A method for calculating the oil-water interfacial area and mass transfer coefficient in two-phase flow in porous media

Abstract

The present application is applicable to the technical field of soil and groundwater pollution remediation, and provides a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media, comprising: first establishing a two-phase flow image dataset of porous media, then normalizing the original images in the two-phase flow image dataset to a standard style, identifying the oil phase fluid region therein, and calculating the oil phase saturation based on the oil phase fluid region, then calculating the oil-water two-phase interfacial area based on the surface area of ​​the solid skeleton particles in the two-dimensional porous media, the surface area of ​​the aqueous phase fluid, and the surface area of ​​the oil phase fluid, then calculating the oil-water mass transfer coefficient based on the concentration of the oil dissolved in the aqueous phase fluid and the maximum solubility of the oil in the aqueous phase, and finally plotting the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve. The present application improves the accuracy and efficiency of calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media.

Description

Technical Field

[0001] The present application belongs to the technical field of soil and groundwater pollution remediation, and in particular relates to a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media. Background Art

[0002] Two-phase flow processes in porous media are widely involved in fields such as oil and gas extraction, geological storage of carbon dioxide, and remediation of soil and groundwater pollution. In oil and gas extraction, accurate identification of the phase structure and oil-water interfacial area of ​​two-phase flow can promote understanding of the two-phase flow structure; in geological storage of carbon dioxide, accurate calculation of the interfacial area between supercritical carbon dioxide and brine can promote understanding of its mechanism and improve storage efficiency; in the remediation of non-aqueous liquid contamination of soil and groundwater, accurate identification of the oil-water interface in porous media and calculation of the mass transfer coefficient can analyze the microscopic remediation mechanism and improve the remediation effect. Therefore, accurate calculation of the oil-water interfacial area and mass transfer coefficient is an important prerequisite for understanding the two-phase flow mechanism and improving the efficiency of related projects.

[0003] In previous studies, many methods have been used to calculate the oil-water interfacial area and mass transfer coefficient in two-phase flow. First, through sand box-type "black box" experiments, scholars can calculate the lumped mass transfer rate coefficient, but they cannot directly observe the internal structure of the medium and thus determine the two-phase interfacial area. Secondly, CT scanning technology can accurately identify multiphase interfaces, but the long scanning cycle brings large errors to the calculation of the two-phase mass transfer coefficient. In addition, the transparent glass column experiment based on laser confocal microscopy can accurately identify multiphase interfaces and calculate the mass transfer coefficient, but its cost is too high. Therefore, there is an urgent need to develop a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media with low cost, fast scanning, high accuracy and rapid calculation. Summary of the Invention

[0004] The embodiment of the present application provides a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media, which can solve the problems of high technical cost, low calculation accuracy and poor timeliness in the existing calculation of the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media.

[0005] In the first aspect, the embodiment of the present application provides a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media, including: S1, establishing a two-phase flow image data set of porous media: building a visualization experimental platform to conduct two-phase flow experiments in porous media, and obtaining high-precision images of the two-phase flow process through an industrial camera to establish a two-phase flow image data set; S2, normalizing the original images in the two-phase flow image data set to a standard style and identifying the oil phase fluid area therein, and calculating the oil phase saturation based on the oil phase fluid area; S3, identifying and calculating the surface area of ​​solid skeleton particles, the surface area of ​​water phase fluid, and the surface area of ​​oil phase fluid in the two-dimensional porous medium, and calculating the oil phase saturation based on the two-dimensional porous medium. The surface area of ​​the solid skeleton particles in the porous medium, the surface area of ​​the aqueous fluid and the surface area of ​​the oil-phase fluid are used to calculate the oil-water two-phase interfacial area; S4, the concentration of the oil dissolved in the aqueous fluid is calculated, and the maximum solubility of the oil in the aqueous phase is calculated. According to the concentration of the oil dissolved in the aqueous fluid and the maximum solubility of the oil in the aqueous phase, the oil-water mass transfer coefficient is calculated; S5, the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve are plotted: based on the oil-water two-phase interfacial area and the oil-water mass transfer coefficient obtained in S1 to S4, the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve of the porous medium two-phase flow process are plotted.

