A method for determining the condensation ratio of the pore structure, a key parameter of the capillary condensation amount

Abstract

The present invention discloses a method for determining the condensation ratio of pore structures, which is a key parameter of capillary condensation amount, including: preparing a clay mineral particle sample and performing secondary electron imaging to obtain a secondary electron grayscale image; extracting pores based on the secondary electron grayscale image; performing polygon fitting on different pores in the extracted pore map and counting the angles corresponding to the endpoints of each fitted polygon; establishing an oil-water-rock model and performing molecular dynamics simulations; obtaining a density distribution map according to the results of the molecular dynamics simulations; calculating the contact angle based on the density distribution map; fitting the capillary condensation liquid surface of a single angle of the pore polygon based on the contact angle and the angles corresponding to the endpoints of each fitted polygon; and determining the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface of a single angle of the pore polygon. Starting from the mechanism, the present invention determines the condensation ratio coefficient of the pore structure, thereby determining the adsorption amount of shale oil, and the fitting result is more accurate, and it saves more material and financial resources.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil adsorption, and particularly to a method for determining the condensation ratio of pore structures, which is a key parameter of capillary condensation amount. Background Art

[0002] Shale oil usually exists in three occurrence states: adsorbed, free, and dissolved. It mainly exists in the adsorbed or free state, with a small amount in the dissolved state. The mutually dissolved shale oil is absorbed in kerogen and is almost immobile (i.e., non-recoverable), while the adsorbed-free shale oil is potentially recoverable (i.e., mobile); however, under current technical conditions, the free shale oil is the most recoverable part.

[0003] High-temperature and high-pressure methane adsorption and oil solution adsorption experiments are currently common technical methods for testing shale adsorption capacity in the oil and gas industry. For shale, the former is more suitable for analyzing the adsorption capacity of gaseous hydrocarbons such as methane, but it has poor applicability in the study of oil adsorption capacity and adsorption amount. The oil solution adsorption experiment cannot test the change in oil adsorption with increasing pressure. However, in the actual formation, pressure is one of the important factors affecting shale oil adsorption.

[0004] Hydrocarbon vapor adsorption is an important experiment for characterizing the adsorption capacity of shale and its main constituent minerals. The results of hydrocarbon vapor adsorption experiments include two parts: adsorption amount and capillary condensation amount (free amount). Currently, the adsorption amount of gaseous hydrocarbons and the condensation amount are mainly calculated by molecular dynamics simulation and the Kelvin formula respectively. However, due to the lack of understanding of the microscopic surface and pore structure properties of shale and its main constituent minerals, a large number of hydrocarbon vapor adsorption experiment results are needed to calibrate the calculation formula of the condensation amount, that is, to determine the pore structure condensation ratio coefficient. Obviously, this method will waste a large amount of resources. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for determining the condensation ratio of pore structures, which is a key parameter of capillary condensation amount. By characterizing the microscopic surface and pore structure properties of minerals, starting from the mechanism, the pore structure condensation ratio coefficient is determined, so as to determine the shale oil adsorption amount.

[0006] To achieve the above purpose, the present invention provides the following solution:

[0007] A method for determining the condensation ratio of pore structures, which is a key parameter of capillary condensation amount, includes:

[0008] Preparing a clay mineral particle sample and performing secondary electron imaging to obtain a secondary electron gray-scale image;

[0009] Extracting pores based on the secondary electron gray-scale image;

[0010] Perform polygon fitting on different pores in the extracted pore map, and count the angles corresponding to the endpoints of each fitted polygon;

[0011] Establish an oil-water-rock model and conduct molecular dynamics simulations;

[0012] Obtain a density distribution map based on the results of molecular dynamics simulations;

[0013] Calculate the contact angle based on the density distribution map;

[0014] Based on the contact angle and the angles corresponding to the endpoints of each fitted polygon, fit the capillary condensation liquid surface of a single angle of the pore polygon; the condensed part in the capillary condensation liquid surface of a single angle of the pore polygon is the part enclosed by the meniscus and the top of the single angle;

[0015] Determine the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface of a single angle of the pore polygon.

[0016] Optionally, the pore extraction based on the secondary electron grayscale image specifically includes:

[0017] Use the median filtering method to denoise the secondary electron grayscale image;

[0018] Perform grayscale statistics on the denoised secondary electron grayscale image and draw a grayscale histogram;

[0019] Based on the threshold between the mineral peak and the pore peak in the grayscale histogram, perform pore extraction,

[0020] Perform binarization processing on the extracted image.

