Method and device for synchronous characterization of capillary pressure and contact angle of microfluidic fluid interface

Abstract

The application discloses a capillary pressure and contact angle synchronous characterization method and device of a micro-fluidic interface, relates to the field of interface analysis in a porous medium and multiphase seepage, and comprises the following steps: based on a pre-configured pore, particle and fluid binary image, distinguishing and extracting a fluid-particle contact interface contour and an attack / defense fluid interface contour, fitting and determining the curvature radius of each fluid interface contour through watershed region division algorithm and reordering smoothing of a Fourier descriptor; generating a multi-level size pore space based on the pore binary image, and obtaining a pore apparent radius; combining the curvature radius and the multi-level size pore space, calculating a necking angle, and obtaining an apparent contact angle and an intrinsic contact angle; and combining the curvature radius, the pore apparent radius, a chip depth and an interface tension, calculating the capillary pressure of the attack / defense fluid interface. The application provides high-precision technical support for micro-fluidic multiphase seepage research.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of interface analysis in porous media and multiphase percolation, in particular, to a capillary pressure and contact angle synchronous characterization method and device for microfluidic fluid interface. BACKGROUND

[0002] Capillary pressure and contact angle are important information for revealing the fluid percolation law, interface stability and interfacial mass transfer mechanism in porous media. Accurate measurement and characterization play a decisive role in understanding the interface behavior in CO2 geological storage, optimizing the efficiency of underground oil and gas resource exploitation, and improving the control accuracy of microfluidic devices. It is a core demand for basic research and engineering application in the fields of energy geology, environmental engineering and analytical chemistry. It is suitable for basic research in the fields of CO2 geological storage, underground resource exploitation, geological energy storage and analytical chemistry.

[0003] The testing methods of capillary pressure and contact angle have evolved from traditional intrusion method and mercury injection method to visual dynamic characterization technology. Early methods relying on pressure sensors or static image analysis were difficult to capture the dynamic interface behavior in complex pores. The rise of microfluidic technology has promoted the innovation of visual characterization technology. By reproducing real pore structures in micrometer-scale flow channels and combining high-speed photography and fluorescence microscopy imaging technology, real-time observation of multiphase flow interface morphology is realized. This kind of visual technology provides a new way for dynamic analysis of interface behavior information (such as interface curvature and contact line migration). However, how to accurately extract capillary pressure and contact angle from dynamic images still faces challenges in algorithms and models.

[0004] Current technologies have explored the characterization of capillary pressure or contact angle in porous media. Patent CN118425471A proposes to adjust the height of the non-wetting phase tank to balance the capillary pressure by gravity difference, and realize the test of capillary hysteresis curve in drainage-invasion process. Scholars have developed fluid interface fitting technology to characterize the contact angle by the tangent of the contact between particle edges. This method works well in microfluidic models with smooth particle edges. Scholars have proposed an automatic measurement algorithm for three-phase contact angle in microfluidic models. By locating the common contact point of rock particles and two-phase fluid, the angle between the rock edge straight line and the tangent line is quantified to represent the contact angle.

[0005] Although existing methods provide a basis for related characterization, there is still room for improvement in practical applications. In complex pore space, the edges of rock particles often exhibit irregular curved shapes. The existing method lacks a clear explanation for the demarcation of rock edges, which directly affects the accuracy of contact angle measurement. In addition, the existing contact angle characterization relies on the three-phase contact point of rock particles and fluid. This method is easily disturbed by interface pinning effect, resulting in a lag phenomenon in the characterized contact angle, which makes it difficult to objectively reflect the essential characteristics of the wetting angle.

[0006] At present, in the field of microfluidic technology, there is no patent that can realize the synchronous and accurate characterization of capillary pressure and contact angle; the present patent quantifies capillary pressure and contact angle by extracting the curvature information of the fluid meniscus, and maximally reduces the interference of particle wall pinning effect; by means of the mathematical model of interface curvature in the limited space derived, the synchronous dynamic characterization of capillary pressure and contact angle in the complex pore structure is realized, which provides key technical support for high-precision analysis of microfluidic multiphase flow.

[0007] At present, there is no effective solution to the problems in the related art. SUMMARY

[0008] In view of the problems in the related art, the present application proposes a method and device for synchronous characterization of capillary pressure and contact angle of microfluidic fluid interface to overcome the above technical problems existing in the prior art.

[0009] To this end, the specific technical solutions adopted by the present application are as follows:

[0010] In a first aspect, the present application proposes a method for synchronous characterization of capillary pressure and contact angle of microfluidic fluid interface, comprising:

[0011] S1, based on the pre-configured pore binary graph, particle binary graph and fluid binary graph, distinguishing and extracting the fluid-particle contact interface contour and the attack / defense fluid interface contour;

[0012] S2, the attack / defense fluid interface contour is regionally divided by a watershed region division algorithm, and the contour points are sequentially reordered and smoothed by a reordering algorithm and sorting processing in combination with a Fourier descriptor, and the attack / defense fluid interface contour after sorting processing is fitted with a curvature circle to determine the curvature radius of the attack / defense fluid interface;

[0013] S3, based on the pore binary graph, a multi-level size pore space is generated, and a pore apparent radius is obtained;

[0014] S4, based on the curvature radius and the multi-level size pore space, the neck angle is calculated to obtain the apparent contact angle and the intrinsic contact angle;

[0015] S5, based on the curvature radius, the pore apparent radius, the chip depth and the interfacial tension, the capillary pressure of the attack / defense fluid interface is calculated.

[0016] Further, the distinguishing and extracting of the fluid-particle contact interface contour and the attack / defense fluid interface contour based on the pre-configured pore binary graph, particle binary graph and fluid binary graph comprises:

[0017] Performing an expansion operation on the particle region in the particle binary image based on an expansion operation function, performing an intersection operation on the expanded particle region and the fluid contour, and obtaining a fluid / particle contact interface;

[0018] Separating the attack / defense fluid interface by performing an exclusive OR operation on the fluid / particle contact interface and the fluid contour;

[0019] Based on the binary image function, performing skeleton thinning processing on the attack / defense fluid interface to extract the skeleton of the attack / defense fluid interface contour.