[0006] In a possible implementation of the first aspect, step S1 specifically includes the following steps:

[0007] S101. Build a visualization experiment platform, including a visible light source, a high-resolution camera, a two-dimensional transparent porous medium, a syringe pump, a syringe tube, a computer, and a connecting frame;

[0008] S102. Preparation of two-dimensional transparent porous medium: Determine the material and porosity of the two-dimensional transparent porous medium Flow channel area s, flow channel depth h and heterogeneity;

[0009] S103, performing a porous medium two-phase flow experiment, including the following steps:

[0010] S1031, immersing the two-dimensional transparent porous medium in a beaker filled with deionized water, and then placing the beaker in a vacuum chamber to completely saturate the two-dimensional transparent porous medium;

[0011] S1032, injecting the dyed oil phase fluid into the two-dimensional transparent porous medium, and recording the type of dye;

[0012] S1033, displacing the dyed oil phase fluid with deionized water to obtain an oil phase residual state;

[0013] S1034. Injecting a water-phase fluid into a two-dimensional transparent porous medium at a flow rate v, and recording the process of the porous medium two-phase flow experiment using a camera with an image resolution of δ to establish a two-phase flow image dataset.

[0014] Optionally, in another possible implementation of the first aspect, step S2 specifically includes the following steps:

[0015] S201, image correction: cropping the normalized original image to the target area according to the shape and size of the two-dimensional transparent porous medium flow channel, and then rotating the original image to the horizontal direction or vertical direction between the flow channel and the screen;

[0016] S202, oil phase identification: Identify the oil phase fluid in the original image based on a preset oil phase fluid RGB range and determine whether the identification is accurate. If accurate, determine the oil phase fluid region in the original image. If inaccurate, adjust the preset oil phase fluid RGB range and identify the oil phase fluid in the original image again until accurate identification is achieved.

[0017] S203, Saturation calculation: Calculate the saturation S of the oil phase fluid region in a two-dimensional transparent porous medium o , the calculation formula is:

[0018]

[0019] Where N o is the number of pixels occupied by the oil phase fluid area in the original image; δ is the original image resolution;

[0020] The original image resolution δ is the actual area represented by each pixel in the original image, and the calculation formula is:

[0021] δ=LW / xy (2)

[0022] Where L is the actual length of the original image after image correction; W is the actual width of the original image after image correction; x is the number of pixels of the original image in the horizontal direction of the screen; y is the number of pixels of the original image in the vertical direction of the screen.

[0023] Optionally, in another possible implementation of the first aspect, step S3 specifically includes the following steps:

[0024] S301. Identify and calculate the surface area of ​​solid skeleton particles in a two-dimensional porous medium: Identify the flow channel range according to a preset RGB range, determine the relative position of the solid skeleton in the two-dimensional porous medium, and modify the regionprops built-in program in MATLAB to calculate the surface area of ​​the solid skeleton. The surface area of ​​the solid skeleton includes the interfacial length and interfacial area of ​​the solid skeleton.

[0025] S302, identifying and calculating the surface area of ​​the aqueous fluid: identifying the aqueous fluid according to a preset RGB range, determining the spatial position of the aqueous fluid, and calculating the surface area of ​​the aqueous fluid. The surface area of ​​the aqueous fluid includes the interfacial length and interfacial area of ​​the aqueous fluid;

[0026] S303, identifying and calculating the surface area of ​​the oil-phase fluid: identifying the oil-phase fluid according to a preset RGB range, determining the spatial position of the oil-phase fluid, and calculating the surface area of ​​the oil-phase fluid. The surface area of ​​the oil-phase fluid includes the interfacial length and interfacial area of ​​the oil-phase fluid;

[0027] S304. Calculate the oil-water interfacial area using the following formula:

[0028] S o-w =L o-w ×h (3)

[0029] L s+o =L s-w +L o-w (4)

[0030] L o =L c-o +L o-w (5)

[0031] L s =L s-w +L s-o (6)

[0032] L o-w =(L s+o +L o -L s ) / 2 (7)

[0033] Where S o-w is the oil-water interface area; L o-w is the length of the oil-water interface; the perimeters of the solid skeleton, oil phase fluid, and water phase fluid are L s , L o , L w The interface lengths of solid skeleton-oil phase fluid, oil phase fluid-water phase fluid, and solid skeleton-water phase fluid are L s-o , L o-w , L s-w The interface length between the solid skeleton and the oil phase fluid fusion body and the water phase fluid is L s+o .