[0021] Optionally, the polygon fitting of different pores in the extracted pore map and the counting of the angles corresponding to the endpoints of each fitted polygon specifically include:

[0022] Use the convexhull function in matlab to perform polygon fitting on different pores in the extracted pore map and count the vertices of the polygon fitted for each pore;

[0023] Count the angles of the triangles formed by every three vertices. When the angle is greater than 165°, delete the current vertex and simplify the fitted polygon;

[0024] Count the angles corresponding to the endpoints of each simplified fitted polygon.

[0025] Optionally, the calculation of the contact angle based on the density distribution map specifically includes:

[0026] Perform binarization processing on the density distribution map using 0.5 times the density of liquid n-pentane as the threshold;

[0027] Perform a closing operation on the binary image using ImageJ to remove noise;

[0028] Perform edge recognition on the image after noise removal to obtain the gas-liquid interface;

[0029] Take the intersection point of the gas-liquid interface and the horizontal plane as the triple point and measure the contact angle.

[0030] Optionally, determine the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface at a single corner of the pore polygon, specifically including:

[0031] Draw a condensation process diagram at different partial pressures according to the capillary condensation radius and gas relative pressure in the capillary condensation liquid surface at a single corner of the pore polygon;

[0032] Count the number of pixel points in the condensed part of the condensation process diagrams at different partial pressures;

[0033] Determine the condensation ratio corresponding to different partial pressures according to the ratio of the number of pixel points in the condensed part to the number of initial pore pixel points.

[0034] The present invention also provides a system for determining the condensation ratio of the pore structure, a key parameter of the capillary condensation amount, including:

[0035] A secondary electron imaging module for preparing a clay mineral particle sample and performing secondary electron imaging to obtain a secondary electron grayscale image;

[0036] An extraction module for extracting pores based on the secondary electron grayscale image;

[0037] A first fitting module for polygonally fitting different pores in the extracted pore map and counting the angles corresponding to the endpoints of each fitted polygon;

[0038] A model establishment module for establishing an oil-water-rock model and performing molecular dynamics simulations;

[0039] A density distribution map determination module for obtaining a density distribution map according to the results of molecular dynamics simulations;

[0040] A contact angle calculation module for calculating the contact angle based on the density distribution map;

[0041] A second fitting module for fitting the capillary condensation liquid surface at a single corner of the pore polygon based on the contact angle and the angles corresponding to the endpoints of each fitted polygon; the condensed part in the capillary condensation liquid surface at a single corner of the pore polygon is the part enclosed by the curved liquid surface and the top of the single corner;

[0042] The condensation ratio determination module corresponding to different partial pressures is configured to determine the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface at a single corner of the pore polygon.

[0043] Optionally, the extraction module specifically includes:

[0044] The first denoising unit is configured to denoise the secondary electron grayscale image by using the median filtering method;

[0045] The grayscale histogram drawing unit block is configured to perform grayscale statistics on the denoised secondary electron grayscale image and draw a grayscale histogram;

[0046] The pore extraction unit is configured to extract pores based on the threshold between the mineral peak and the pore peak in the grayscale histogram,

[0047] The first binarization processing unit is configured to perform binarization processing on the extracted image.

[0048] Optionally, the first fitting module specifically includes:

[0049] The fitting unit is configured to perform polygon fitting on different pores in the extracted pore image by using the convexhull function in matlab and count the vertices of the polygon fitted for each pore;

[0050] The simplification unit is configured to count the angles of the triangles formed by every three vertices, and when the angle is greater than 165°, delete the current vertex to simplify the fitted polygon;

[0051] The angle statistics unit is configured to count the angles corresponding to the endpoints of each simplified fitted polygon.

[0052] Optionally, the contact angle calculation module specifically includes:

[0053] The second binarization processing unit is configured to perform binarization processing on the density distribution map by using 0.5 times the density of liquid n-pentane as the threshold;

[0054] The second denoising unit is configured to perform a closing operation on the binarized image by using ImageJ to remove noise;

[0055] The edge recognition unit is configured to perform edge recognition on the image after removing noise to obtain the gas-liquid interface;

[0056] The contact angle measurement unit is configured to use the intersection point of the gas-liquid interface and the horizontal plane as the triple point to measure the contact angle.

