Method for determining effective diffusion coefficient of wax molecules and computer equipment

Abstract

The present application relates to the technical field of waxy crude oil pipeline transportation and storage, and particularly relates to a method for determining the effective diffusion coefficient of wax molecules, comprising the following steps: S1, establishing a calculation model of the effective diffusion coefficient of wax molecules in wax deposits; S2, obtaining multiple wax crystal microscopic images of the wax deposit sample at different temperatures through a microscopic observation device; S3, performing image preprocessing on each wax crystal microscopic image, and combining the preprocessed wax crystal microscopic images, the calculation model of step S1 is used to calculate the effective diffusion coefficient of wax molecules in the wax deposit sample in each wax crystal microscopic image; S4, fitting the effective diffusion coefficient of wax molecules in the wax deposit sample in each wax crystal microscopic image, and obtaining the change relationship between the ratio of the effective diffusion coefficient of wax molecules in the wax deposit and the diffusion coefficient of wax molecules in the crude oil and the solid-phase wax crystal particle concentration. The method for determining the effective diffusion coefficient of wax molecules can accurately calculate the effective diffusion coefficient of wax molecules.

Description

Technical Field

[0001] This invention relates to the field of pipeline transportation and storage technology for waxy crude oil, and in particular to a method and computer equipment for determining the effective diffusion coefficient of wax molecules. Background Technology

[0002] Most of the crude oil produced in my country is waxy crude oil. This type of oil has a high wax content, and when the pipe wall temperature is below the wax precipitation point during pipeline transportation, a gel-like wax deposit will gradually form on the pipe wall, consisting of wax crystal particles as a framework and liquid oil encapsulated within them. The formation of this wax deposit reduces the pipeline's flow area, increases crude oil transportation costs, and can even clog the pipeline, seriously threatening its safe and efficient operation. The main influencing factor for wax deposition is molecular diffusion.

[0003] Currently, the calculation of the effective diffusion coefficient of wax molecules in wax deposits mainly relies on the Cussler classical formula. However, calculations using the Couette wax deposition experimental setup under different conditions revealed that the classical formula leads to inaccurate results. Therefore, accurately determining the effective diffusion coefficient of wax molecules is a pressing issue that needs to be addressed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in order to solve the problem of inaccurate calculation results of the diffusion coefficient of wax molecules in the prior art, the present invention provides a method for determining the effective diffusion coefficient of wax molecules, which can accurately calculate the effective diffusion coefficient of wax molecules.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for determining the effective diffusion coefficient of wax molecules, comprising the following steps:

[0006] S1: Establish a calculation model for the effective diffusion coefficient of wax molecules in wax deposits;

[0007] S2: Multiple microscopic images of wax crystals were obtained from wax deposit samples at different temperatures using a microscopic observation device;

[0008] S3: Perform image preprocessing on each of the wax crystal micro images, and combine the preprocessed wax crystal micro images with the calculation model described in step S1 to calculate the effective diffusion coefficient of wax molecules in the wax deposit sample in each of the wax crystal micro images.

[0009] S4: Fit the effective diffusion coefficient of wax molecules in the wax deposit sample in each of the wax crystal micro images, and obtain the relationship between the ratio of the effective diffusion coefficient of wax molecules in the wax deposit to the diffusion coefficient of wax molecules in crude oil and the concentration of solid wax crystal particles.

[0010] Furthermore, specifically, in step S1, establishing a calculation model for the effective diffusion coefficient of wax molecules in wax deposits includes the following steps:

[0011] S11: Obtain a tiny unit at any point in the wax deposit. The tiny unit is a rectangular region bounded by a left boundary line, a right boundary line, a top boundary line, and a bottom boundary line. Let the length of the rectangular region be L and the width be W. The center of the tiny unit has wax crystal particles.