[0020] Further, the attack / defense fluid interface contour is divided by the watershed region division algorithm, and the contour points are sequentially reordered and sorted by combining the Fourier descriptor and the reordering smoothing algorithm. The curvature radius of the sorted attack / defense fluid interface contour is fitted, and the curvature radius of the attack / defense fluid interface is determined, including:

[0021] S21, based on the original image size, an initialization matrix is constructed, and the attack / defense fluid interface contour is subjected to local minimization processing. The fluid-particle contact interface is set as a maximization seed point; and the attack / defense fluid interface contour is divided into multiple independent regions by the watershed algorithm;

[0022] S22, the independent regions are traversed, and the attack / defense fluid interface contour of the current traversal is extracted. The Fourier descriptor is used to project the contour data to the Fourier space, and a preset proportion of the descriptor is selected to filter out high-frequency noise and achieve smoothing reconstruction. After smoothing reconstruction, the generated contour points are sequentially sorted in a clockwise direction;

[0023] S23, the curvature radius of the attack / defense fluid interface contour point is represented by circle fitting;

[0024] S24, step S22 is repeatedly executed until all attack / defense fluid interface regions are traversed, and the curvature radius of each attack / defense fluid interface is output.

[0025] Further, based on the pore binary image, a multi-level size pore space is generated, and a pore overhead radius is obtained, including:

[0026] S31, distance transformation and extraction of the central axis skeleton are performed on the pore binary image. The distance transformation result and the central axis skeleton are superimposed and fused to generate a pore radius information skeleton. The distance elements in the central axis skeleton are counted to form a pore size set, and the elements in the pore size set are arranged in descending order;

[0027] S32, the pore size set is traversed, and a circle expansion operation is performed based on the position point of the preset radius in the pore radius information skeleton;

[0028] S33, change the preset radius to the next element in the set of pore sizes, and determine whether the elements in the set of pore sizes have been traversed, if not, re-execute step S32, if completed, generate a multi-level size pore space.

[0029] Further, the calculation of the necking angle based on the radius of curvature and the multi-level size pore space to obtain the apparent contact angle and the intrinsic contact angle comprises:

[0030] S41, traverse the region divided by the watershed algorithm, and extract the current traversed attack / defense fluid interface;

[0031] S42, based on the radius of curvature and the multi-level size pore space, determine the pore overhead radius corresponding to the central part and the end of the attack / defense fluid interface respectively;

[0032] S43, project the attack / defense fluid interface profile on the pore center axis skeleton, and calculate the projection distance of the attack / defense fluid interface end and the central part on the center axis line through the projection position;

[0033] S44, based on the pore overhead radius corresponding to the central part and the end of the attack / defense fluid interface respectively and the projection distance of the attack / defense fluid interface end and the central part on the center axis line, calculate the necking angle;

[0034] S45, based on the radius of curvature, the pore overhead radius of the attack / defense fluid interface end, and the necking angle, calculate the apparent contact angle of the attack / defense fluid interface;

[0035] S46, based on the radius of curvature and the pore overhead radius of the attack / defense fluid interface end, calculate the intrinsic contact angle of the attack / defense fluid interface;

[0036] S47, repeat steps S41-S46 until all attack / defense fluid interface regions are traversed, and output the apparent contact angle and the intrinsic contact angle of each attack / defense fluid interface.

[0037] Further, after calculating the capillary pressure of the attack / defense fluid interface based on the radius of curvature, the pore overhead radius, the chip depth, and the interfacial tension, it further comprises:

[0038] S51, statistically analyze the capillary pressure of the attack / defense fluid interface, and select the arithmetic mean or the median as the target capillary pressure of the attack / defense fluid interface under the current saturation degree according to the frequency distribution characteristics;

[0039] S52, draw a capillary pressure-saturation relationship curve by traversing the images under different attack / defense fluid interface saturations one by one.

[0040] S53, the capillary pressure and the attack / defense fluid interface saturation relationship curve is fitted by using the seepage characteristic model.

[0041] Further, the necking angle expression is:

[0042] ;

[0043] In the formula, represents the necking angle, R p represents the pore apparent radius corresponding to the meniscus end, R pm represents the pore apparent radius corresponding to the meniscus central part, L a represents the projection distance of the meniscus end and the central part on the central axis;

[0044] The apparent contact angle expression is:

[0045] ;

[0046] In the formula, represents the apparent contact angle, represents the pore apparent radius corresponding to the attack / defense fluid interface profile end, represents the curvature radius of the attack / defense fluid interface profile, represents the necking angle.

[0047] Further, the capillary pressure expression is:

[0048] ;

[0049] In the formula, P c represents the capillary pressure of the attack / defense fluid interface, H represents the chip depth ，R p represents the pore apparent radius, R c represents the curvature radius, represents the tension of the attack / defense fluid interface.

[0050] Further, the intrinsic contact angle expression is:

[0051] ;

[0052] In the formula, represents the intrinsic contact angle, represents the pore apparent radius corresponding to the attack / defense fluid interface profile end, A curvature radius of the attack / defense fluid interface profile.

[0053] In a second aspect, the present application further provides a capillary pressure and contact angle synchronous characterization system for a microfluidic fluid interface, comprising:

[0054] An interface profile identification module, configured to distinguish and extract the fluid-particle contact interface profile and the attack / defense fluid interface profile based on the pre-configured pore binary image, particle binary image and fluid binary image;

[0055] An interface curvature characterization module, configured to perform region division on the attack / defense fluid interface profile by a watershed region division algorithm, and sequentially perform reordering smoothing algorithm and ordering processing on the profile points in combination with a Fourier descriptor, to perform curvature circle fitting on the attack / defense fluid interface profile after the ordering processing, and determine the curvature radius of the attack / defense fluid interface by the fitting;

[0056] A pore width characterization module, configured to generate multi-level size pore spaces based on the pore binary image, and obtain a pore apparent radius;

[0057] A contact angle characterization module, configured to calculate a neck angle, obtain an apparent contact angle and an intrinsic contact angle based on the curvature radius and the multi-level size pore spaces;

[0058] A capillary pressure characterization module, configured to calculate the capillary pressure of the attack / defense fluid interface based on the curvature radius, pore apparent radius, chip depth and interfacial tension.

[0059] In a third aspect, the present application further provides a capillary pressure and contact angle synchronous characterization device for a microfluidic fluid interface, comprising: a micro-flow injection pump, a piston container, a pressure sensor, a microscope, a chip pressure-bearing clamp, an image acquisition system and a back pressure valve.

[0060] The micro-flow injection pump is configured to control the injection speed of the fluid.

[0061] The piston container is arranged on one side of the micro-flow injection pump, configured to store the experimental fluid, and cooperate with the micro-flow injection pump to maintain the fluid delivery.

[0062] The pressure sensor is arranged on the top of the piston container, configured to monitor the pressure change of the injection end.

[0063] The microscope is arranged on the top of the chip pressure-bearing clamp, and cooperates with the image acquisition system, configured to observe the fluid interface morphology in the microfluidic chip.