[0057] Optionally, the condensation ratio determination module corresponding to different partial pressures specifically includes:

[0058] A condensation process diagram drawing unit under different partial pressures is used to draw a condensation process diagram under different partial pressures according to the capillary condensation radius and the relative gas pressure in the capillary condensation liquid surface at a single corner of the pore polygon;

[0059] A pixel number statistical unit is used to count the number of pixels in the condensed part of the condensation process diagram of the different partial pressures;

[0060] A condensation ratio determination unit corresponding to different partial pressures is used to determine the condensation ratio corresponding to different partial pressures according to the ratio of the number of pixels in the condensed part to the number of initial pore pixels.

[0061] According to the specific embodiments provided by the present invention, the following technical effects are disclosed:

[0062] The present invention conducts field emission electron microscope experiments to determine the true pore structure of the sample, and uses image processing technology to quantitatively characterize the empty structure characteristics of shale and its main constituent minerals morphologically. Molecular dynamics simulation is applied to determine the fluid-solid interaction characteristics between gaseous hydrocarbons and shale from the mechanism, and the contact angle is quantitatively calculated. Finally, starting from the pore morphology and the mechanism of fluid-solid interaction, the condensation ratio coefficient of the pore structure is calculated to determine the adsorbed amount of shale oil. The present invention is more cost-effective and the fitting result is more accurate. Description of the Drawings

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0064] Figure 1 It is a flow chart of a method for determining the pore structure condensation ratio, which is a key parameter of the capillary condensation amount, in an embodiment of the present invention;

[0065] Figure 2 It is a secondary electron grayscale image of soil mineral particles, where (a) is the original image and (b) is the image after median filtering denoising;

[0066] Figure 3 It is a grayscale histogram;

[0067] Figure 4 It is a flow chart of image processing, where (a) is a pore extraction image, (b) is a binary image, (c) is a polygon fitting image, and (d) is a simplified polygon fitting image;

[0068] Figure 5 It is a calculation model of the contact angle between n-pentane and kaolinite, where (a) is the left side view of the model and (b) is the top view of the model;

[0069] Figure 6 is the density distribution diagram of n-pentane along the X-Z plane;

[0070] Figure 7 is the density binarization diagram;

[0071] Figure 8 is the contact angle measurement diagram;

[0072] Figure 9 is the schematic diagram for calculating the single-angle capillary condensation liquid surface;

[0073] Figure 10 is the condensation process diagram under different partial pressures;

[0074] Figure 11 is the diagram of the relationship between different partial pressures and the condensation ratio. Specific Embodiments

[0075] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0076] The purpose of the present invention is to provide a method for determining the pore structure condensation ratio, a key parameter of capillary condensation amount. By characterizing the microscopic surface and pore structure properties of minerals, starting from the mechanism, the pore structure condensation ratio coefficient is determined, thereby determining the shale oil adsorption amount.

[0077] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0078] As Figure 1 shown, the method for determining the pore structure condensation ratio, a key parameter of capillary condensation amount, provided by the present invention includes the following steps:

[0079] Step 101: Prepare a clay mineral particle sample and perform secondary electron imaging to obtain a secondary electron grayscale image.

[0080] (1) Take 1 g of montmorillonite clay mineral particles and pile them up in the central part of the aluminum stage of the scanning electron microscope. Use a syringe to suck 2 ml of graphene conductive glue, and use a stirring rod with a diameter of 0.5 mm to mix the graphene conductive glue and the montmorillonite clay mineral particles evenly. First, cool at room temperature for 24 hours, then put it in an oven at 100 °C and dry for 2 hours. Raise the oven temperature to 150 °C and continue to dry for 2 hours.

[0081] (2) Mechanically polish the dried sample. First, use a 12-μm diamond suspension to polish the sample until a large amount of clay mineral powder appears, then polish with a 6-μm diamond suspension for 5 minutes, a 3-μm diamond suspension for 5 minutes, and a 1-μm diamond suspension for 10 minutes, and a 0.25-μm diamond suspension for 10 minutes. Using an argon ion polishing instrument, set the polishing surface and the argon ion beam direction to 3°. First, polish for 1 hour under the conditions of 5 kV and 2 mA, and then polish for 1 hour under the conditions of 2 kV and 2 mA.