[0012] S12: Calculate the wax molecule concentration value of the micro-unit;

[0013] S13: Obtain the concentration value C at the upper boundary line of the micro-unit based on the concentration value. S and the concentration value C at the lower boundary of the micro-unit. X ;

[0014] S14: Based on the concentration value C at the upper boundary line S and the concentration value C at the lower boundary line. X Based on the equilibrium state, the diffusion mass flux of the wax molecules of the micro-unit in the region without the wax crystal particles is obtained. J The diffusion mass flux of the wax molecules in the region of the wax crystal particles, and the wax molecules of the micro-units. J* ;

[0015] S15: Based on the diffusion mass flux of the wax molecules in the region without the wax crystal particles. J and the diffusion mass flux of the wax molecules in the region of the wax crystal particles. J* To obtain the effective diffusion coefficient D of wax molecules in wax deposits. e The diffusion coefficient D of wax molecules in crude oil wo The calculation formula is as follows:

[0016] (1);

[0017] Furthermore, specifically, in step S12, the governing equation for the wax molecule concentration of the micro-unit satisfies Fick's diffusion law, and the governing equation is:

[0018] (2);

[0019] in, C t represents the concentration of wax molecules, in wt%; t represents time, in seconds. D Let m be the diffusion coefficient of the wax molecules. 2 / s; The Laplace operator is defined by the following formula:

[0020] (3);

[0021] The wax molecule concentration of the micro-unit is calculated based on the lattice Boltzmann method, using the following formula:

[0022] (4);

[0023] in, It is the position at time t. Distribution function of wax molecule concentration, i = 1~4; concentration of wax molecules = ; Let be the equilibrium distribution function. ,in , For discrete velocity, the definition is: , , , .

[0024] Furthermore, specifically, in step S13, when t=0, the concentration value C=C at any point of the micro-unit is obtained. l That is, the concentration value C at the upper boundary line. S =C l ;

[0025] When t=1, the concentration value C at the lower boundary line X By C l Transform into C h That is, the concentration value C at the lower boundary line. X =C h ;

[0026] Furthermore, specifically, in step S14, the diffusion mass flux of the wax molecules of the micro-unit in the region without the wax crystal particles is obtained. J The calculation formula is:

[0027] (5);

[0028] When the wax molecules of the micro-unit are in the region of the wax crystal particles, the diffusion mass flux of the wax molecules... J* The calculation formula is:

[0029] (6);

[0030] Among them, when the tiny unit x When wax crystal particles are present, the diffusion coefficient of wax molecules D x =0, when the micro-unit has no wax crystal particles, the diffusion coefficient of wax molecules is 0.D x =D, To account for the concentration gradient of wax molecules at the locations of wax crystal particles, y c It can be any value within the tiny unit.

[0031] Furthermore, specifically, under the same diffusion area and concentration gradient conditions, if the micro-unit contains wax crystal particles, the diffusion mass flux of the wax molecules decreases, and the diffusion mass flux J* of the wax molecules decreases. <J。

[0032] Furthermore, specifically, in step S4, the method for fitting the effective diffusion coefficient of wax molecules in the wax deposit sample in each of the wax crystal microscopic images is the least squares method.

[0033] Furthermore, specifically, the ratio of the effective diffusion coefficient of wax molecules in wax deposits to the diffusion coefficient of wax molecules in crude oil varies with the concentration of solid-phase wax crystal particles as follows:

[0034] (7);

[0035] in, F w , where is the concentration of solid wax crystal particles, in wt%.

[0036] Furthermore, specifically, in step S3, the image preprocessing includes the following steps:

[0037] Each of the aforementioned wax crystal microscopic images is processed to grayscale, thereby converting the wax crystal microscopic images into grayscale images;

[0038] A grayscale image is binarized to obtain a binary image;

[0039] Based on the binary image, the microscopic characteristics of the waxy sediment sample are obtained.

[0040] A computer device includes: one or more non-volatile computer-readable storage media containing computer-executable instructions; and one or more processors, which, when the computer-executable instructions stored in the computer-readable storage medium are executed by the one or more processors, cause the processors to perform the method for determining the effective diffusion coefficient of wax molecules as described above.

