected (the kernel size is 15 in this example. The larger the value, the smoother the outer surface of the reference surface data individual and the lower the degree of wrapping of the rock sample). Without changing the basic morphology of the rock sample's outer contour, the concave space on the outer surface is filled, and a new binary image data volume D with a relatively smooth outer surface is obtained. 基准面ROI , Figure 2 e shows the corresponding Figure 3 D after smoothing 基准面ROI Binary image result;

[0097] The binary image data volume D 基准面ROI and D 实ROI Perform spatial subtraction to obtain the difference spatial data volume D between the two 差值ROI , Figure 2 f shows Figure 2 e and Figure 2 The binary image obtained by subtracting the slices of the data volume shown in d is subjected to image unit voxel connectivity analysis. In this example, the data volume is divided into multiple discrete unit data volumes D according to the six-connectivity principle. 差值-multiROI , analyze and count the voxel size of each unit, and remove the units with smaller voxels. In this example, remove D 差值-multiROI For units with less than 100 voxels, obtain the data volume D 凹-multiROI , Figure 2 g is shown in Figure 2 f shows the data body D 差值 -multi ROI The concave unit data volume D on the outer surface of the rock sample obtained after removing noise 凹-multiROI The corresponding slice image;

[0098] The data body is resampled by using regular geometric bodies inside the rock to obtain a data body with smooth surface and regular shape, such as Figure 3 a. In this example, a cylinder is used for internal resampling to obtain a data volume with a relatively small internal volume. The pore space within the data is identified and characterized. In this example, the Otsu method is used to calculate its threshold and segment and extract the binary image data volume D. 孔 ( Figure 3 b) Further, according to the connectivity analysis results of the pore voxels, it is parsed into a binary image data volume D with multiple discrete units according to the six-connectivity principle. 孔-multiROI , extract the pore data volume units connected to the outer surface to obtain discrete binary image data volume units and remove the noise units with less than 100 voxels to obtain a new binary image data volume D 外孔-multiROI ( Figure 3c) Calculate the pore volume / surface area parameter value of each unit, and statistically analyze to determine the distribution range of the pore volume / surface area characteristic parameters of the real pores in the rock sample, and use them as the characteristic parameters and standards for distinguishing the origin of pores. If the statistical sample data obtained from a single resampling is small, this step can be repeated. By changing the sampling position or the diameter of the geometric body, multiple samplings can be performed to calculate the structural pore volume / surface area parameters of the pores connected to the surface. The statistical results in this example are shown in Figure 3 d, the characteristic parameter distribution range is 0.00526~0.03229;

[0099] For discrete data volume unit D 凹-multiROI The pore volume / surface area parameters are calculated, and the cause of the depression is judged based on the distribution range of the characteristic parameters established in step 6. The depression units outside the standard range are removed, and the units that meet the standard are retained as the naturally developed pores D on the outer surface of the rock. 表孔-multiROI Calculate the volume of each unit space and sum it up to obtain the total volume of pores on the outer surface of the rock sample V 表孔 . Figure 2 h and Figure 2 i shows the data volume D that can characterize the pores developed on the outer surface after screening according to the standards. 表孔-multiROI Slice binary image and 3D rendering.

[0100] Calculate the data volume D separately 实ROI and data body D 表孔-multiROI The volume of 实 With V 表孔 The volume obtained by adding the two is the corrected surface volume V of the rock sample. 外表体积 , the volume parameter calculation results in this example are shown in Table 1 below:

[0101] Table 1 Volume parameter calculation results

[0102] parameter <![CDATA[Value (mm 3 )]]> <![CDATA[V 实 ]]> 9958.51 <![CDATA[V 表孔 ]]> 61.54 <![CDATA[V 外表体积 ]]> 10020.05

[0103] The present application also provides an external volume correction device for measuring the porosity of rock samples with rough surfaces, which comprises a scanning raw slice data acquisition module, a D 骨架ROI Acquisition module, volume acquisition module, external surface developed pore volume sum acquisition module and corrected rock sample surface volume acquisition module, wherein,

[0104] The scanning original slice data acquisition module is used to obtain each scanning original slice data of the rock sample scanned by CT scanning;

[0105] D 骨架ROIThe acquisition module is used to reconstruct the three-dimensional data volume of each scanned original slice data to obtain the binary image data volume D that can characterize the rock skeleton components. 骨架ROI ;

[0106] The volume acquisition module is used to obtain the binary image data volume D of the rock sample solid skeleton. 骨架ROI The outer contour of the image is identified and the space inside the outer contour is processed by averaging, thereby obtaining the binary image data volume D after averaging. 实ROI , and calculate the binary image data volume D after mean processing 实ROI Volume V 实 ;

[0107] The module for obtaining the total volume of pores on the external surface is used to obtain the binary image data volume D after mean processing. 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 ;

[0108] The corrected rock sample surface volume acquisition module is used to obtain the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 .