[0064] The chip pressure-bearing clamp is arranged on the bottom of the microscope, configured to fix the microfluidic chip, and the chip pressure-bearing clamp is in a small volume pressure-bearing structure.

[0065] The chip pressure bearing clamp is composed of a pressure bearing base, a chip, a pressure sealing plate and a cavity cover from bottom to top, and the chip and the pressure sealing plate are located between the pressure bearing base and the cavity cover.

[0066] The image acquisition system is connected to one side of the microscope and is used for shooting the multiphase flow interface in the chip.

[0067] The back pressure valve is arranged on one side of the chip pressure bearing clamp and is used for controlling the back pressure of the system.

[0068] The beneficial effects of the present application are:

[0069] By deeply fusing the microfluidic visualization technology and the image processing algorithm, the capillary pressure and the contact angle of the fluid meniscus in the microfluidic image can be quantitatively characterized in batches, which not only provides a standardized characterization scheme for the basic research of the interface physical and chemical properties, but also provides key interface behavior data support for the microfluidic device design, the optimization of the geological energy storage engineering and other application scenarios; meanwhile, the capillary pressure and the contact angle are automatically and synchronously characterized, which provides high-precision technical support for the microfluidic multiphase seepage research in the fields of CO2 geological storage, underground resource exploitation and the like. BRIEF DESCRIPTION OF DRAWINGS

[0070] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0071] Figure 1 It is a relationship diagram between each module in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the present application;

[0072] Figure 2 It is a schematic diagram of a microfluidic displacement experiment of the capillary pressure and contact angle synchronous characterization device of the microfluidic fluid interface according to the embodiment of the present application;

[0073] Figure 3 It is a perspective assembly view of a chip pressure bearing clamp in the capillary pressure and contact angle synchronous characterization device of the microfluidic fluid interface according to the embodiment of the present application;

[0074] Figure 4 It is a schematic diagram of contact angle characterization in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the present application;

[0075] Figure 5Figure is a mark and circle fitting result diagram of CO2 / saline meniscus 1 in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application;

[0076] Figure 6 Figure is a mark and circle fitting result diagram of CO2 / saline meniscus 2 in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application;

[0077] Figure 7 Figure is a pore size distribution diagram in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application;

[0078] Figure 8 Figure is an intrinsic contact angle distribution diagram of each meniscus in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application;

[0079] Figure 9 Figure is a relationship diagram of the intrinsic contact angle and the apparent contact angle in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application;

[0080] Figure 10 Figure is a capillary pressure distribution diagram of each meniscus in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application;

[0081] Figure 11 Figure is a relationship diagram of the CO2 saturation and the capillary pressure in the capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application.

[0082] Figure:

[0083] 1, micro flow injection pump; 2, piston container; 3, pressure sensor; 4, microscope; 5, chip pressure bearing clamp; 501, pressure bearing base; 502, chip; 503, pressure sealing plate; 504, cavity cover; 6, image acquisition system; 7, back pressure valve. DETAILED DESCRIPTION

[0084] To further illustrate the embodiments, the present application provides drawings which are part of the disclosure of the present application, mainly used to illustrate the embodiments, and can be used to explain the operating principle of the embodiments in conjunction with the related description of the specification. Those skilled in the art should understand other possible implementations and advantages of the present application by referring to these contents. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0085] According to the embodiments of the present application, a capillary pressure and contact angle synchronous characterization method and device of a microfluidic fluid interface are provided.

[0086] The application will be further described in conjunction with the drawings and specific embodiments, as shown in the drawings Figure 1 The capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface according to the embodiment of the application comprises the following steps:

[0087] Step S1, based on the pre-configured pore binary image, particle binary image and fluid binary image, distinguish and extract the fluid-particle contact interface contour and the attack / defense fluid interface contour;

[0088] Step S2, perform region division on the attack / defense fluid interface contour by a watershed region division algorithm, and sequentially perform reordering smoothing algorithm and ordering processing on the contour points in combination with a Fourier descriptor, perform curvature circle fitting on the ordered attack / defense fluid interface contour, and determine the curvature radius of the attack / defense fluid interface by fitting;

[0089] Step S3, based on the pore binary image, generate a multi-level size pore space, and obtain a pore apparent radius;

[0090] Step S4, based on the curvature radius and the multi-level size pore space, calculate the necking angle, and obtain the apparent contact angle and the intrinsic contact angle;

[0091] Step S5, based on the curvature radius, pore apparent radius, chip depth and interfacial tension, calculate the capillary pressure of the attack / defense fluid interface.

[0092] In the optional embodiment, the distinguishing and extracting of the fluid-particle contact interface contour and the attack / defense fluid interface contour based on the pre-configured pore binary image, particle binary image and fluid binary image comprises:

[0093] Perform dilation operation on the particle region in the particle binary image based on an expansion operation function, perform intersection operation on the dilated particle region and the fluid contour, and obtain the contact interface of the fluid / particle;

[0094] Separate out the attack / defense fluid interface by performing exclusive OR operation on the contact interface of the fluid / particle and the fluid contour;

[0095] Perform skeleton thinning processing on the attack / defense fluid interface based on a binary image function, and extract the skeleton of the attack / defense fluid interface contour.

[0096] Specifically, first, the attacking fluid and particle regions in the photographed image are accurately segmented to generate an attacking fluid binary image (i.e., a fluid binary image) and a particle binary image (i.e., a pore binary image, a particle binary image) respectively; in the attacking fluid binary image, an attacking fluid contour (i.e., an attacking / defending fluid interface contour) is extracted by using a skeleton thinning method; then, an inflation operation is performed on the particle region in the particle binary image, and an intersection operation is performed between the particle region and the attacking fluid contour to determine the contact interface between the attacking fluid and the particle; then, an exclusive or operation is performed between the attacking fluid contour and the contact interface to separate the attacking fluid and the defending fluid interface; and then, a skeleton thinning process is performed on the separated attacking / defending fluid interface to extract the skeleton of the attacking / defending fluid interface, thereby accurately determining the attacking / defending fluid interface contour.