[0041] The beneficial effects of this invention are that the method for determining the effective diffusion coefficient of wax molecules is based on the actual wax crystal microstructure of wax deposits at different temperatures. This method calculates the effective diffusion coefficient of wax molecules in wax deposits and obtains a formula relating the effective diffusion coefficient of wax molecules to the concentration of solid wax crystal particles. This solves the problem of the Cussler classical calculation formula yielding low results. The diffusion coefficient of wax molecules in crude oil and wax deposits is an important parameter determining the wax deposition rate of waxy crude oil and the aging rate of wax deposits. Therefore, the calculation of the effective diffusion coefficient of wax molecules is of great significance for improving the economy and safety of pipeline operation and promoting the development of flow safety assurance technology in the petroleum industry. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Figure 1 This is a schematic diagram of a micro-unit in one embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram showing the variation of ideal wax deposits under different porosity conditions;

[0045] Figure 3 This is a schematic diagram showing the variation of ideal wax deposits under different wax crystal aspect ratios;

[0046] Figure 4 This is a schematic diagram showing the variation of ideal wax deposits under different principal axis dip angles;

[0047] Figure 5 This is a schematic diagram illustrating the changes in ideal wax deposits under different overlapping conditions;

[0048] Figure 6 This is a schematic diagram of a method flow according to an embodiment of the present invention;

[0049] Figure 7 This is a schematic diagram of the calculation model for the effective diffusion coefficient of wax molecules in wax deposits in one embodiment of the present invention;

[0050] Figure 8 This is a wax crystal microscopic image processing process according to an embodiment of the present invention;

[0051] Figure 9 These are microscopic images of wax crystals from the same wax deposit sample at different temperatures according to an embodiment of the present invention.

[0052] Figure 10 This is the effective diffusion coefficient of wax molecules under different solid phase wax crystal particle concentrations in one embodiment of the present invention. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0054] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0055] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] It is important to understand that the concentration of wax crystals, the aspect ratio of wax crystals, the principal axis tilt angle, and the overlap pattern of ideal wax deposits all affect the effective diffusion coefficient of wax molecules. The ratio of the effective diffusion coefficient of wax molecules in ideal wax deposits to their diffusion coefficient in crude oil varies with the concentration of wax crystals as follows: Figure 2 As shown, the effective diffusion coefficient of wax molecules gradually decreases with increasing wax crystal concentration; the ratio of the effective diffusion coefficient of wax molecules to the diffusion coefficient in crude oil varies with aspect ratio as shown in the figure. Figure 3 As shown, with a fixed wax crystal concentration, as the aspect ratio of the wax crystals increases, the ratio of the effective diffusion coefficient of wax molecules in the ideal wax deposit to the diffusion coefficient in crude oil gradually decreases; the relationship between the ratio of the effective diffusion coefficient of wax molecules in the ideal wax deposit to the diffusion coefficient in crude oil and the direction of the principal axis of the wax crystals is as follows: Figure 4As shown, under the condition of constant porosity and aspect ratio of wax crystals, the ratio of the effective diffusion coefficient of wax molecules to the diffusion coefficient in crude oil varies little with the main axis direction; the relationship between the ratio of the effective diffusion coefficient of ideal wax deposits to the diffusion coefficient in crude oil and the overlap angle of wax crystals is as follows. Figure 5 As shown, the ratio of the effective diffusion coefficient to the overall diffusion coefficient of wax molecules gradually decreases with increasing overlap axis inclination angle. The influence of the aspect ratio and overlap method of wax crystal particles on the wax molecule concentration is related to the axis inclination angle of the wax crystal particles; the larger the projected area perpendicular to the wax molecule concentration gradient direction, the greater the influence on the wax molecule concentration. Currently, the effective diffusion coefficient of wax molecules only applies to ideal wax crystal particles. In actual wax deposits, the size, aspect ratio, and axis direction of the wax crystal particles are continuously distributed. In this embodiment of the invention, wax deposits from oil pipelines are selected as wax deposit samples to obtain the actual microstructure of wax crystal particles.