[0034] Optionally, in another possible implementation of the first aspect, step S4 specifically includes the following steps:

[0035] S401. Calculate the concentration C of the oil dissolved in the aqueous fluid using the following formula:

[0036]

[0037]

[0038] Where ρ is the density of oil; V M is the pore volume of the medium; ΔS o is the change in oil saturation; Q is the water injection flow rate; Δt is the water injection time; the medium pore volume is V M ;

[0039] S402. Calculate the maximum solubility C of oil in water phase s : Calculate the maximum solubility of oil in the water phase based on the oil phase type, solute composition and solute concentration in the water phase;

[0040] S403. Calculate the oil-water two-phase mass transfer coefficient k. The calculation formula is:

[0041]

[0042]

[0043] Where C s is the maximum solubility of oil in water phase; a s is the overall specific surface area of ​​the oil.

[0044] Optionally, in another possible implementation of the first aspect, step S5 specifically includes the following steps:

[0045] S501. Count the time t and oil-water interface area S during the two-phase flow process o-w , oil-water mass transfer coefficient k;

[0046] S502, with time t as the horizontal axis, the oil-water interface area S o-w and the oil-water mass transfer coefficient k as the ordinate, and draw the oil-water interface area evolution curve S o-w-t Figure and oil-water mass transfer coefficient evolution curve kt diagram.

[0047] In the technical solution of the present application, a two-phase flow image dataset of porous media is first established, and then the original images in the two-phase flow image dataset are normalized to a standard style to identify the oil phase fluid area therein, and the oil phase saturation is calculated based on the oil phase fluid area. Then, the oil-water two-phase interface area is calculated based on the surface area of ​​the solid skeleton particles in the two-dimensional porous medium, the surface area of ​​the aqueous phase fluid, and the surface area of ​​the oil phase fluid. Then, the oil-water mass transfer coefficient is calculated based on the concentration of oil dissolved in the aqueous phase fluid and the maximum solubility of oil in the aqueous phase. Finally, the oil-water interface area evolution curve and the oil-water mass transfer coefficient evolution curve are plotted. This application improves the calculation accuracy and efficiency of the oil-water interface area and mass transfer coefficient of two-phase flow in porous media. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0049] Figure 1 This is a flow chart of a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media provided in one embodiment of the present application;

[0050] Figure 2 This is a schematic diagram of a scenario of a visualization experiment platform provided in one embodiment of the present application;

[0051] Figure 3 is a schematic diagram of a two-dimensional transparent porous medium and its internal structure provided by an embodiment of the present application;

[0052] Figure 4 is the image correction result provided by an embodiment of the present application;

[0053] Figure 5 This is the oil phase identification result provided by an embodiment of the present application;

[0054] Figure 6 is the solid skeleton recognition result provided by an embodiment of the present application;

[0055] Figure 7 This is the oil-water interface result provided by an embodiment of the present application;

[0056] Figure 8 is an oil-water interface area evolution curve provided in an embodiment of the present application;

[0057] Figure 9 This is an oil-water mass transfer coefficient evolution curve provided in an embodiment of the present application. DETAILED DESCRIPTION

[0058] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0059] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0060] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0061] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0062] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0063] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0064] The following describes in detail a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media provided by the present application with reference to the accompanying drawings.

[0065] Figure 1 A flow chart of a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media provided in an embodiment of the present application is shown.

[0066] like Figure 1 As shown, the method for calculating the oil-water interfacial area and mass transfer coefficient of the porous medium two-phase flow includes the following steps:

[0067] S1. Establishment of a two-phase flow image dataset in porous media: Build a visualization experimental platform to conduct two-phase flow experiments in porous media, and use an industrial camera to obtain high-precision images of the two-phase flow process to establish a two-phase flow image dataset;

[0068] S2, normalizing the original image in the two-phase flow image dataset to a standard pattern, identifying the oil phase fluid region therein, and calculating the oil phase saturation based on the oil phase fluid region;

