CN111504875A - Extraction and calculation method and extraction device for pore throat parameters of tight sandstone - Google Patents

Extraction and calculation method and extraction device for pore throat parameters of tight sandstone Download PDF

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CN111504875A
CN111504875A CN202010354841.8A CN202010354841A CN111504875A CN 111504875 A CN111504875 A CN 111504875A CN 202010354841 A CN202010354841 A CN 202010354841A CN 111504875 A CN111504875 A CN 111504875A
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久博
黄文辉
李媛
何明倩
孙启隆
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China University of Geosciences Beijing
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Abstract

The embodiment of the invention discloses a method for extracting and calculating pore throat parameters of tight sandstone, which comprises the steps of obtaining an SEM image of a casting sheet of the tight sandstone, performing parameter conversion on the casting sheet of the tight sandstone and the SEM image by using MAT L AB to form a binary image, performing quantitative analysis on the binary image by using a built-in function in MAT L AB, and generating a pore radius distribution histogram.

Description

Extraction and calculation method and extraction device for pore throat parameters of tight sandstone
Technical Field
The embodiment of the invention relates to the technical field of tight sandstone, in particular to a method and a device for extracting and calculating pore throat parameters of tight sandstone.
Background
Tight sandstone is broadly defined as sandstone with a porosity of less than 10% and an air permeability of less than 1 mD. Compared with the conventional sandstone reservoir, the compact sandstone reservoir has small pore throat size, complex pore structure, strong heterogeneity and large representation difficulty. At present, the pore throat structure research means aiming at the compact sandstone reservoir is various and can be divided into three main categories according to experimental characteristics: direct observation, indirect testing, digital core methods. Direct observation included casting sheet, scanning electron microscope FIB image. Indirect testing methods include nitrogen adsorption technology, high-pressure mercury injection technology and nuclear magnetic resonance technology.
The above-mentioned problems with pore observation for tight sandstones:
the distribution characteristics of millimeter, micron, nanometer pores and pore throats can be directly observed by experimental methods such as a Scanning Electron Microscope (SEM), a casting sheet, FIB and the like, but the observed result cannot be quantitatively extracted, and other computer software is generally needed.
The indirect experimental method represented by high-pressure mercury intrusion and nuclear magnetic resonance can indirectly carry out quantitative analysis on pore throat distribution of pores with different sizes in the compact sandstone, and reflects a complete sample characteristic. However, mercury intrusion experiments and the like cannot directly observe features as in SEM, and measurement is inaccurate for micropores smaller than 20-50 nm.
Disclosure of Invention
Therefore, the embodiment of the invention provides a method and a device for extracting and calculating pore throat parameters of tight sandstone, which solve the problems that the distribution characteristics of millimeter, micron and nanometer pores and pore throats can be directly observed by experimental methods such as a Scanning Electron Microscope (SEM), a casting sheet, an FIB and the like, but the observed results cannot be quantitatively extracted and the pore measurement is inaccurate by preprocessing the casting sheet and extracting an SEM image of the casting sheet scanned by an electron microscope by using a built-in algorithm MAT L AB.
In order to achieve the above object, an embodiment of the present invention provides the following:
a method for extracting and calculating pore throat parameters of tight sandstone comprises the following steps:
s100, extracting a compact sandstone casting slice through an extraction device, and acquiring an SEM image of the compact sandstone casting slice through a scanning electron microscope;
s200, calling ColorThresholders in MAT L AB to perform parameter transformation on the compact sandstone casting slice and the SEM image to form a binary image;
and S300, quantitatively analyzing the acquired binary image with the pore throat information by using built-in functions impixel, bwabel, bwearea and bwboundaries in MAT L AB.
S400, generating a pore radius distribution histogram by an imhist function in MAT L AB according to the quantitative analysis result of the binary image.
As a preferred embodiment of the present invention, in S200, dark mineral pore information, red mineral pore information, and gray mineral pore information are extracted using L a b color pattern in colorthreshold and through L, a, and b three parameters in L a b color pattern, respectively;
l is between 30-80 for main color control and information extraction factor, a is-20-80 for main color control and information extraction factor, and b is 20-80 for main color control and information extraction factor.