[0057] Example 1

[0058] like Figure 6 The image shows Embodiment 1 of the present invention, a method for determining the effective diffusion coefficient of wax molecules, comprising the following steps:

[0059] S1: Establish a calculation model for the effective diffusion coefficient of wax molecules in wax deposits;

[0060] S2: Multiple microscopic images of wax crystals were obtained from wax deposit samples at different temperatures using a microscopic observation device;

[0061] S3: Perform image preprocessing on each wax crystal microscopic image, and combine the preprocessed wax crystal microscopic images with the calculation model in step S1 to calculate the effective diffusion coefficient of wax molecules in the wax deposit sample in each wax crystal microscopic image.

[0062] S4: Fit the effective diffusion coefficient of wax molecules in the wax deposit sample in each wax crystal micro-image to obtain the relationship between the ratio of the effective diffusion coefficient of wax molecules in the wax deposit and the diffusion coefficient of wax molecules in crude oil as a function of the concentration of solid wax crystal particles.

[0063] In step S1, a calculation model for the effective diffusion coefficient of wax molecules in wax deposits is established, which specifically includes the following steps:

[0064] S11: Obtain a micro-unit at any point in the wax deposit. The micro-unit is a rectangular region bounded by a left boundary line, a right boundary line, a top boundary line, and a bottom boundary line. Let the length of the rectangular region be L and the width be W. The center of the micro-unit contains wax crystal particles; the diffusion direction of wax molecules is from bottom to top. Figure 1As shown, in areas where there are no wax crystal particles in the micro-units, the diffusion of wax molecules is not hindered by the wax crystal particles; in areas where there are wax crystal particles in the micro-units, the diffusion of wax molecules is affected by the wax crystal particles.

[0065] S12: Calculate the wax molecule concentration value of the micro-unit;

[0066] The governing equation for the concentration of wax molecules in the micro-units satisfies Fick's diffusion law, and the governing equation is:

[0067] (2);

[0068] in, C t represents the concentration of wax molecules, in wt%; t represents time, in seconds. D Let m be the diffusion coefficient of the wax molecules. 2 / s; The Laplace operator is defined by the following formula:

[0069] (3);

[0070] The concentration of wax molecules in a small unit is calculated using the lattice Boltzmann method. The formula is as follows:

[0071] (4);

[0072] in, It is the position at time t. Distribution function of wax molecule concentration, i = 1~4; concentration of wax molecules = ; Let be the equilibrium distribution function. ,in , For discrete velocity, the definition is: , , , .

[0073] S13: Obtain the concentration value C at the upper boundary of the micro-unit based on the concentration value. S And the concentration value C at the lower boundary of the micro-unit. X ;

[0074] When t=0, obtain the concentration value C=C at any point in the micro-unit. l That is, the concentration value C at the upper boundary line. S =C l ;

[0075] When t=1, the concentration value C at the lower boundary line X By Cl Transform into C h That is, the concentration value C at the lower boundary line. X =C h ;

[0076] S14: Based on the concentration value C at the upper boundary line S and the concentration value C at the lower boundary line X Based on equilibrium conditions, the diffusion mass flux of wax molecules in a region without wax crystal particles is obtained. J And the diffusion mass flux of wax molecules in the region of wax crystal particles, and the diffusion mass flux of wax molecules in tiny units. J* ;

[0077] Obtain the diffusion mass flux of wax molecules in a region without wax crystal particles, using tiny wax units. J The calculation formula is:

[0078] (5);

[0079] The diffusion mass flux of wax molecules in the region of wax crystal particles at the micro-unit level. J* The calculation formula is:

[0080] (6);

[0081] Among them, when the tiny unit x When wax crystal particles are present, the diffusion coefficient of wax molecules D x =0, when there are no wax crystal particles in the micro-unit, the diffusion coefficient of wax molecules is 0. D x =D, To account for the concentration gradient of wax molecules at the locations of wax crystal particles, y c It can be any value within a tiny unit.