[0069] S3. Identify and calculate the surface area of ​​solid skeleton particles, the surface area of ​​the aqueous fluid, and the surface area of ​​the oil-phase fluid in the two-dimensional porous medium, and calculate the oil-water two-phase interface area based on the surface area of ​​the solid skeleton particles, the surface area of ​​the aqueous fluid, and the surface area of ​​the oil-phase fluid in the two-dimensional porous medium;

[0070] S4. Calculating the concentration of the oil dissolved in the aqueous fluid and the maximum solubility of the oil in the aqueous phase; and calculating the oil-water mass transfer coefficient based on the concentration of the oil dissolved in the aqueous fluid and the maximum solubility of the oil in the aqueous phase;

[0071] S5. Draw the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve: Based on the oil-water two-phase interfacial area and oil-water mass transfer coefficient obtained in S1 to S4, draw the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve of the porous medium two-phase flow process.

[0072] Furthermore, in an embodiment of the present application, the above step S1 specifically includes the following steps:

[0073] S101. Build a visualization experiment platform, including a visible light source, a high-resolution camera, a two-dimensional transparent porous medium, a syringe pump, a syringe tube, a computer, and a connecting frame;

[0074] S102. Preparation of two-dimensional transparent porous medium: Determine the material and porosity of the two-dimensional transparent porous medium Flow channel area s, flow channel depth h and heterogeneity;

[0075] S103, performing a porous medium two-phase flow experiment, including the following steps:

[0076] S1031, immersing the two-dimensional transparent porous medium in a beaker filled with deionized water, and then placing the beaker in a vacuum chamber to completely saturate the two-dimensional transparent porous medium;

[0077] S1032, injecting the dyed oil phase fluid into the two-dimensional transparent porous medium, and recording the type of dye;

[0078] S1033, displacing the dyed oil phase fluid with deionized water to obtain an oil phase residual state;

[0079] S1034. Injecting a water-phase fluid into a two-dimensional transparent porous medium at a flow rate v, and recording the process of the porous medium two-phase flow experiment using a camera with an image resolution of δ to establish a two-phase flow image dataset.

[0080] Optionally, in an embodiment of the present application:

[0081] 1) Build a porous media visualization experimental platform: Figure 2 As shown, it includes a visible light source, a high-resolution camera, a two-dimensional transparent porous medium, a syringe pump, a syringe tube, a computer, and a connecting frame;

[0082] 2) Preparation of two-dimensional transparent porous medium: Figure 3 As shown, the porous medium is made of glass, the porosity is 0.50, the flow channel area is 200 mm2, the flow channel depth is 0.03 mm, and the structure inside the rectangular flow channel is a replica of the real sandstone structure;

[0083] 3) Conducting two-phase flow experiments in porous media, including the following steps:

[0084] a. Immerse the two-dimensional transparent porous medium in a beaker filled with deionized water, and then place the beaker in a vacuum chamber to completely saturate the porous medium;

[0085] b. Injecting trichloroethylene stained with Oil Red-O into a two-dimensional transparent porous medium;

[0086] c. displacing the oil phase fluid with deionized water to obtain the residual oil phase;

[0087] d. Tween 80 aqueous solution was injected into the two-dimensional transparent porous medium at a flow rate of 4 μL / min, and the two-phase flow process was captured with a camera to establish a two-phase flow image dataset. The camera image resolution was 4.8 μm × 4.8 μm.

[0088] Furthermore, in an embodiment of the present application, the above step S2 specifically includes the following steps:

[0089] S201, image correction: cropping the normalized original image to the target area according to the shape and size of the two-dimensional transparent porous medium flow channel, and then rotating the original image to the horizontal direction or vertical direction between the flow channel and the screen;

[0090] S202, oil phase identification: Identify the oil phase fluid in the original image based on a preset oil phase fluid RGB range and determine whether the identification is accurate. If accurate, determine the oil phase fluid region in the original image. If inaccurate, adjust the preset oil phase fluid RGB range and identify the oil phase fluid in the original image again until accurate identification is achieved.