[0082] (3) After the sample preparation is completed, use a field emission scanning electron microscope to perform secondary electron imaging on the microscopic pores of the etched surface of the clay mineral particle sample under low voltage and low current conditions of 1.2 kV to 0.8 kV and 200 pA to 80 pA, as Figure 2 (a) shown.

[0083] Step 102: Extract pores based on the secondary electron grayscale image.

[0084] Use the median filtering method to denoise the secondary electron grayscale image of clay mineral particles, as Figure 2 (b) shown. Perform grayscale statistics on the denoised secondary electron grayscale image of clay mineral particles, and draw a grayscale histogram, as Figure 3 shown. Take the threshold (60) between the main mineral peak and the pore peak in the grayscale histogram for pore extraction. The extracted image is as Figure 4 (a) shown. Binarize the extracted image, as Figure 4 (b) shown.

[0085] Step 103: Fit different pores in the extracted pore image with polygons and count the angles corresponding to the endpoints of each fitted polygon.

[0086] Use the convexhull function in matlab to fit different pores with polygons, and count the vertices of the polygons fitted for each pore. The fitted image is as Figure 4 (c) shown.

[0087] Count the angles of the triangles formed by every three vertices. When this angle is greater than 165°, delete this vertex and simplify the fitted polygon, as Figure 4 (d) shown. Count the number of white pixel points as 1,129,747, and record the angles corresponding to the endpoints of each fitted polygon.

[0088] Step 104: Establish an oil-water-rock model and perform molecular dynamics simulations.

[0089] The selected kaolinite unit cell without isomorphic substitution is used as the research object of clay minerals. Its chemical formula is Al2Si2O5(OH)4, and its initial atomic positions refer to AMSCD (American Mineralogist Crystal Structure Database). Its original lattice parameters are α = 91.926°, β = 105.046°, γ = 89.797°. The lattice parameters α, β, and γ are set to 90° to facilitate the subsequent construction of the "oil-water-rock" model.

[0090] First, the kaolinite unit is expanded 60, 5, and 3 times in the X, Y, and Z directions respectively to obtain a model with dimensions of 30.61×4.47×1.90 nm 3 for the top and bottom surfaces of the model. Similarly, the unit is expanded 25, 5, and 3 times in the X, Y, and Z directions respectively to obtain a model with dimensions of 8.50×4.47×1.90 nm 3 for the left side of the model, as shown in Figure 5 (a). Finally, the top, bottom, and left sides are assembled as required, and the model is completed, as shown in Figure 5 (b). The blank areas in the model are filled with n-pentane molecules, and the filling quantity should ensure that the density of n-pentane in the model is the same as that of liquid n-pentane under experimental conditions. Note that a certain blank area should still be reserved on the right side of the model to form a gas-liquid interface.

[0091] The calculation of the kaolinite crystal uses the CLAYFF force field, and n-pentane uses the CHARMM force field for calculation.

[0092] First, the initial model is energy-minimized to remove molecular overlaps and situations where distances are too close. Then, the model is relaxed for 50 ps with the following parameters: NVT ensemble, temperature selected as 303 K, temperature control method selected as V-rescale, and XYZ periodic boundary conditions are used. Finally, the kaolinite molecules are fixed, and a 30-ns molecular dynamics simulation is performed. The parameter settings are as follows: NVT ensemble is used, the temperature is 303 K, the temperature control method is selected as Nose-Hoover, and XYZ periodic boundary conditions are used.

[0093] Step 105: Obtain the density distribution map based on the results of the molecular dynamics simulation.

[0094] Calculate the RMSD of the n-pentane system. Select the simulation results from 20 to 30 ns for data processing to ensure the equilibrium of the simulation results. Use the densmap module to calculate the density distribution map of n-pentane along the X-Z plane, as shown in Figure 6 shown.

[0095] Step 106: Calculate the contact angle based on the density distribution map.

[0096] Use 0.5 times the density of liquid n - pentane as the threshold to binarize the n - pentane density distribution map, as shown in Figure 7 . Use ImageJ to perform a closing operation on the binarized image to remove noise, and then perform edge recognition on the graph to obtain the gas - liquid interface, as shown in Figure 8 . Take the intersection point of the gas - liquid interface and the horizontal plane as the triple point, and measure the contact angle φ. As shown in Figure 8 , the contact angle is ).