[0082] S15: Based on the diffusion mass flux of wax molecules in the region without wax crystal particles. J and the diffusion mass flux of wax molecules in the region of wax crystal particles. J* To obtain the effective diffusion coefficient D of wax molecules in wax deposits. e The diffusion coefficient D of wax molecules in crude oil wo The calculation formula is as follows:

[0083] (1);

[0084] It should be noted that, under the same diffusion area and concentration gradient conditions, if there are wax crystal particles in the micro-unit, the diffusion mass flux of wax molecules decreases, and the diffusion mass flux J* of wax molecules decreases. <J。

[0085] In this embodiment, in step S2, the microscopic observation device is, but is not limited to, a Nikon OPTIPHOT2-POL polarizing microscope or an OlyMPUS BX51 polarizing microscope. Figure 9 The images show the corresponding wax crystal microstructures of wax deposit samples at different temperatures in one embodiment. As can be seen from Figures (9d) to (9k), the wax crystal particles become smaller as the temperature increases.

[0086] In this embodiment, step S3, image preprocessing includes the following steps:

[0087] S31: Perform grayscale processing on each wax crystal microscopic image to convert the wax crystal microscopic image into a grayscale image;

[0088] S32: Binarize the grayscale image to obtain a binary image;

[0089] S33: Based on binary images, obtain the microscopic characteristics of waxy sediment samples.

[0090] In this embodiment, under a given concentration boundary condition, based on the characteristics of the microstructure of the obtained waxy sediment samples, the concentration of wax molecules in all wax sediments at different temperatures is obtained by calculation using formula (4), and the effective diffusion coefficient of wax molecules in the wax sediment is calculated. The given concentration boundary condition is: The initial wax molecule concentration C at the lower boundary line is set as follows: X =C h The initial wax molecule concentration C at the upper boundary line S =C l The left and right boundary lines are periodic boundary conditions.

[0091] It should be noted that in the microscopic image of wax crystals, the white bright spots are wax crystal particles, and the black areas are liquid crude oil, such as... Figure 8 As shown, after image preprocessing, the microscopic images of wax crystals clearly reveal the microscopic characteristics of wax-containing sediment samples, making it easier to obtain the location of wax crystal particles and liquid crude oil, which is beneficial for calculating the diffusion coefficient in subsequent steps.

[0092] In this embodiment, the method used to fit the effective diffusion coefficient of wax molecules in the wax deposit sample in each wax crystal micro-image in step S4 is the least squares method.

[0093] In the embodiments, the ratio of the effective diffusion coefficient of wax molecules in wax deposits to the diffusion coefficient of wax molecules in crude oil varies with the concentration of solid wax crystal particles as follows:

[0094] (7);

[0095] in, F wThe concentration of solid wax crystals is expressed in wt%. As the concentration of solid wax crystals increases, the ratio of the effective diffusion coefficient in the wax deposit to the diffusion coefficient of wax molecules in crude oil decreases. Figure 10 As shown.

[0096] It should be noted that the concentration of solid wax crystal particles... F w This is the ratio of the pixel value of the wax crystal particles in the wax crystal micro-image to the total pixel value of the wax crystal micro-image.

[0097] In a specific embodiment of the present invention, Table 1 shows the concentration of solid wax crystal particles calculated based on the microscopic images of wax crystals at different temperatures, and the ratio of the effective diffusion coefficient of wax molecules in wax deposits to the diffusion coefficient of wax molecules in crude oil. The relationship between the ratio of the effective diffusion coefficient of wax molecules in wax deposits to the diffusion coefficient of wax molecules in crude oil and the concentration of solid wax crystal particles is as follows:

[0098] ;

[0099] Table 1

[0100]

[0101] A method for determining the effective diffusion coefficient of wax molecules is proposed. Based on the actual wax crystal microstructure of wax deposits at different temperatures, the effective diffusion coefficient of wax molecules in wax deposits is calculated, and the calculation relationship between the effective diffusion coefficient of wax molecules and the concentration of solid wax crystal particles is obtained. This method solves the problem of the low result of the Cussler classical calculation formula. The diffusion coefficient of wax molecules in crude oil and wax deposits is an important parameter that determines the wax deposition rate of waxy crude oil and the aging rate of wax deposits. Therefore, the calculation of the effective diffusion coefficient of wax molecules is of great significance for improving the economy and safety of pipeline operation and promoting the development of flow safety assurance technology in the petroleum industry.