[0091] S203, Saturation calculation: Calculate the saturation S of the oil phase fluid region in a two-dimensional transparent porous medium o , the calculation formula is:

[0092]

[0093] Where N o is the number of pixels occupied by the oil phase fluid area in the original image; δ is the original image resolution;

[0094] The original image resolution δ is the actual area represented by each pixel in the original image, and the calculation formula is:

[0095] δ=LW / xy (2)

[0096] Where L is the actual length of the original image after image correction; W is the actual width of the original image after image correction; x is the number of pixels of the original image in the horizontal direction of the screen; y is the number of pixels of the original image in the vertical direction of the screen.

[0097] Optionally, in an embodiment of the present application:

[0098] 1) Image correction: Figure 4 As shown, according to the shape and size of the two-dimensional transparent porous medium flow channel, the original image is cropped to the target area, and then the image is rotated until the flow channel is consistent with the horizontal direction of the screen;

[0099] 2) Oil phase identification: Figure 5 As shown, the oil phase fluid is identified according to the preset RGB range of the oil phase fluid and whether the identification is accurate is determined. If it is inaccurate, the RGB range is adjusted and the identification is repeated until the identification is accurate.

[0100] 3) Saturation calculation: Calculate the saturation S of the oil phase fluid in a two-dimensional transparent porous medium o , and its calculation formula is:

[0101]

[0102] Where N o is the number of pixels occupied by the oil phase fluid in the image; δ is the image resolution (L 2 ); h is the flow channel depth (L); s is the flow channel area (L2 ); is the porosity.

[0103] Among them, the image resolution δ is the actual area represented by each pixel in the image, and its calculation formula is:

[0104] δ=LW / xy

[0105] Where L is the actual length of the corrected image (L); W is the actual width of the corrected image (L); x is the number of pixels in the image in the horizontal direction of the screen; y is the number of pixels in the image in the vertical direction of the screen.

[0106] like Figure 5 As shown, under this target range, the saturation of trichloroethylene is 19.7%.

[0107] Furthermore, in an embodiment of the present application, the above step S3 specifically includes the following steps:

[0108] S301. Identify and calculate the surface area of ​​solid skeleton particles in a two-dimensional porous medium: Identify the flow channel range according to a preset RGB range, determine the relative position of the solid skeleton in the two-dimensional porous medium, and modify the regionprops built-in program in MATLAB to calculate the surface area of ​​the solid skeleton. The surface area of ​​the solid skeleton includes the interfacial length and interfacial area of ​​the solid skeleton.

[0109] S302, identifying and calculating the surface area of ​​the aqueous fluid: identifying the aqueous fluid according to a preset RGB range, determining the spatial position of the aqueous fluid, and calculating the surface area of ​​the aqueous fluid. The surface area of ​​the aqueous fluid includes the interfacial length and interfacial area of ​​the aqueous fluid;

[0110] S303, identifying and calculating the surface area of ​​the oil-phase fluid: identifying the oil-phase fluid according to a preset RGB range, determining the spatial position of the oil-phase fluid, and calculating the surface area of ​​the oil-phase fluid. The surface area of ​​the oil-phase fluid includes the interfacial length and interfacial area of ​​the oil-phase fluid;

[0111] S304. Calculate the oil-water interfacial area using the following formula:

[0112] S o-w =L o-w ×h (3)

[0113] L s+o =L s-w +L o-w (4)

[0114] L o =L c-o +L o-w (5)

[0115] L s =L s-w +L s-o (6)

[0116] L o-w =(L s+o +L o -L s ) / 2 (7)

[0117] Where S o-w is the oil-water interface area; L o-w is the length of the oil-water interface; the perimeters of the solid skeleton, oil phase fluid, and water phase fluid are L s , L o , L w The interface lengths of solid skeleton-oil phase fluid, oil phase fluid-water phase fluid, and solid skeleton-water phase fluid are L s-o , L o-w , L s-w The interface length between the solid skeleton and the oil phase fluid fusion body and the water phase fluid is L s+o .

[0118] Optionally, in an embodiment of the present application:

[0119] 1) Solid skeleton recognition: Figure 6 As shown, in the preliminary experiment, the flow channel range was identified according to the preset RGB range to determine the relative position of the solid skeleton in the two-dimensional porous medium;

[0120] 2) Water phase interface identification: In this example, after the solid skeleton position and the oil phase position are identified, the remaining space is the water phase position;

[0121] 3) Oil phase interface identification: Figure 6 As shown, the oil phase fluid is identified according to the preset RGB range to determine the spatial position of the oil phase fluid;

[0122] 4) Calculation of oil-water interface area: Figure 7 As shown in Figure 2, the oil-water interface area in a two-dimensional transparent porous medium is calculated using the following formula:

[0123] S o-w =L o-w ×h

[0124] Where S o-w is the oil-water interfacial area (L 2 );L o-w is the oil-water interface length (L); h is the medium flow channel depth (L).