[0097] Then, the interface contour identification module E is run to perform image segmentation and interface preliminary extraction; the saturated water chip image and the CO2 intrusion image at a specific time are processed to obtain a CO2 (fluid) binary image and a particle binary image; in the particle binary image, the white region is a particle region, and the black region is a pore region; similarly, in the CO2 binary image, the white region is the intrusion region of the attacking fluid CO2. The bwperim function (i.e., a contour extraction function for a binary image) is used to extract the CO2 contour (i.e., the attacking / defending fluid interface contour) from the CO2 intrusion region; a circular structural element with a radius of 3 is used to perform an inflation operation on the particle region in the particle binary image by using the imdilate function (i.e., an inflation operation function); an intersection operation is performed between the inflated particle region and the CO2 contour to obtain the contact interface between the CO2 and the particle; the contact interface between the CO2 and the particle is separated from the CO2 contour by using an exclusive or operation to obtain the meniscus (i.e., the attacking / defending fluid interface) between the CO2 and the salt water; the meniscus is skeleton thinned by using the skel mode in the bwmorph function (i.e., a skeleton extraction function for a binary image) to perform a skeleton thinning process on the extracted meniscus between the CO2 and the salt water, thereby extracting the meniscus skeleton between the CO2 and the salt water. Figure 5 (a) in FIG. 1 and Figure 6 (a) in FIG. 1 is the meniscus between the CO2 and the salt water marked in two in this embodiment.

[0098] In this optional embodiment, the attacking / defending fluid interface contour is regionally divided by using the watershed region division algorithm, and the contour points are sequentially reordered and smoothed by using the Fourier descriptor, and the reordered attacking / defending fluid interface contour is subjected to curvature circle fitting to determine the curvature radius of the attacking / defending fluid interface, including:

[0099] S21, construct an initialization matrix based on the original image size, and perform local minimization processing on the attack / defense fluid interface profile, and set the fluid-particle contact interface as a maximization seed point; and the attack / defense fluid interface profile is divided into multiple independent regions by a watershed algorithm;

[0100] S22, traverse the divided independent regions, and extract the current traversed attack / defense fluid interface profile; the profile data is projected into Fourier space using Fourier descriptors, and a preset proportion of descriptors is selected to filter out high-frequency noise and achieve smooth reconstruction; after smooth reconstruction, the generated profile points are sequentially sorted in a clockwise direction;

[0101] S23, the curvature radius of the attack / defense fluid interface profile point is represented by a circle fitting method;

[0102] S24, repeat step S22 until all attack / defense fluid interface regions are traversed, and output the curvature radius of each attack / defense fluid interface.

[0103] The interface curvature representation module C; the core function is to traverse the identified interface profile one by one, and perform curvature circle fitting operation on the scattered points, and then determine the curvature radius R c ; According to the original image size, an initialization matrix is constructed, in which the attack / defense fluid interface profile is processed by local minimization, the attack fluid / particle interface is set as a maximization seed point, and a clear gradient is formed; then the watershed algorithm is used to divide the image, so that it is divided into multiple independent regions, and each independent region contains only one attack / defense fluid interface (meniscus) profile.

[0104] Then, the region divided by the watershed algorithm is traversed, and the current traversed meniscus profile is extracted; considering that there are local noise and burrs between the profile points extracted by the image, Fourier descriptors are used to project the profile data into Fourier space, and a certain proportion (i.e. A preset proportion) of descriptors is selected to filter out high-frequency noise and achieve smooth reconstruction; after smooth reconstruction, the profile points are reordered to ensure that the generated profile points are sequentially arranged in a clockwise direction; the multiple sorting and data merging based on spatial distance checking are used to ensure the correctness of the profile point order; The profile point after sorting is the meniscus profile to be fitted; at the same time, the meniscus profile is represented by curvature; the curvature radius of the meniscus profile point is represented by a circle fitting method, and the specific principle is as follows, the equation of the fitted circle is expressed as:

[0105] ;

[0106] In the formula, x and y represent known variables on the meniscus profile, a, b, c represents an unknown variable to be solved.

[0107] The corresponding center position is , and the circle radius (curvature radius R c ) is specifically:

[0108] ;

[0109] In the formula, x and y represent known variables on the meniscus profile, R c represents a curvature radius, a, b, c represents an unknown variable to be solved.

[0110] In the process of interface profile fitting, x and y in the formula are known variables on the meniscus profile, and x, x , y are unknown variables to be solved, the formula becomes a multivariate linear equation, and considering that there are N coordinate points on the meniscus profile, it can be written as: a b c

[0111] ;

[0112] In the formula, x and y represent known variables on the meniscus profile, x y , and x represents an unknown variable to be solved. a, b, c

[0113] Through matrix solution, the coefficients a, a b , and b can be obtained, and the curvature radius R c c . R

[0114] ; In the formula, x and y represent known variables on the meniscus profile,

[0115] x , x represents an unknown variable to be solved, and c represents a constant. y a, b, c N

[0116] If all the meniscus regions have not been traversed, repeat the step; if the traversal is completed, output the curvature radii of the menisci.

[0117] ​​​​​​​​​​Specifically, the image is divided into watershed regions; an initialization matrix is ​​constructed based on the original image size, and the CO2 / saltwater crescent contour is locally minimized. At the same time, the contact interface between CO2 and particles is set as the seed point for maximization, thereby constructing a clear gradient field; the watershed segmentation of the image is achieved through the function watershed (image segmentation function), ensuring that each segmented region contains only a single CO2 / saltwater crescent contour.

[0118] Contour point processing and sorting: Each divided region is traversed, and the contour point set of each meniscus is extracted. Fourier descriptors are used to denoise the contour points. A custom function `frdescp` (custom feature description function) is used to project the contour data into Fourier space, selecting the top 45% of descriptors to filter high-frequency noise. Then, the custom function `frdescp` is used to complete the analytical reconstruction of the Fourier space. The reconstructed contour points are then sorted and merged multiple times using the custom function `Fun sort` (custom sorting function) to ensure that the contour points are arranged in a clockwise order.

[0119] Curvature circle fitting and radius calculation: Using a self-developed function Mcircle Fit, a circle fitting is performed on the sorted meniscus contour points based on the formula to solve for the curvature radius of each meniscus. R c ;like Figure 5 (bc) and Figure 6 As shown in (bc), the meniscus circle fitting degree in this embodiment R 2 The results were 0.963 and 0.994 respectively, verifying the fitting accuracy and completing the traversal of each meniscus.

[0120] Figure 5 (a) in the text is marked CO2 / saltwater crescent 1; Figure 5 (b) shows the effect of circular fitting on meniscus 1; Figure 5 (c) in the figure is an enlarged view of the meniscus fitted to a circle; Figure 6 (a) in the text is labeled CO2 / saltwater crescent 2; Figure 6 (b) in the diagram presents its circle fitting effect; Figure 6 (c) is an enlarged view of the meniscus fitted by two circles.