[0097] Step 107: Based on the contact angle and the angles corresponding to the endpoints of each fitted polygon, fit the capillary condensation liquid surface at a single corner of the pore polygon; the condensed part in the capillary condensation liquid surface at a single corner of the pore polygon is the part enclosed by the meniscus and the top of the single corner.

[0098] Figure 9 It is a schematic diagram for fitting the capillary condensation liquid surface at a single corner of the pore polygon, and the condensed part is the part enclosed by the meniscus and the top of the single corner.

[0099] Arc length of the liquid surface: L=(2×θ5 / 180)×π×R

[0100] θ5 = 90 - θ4

[0101] R = r k / (sinθ5)

[0102] θ5 = 90 - θ4

[0103] θ4 = 90 - θ3

[0104] θ3 = 90-(θ1 / 2)-θ2

[0105]

[0106] θ is the contact angle obtained in step 106, and θ1 is the angle of a single corner of the fitted pore polygon statistically obtained in step 103.

[0107] Step 108: Determine the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface at a single corner of the pore polygon.

[0108] Assume that the initial pore is light gray (gaseous part), and set the part enclosed by the meniscus and the top of the single corner (condensed part) to black. Use the radius and gas relative pressure calculation formula to draw the condensation process diagram at different partial pressures, as shown in Figure 10 . Count the number of black pixel points in the condensation process diagram at different partial pressures, and divide it by the number of initial pore pixel points 1129747, which is the condensation ratio corresponding to different partial pressures, as shown in Figure 11 .

[0109] Calculation formula for capillary condensation radius and relative gas pressure:

[0110]

[0111] r k is the capillary condensation radius; σ is the surface tension, taking 18.7 dyn / cm; V L is the molar volume of n-pentane, taking 0.000119087 m 3 / L; P / P0 is the relative pressure, dimensionless; R is the gas constant, 8.314 P·m3 / mol / K; T is the temperature, taking 313 K..

[0112] The present invention conducts field emission electron microscope experiments to determine the true pore structure of the sample, and uses image processing technology to quantitatively determine the empty structure characteristics of shale and its main constituent minerals morphologically. Molecular dynamics simulation is applied to determine the fluid-solid interaction characteristics between gaseous hydrocarbons and shale mechanically and quantitatively calculate the contact angle. Finally, the pore structure condensation proportion coefficient is calculated based on the pore morphology and fluid-solid interaction mechanism.

[0113] The present invention also provides a system for determining the pore structure condensation proportion, a key parameter of the capillary condensation amount, including:

[0114] A secondary electron imaging module, used for preparing a clay mineral particle sample and performing secondary electron imaging to obtain a secondary electron grayscale image;

[0115] An extraction module, used for pore extraction based on the secondary electron grayscale image;

[0116] A first fitting module, used for polygon fitting of different pores in the extracted pore map and counting the angles corresponding to the endpoints of each fitted polygon;

[0117] A model establishment module, used for establishing an oil-water-rock model and performing molecular dynamics simulation;

[0118] A density distribution map determination module, used for obtaining a density distribution map according to the results of molecular dynamics simulation;

[0119] A contact angle calculation module, used for calculating the contact angle based on the density distribution map;

[0120] A second fitting module, used for fitting the capillary condensation liquid surface of a single angle of the pore polygon based on the contact angle and the angles corresponding to the endpoints of each fitted polygon; the condensed part in the capillary condensation liquid surface of a single angle of the pore polygon is the part enclosed by the curved liquid surface and the top of the single angle;

[0121] A condensation proportion determination module corresponding to different partial pressures, used for determining the condensation proportion corresponding to different partial pressures based on the capillary condensation liquid surface of a single angle of the pore polygon.

[0122] Among them, the extraction module specifically includes:

[0123] The first denoising unit is used to denoise the secondary electron grayscale image by using the median filtering method;

[0124] The grayscale histogram drawing unit block is used to perform grayscale statistics on the denoised secondary electron grayscale image and draw a grayscale histogram;

[0125] The pore extraction unit is used to extract pores based on the threshold between the mineral peak and the pore peak in the grayscale histogram,

[0126] The first binarization processing unit is used to binarize the extracted image.