[0125] Among them, the oil-water interface length Lo-w (L) is calculated as follows:

[0126] Define the perimeters of the solid skeleton, oil phase fluid, and water phase fluid as L s , L o , L w The interface lengths of solid skeleton-oil phase fluid, oil phase fluid-water phase fluid, and solid skeleton-water phase fluid are: L s-o , L o-w , L s-w The interface length between the solid skeleton and the oil phase fluid fusion body and the water phase fluid is L s+o , we can know that:

[0127] L s+o =L s-w +L o-w

[0128] L=L+L

[0129] o co ow

[0130] L=L+L

[0131] s sw so

[0132] Combining the above three formulas, the oil-water interface length can be obtained as:

[0133] L o-w =(L s+o +L o -L s ) / 2

[0134] like Figure 7 As shown in Figure 2, under this target range, the interfacial area of ​​trichloroethylene-Tween80 aqueous solution is 0.066 mm 2 .

[0135] Furthermore, in an embodiment of the present application, the above step S4 specifically includes the following steps:

[0136] S401. Calculate the concentration C of the oil dissolved in the aqueous fluid using the following formula:

[0137]

[0138]

[0139] Where ρ is the density of oil; V M is the pore volume of the medium; ΔS o is the change in oil saturation; Q is the water injection flow rate; Δt is the water injection time; the medium pore volume is V M ;

[0140] S402. Calculate the maximum solubility C of oil in water phase s : Calculate the maximum solubility of oil in the water phase based on the oil phase type, solute composition and solute concentration in the water phase;

[0141] S403. Calculate the oil-water two-phase mass transfer coefficient k. The calculation formula is:

[0142]

[0143]

[0144] Where C s is the maximum solubility of oil in water phase; a s is the overall specific surface area of ​​the oil.

[0145] Optionally, in an embodiment of the present application:

[0146] 1) Calculation of oil concentration in water phase: Calculate the concentration C of oil dissolved in water phase fluid. The calculation formula is:

[0147]

[0148] Where ρ is the density of oil (ML -3 );V M is the pore volume of the medium (L 3 );ΔS o is the change in oil saturation; Q is the water injection flow rate (L 3 T -1 ); Δt is the water injection time (T).

[0149] Among them, the pore volume of the medium V M The calculation is as follows:

[0150]

[0151] Where s is the medium flow area (L 2 ); h is the medium flow channel depth (L); is the porosity.

[0152] 2) Calculation of the equilibrium solubility of oil in water: In this example, the equilibrium solubility of trichloroethylene in Tween 80 solution can be calculated as:

[0153] C s-TCE =26.414C Tween +0.971

[0154] Where C s-TCE is the equilibrium solubility of trichloroethylene in Tween 80 solution, expressed as weight percentage; CTween is the weight percentage of Tween 80 in the solution.

[0155] 3) Calculation of oil-water mass transfer coefficient: Calculate the oil-water mass transfer coefficient k in a two-dimensional transparent porous medium. The calculation formula is:

[0156]

[0157] Where C s is the equilibrium solubility (maximum solubility) of oil in water (ML -3 );a s is the overall specific surface area of ​​the oil, which can be calculated as:

[0158]

[0159] Furthermore, in an embodiment of the present application, the above step S5 specifically includes the following steps:

[0160] S501. Count the time t and oil-water interface area S during the two-phase flow process o-w , oil-water mass transfer coefficient k;

[0161] S502, with time t as the horizontal axis, the oil-water interface area S o-w and the oil-water mass transfer coefficient k as the ordinate, and draw the oil-water interface area evolution curve S o-w-t Figure and oil-water mass transfer coefficient evolution curve kt diagram.