In a preferred embodiment of the present invention, L a and a b are used as factors for combining color control and information extraction, and the parameter control range is dynamically controlled to-20 to 80.
As a preferable scheme of the invention, in S300, the obtained binary image with the pore throat information is quantitatively analyzed by using built-in functions impixel, bwabel, bwearea and bwboundaries in MAT L AB, and quantitative parameters of quantitative analysis comprise porosity and micron-scale poresThe radius and the distribution of the gap, the radius and the distribution of the nanometer roar and the ratio S of the pore volume to the area is represented by the white pixel value in the binary imagewThe black pixel value in the binary image is the ratio S of the volume to the area excluding the pore spacebThe built-in functions impixel, bwleal, bwearea and bwbuildings use SwAnd SbAnd (3) calculating the porosity P in the quantitative parameters, wherein the formula for specifically calculating the porosity P is as follows:
Figure BDA0002471398660000031
as a preferred scheme of the invention, a built-in function bwleal is used for identifying and counting communicated regions with the same pixel value in a binary image, a planar rectangular coordinate system is established for the binary image by using a built-in function axis in MAT L AB, and the distance on the axis of the binary image is calibrated by the X axis and the Y axis in the planar rectangular coordinate system, so that the X axis in the communicated regions is calibratedmin、Xmax、YminAnd YmaxCounting the numerical values to obtain the radius d of the pores in the single communication area, wherein the average radius d of the pores in the single communication area is as follows:
Figure BDA0002471398660000032
wherein Xmin、Xmax、YminAnd YmaxMaximum along X-axis, minimum along X-axis, and maximum along Y-axis and minimum along Y-axis for the pores of a single communication region, (X)max-Xmin) The diameter of the pore in the X-axis direction of a single communication area, (Y)max-Ymin) Is the Y-axis diameter of the pores of the single communication region.
As a preferred scheme of the present invention, for a single communication area, the average value of the long radius and the short radius of the pore or the pore throat space in the directions of the X axis and the Y axis is the pore throat radius of the single communication area, the average value of the pore throat radii of all the communication areas is the average pore radius D in the binary image of the cast body slice, and the specific calculation formula of the average pore radius D is as follows:
Figure BDA0002471398660000033
as a preferable aspect of the present invention, the step of extracting the cast compact sandstone flakes with the extraction device in S100 comprises:
s101, determining the area and the thickness of a cast body slice to be extracted, and selecting a sandstone base material with the area and the thickness closest to twice of the area and the thickness of the cast body slice to be extracted;
s102, double-sided proofing of a casting body slice to be extracted is carried out on the surface of the sandstone base material, and then shooting and imaging are carried out on the surface of the sandstone base material through a laser infrared imaging system;
s103, carrying out crack and edge extraction on the shot image through Hough linear transformation and a line segment classification and combination algorithm to form an original pore map of the casting body slice.
S104, performing negative pressure permeation filling of transparent colloid on the sandstone base material subjected to sampling by the extraction device;
and S105, after the transparent colloid is completely solidified, polishing the transparent colloid into a casting body slice to be extracted.
As a preferred embodiment of the present invention, after the original pore map of the cast body sheet is formed in S103, binarization is performed, and a plurality of characteristic points with the brightest brightness on the original pore map are selected as the penetration points of the transparent colloid of the extraction device.
The invention provides a dense sandstone pore throat parameter extraction device, which comprises a glass box vertically arranged on a substrate, wherein a clamping cavity formed by two parallel partition plates and used for placing sandstone base materials is arranged in the middle of the glass box, adjusting mechanisms for adjusting the positions of the two partition plates are arranged on two sides of each partition plate, rubber seepage tubes and negative pressure tubes are respectively arranged on the outer side walls of the partition plates on two sides of the clamping cavity, silica gel gaskets are arranged on the inner side walls of the partition plates on two sides of the clamping cavity, the negative pressure tubes are connected with a negative pressure generating pump through pipelines, retention pads are arranged in the rubber seepage tubes, through holes are arrayed on the retention pads, silica gel plungers are filled in the through holes, and the rubber seepage tubes are connected with an external rubber supply device through pipelines;
the interior of the negative pressure pipe is axially provided with a rotating shaft driven by a micro motor, and the rotating shaft is provided with a polishing head at the tail end of the silica gel gasket.