[0109] This application takes into account the influence of rock sample surface roughness on helium porosity measurement values and optimizes the surface volume measurement method.

[0110] This method for characterizing the rock sample's external surface and quantifying its external volume based on CT 3D data removes the "artificial" pore volume caused by grain collapse during sampling, while retaining the true pore volume of the rock itself, connected to the external surface. The resulting external volume of the rock sample can more accurately reflect the rock's pore development when used in helium porosity testing.

[0111] This application establishes a method for determining the cause of depressions on the outer surface of rock samples based on CT scan data, which removes the volume of depressions caused by humans on the rock surface while retaining the volume of naturally developed pore spaces on the rock surface.

[0112] Based on the characterization of the actual development of the rock sample's external surface, a surface smoothing technique was used to calculate the reference plane of the rock sample's external surface. The volume of the surface depressions was then determined by calculating the spatial difference between the actual rock sample's external surface and the reference plane. Furthermore, by analyzing the characteristics of structural parameters such as the pore volume and surface area within the rock sample, their distribution range was determined. This was used to screen the causes of the surface depressions and identify which surface depressions were caused by artificial sampling and which were naturally occurring pores in the rock.

[0113] Existing helium porosity measurement techniques for irregular rock samples (such as the wax sealing and drainage method and the mercury drainage method) are inherently destructive tests. Because the sample is contaminated by wax or mercury, it cannot be reused for other subsequent testing and analysis experiments. Furthermore, current testing standards require the use of parallel samples when testing particle samples. This means that parallel block samples are used to test the surface volume and apparent density, which are not truly the same sample as the particle sample measured by helium. The technical solution of the present invention, however, is a fully non-destructive test, using the same sample to complete the entire testing process, maximizing sample integrity and data system consistency.

[0114] Conventional technical solutions do not detect or evaluate the coating of irregular rock samples. For example, the wax sealing method cannot avoid or promptly detect cavities that may form during wax coating, and the mercury exclusion method cannot assess the impact of the intergranular volume of granular sample accumulation on the measured surface volume. Compared with existing technical solutions, the present invention improves the reliability of helium porosity test results for irregular rock samples in principle, taking into account the impact of the smoothness of the rock sample surface on the porosity test results. Visual inspection of rock sample surface depressions can be performed on a visualization software platform, minimizing the removal of artificial pore spaces formed by the collapse and loss of mineral particles, while retaining the naturally developed pores on the rock surface.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surface volume correction method for porosity measurement of rock samples with rough surfaces, characterized in that: The surface volume correction method applicable to the porosity measurement of rock samples with rough surfaces includes: Acquire raw slice data of each scanned rock sample scanned by CT scanning; The three-dimensional data volume is reconstructed for each scanned original slice data to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI ; The rock sample solid skeleton binary image data volume D 骨架ROI The outer contour of the image is identified and the space inside the outer contour is processed by averaging, thereby obtaining the binary image data volume D after averaging. 实ROI , and calculate the mean to obtain the binary image data volume D after mean processing 实ROI Volume V 实 ; According to the binary image data volume D after mean processing 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 ; According to the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 .

2. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 1, characterized in that: The three-dimensional data volume is reconstructed for each scanned original slice data to obtain a binary image data volume D that can characterize the rock skeleton components. 骨架ROI include: The grayscale range of the rock solid skeleton is determined by using the Otsu algorithm, and on this basis, the three-dimensional image data volume of the rock sample solid part is segmented and extracted to obtain the binary image data volume D that can characterize the rock skeleton components. 骨架ROI .

3. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 2, characterized in that: The binary image data volume D after mean processing 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 include: According to the binary image data volume D after the mean processing 实ROI Obtain a concave data volume D with multiple discrete units that can represent the concave space volume on the rock sample surface 凹 -multi ROI ; According to the concave data volume D with multiple discrete units that can characterize the concave space volume of the rock sample surface 凹 -multi ROI Obtain the naturally developed pores D on the outer surface of the rock 表孔 -multi ROI ; According to the pores D that develop naturally on the outer surface of each rock 表孔 -multi ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 .

4. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 3, characterized in that: The binary image data volume D processed according to the mean value 实ROI Obtain a data volume D with multiple discrete units that can represent the concave spatial volume of the rock sample surface 凹 -multi ROI include: The binary image data volume D after mean processing 实ROI Perform image morphological closing operation to obtain a binary image data volume D with a relatively smooth appearance 基准面ROI ; The binary image data volume D with a relatively smooth appearance 基准面ROI The outer surface of the rock is taken as the reference surface, the outer surface is the convex part of the rock surface, and the inner surface is the concave part of the rock surface. 基准面ROI -D 实ROI Obtain the difference space data volume D 差值ROI ; For the difference space data volume D 差值ROI Perform voxel connectivity analysis and resolve it into multiple discrete unit difference data volumes D 差值 -multi ROI ; And for each discrete unit difference data volume D 差值 -multi ROI The voxel size is measured, and the data information with insufficient spatial resolution to represent the credible pore space is removed. The difference data volume D of the remaining discrete units is 差值 -multi ROI As the concave data volume D 凹 -multi ROI .

5. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 4, characterized in that: The concave data volume D having multiple discrete units capable of characterizing the concave spatial volume of the rock sample surface is 凹 -multi ROI Obtain the naturally developed pores D on the outer surface of the rock 表孔 -multi ROI include: Obtaining a standard image data volume; Obtain a binary image data volume D according to the standard image data volume 孔 ; For binary image data volume D 孔 According to the results of pore voxel connectivity analysis, binary image data volume D of multiple discrete units is obtained. 孔 -multi ROI ; Extract binary image data volume D 孔 -multi ROI The pore data volume connected to the outer surface is used to obtain discrete binary image data volume units and the noise units with smaller voxels are removed to obtain the outer pore binary image data volume D 外孔 -multi ROI ; According to each outer hole binary image data volume D 外孔 -multi ROI Obtain characteristic parameters and standards for determining the origin of pores; According to the characteristic parameters and standards for distinguishing the origin of pores, the concave data volume D 凹 -multi ROI The individual discrete units in the rock are screened to obtain the naturally developed pores D on the rock surface. 表孔 -multi ROI .

6. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 5, characterized in that: The pores D that are naturally developed on the outer surface of each rock 表孔 -multi ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 include: Calculate and count the naturally developed pores D on the outer surface of each rock 表孔 -multi ROI The volume of the unit space is summed up to obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 .

7. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 6, characterized in that: According to the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 include: Get volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔之和 As the corrected rock sample surface volume V 外表体积 .

8. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 7, characterized in that: The surface volume correction method for porosity measurement of rock samples with rough surfaces further comprises: Obtain helium porosity of test rock samples.

9. The surface volume correction method for porosity measurement of rock samples with rough surfaces according to claim 8, characterized in that: The obtaining of the helium porosity of the test rock sample comprises: Obtain pressure change information and known volume information obtained during the helium porosity test experiment; According to the gas equation, calculate the skeleton volume V of the rock sample being tested solid ; According to the skeleton volume V of the rock sample being tested solid , the corrected rock sample surface volume V 外表体积 Obtain helium porosity of test rock samples.

10. An external volume correction device suitable for measuring the porosity of rock samples with rough surfaces, characterized in that: The surface volume correction device suitable for measuring the porosity of rock samples with rough surfaces comprises: A scanning original slice data acquisition module, wherein the scanning original slice data acquisition module is used to acquire each scanning original slice data of the rock sample scanned by CT scanning; D 骨架ROI Get module, the D 骨架ROI The acquisition module is used to reconstruct the three-dimensional data volume of each scanned original slice data to obtain the binary image data volume D that can characterize the rock skeleton components. 骨架ROI ; Volume acquisition module, the volume acquisition module is used to obtain the rock sample solid skeleton binary image data volume D 骨架ROI The outer contour of the image is identified and the space inside the outer contour is processed by averaging, thereby obtaining the binary image data volume D after averaging. 实ROI , and calculate the binary image data volume D after mean processing 实ROI Volume V 实 ; The module for obtaining the total volume of the pores on the outer surface is used to obtain the total volume of the pores on the outer surface according to the binary image data volume D after mean processing. 实ROI Obtain the total volume of pores developed on the outer surface of the rock sample V 表孔 ; The corrected rock sample surface volume acquisition module is used to obtain the corrected rock sample surface volume according to the volume V 实 And the total volume of pores developed on the outer surface of the rock sample V 表孔 Get the corrected rock sample surface volume V 外表体积 .

Images