[0162] Optionally, in an embodiment of the present application:

[0163] 1) Statistical analysis of the time t and oil-water interface area S during the two-phase flow process o-w , oil-water mass transfer coefficient k;

[0164] 2) If Figure 8 and Figure 9 As shown, with time t as the horizontal axis, the oil-water interface area S o-w The interfacial area evolution curve S of trichloroethylene-Tween80 aqueous solution was drawn with the oil-water mass transfer coefficient k as the vertical axis. o-w -t diagram and kt diagram of mass transfer coefficient evolution curve of trichloroethylene-Tween80 aqueous solution.

[0165] The present application provides a method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media. The method first establishes a two-phase flow image data set of porous media, then normalizes the original images in the two-phase flow image data set to a standard style, identifies the oil phase fluid region therein, and calculates the oil phase saturation based on the oil phase fluid region. The oil-water two-phase interfacial area is then calculated based on the surface area of ​​the solid skeleton particles, the surface area of ​​the aqueous fluid, and the surface area of ​​the oil phase fluid in the two-dimensional porous medium. The oil-water mass transfer coefficient is then calculated based on the concentration of the oil dissolved in the aqueous fluid and the maximum solubility of the oil in the aqueous phase. Finally, the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve are plotted. The present application improves the calculation accuracy and efficiency of the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media.

[0166] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0167] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0168] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for calculating the oil-water interfacial area and mass transfer coefficient of two-phase flow in porous media, characterized in that: The following steps are involved: S1. Establishment of a two-phase flow image dataset in porous media: Build a visualization experimental platform to conduct two-phase flow experiments in porous media, and use an industrial camera to obtain high-precision images of the two-phase flow process to establish a two-phase flow image dataset; S2. normalizing the original images in the two-phase flow image dataset to a standard pattern, identifying the oil phase fluid region therein, and calculating the oil phase saturation based on the oil phase fluid region; S3. Identify and calculate the surface area of ​​solid skeleton particles in the two-dimensional porous medium, the surface area of ​​the aqueous fluid, and the surface area of ​​the oil-phase fluid, and calculate the oil-water two-phase interface area based on the surface area of ​​the solid skeleton particles in the two-dimensional porous medium, the surface area of ​​the aqueous fluid, and the surface area of ​​the oil-phase fluid; S4. Calculating the concentration of the oil dissolved in the aqueous fluid and the maximum solubility of the oil in the aqueous phase, and calculating the oil-water mass transfer coefficient based on the concentration of the oil dissolved in the aqueous fluid and the maximum solubility of the oil in the aqueous phase; S5. Draw the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve: Based on the oil-water two-phase interfacial area and oil-water mass transfer coefficient obtained in S1 to S4, draw the oil-water interfacial area evolution curve and the oil-water mass transfer coefficient evolution curve of the porous medium two-phase flow process.

2. The method for calculating the oil-water interfacial area and mass transfer coefficient of porous medium two-phase flow according to claim 1, characterized in that: The step S1 specifically includes the following steps: S101. Build a visualization experiment platform, including a visible light source, a high-resolution camera, a two-dimensional transparent porous medium, a syringe pump, a syringe tube, a computer, and a connecting frame; S102. Preparation of two-dimensional transparent porous medium: Determine the material and porosity of the two-dimensional transparent porous medium Flow channel area s, flow channel depth h and heterogeneity; S103, performing a porous medium two-phase flow experiment, including the following steps: S1031, immersing the two-dimensional transparent porous medium in a beaker filled with deionized water, and then placing the beaker in a vacuum chamber to completely saturate the two-dimensional transparent porous medium; S1032, injecting the dyed oil phase fluid into the two-dimensional transparent porous medium, and recording the type of dye; S1033, displacing the dyed oil phase fluid with deionized water to obtain an oil phase residual state; S1034. Injecting a water-phase fluid into a two-dimensional transparent porous medium at a flow rate v, and recording the process of the porous medium two-phase flow experiment using a camera with an image resolution of δ to establish a two-phase flow image dataset.