As a preferable scheme of the invention, the rubber seepage pipe and the negative pressure pipe both penetrate through the partition plate and extend to the silica gel gasket, and the rubber seepage pipe and the negative pressure pipe are positioned on the same axis.
The embodiment of the invention has the following advantages:
the MAT L AB pore throat quantitative analysis method based on the casting body slice and the scanning electron microscope image is a 2D image model capable of directly extracting the pore throat in a sample, can make up for the quantitative calculation of parameters which cannot be brought by a direct observation method, simultaneously integrates the direct and accurate quantitative analysis of high-pressure mercury intrusion and nuclear magnetic resonance of the image observation method, and quantitatively outputs the parameters of micron-sized and nano-sized pores and throat channels in the compact sandstone.
Compared with high-pressure mercury intrusion and high-temperature testing methods such as nuclear magnetic resonance, the MAT L AB pore throat quantitative analysis method is relatively cheap and direct to perform experiments on the existing cast body slice and the scanning electron microscope image, and certain experiment cost is reduced.
The method can classify and identify the pore throat types with the sizes of more than 5nm for calculation, and simultaneously, the quantitative superposition results of all the pore throat types can show the complete distribution of the pore throats of the sample.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.
FIG. 1 is a flow chart of a method for extracting and calculating tight sandstone pore throat parameters in an embodiment of the invention;
fig. 2 is a schematic structural diagram of an extraction device according to an embodiment of the present invention.
In the figure:
1-a substrate; 2-a glass box; 3-a separator; 4-a clamping cavity; 5-an adjusting mechanism; 6-glue permeating tube; 7-a negative pressure pipe; 8-silica gel gasket; 9-negative pressure generating pump; 10-retention pads; 11-a through hole; 12-a silica gel plunger; 13-a rotating shaft; 14-a micro motor; 15-grinding head.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the invention provides a method for extracting and calculating pore throat parameters of tight sandstone, which comprises the following steps:
s100, extracting a compact sandstone casting slice through an extraction device, and acquiring an SEM image of the compact sandstone casting slice through a scanning electron microscope;
s200, calling color threshing colorthreshold in MAT L AB to perform parameter transformation on a compact sandstone casting body slice and an SEM image to form a binary image;
s300, quantitatively analyzing the acquired binary image with the pore throat information by using built-in functions impixel, bwabel, bwearea and bwboundaries in MAT L AB;
s400, generating a pore radius distribution histogram by an imhist function in MAT L AB according to the quantitative analysis result of the binary image.
In S200, using L a b color pattern in colorthreshold and extracting dark mineral pore information, red mineral pore information, and gray mineral pore information, respectively, through L, a, and b parameters in L a b color pattern;
l is between 30-80 for main color control and information extraction factor, a is-20-80 for main color control and information extraction factor, and b is 20-80 for main color control and information extraction factor.
Meanwhile, L a and a b are used as factors for controlling and extracting the combined color, the parameter control range is dynamically controlled to be-20-80, and through a L a and a b combined extraction mode, gap information of transition colors among dark color mineral pore information, red mineral pore information and gray mineral pore information can be accurately captured, so that accurate extraction of the pore information is improved.
In S300, the obtained binary image with pore throat information is subjected to quantitative analysis by using built-in functions impixel, bwleal, bwearea and bwboundaries in MAT L AB, quantitative parameters of the quantitative analysis comprise porosity, micron-scale pore radius and distribution thereof, nano-scale throat radius and distribution thereof, and the ratio S of pore volume to pore area is represented by white pixel values in the binary imagewThe black pixel value in the binary image is the ratio S of the volume to the area excluding the pore spacebThe built-in functions impixel, bwleal, bwearea and bwbuildings use SwAnd SbAnd (3) calculating the porosity P in the quantitative parameters, wherein the formula for specifically calculating the porosity P is as follows:
Figure BDA0002471398660000061
using a built-in function bwleael to identify same in a binarized imageEstablishing a rectangular plane coordinate system for the binary image by using a built-in function axis in MAT L AB, and calibrating the axial distance of the binary image by the X axis and the Y axis in the rectangular plane coordinate system so as to calibrate the X axis in the communication areamin、Xmax、YminAnd YmaxCounting the numerical values to obtain the radius d of the pores in the single communication area, wherein the average radius d of the pores in the single communication area is as follows:
Figure BDA0002471398660000071
wherein Xmin、Xmax、YminAnd YmaxMaximum along X-axis, minimum along X-axis, and maximum along Y-axis and minimum along Y-axis for the pores of a single communication region, (X)max-Xmin) The diameter of the pore in the X-axis direction of a single communication area, (Y)max-Ymin) Is the Y-axis diameter of the pores of the single communication region.