[0121] S31. Perform distance transformation on the pore binary map and extract the central skeleton. Overlay and fuse the distance transformation result and the central skeleton to generate a pore radius information skeleton. Count the distance elements in the central skeleton to form a pore size set, and arrange the elements in the pore size set in descending order.

[0122] S32, perform a traversal operation on the pore size set, find a position point with a preset radius in the skeleton based on the pore radius information, and perform a circle inflation operation;

[0123] S33, change the preset radius to the next element in the pore size set, and determine whether the elements in the pore size set have been traversed, if not, re-execute step S32, if completed, generate a multi-level size pore space.

[0124] Specifically, the pore size representation module S; the pore size representation theory can adopt the form of distance change graph, but the principle of distance change graph is to calculate the distance from any point to the nearest particle, and its essence is to represent the spatial relationship between the point and the particle; In the actual distance change graph, the smaller value area represents that the distance from the point to the particle is smaller, but it may belong to a large pore space; Therefore, a pore size space division method needs to be established to realize the pore size representation of the microfluidic image, and the specific execution steps are as follows.

[0125] First, perform distance transformation on the particle binary image, and then extract the center axis skeleton; Finally, superimpose the skeleton and the distance transformation result to obtain the skeleton fused with pore radius information, wherein the value of each point of the skeleton corresponds to the radius of the pore.

[0126] Then, count the distance elements on the center axis skeleton to form a pore size set R p , and ensure that the pore size set R p is arranged in descending order of the middle element; Traverse the pore size set R p in the center axis skeleton; find a position point with a radius of r i (namely, a preset radius) on the skeleton fused with pore radius information, and perform a circle inflation operation with a radius of r i ; change the current radius r i to the next element in the pore size set R p ; Finally, determine whether the elements in the pore size set R p have been traversed, if not, re-execute the above steps; if completed, a multi-level size pore space can be generated. Distance transformation and center axis skeleton extraction; for the particle binary image, use the function bwdist (namely, binary image) to perform distance transformation, calculate the distance from each pixel point in the pore region to the nearest particle boundary, and generate a distance change graph; use the skel method in the function bwmorph (namely, extract the skeleton of the binary image) to perform center axis skeleton extraction on the pore region (namely, the black region in the particle binary image), and obtain the center axis skeleton of the pore.

[0127] Next, pore radius information is fused and size statistics are performed. The central axis skeleton is superimposed with the distance transformation map through dot product operation, so that the value of each point on the skeleton corresponds to the pore radius at its location. All distance elements on the central axis skeleton are counted to form a set of pore sizes. R p And sort them in descending order of value.

[0128] Finally, a multi-level pore space is generated; the sorted set of pore sizes is then traversed. R p Each element ri in the matrix is ​​located on the skeleton of the fused radius information with a radius of 1. r i The location point is then subjected to an expansion operation using the function `imdilate` (i.e., the expansion function) with a radius of [missing value]. r i Circular expansion operation; until the distance set R p After traversing all elements, a multi-level pore space is generated. Figure 7 The diagram shown in the embodiment illustrates the distribution of pore sizes, presenting the size and distribution characteristics of each pore size.

[0129] In this optional embodiment, the calculation of the necking angle based on the radius of curvature and the multi-level sized pore space to obtain the apparent contact angle and the intrinsic contact angle includes:

[0130] S41. Traverse the regions divided by the watershed algorithm and extract the attack / defense fluid interface of the current traversal.

[0131] S42. Based on the radius of curvature and multi-level pore space, determine the top-view radii of the pores corresponding to the central part and the end of the attack / defense fluid interface, respectively.

[0132] S43. Project the profile of the offensive / defensive fluid interface onto the central axis skeleton of the pore, and calculate the projection distance between the end of the offensive / defensive fluid interface and the central part on the central axis through the projection position.

[0133] S44. Calculate the necking angle based on the porosity of the central and terminal parts of the offensive / defensive fluid interface and the projection distance between the terminal and central parts of the offensive / defensive fluid interface on the central axis.

[0134] S45. Calculate the apparent contact angle of the attack / defense fluid interface based on the radius of curvature, the top view radius of the porosity at the end of the attack / defense fluid interface, and the necking angle.

[0135] S46. Calculate the intrinsic contact angle of the attack / defense fluid interface based on the radius of curvature and the top-view radius of the pores at the end of the attack / defense fluid interface.

[0136] S47, repeat the steps S41-S46 until all the attack / defense fluid interface region traversal is completed, output each attack / defense fluid interface visual contact angle and intrinsic contact angle.

[0137] Specifically, the contact angle characterization module A; to achieve the calculation of the contact angle formula, the specific steps are as follows: the watershed algorithm is traversed to extract the current meniscus; the multi-level size pore space and the meniscus profile are determined R pm With R p ; the meniscus profile is projected on the pore center axis skeleton, and the distance is calculated by the nearest position of the meniscus profile point on the center axis skeleton and the projection position on the center axis skeleton L a ; the necking angle is calculated according to the above formula ; combined with the curvature radius R c , the visual contact angle of the meniscus is calculated according to the formula ; the intrinsic contact angle of the meniscus is calculated according to the formula ; if all the meniscus regions are not traversed, repeat the step; if the traversal is completed, output the visual contact angle and the intrinsic contact angle of each meniscus . The meniscus often faces expansion and necking in the pore limited space, as shown in Figure 4 , the meniscus has two contact angles: one is the visual contact angle affected by the expansion / necking , and the other is the intrinsic contact angle reflecting the essential characteristics θ ins . Figure 8 is the intrinsic contact angle distribution diagram of each meniscus in this embodiment, which shows the size and distribution characteristics of the intrinsic contact angle of different menisci; Figure 9 is the relationship diagram of the intrinsic contact angle and the visual contact angle in the embodiment.

[0138] In this optional embodiment, after calculating the capillary pressure of the attack / defense fluid interface based on the curvature radius, the pore apparent radius, the chip depth and the interfacial tension, it further comprises:

[0139] S51, statistical analysis is performed on the capillary pressure of the attack / defense fluid interface, and the arithmetic mean or the median is selected as the target capillary pressure of the attack / defense fluid interface under the current saturation degree according to the frequency distribution characteristics;

[0140] S52, draw the curve of capillary pressure and attack / defense fluid interface saturation by traversing the images under different attack / defense fluid interface saturations one by one;

[0141] S53, the curve of capillary pressure and attack / defense fluid interface saturation is fitted by using the seepage characteristic model.