[0127] Among them, the first fitting module specifically includes:

[0128] The fitting unit is used to perform polygon fitting on different pores in the extracted pore image by using the convexhull function in matlab and count the vertices of the polygon fitted for each pore;

[0129] The simplification unit is used to count the angles of the triangles formed by every three vertices. When the angle is greater than 165°, the current vertex is deleted to simplify the fitted polygon;

[0130] The angle statistics unit is used to count the angles corresponding to the endpoints of each simplified fitted polygon.

[0131] Among them, the contact angle calculation module specifically includes:

[0132] The second binarization processing unit is used to binarize the density distribution map by using 0.5 times the density of liquid n-pentane as the threshold;

[0133] The second denoising unit is used to remove noise by performing a closing operation on the binarized image using ImageJ;

[0134] The edge recognition unit is used to recognize the edge of the image after removing noise to obtain the gas-liquid interface;

[0135] The contact angle measurement unit is used to measure the contact angle with the intersection point of the gas-liquid interface and the horizontal plane as the triple point.

[0136] Among them, the module for determining the condensation ratio corresponding to different partial pressures specifically includes:

[0137] The condensation process diagram drawing unit under different partial pressures is used to draw the condensation process diagram under different partial pressures according to the capillary condensation radius and the gas relative pressure in the capillary condensation liquid surface of a single angle of the pore polygon;

[0138] A pixel number statistical unit is configured to count the number of pixels in the condensation part of the condensation process diagrams with different partial pressures.

[0139] A condensation ratio determination unit corresponding to different partial pressures is configured to determine the condensation ratio corresponding to different partial pressures according to the ratio of the number of pixels in the condensation part to the number of pixels in the initial pores.

[0140] In the present specification, each embodiment is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0141] In this article, specific examples are used to elaborate on 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.

Claims

1. A method for determining the condensation ratio of the pore structure, which is a key parameter of the capillary condensation amount, is characterized in that Including: Preparing a clay mineral particle sample and performing secondary electron imaging to obtain a secondary electron grayscale image; Performing pore extraction based on the secondary electron grayscale image; Performing polygon fitting on different pores in the extracted pore image and statistically analyzing the angles corresponding to the endpoints of each fitted polygon; Establishing an oil-water-rock model and performing molecular dynamics simulations; Obtaining a density distribution map according to the molecular dynamics simulation results; Calculating the contact angle based on the density distribution map; the contact angle is the contact angle between the gas-liquid interface and the horizontal plane in the density distribution map; Based on the contact angle and the angles corresponding to the endpoints of each fitted polygon, fitting the capillary condensation liquid surface of a single angle of the pore polygon; the condensed part in the capillary condensation liquid surface of a single angle of the pore polygon is the part enclosed by the curved liquid surface and the top of the single angle; Determining the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface of a single angle of the pore polygon.

2. The method for determining the condensation ratio of the pore structure of the key parameters of the capillary condensation amount according to claim 1, wherein The performing pore extraction based on the secondary electron grayscale image specifically includes: Performing denoising processing on the secondary electron grayscale image by using the median filtering method; Performing grayscale statistics on the denoised secondary electron grayscale image and plotting a grayscale histogram; Performing pore extraction based on the threshold between the mineral peak and the pore peak in the grayscale histogram, Performing binarization processing on the extracted image.

3. The method for determining the condensation ratio of the pore structure of the key parameters of the capillary condensation amount according to claim 1, characterized in that The performing polygon fitting on different pores in the extracted pore image and statistically analyzing the angles corresponding to the endpoints of each fitted polygon specifically includes: Using the convexhull function in matlab to perform polygon fitting on different pores in the extracted pore image and statistically analyzing the vertices of the polygon fitted for each pore; Statistically analyzing the angles of the triangles formed by every three vertices, and when the angle is greater than 165°, deleting the current vertex to simplify the fitted polygon; Statistically analyzing the angles corresponding to the endpoints of each simplified fitted polygon.

4. The method for determining the condensation ratio of the pore structure of the key parameters of the capillary condensation amount according to claim 1, characterized in that The calculating the contact angle based on the density distribution map specifically includes: Performing binarization processing on the density distribution map by using 0.5 times the density of liquid n-pentane as the threshold; Using ImageJ to perform a closing operation on the binarized image to remove noise; Performing edge recognition on the image after removing noise to obtain the gas-liquid interface; Using the intersection point of the gas-liquid interface and the horizontal plane as the triple point to measure the contact angle.