For a single communication area, the average value of the long radius and the short radius of the pores or pore throat spaces in the X-axis direction and the Y-axis direction is the pore throat radius of the single communication area, the average value of the pore throat radii of all the communication areas is the average pore radius D in the binary image of the cast body slice, and the specific calculation formula of the average pore radius D is as follows:
Figure BDA0002471398660000072
in S100, the specific step of extracting the compact sandstone cast slab by the extraction device includes:
s101, determining the area and the thickness of a cast body slice to be extracted, and selecting a sandstone base material with the area and the thickness closest to twice of the area and the thickness of the cast body slice to be extracted;
s102, double-sided proofing of a casting body slice to be extracted is carried out on the surface of the sandstone base material, and then shooting and imaging are carried out on the surface of the sandstone base material through a laser infrared imaging system;
the sampling mode is that a circumferential groove for extracting the casting body slice is punched on the surface of the sandstone base material, the thickness of the circumferential groove is 0.1-1 mm, and the penetration of later-stage transparent colloid is facilitated.
S103, carrying out crack and edge extraction on the shot image through Hough linear transformation and a line segment classification and combination algorithm to form an original pore map of the casting body slice.
S104, performing negative pressure permeation filling of transparent colloid on the sandstone base material subjected to sampling by the extraction device;
and S105, after the transparent colloid is completely solidified, polishing the transparent colloid into a casting body slice to be extracted.
After the original pore map of the cast body slice is formed in S103, binarization is performed, and a plurality of characteristic points with the brightest brightness on the original pore map are selected as the penetration points of the transparent colloid of the extraction device.
Example 2:
in order to verify the invention, the micron-scale and nano-scale pore throat parameters of the compact sandstone reservoir in the Ordos basin cascade system are quantitatively analyzed by the high-pressure mercury intrusion test and a means based on MAT L AB and image analysis.
Based on the observation of the compact sandstone casting slice sample, the compact sandstone in the research area consists of four reservoir spaces, namely a quartz sandstone debris dissolution hole, a debris quartz sandstone residual intergranular hole, a quartz sandstone residual intergranular hole and a quartz sand dissolution hole, and the debris dissolution hole and the residual intergranular hole of the debris quartz sandstone are mainly developed.
Firstly, performing binarization conversion on cast slices of four reservoir layers in a research area by using a Matlab algorithm, further performing statistical calculation on each white connected area of a binary image by using built-in functions of bwearea, bwelabel and impixel, and finally deriving each calculation area.
Compared with the original cast body slice, most of the pore space can be identified, including the rock debris dissolved pores with lower pore diameter, the residual inter-granular pores with uneven distribution and the dissolved pores with larger pore diameter, and finally the imhist function is applied to count and output the pore diameter parameters of each image.
Similarly, sandstone in the research region is observed through a scanning electron microscope, and the dense sandstone pore throat types in the research region comprise clay mineral intercrystalline pores, the throat between the developing siliceous cemented quartz, and matrix erosion pores.
The Matlab algorithm can extract throat characteristic parameters in a single SEM image, a high-pressure mercury intrusion test can indirectly analyze the whole research sample, and in order to describe the pore throat characteristics more comprehensively and objectively, the high-pressure mercury intrusion test and the Matlab are respectively applied to research the nanoscale pore throats in a research area.
And outputting results by applying an imhist function, wherein the output results respectively correspond to illite intergranular pores, kaolinite intergranular pores, quartz intergranular pore throats and heterobase internal dissolution pores, and the average pore throat radius is continuously increased.