[0142] Specifically, the capillary pressure characterization module P; in the pore limited space, the capillary pressure P c is determined by the curvature of two directions, specifically as follows:

[0143] ;

[0144] In the formula, P c represents the capillary pressure of the meniscus, represents the interfacial tension of the attack fluid and the defense fluid, R s represents the curvature radius in the overhead direction, R v represents the curvature radius in the depth direction.

[0145] Wherein, P c is the capillary pressure of the meniscus, unit: kPa; is the interfacial tension of the attack fluid and the defense fluid, unit: mN / m; R s is the curvature radius in the overhead direction, unit: μm; R v is the curvature radius in the depth direction, unit: μm.

[0146] Traverse the region divided by the watershed algorithm, and extract the current traversed meniscus and the curvature radius of the meniscus corresponding to the meniscus R s ; by correlating the multi-level size pore space and the meniscus profile, the radius of the pore where the meniscus is located R p is determined. If all meniscus regions have not been traversed, return to the above steps to continue execution; if the traversal of all meniscus regions is completed, output the capillary pressure value of each meniscus.

[0147] Statistical analysis is performed on the capillary pressure data of all menisci, and according to the frequency distribution characteristics, the arithmetic mean or the median is selected as the representative capillary pressure of the attack fluid under the current saturation. By traversing the images under different attack fluid saturations one by one, the relationship curve of capillary pressure and attack fluid saturation is finally drawn; wherein, the calculation of the attack fluid saturation of the current image is as follows:

[0148] ;

[0149] wherein, S in represents the saturation of the invading fluid, represents the total number of pixels of the invading region of the invading fluid, represents the total number of pixels of the pore region in the particle binary image.

[0150] S in is the saturation of the invading fluid, unit: %; is the total number of pixels of the invading region of the invading fluid; is the total number of pixels of the pore region in the particle binary image.

[0151] The relationship curve between capillary pressure and saturation can be fitted by Van Genuchten formula (i.e. seepage characteristic model), as follows:

[0152] ;

[0153] wherein, P c represents the capillary pressure of the meniscus, represents the overall level of capillary pressure, m is between 0 and 1, represents the dimensionless saturation.

[0154] wherein, determines the overall level of capillary pressure; m is between 0 and 1, the closer the value is to 1, the flatter the capillary pressure curve is; on the contrary, the closer the value is to 0, the steeper the curve is; is the dimensionless saturation, as follows:

[0155] ;

[0156] wherein, represents the dimensionless saturation, represents the residual saturation.

[0157] wherein, is the residual saturation, unit: %.

[0158] Specifically, the capillary pressure characterization module P is run, the meniscus parameter extraction and capillary pressure calculation; the regions divided by the watershed algorithm are traversed one by one, the current meniscus and its curvature radius are extracted R c , and the multi-level size pore space and meniscus profile are associated to determine the radius of the pore where the meniscus is located R p .

[0159] In this embodiment, the depth of the chip is 15 μm, the CO2 / saline interfacial tension is 72 mN / m, and the capillary pressure of each meniscus is calculated according to the above formula. H P c .

[0160] After traversing all the menisci, the capillary pressure value of each meniscus is output.

[0161] The frequency distribution of the capillary pressure data of all the menisci is analyzed, and the arithmetic mean value is selected as the representative capillary pressure at the current saturation in this embodiment. The CO2 saturation of the current image is calculated using the formula, and the corresponding relationship between the CO2 saturation and the capillary pressure is established.

[0162] The relationship curve between the saturation and the capillary pressure is fitted using the formula. In this embodiment, the fitting parameters are 5.45, ,0.9745, and the residual saturation is 46.5%; the relationship between the CO2 saturation and the capillary pressure is shown in FIG. 2B. m S ir Figure 11

[0163] Figure 11 In FIG. 2A, (a) is a frequency distribution diagram of the capillary pressure of the meniscus at a specific saturation, and (b) shows the change trend of the capillary pressure at the CO2 saturation, in which the dashed line is the result after fitting the formula. Figure 11

[0164] In this alternative embodiment, the expression of the neck angle is:

[0165] ;

[0166] In the formula, the neck angle is represented by , R p the pore apparent radius corresponding to the end of the meniscus is represented by R pm the pore apparent radius corresponding to the central part of the meniscus is represented by L a the projection distance of the end and the central part of the meniscus on the central axis is represented by

[0167] The expression of the apparent contact angle is:

[0168] ;

[0169] In the formula, the apparent contact angle is represented by , ​​​​​represents the pore apparent radius corresponding to the end of the attack / defense fluid interface profile, represents the curvature radius of the attack / defense fluid interface profile, represents the necking angle.

[0170] In this optional embodiment, the capillary pressure expression is:

[0171] ;

[0172] wherein, P c represents the capillary pressure of the attack / defense fluid interface, H represents the chip depth ，R p represents the pore apparent radius, R c represents the curvature radius, represents the tension of the attack / defense fluid interface.

[0173] In this optional embodiment, the intrinsic contact angle expression is:

[0174] ;

[0175] wherein, represents the intrinsic contact angle, represents the pore apparent radius corresponding to the end of the attack / defense fluid interface profile, represents the curvature radius of the attack / defense fluid interface profile.

[0176] As Figure 1 shown, according to another embodiment of the present application, the present application also provides a capillary pressure and contact angle synchronous characterization system of a microfluidic fluid interface, comprising:

[0177] an interface profile identification module E: for distinguishing and extracting the fluid-particle contact interface profile and the attack / defense fluid interface profile based on the pre-configured pore binary graph, particle binary graph and fluid binary graph;

[0178] an interface curvature characterization module C: for performing region division on the attack / defense fluid interface profile by a watershed region division algorithm, and sequentially performing reordering smoothing algorithm and ordering processing on the profile points by combining a Fourier descriptor, and performing curvature circle fitting on the ordered attack / defense fluid interface profile, so as to determine the curvature radius of the attack / defense fluid interface;

[0179] a pore width characterization module S: for generating multi-level size pore space based on the pore binary graph, and obtaining the pore apparent radius;

[0180] Contact angle characterization module A: used to calculate the necking angle based on the radius of curvature and multi-level sized pore space, and obtain the apparent contact angle and intrinsic contact angle;

[0181] Capillary pressure characterization module P: Used to calculate the capillary pressure at the attack / defense fluid interface based on the radius of curvature, the top-view radius of the pore, the chip depth, and the interfacial tension.

[0182] like Figure 2 As shown, according to another embodiment of the present invention, the present invention also provides a device for synchronous characterization of capillary pressure and contact angle of microfluidic fluid interface, including: microflow injection pump 1, piston container 2, pressure sensor 3, microscope 4, chip pressure holder 5, image acquisition system 6 and back pressure valve 7.