5. The method for determining the condensation ratio of the pore structure, which is a key parameter of the capillary condensation amount, according to claim 1, is characterized in that The determining the condensation ratio corresponding to different partial pressures based on the capillary condensation liquid surface of a single angle of the pore polygon specifically includes: Drawing a condensation process diagram at different partial pressures according to the capillary condensation radius and the gas relative pressure in the capillary condensation liquid surface of a single angle of the pore polygon; Statistically analyzing the number of pixel points in the condensed part in the condensation process diagrams at different partial pressures; Determining the condensation ratio corresponding to different partial pressures according to the ratio of the number of pixel points in the condensed part to the number of initial pore pixel points.

6. A system for determining the condensation ratio of a pore structure, which is a key parameter of capillary condensation amount, is characterized in that Including: A secondary electron imaging module for preparing a clay mineral particle sample and performing secondary electron imaging to obtain a secondary electron grayscale image; An extraction module for performing pore extraction based on the secondary electron grayscale image; A first fitting module for performing polygon fitting on different pores in the extracted pore image and statistically analyzing the angles corresponding to the endpoints of each fitted polygon; A model establishment module for establishing an oil-water-rock model and performing molecular dynamics simulations; A density distribution map determination module for obtaining a density distribution map based on the results of molecular dynamics simulations; A contact angle calculation module for calculating a contact angle based on the density distribution map; the contact angle is the contact angle between the gas-liquid interface and the horizontal plane in the density distribution map; A second fitting module for fitting the capillary condensation liquid surface of a single angle of the pore polygon based on the contact angle and the angles corresponding to the endpoints of each fitting polygon; the condensed part in the capillary condensation liquid surface of a single angle of the pore polygon is the part enclosed by the curved liquid surface and the top of the single angle; A condensed ratio determination module corresponding to different partial pressures for determining the condensed ratios corresponding to different partial pressures based on the capillary condensation liquid surface of a single angle of the pore polygon.

7. The determination system for the capillary condensation ratio of the key parameters of the capillary condensation amount according to claim 6, characterized in that The extraction module specifically includes: A first denoising unit for denoising the secondary electron grayscale image using the median filtering method; A grayscale histogram plotting unit block for performing grayscale statistics on the denoised secondary electron grayscale image and plotting a grayscale histogram; A pore extraction unit for extracting pores based on the threshold between the mineral peak and the pore peak in the grayscale histogram; A first binarization processing unit for binarizing the extracted image.

8. The determination system for the condensation ratio of the pore structure of the key parameters of the capillary condensation amount according to claim 6, characterized in that The first fitting module specifically includes: A fitting unit for polygonally fitting different pores in the extracted pore image using the convexhull function in matlab and counting the vertices of the polygons fitted for each pore; A simplification unit for counting the angles of the triangles formed by every three vertices, and when the angle is greater than 165°, deleting the current vertex to simplify the fitting polygon; An angle statistics unit for counting the angles corresponding to the endpoints of each simplified fitting polygon.

9. The determining system for the condensation ratio of the pore structure of the key parameters of the capillary condensation amount according to claim 6, characterized in that, The contact angle calculation module specifically includes: A second binarization processing unit for binarizing the density distribution map using 0.5 times the density of liquid n-pentane as the threshold; A second denoising unit for removing noise points from the binarized image using ImageJ for closing operation; An edge recognition unit for performing edge recognition on the image after removing noise points to obtain the gas-liquid interface; A contact angle measurement unit for measuring the contact angle with the intersection point of the gas-liquid interface and the horizontal plane as the triple point.

10. The determination system for the condensation ratio of the pore structure of the key parameters of the capillary condensation amount according to claim 6, characterized in that, The condensed ratio determination module corresponding to different partial pressures specifically includes: A condensed process diagram plotting unit corresponding to different partial pressures for plotting a condensed process diagram corresponding to different partial pressures based on the capillary condensation radius and the gas relative pressure in the capillary condensation liquid surface of a single angle of the pore polygon; A pixel point number statistics unit for counting the number of pixel points in the condensed part of the condensed process diagram corresponding to different partial pressures; A condensed ratio determination unit corresponding to different partial pressures for determining the condensed ratios corresponding to different partial pressures according to the ratio of the number of pixel points in the condensed part to the number of initial pore pixel points.

Images