And finally outputting the result of the pore throat radius of the compact sandstone in the research area based on the casting sheet and the SEM image as the superposition output of each sample.
Similarly, pore throat radius calculations were performed on the same samples in the study area using a high pressure mercury intrusion experiment.
According to the output results of the two experiments, the pore radius distribution range of the two experiment results is very similar to the pore distribution, but the radius distribution of a certain pore throat type cannot be independently calculated for the high-pressure mercury intrusion experiment.
Example 3:
the traditional cast body slice is a rock slice which is prepared by injecting colored liquid glue into a rock pore space under vacuum pressurization and grinding after the liquid glue is cured, and in compact sandstone, compared with a conventional sandstone reservoir, the compact sandstone reservoir has small pore throat size, complex pore structure, strong heterogeneity and high characterization difficulty, and the injection by the vacuum pressurization method is easy to cause that colloid is not completely penetrated, the colloid part in the sandstone is reversely solidified, and the interior of the sandstone is expanded under the action of the vacuum pressurization.
Further, the sandstone is damaged, so that errors occur during later scanning by an electron microscope (SEM), and the diameter of the pores at the expansion position is increased when the pores of the cast body slice image obtained by the SEM are calculated, so that the problem that the pores are enlarged due to the fact that the diameter of the pores at the expansion position is increasedWhen a plane rectangular coordinate system is established for the binary image by using a built-in function axis in MAT L AB, (X)max-Xmin) The diameter of the pore in the X-axis direction of a single communication area, (Y)max-Ymin) Obvious errors are generated for the diameter of the single communication area pore in the Y-axis direction, and the measurement result is inaccurate.
Therefore, as shown in fig. 2, the invention also provides a device for extracting pore throat parameters of tight sandstone, which comprises a glass box 2 vertically arranged on a substrate 1, wherein a clamping cavity 4 formed by two parallel partition plates 3 and used for placing sandstone base materials is arranged in the middle of the glass box 2, and two sides of the clamping cavity 4 are open.
Two sides of the partition board 3 are provided with adjusting mechanisms 5 for adjusting the positions of the two partition boards 3, and the adjusting mechanisms 5 can be manual screw-nut assemblies or hydraulic telescopic rods and pneumatic telescopic rods.
The outer side walls of the partition boards 3 at the two sides of the clamping cavity 4 are respectively provided with a rubber seepage pipe 6 and a negative pressure pipe 7, the inner side walls of the partition boards 3 at the two sides of the clamping cavity 4 are provided with silica gel gaskets 8, the outer diameter of each silica gel gasket 8 is the inner diameter of a casting body slice to be extracted, which is subjected to sample drawing on a sandstone base material, and thus a circumferential groove formed by sample drawing is positioned at the outer side of each silica gel gasket 8 and is contacted with air;
the negative pressure tube 7 is connected with a negative pressure generating pump 9 through a pipeline, a retention pad 10 is arranged inside the glue permeation tube 6, through holes 11 are arrayed on the retention pad 10, silica gel plungers 12 are filled inside the through holes 11, needle bodies are inserted when the silica gel plungers 12 are used, the through holes 11 which are not used are blocked on the other hand, and the glue permeation tube 6 is connected with an external glue supply device through a pipeline.
When the device works, a sandstone base material is placed into a clamping cavity 4, the sandstone base material is clamped through an adjusting mechanism 5, a silica gel gasket 8 is tightly attached to the sandstone base material at the moment to form a seal for a thin part of a casting body to be extracted, a negative pressure generator works to apply negative pressure to a negative pressure pipe 7, then an external glue supply device works, colorless glue is sent into a glue seepage pipe 6, and colorless glue is conveyed through needle bodies inserted into through holes 11 arrayed in a retention pad 10.
In the invention, the through holes 11 are arrayed on the retention pad 10, the needle bodies are arranged in the through holes, the specific arrangement positions of the needle bodies are binarized after the original pore map of the cast body slice is formed in S103 according to the embodiment 1, a plurality of characteristic points with the brightest brightness on the original pore map are selected as the permeation points of the transparent colloid of the extraction device, and the permeation points correspond to the positions of the needle bodies, so that the colorless colloid can rapidly permeate into the sandstone base material through the optimal pores.