[0183] The micro-flow injection pump 1 is used to control the injection rate of the fluid;

[0184] The piston container 2 is located on one side of the micro-flow injection pump 1 and is used to store experimental fluid and work with the micro-flow injection pump 1 to maintain fluid delivery.

[0185] The pressure sensor 3 is located on the top of the piston container 2 and is used to monitor pressure changes at the injection end.

[0186] The microscope 4 is mounted on top of the chip pressure fixture 5 and works in conjunction with the image acquisition system 6 to observe the fluid interface morphology within the microfluidic chip.

[0187] The chip pressure-bearing fixture 5 is disposed at the bottom of the microscope 4 and is used to fix the microfluidic chip. The chip pressure-bearing fixture 5 has a small volume pressure-bearing structure.

[0188] like Figure 3 As shown, the chip pressure-bearing fixture is composed of a pressure-bearing base 501, a chip 502, a sealing plate 503 and a cavity cover 504 from bottom to top, and the chip 502 and the sealing plate 503 are located between the pressure-bearing base 501 and the cavity cover 504.

[0189] The image acquisition system 6 is connected to one side of the microscope 4 and is used to photograph the multiphase flow interface within the chip.

[0190] The back pressure valve 7 is located on one side of the chip pressure-bearing fixture 5 and is used to control the back pressure of the system.

[0191] Specifically, the experimental setup is as follows: Figure 2 As shown, it consists of a micro-flow injection pump 1, a piston container 2, a pressure sensor 3, a microscope 4, a chip pressure holder 5, an image acquisition system 6, and a back pressure valve 7.

[0192] In the experimental device, the micro-flow injection pump 1 can accurately control the injection speed of the fluid, providing stable fluid driving conditions for the experiment and ensuring that the fluid flows in the micro-fluidic chip at the preset rate.

[0193] The piston container 2 is used to store the experimental fluid, and the volume of the fluid is accurately controlled by the movement of the piston, which cooperates with the micro-flow injection pump to maintain the stability of the fluid delivery.

[0194] The pressure sensor 3 monitors the pressure change of the injection end in real time.

[0195] The microscope 4 includes but is not limited to a stereomicroscope, an inverted microscope, a metallographic microscope, etc., which cooperates with the image acquisition system 6 to observe the fluid interface morphology in the micro-fluidic chip at high magnification, facilitating the image acquisition system to capture the details of the dynamic changes of the interface.

[0196] The chip pressure clamp 5 is used to fix the micro-fluidic chip, providing a stable pressure environment for the chip and ensuring that the chip does not displace or damage during the experiment.

[0197] The image acquisition system 6 is composed of a high-resolution camera, which can take real-time high-definition photos of the multiphase flow interface in the chip, record the interface morphology evolution process, and provide image basis for subsequent data processing.

[0198] The back pressure valve 7 is used to control the back pressure of the system, maintain the stability of the pressure in the system, and prevent pressure fluctuations from interfering with the experimental results.

[0199] To realize the characterization of capillary pressure and contact angle of CO2 / saline meniscus in the image of micro-fluidic chip, the interface profile recognition module E, interface curvature characterization module C, pore width characterization module S, contact angle characterization module A and capillary pressure characterization module P need to be executed in turn. Based on the images recorded by the experimental device, the following five modules are used to realize the synchronous characterization of the capillary pressure and contact angle of the fluid interface. The five modules are: interface profile recognition module E, interface curvature characterization module C, pore width characterization module S, contact angle characterization module A and capillary pressure characterization module P, and the relationship between each module is as shown in Figure 1

[0200] The combination of the five modules realizes: the interface profile recognition module E accurately separates the fluid-particle interface and the meniscus profile between fluids; the interface curvature characterization module C uses the circle fitting method to quantify the curvature radius Rc of the meniscus; the pore size characterization module S determines the multi-level pore radius R p Spatial distribution; the contact angle characterization module A calculates the apparent contact angle and the intrinsic contact angle ​The capillary pressure characterization module P is based on the Laplace formula (integral transform formula) of the adaptive chip, and fuses R c 、 R p , the chip depth H and the interfacial tension , to realize dynamic calculation of the meniscus capillary pressure and saturation curve characterization.

[0201] In this embodiment, the CO2 storage in a saline aquifer is taken as an example, the attacking fluid is CO2, and the defending fluid is the saline water.

[0202] According to the microfluidic experimental device flow chart Figure 2 , the microfluidic chip with etched pore flow channels is fixed in the chip pressure bearing clamp 5, so that the chip is well sealed and the position is stable.

[0203] The micro-flow injection pump 1, the piston container 2, the pressure sensor 3, the microscope 4, the image acquisition system 6 and the back pressure valve 7 are connected in sequence to form a complete fluid displacement and monitoring circuit. Start the microscope 4 and the image acquisition system 6, adjust the magnification to the appropriate, and in this embodiment, a 2.5x objective lens is used for magnification, so that all flow channels in the microfluidic chip can be globally visible.

[0204] The pressure of the back pressure valve 7 at the outlet end is set to 10 MPa, and the saline water is injected into the microfluidic chip through the micro-flow injection pump 1, so that all the pore nodes in the chip are saturated with water, and the pressure in the chip is lifted to more than 10 MPa. During the saturation of water, check whether the connection of each component leaks, and observe whether the reading of the pressure sensor 3 exceeds the set value of the outlet back pressure valve 7, to verify the sealing performance and reliability of the device. CO2 is loaded into the piston container, and attention is paid to avoid mixing air bubbles; the injection speed of the micro-flow injection pump 1 is set to 10 μL / min, the micro-flow injection pump 1 is started to slowly displace the defending fluid with CO2, the pressure sensor 3 is used to record the pressure change at the injection end in real time, and the image acquisition system 6 is used to acquire dynamic images of the fluid interface in the chip at a rate of 5 seconds / frame, so as to capture the advancing process and morphological changes of the meniscus.