3. The method for calculating the oil-water interfacial area and mass transfer coefficient of porous medium two-phase flow according to claim 1, characterized in that: The step S2 specifically includes the following steps: S201, image correction: cropping the normalized original image to the target area according to the shape and size of the two-dimensional transparent porous medium flow channel, and then rotating the original image to the horizontal direction or vertical direction between the flow channel and the screen; S202, oil phase identification: Identify the oil phase fluid in the original image based on a preset oil phase fluid RGB range and determine whether the identification is accurate. If accurate, determine the oil phase fluid region in the original image. If inaccurate, adjust the preset oil phase fluid RGB range and identify the oil phase fluid in the original image again until accurate identification is achieved. S203, Saturation calculation: Calculate the saturation S of the oil phase fluid region in a two-dimensional transparent porous medium o , the calculation formula is: Where N o is the number of pixels occupied by the oil phase fluid area in the original image; δ is the original image resolution; The original image resolution δ is the actual area represented by each pixel in the original image, and the calculation formula is: δ=LW / xy (2) Where L is the actual length of the original image after image correction; W is the actual width of the original image after image correction; x is the number of pixels of the original image in the horizontal direction of the screen; y is the number of pixels of the original image in the vertical direction of the screen.

4. The method for calculating the oil-water interfacial area and mass transfer coefficient of porous medium two-phase flow according to claim 1, characterized in that: The step S3 specifically includes the following steps: S301. Identify and calculate the surface area of ​​solid skeleton particles in a two-dimensional porous medium: Identify the flow channel range according to a preset RGB range, determine the relative position of the solid skeleton in the two-dimensional porous medium, and modify the regionprops built-in program in MATLAB to calculate the surface area of ​​the solid skeleton. The surface area of ​​the solid skeleton includes the interfacial length and interfacial area of ​​the solid skeleton. S302, identifying and calculating the surface area of ​​the aqueous fluid: identifying the aqueous fluid according to a preset RGB range, determining the spatial position of the aqueous fluid, and calculating the surface area of ​​the aqueous fluid, wherein the surface area of ​​the aqueous fluid includes the interfacial length and interfacial area of ​​the aqueous fluid; S303, identifying and calculating the surface area of ​​the oil-phase fluid: identifying the oil-phase fluid according to a preset RGB range, determining the spatial position of the oil-phase fluid, and calculating the surface area of ​​the oil-phase fluid, wherein the surface area of ​​the oil-phase fluid includes the interfacial length and interfacial area of ​​the oil-phase fluid; S304. Calculate the oil-water interfacial area using the following formula: S o-w =L o-w ×h (3) L s+o =L s-w +L o-w (4) L o =L s-o +L o-w (5) L s =L s-w +L s-o (6) L o-w =(L s+o +L o -L s ) / 2 (7) Where S o-w is the oil-water interfacial area; L o-w is the length of the oil-water interface; the perimeters of the solid skeleton, oil phase fluid, and water phase fluid are L s 、L o 、L w The interface lengths of solid skeleton-oil phase fluid, oil phase fluid-water phase fluid, and solid skeleton-water phase fluid are L s-o 、L o-w 、L s-w The interface length between the solid skeleton and the oil phase fluid fusion body and the water phase fluid is L s+o .

5. The method for calculating the oil-water interfacial area and mass transfer coefficient of porous medium two-phase flow according to claim 1, characterized in that: The step S4 specifically includes the following steps: S401. Calculate the concentration C of the oil dissolved in the aqueous fluid using the following formula: Where ρ is the density of oil; V M is the pore volume of the medium; ΔS o is the change in oil saturation; Q is the water injection flow rate; Δt is the water injection time; the medium pore volume is V M ; S402. Calculate the maximum solubility C of oil in water phase s : Calculate the maximum solubility of oil in the water phase based on the oil phase type, solute composition and solute concentration in the water phase; S403. Calculate the oil-water two-phase mass transfer coefficient k. The calculation formula is: Where C s is the maximum solubility of oil in water phase; a s is the overall specific surface area of ​​the oil.

6. The method for calculating the oil-water interfacial area and mass transfer coefficient of porous medium two-phase flow according to claim 1, characterized in that: The step S5 specifically includes the following steps: S501. Count the time t and oil-water interface area S during the two-phase flow process o-w , oil-water mass transfer coefficient k; S502, with time t as the horizontal axis, the oil-water interface area S o-w and the oil-water mass transfer coefficient k as the ordinate, and draw the oil-water interface area evolution curve S o-w-t Figure and oil-water mass transfer coefficient evolution curve kt diagram.

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