The invention does not inject the colorless colloid in a vacuum pressurization mode, but applies negative pressure on one side of the sandstone base material and injects glue on the other side, further, the side surface of the sandstone base material is contacted with air, and the colorless colloid can be quickly drained in sandstone pores while no external force is applied to the sandstone base material through a mode of synchronously applying negative pressure with the negative pressure pipe 7 under atmospheric pressure, thereby accelerating the forming rate of the cast body slice to be extracted.
Firstly, in the process of clamping the sandstone base material by the partition plate, because of the surface fault of the sandstone base material formed by the circumferential groove, the clamping acting force of the partition plate on the sandstone base material is converted into the stress change of the surface of the sandstone base material, and the stress change is disconnected at the circumferential groove, so that the damage to the surface pores of the cast body slice to be extracted in the clamping process is reduced;
secondly, the contact pore between the sandstone base material on the outer side of the cast body slice to be extracted and the air is increased, so that the atmospheric pressure can be quickly connected into the sandstone base material when the negative pressure pipe 7 works.
A rotating shaft 13 driven by a micro motor 14 is axially arranged in the negative pressure pipe, the rotating shaft 13 is a micro telescopic rod to realize the extension and contraction of a polishing head 15, external power supply is carried out through an electric slip ring sleeved on the micro motor 14, and the rotating shaft 13 is provided with the polishing head 15 at the tail end of the silica gel gasket 8;
the diameter of a specific polishing head 15 is consistent with that of the negative pressure pipe 7, scrap guide spiral grooves are arrayed on the circumference of the polishing head 15, and when the glue permeation pipe 6 and the negative pressure pipe 7 work, the polishing head 15 is close to the surface of the sandstone base material by 1-2 mm.
The glue permeating tube 6 and the negative pressure tube 7 penetrate through the partition plate 3 and extend to the silica gel gasket 8, and the glue permeating tube 6 and the negative pressure tube 7 are located on the same axis.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (10)

1. A method for extracting and calculating pore throat parameters of tight sandstone is characterized by comprising the following steps:
s100, extracting a compact sandstone casting slice through an extraction device, and acquiring an SEM image of the compact sandstone casting slice through a scanning electron microscope;
s200, calling color threshing colorthreshold in MAT L AB to perform parameter transformation on a compact sandstone casting body slice and an SEM image to form a binary image;
s300, quantitatively analyzing the acquired binary image with the pore throat information by using built-in functions impixel, bwabel, bwearea and bwboundaries in MAT L AB;
s400, generating a pore radius distribution histogram by an imhist function in MAT L AB according to the quantitative analysis result of the binary image.
2. The method of claim 1, wherein in S200, dark mineral pore information, red mineral pore information, and gray mineral pore information are extracted using L a b color pattern in colorthreshold and L, a, and b parameters in L a b color pattern, respectively;
l is between 30-80 for main color control and information extraction factor, a is-20-80 for main color control and information extraction factor, and b is 20-80 for main color control and information extraction factor.
3. The method for extracting and calculating tight sandstone pore throat parameters according to claim 2, wherein L a and a b are used as factors for combining color control and information extraction, and the parameter control range is dynamically controlled to be-20-80.