[0205] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for simultaneous characterization of capillary pressure and contact angle of a microfluidic fluidic interface, characterized in that, The method comprises the following steps: S1, based on the pre-configured pore binary image, particle binary image and fluid binary image, distinguish and extract the fluid-particle contact interface contour and the attack / defense fluid interface contour; S2, the attack / defense fluid interface contour is divided into regions by a watershed region division algorithm, and the contour points are sequentially reordered and sorted by combining a Fourier descriptor, the attack / defense fluid interface contour after sorting is subjected to curvature circle fitting, and the curvature radius of the attack / defense fluid interface is determined by fitting; S3, based on the pore binary image, a multi-level size pore space is generated, and a pore apparent radius is obtained; S4, based on the curvature radius and the multi-level size pore space, the neck angle is calculated, and the apparent contact angle and the intrinsic contact angle are obtained; The neck-in angle expression is: ; The apparent contact angle expression is: ; The intrinsic contact angle expression is: ; wherein denotes the necking angle, R p denotes the apparent horizontal radius of the tip of the attack / defense fluid interface, R pm denotes the apparent horizontal radius of the center of the attack / defense fluid interface, L a denotes the projection distance of the tip and the center of the attack / defense fluid interface on the mid-axis, denotes the apparent contact angle, denotes the radius of curvature of the profile of the attack / defense fluid interface, denotes the intrinsic contact angle; S5, based on the curvature radius, the pore apparent radius, the chip depth and the interfacial tension, the capillary pressure of the attack / defense fluid interface is calculated.

2. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, The method comprises the following steps: Based on the pre-configured pore binary image, particle binary image and fluid binary image, the fluid-particle contact interface contour and the attack / defense fluid interface contour are distinguished and extracted, which comprises the following steps: An expansion operation function is used to perform expansion operation on the particle region in the particle binary image, the expanded particle region is subjected to intersection operation with the fluid contour, and the fluid / particle contact interface is obtained; The attack / defense fluid interface is separated by performing exclusive OR operation between the fluid / particle contact interface and the fluid contour; 3. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, The attack / defense fluid interface is subjected to skeleton thinning processing based on a binary image function, and the skeleton of the attack / defense fluid interface contour is extracted. The method comprises the following steps: S21, based on the original image size, an initialization matrix is constructed, the attack / defense fluid interface contour is subjected to local minimization processing, the fluid-particle contact interface is set as a maximization seed point, and the attack / defense fluid interface contour is divided into multiple independent regions by a watershed algorithm; S22, the independent regions after division are subjected to traversal operation, the attack / defense fluid interface contour in the current traversal is extracted, the Fourier descriptor is used to project the contour data to the Fourier space, a preset proportion of the descriptor is selected to filter out high-frequency noise, and smoothing reconstruction is realized; after the smoothing reconstruction is completed, the generated contour points are sequentially sorted in a clockwise direction; S23, the curvature radius of the attack / defense fluid interface contour points is represented by using circle fitting; 4. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, S24, step S22 is repeatedly executed until the traversal of all attack / defense fluid interface regions is completed, and the curvature radius of each attack / defense fluid interface is output. The method comprises the following steps: S31, distance transformation and extraction of the pore binary graph, and superimpose and fuse the distance transformation result and the skeleton, to generate a pore radius information skeleton; count the distance elements in the skeleton to form a pore size set, and arrange the elements in the pore size set in descending order; S32, traverse the pore size set, and perform a circle inflation operation based on the position of a preset radius in the pore radius information skeleton; S33, change the preset radius to the next element in the pore size set, and determine whether the elements in the pore size set are traversed completely; if not, execute step S32 again; if yes, generate a multi-level size pore space.

5. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, The calculation of the necking angle based on the curvature radius and the multi-level size pore space to obtain the apparent contact angle and the intrinsic contact angle comprises: S41, traverse the region divided by the watershed algorithm, and extract the current traversed attack / defense fluid interface; S42, determine the pore overhead radius corresponding to the central part and the end of the attack / defense fluid interface based on the curvature radius and the multi-level size pore space; S43, project the attack / defense fluid interface contour on the skeleton of the pore, and calculate the projection distance of the end and the central part of the attack / defense fluid interface on the central axis through the projection position; S44, calculate the necking angle based on the pore overhead radius corresponding to the central part and the end of the attack / defense fluid interface and the projection distance of the end and the central part of the attack / defense fluid interface on the central axis; S45, calculate the apparent contact angle of the attack / defense fluid interface based on the curvature radius, the pore overhead radius of the end of the attack / defense fluid interface, and the necking angle; S46, calculate the intrinsic contact angle of the attack / defense fluid interface based on the curvature radius and the pore overhead radius of the end of the attack / defense fluid interface; S47, repeatedly execute steps S41-S46 until the traversal of all attack / defense fluid interface regions is completed, and output the apparent contact angle and the intrinsic contact angle of each attack / defense fluid interface.

6. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, After the capillary pressure of the attack / defense fluid interface is calculated based on the curvature radius, the pore overhead radius, the chip depth, and the interfacial tension, the following steps are further included: S51, statistically analyze the capillary pressure of the attack / defense fluid interface, and select the arithmetic mean or the median as the target capillary pressure of the attack / defense fluid interface under the current saturation degree according to the frequency distribution characteristics; S52, draw a relationship curve of the capillary pressure and the saturation degree of the attack / defense fluid interface by traversing the images under different saturation degrees of the attack / defense fluid interface one by one; S53, fit the relationship curve of the capillary pressure and the saturation degree of the attack / defense fluid interface using a percolation characteristic model.

7. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, The capillary pressure expression is: ; wherein P c represents the capillary pressure of the attack / defense fluid interface, H represents the chip depth, represents the tension of the attack / defense fluid interface.

8. The capillary pressure and contact angle synchronous characterization method of a microfluidic fluidic interface according to claim 1, wherein, The capillary pressure and contact angle synchronous characterization method of the microfluidic fluid interface is realized by a capillary pressure and contact angle synchronous characterization device of the microfluidic fluid interface. The device comprises a micro-flow injection pump, a piston container, a pressure sensor, a microscope, a chip pressure-bearing clamp, an image acquisition system, and a back pressure valve. The micro-flow injection pump is used to control the injection speed of the fluid. The piston container is arranged on one side of the micro-flow injection pump and is used for storing experimental fluid and cooperating with the micro-flow injection pump to maintain fluid delivery. The pressure sensor is arranged on the top of the piston container and is used for monitoring pressure change of the injection end. The microscope is arranged on the top of the chip pressure support clamp and cooperates with the image acquisition system to observe the fluid interface form in the micro-fluidic chip. The chip pressure support clamp is arranged on the bottom of the microscope and is used for fixing the micro-fluidic chip, and the chip pressure support clamp is in a small volume pressure support structure. The chip pressure support clamp sequentially comprises a pressure support base, a chip, a pressure sealing plate and a cavity cover from bottom to top, and the chip and the pressure sealing plate are located between the pressure support base and the cavity cover. The image acquisition system is connected to one side of the microscope and is used for shooting the multiphase flow interface in the chip. The back pressure valve is arranged on one side of the chip pressure support clamp and is used for controlling back pressure of the system.

Images