4. The method for extracting and calculating the pore throat parameter of tight sandstone according to claim 1, wherein in S300, the obtained binarized image with the pore throat information is subjected to quantitative analysis by using built-in functions impixel, bwelabel, bwearea and bwboundairies in MAT L AB, quantitative parameters of the quantitative analysis comprise porosity, micron-scale pore radius and distribution thereof, nanometer-scale throat radius and distribution thereof, and the ratio S of pore volume to area is represented by a white pixel value in the binarized imagewThe black pixel value in the binary image is the ratio S of the volume to the area excluding the pore spacebThe built-in functions impixel, bwleal, bwearea and bwbuildings use SwAnd SbAnd (3) calculating the porosity P in the quantitative parameters, wherein the formula for specifically calculating the porosity P is as follows:
Figure FDA0002471398650000021
5. the method for extracting and calculating tight sandstone pore throat parameters according to claim 4, wherein a built-in function bwleabel is used for carrying out identification statistics on connected regions with the same pixel value in the binarized image, a rectangular plane coordinate system is established for the binarized image by using a built-in function axis in MAT L AB, and the distance on the axis of the binarized image is calibrated by the X axis and the Y axis in the rectangular plane coordinate system, so that the X axis in the connected regions is calibratedmin、Xmax、YminAnd YmaxCounting the numerical values to obtain the radius d of the pores in the single communication area, wherein the average radius d of the pores in the single communication area is as follows:
Figure FDA0002471398650000022
wherein Xmin、Xmax、YminAnd YmaxMaximum along X-axis, minimum along X-axis, and maximum along Y-axis and minimum along Y-axis for the pores of a single communication region, (X)max-Xmin) The diameter of the pore in the X-axis direction of a single communication area, (Y)max-Ymin) Is the Y-axis diameter of the pores of the single communication region.
6. The method for extracting and calculating tight sandstone pore throat parameters according to claim 5, wherein the average value of the long radius and the short radius of the pore or the pore throat space in the single communication region in the directions of the X axis and the Y axis is the pore throat radius of the single communication region, the average value of the pore throat radii of all the communication regions is the average pore radius D in the binary image of the cast slice, and the specific calculation formula of the average pore radius D is as follows:
Figure FDA0002471398650000023
7. the method for extracting and calculating tight sandstone pore throat parameter according to claim 1, wherein in S100, the specific step of extracting the tight sandstone casting slice by the extraction device comprises:
s101, determining the area and the thickness of a cast body slice to be extracted, and selecting a sandstone base material with the area and the thickness closest to twice of the area and the thickness of the cast body slice to be extracted;
s102, double-sided proofing of a casting body slice to be extracted is carried out on the surface of the sandstone base material, and then shooting and imaging are carried out on the surface of the sandstone base material through a laser infrared imaging system;
s103, performing crack and edge extraction on the shot image through Hough linear transformation and a line segment classification and combination algorithm to form an original pore map of the casting body slice;
s104, performing negative pressure permeation filling of transparent colloid on the sandstone base material subjected to sampling by the extraction device;
and S105, after the transparent colloid is completely solidified, polishing the transparent colloid into a casting body slice to be extracted.
8. The method for extracting and calculating the tight sandstone pore throat parameter as claimed in claim 3, wherein after an original pore map of a casting slice is formed in S103, binarization is performed, and a plurality of characteristic points with the brightest brightness on the original pore map are selected as the penetration points of the transparent colloid of the extraction device.
9. The extraction device for the pore throat parameters of the tight sandstone is characterized by comprising a glass box (2) vertically arranged on a substrate (1), wherein a clamping cavity (4) formed by two parallel partition plates (3) and used for placing sandstone base materials is arranged in the middle of the glass box (2), adjusting mechanisms (5) for adjusting the positions of the two partition plates (3) are arranged on two sides of the partition plates (3), a rubber seepage tube (6) and a negative pressure tube (7) are respectively arranged on the outer side walls of the partition plates (3) on two sides of the clamping cavity (4), a silica gel washer (8) is arranged on the inner side walls of the partition plates (3) on two sides of the clamping cavity (4), the negative pressure tube (7) is connected with a negative pressure generating pump (9) through a pipeline, a retention cushion (10) is arranged inside the rubber seepage tube (6), a through hole (11) is arranged on the retention cushion (10), and a silica gel plunger (12) is filled, the glue seepage pipe (6) is connected with an external glue supply device through a pipeline;
a rotating shaft (13) driven by a micro motor (14) is axially arranged in the negative pressure pipe, and a polishing head (15) is arranged at the tail end, located on the silica gel gasket (8), of the rotating shaft (13).
10. The device for preparing the casting slice of tight sandstone pore-throat parameter according to claim 9, wherein the infiltration pipe (6) and the negative pressure pipe (7) both extend to the silica gel gasket (8) through the partition plate (3), and the infiltration pipe (6) and the negative pressure pipe (7) are positioned on the same axis.
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