[0102] Example 2

[0103] A computer device includes: one or more non-volatile computer-readable storage media containing computer-executable instructions; and one or more processors, which, when the computer-executable instructions stored in the computer-readable storage media are executed by the one or more processors, cause the processors to perform the above-described method for determining the effective diffusion coefficient of wax molecules.

[0104] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media containing computer-usable program code, including but not limited to disk storage, CD-ROM, optical storage, etc.

[0105] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus systems, and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0106] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0107] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0108] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for determining the effective diffusion coefficient of wax molecules, characterized in that, Includes the following steps: S1: Establish a calculation model for the effective diffusion coefficient of wax molecules in wax deposits, specifically including: S11: Obtain a tiny unit at any point in the wax deposit. The tiny unit is a rectangular region bounded by a left boundary line, a right boundary line, a top boundary line, and a bottom boundary line. Let the length of the rectangular region be L and the width be W. The center of the tiny unit has wax crystal particles. S12: Calculate the wax molecule concentration value of the micro-unit; S13: Obtain the concentration value C at the upper boundary line of the micro-unit based on the concentration value. S and the concentration value C at the lower boundary of the micro-unit. X ; S14: Based on the concentration value C at the upper boundary line S and the concentration value C at the lower boundary line. X Based on the equilibrium state, the diffusion mass flux of the wax molecules of the micro-unit is obtained in the region without the wax crystal particles. J The diffusion mass flux of the wax molecules in the region of the wax crystal particles, and the wax molecules of the micro-units. J* ; S15: Based on the diffusion mass flux of the wax molecules in the region without the wax crystal particles. J and the diffusion mass flux of the wax molecules in the region of the wax crystal particles. J* To obtain the effective diffusion coefficient D of wax molecules in wax deposits. e The diffusion coefficient D of wax molecules in crude oil wo The calculation formula is as follows: （1）； S2: Multiple microscopic images of wax crystals were obtained from wax deposit samples at different temperatures using a microscopic observation device; S3: Perform image preprocessing on each of the wax crystal micro images, and combine the preprocessed wax crystal micro images with the calculation model described in step S1 to calculate the effective diffusion coefficient of wax molecules in the wax deposit sample in each of the wax crystal micro images. S4: Fit the effective diffusion coefficient of wax molecules in the wax deposit sample in each of the wax crystal micro images, and obtain the relationship between the ratio of the effective diffusion coefficient of wax molecules in the wax deposit to the diffusion coefficient of wax molecules in crude oil and the concentration of solid wax crystal particles.

2. The method for determining the effective diffusion coefficient of wax molecules as described in claim 1, characterized in that, In step S12, the governing equation for the wax molecule concentration of the micro-unit satisfies Fick's diffusion law, and the governing equation is: （2）； in, C t represents the concentration of wax molecules, in wt%; t represents time, in seconds. D Let m be the diffusion coefficient of the wax molecules. 2 / s; The Laplace operator is defined by the following formula: （3）； The wax molecule concentration of the micro-unit is calculated based on the lattice Boltzmann method, using the following formula: （4）； in, It is the position at time t. Distribution function of wax molecule concentration, i = 1~4; concentration of wax molecules = ; Let be the equilibrium distribution function. ,in , For discrete velocity, the definition is: , , , .

3. The method for determining the effective diffusion coefficient of wax molecules as described in claim 2, characterized in that, In step S13, when t=0, the concentration value C=C at any point of the micro-unit is obtained. l That is, the concentration value C at the upper boundary line. S =C l ; When t=1, the concentration value C at the lower boundary line X By C l Transform into C h That is, the concentration value C at the lower boundary line. X =C h .

4. The method for determining the effective diffusion coefficient of wax molecules as described in claim 3, characterized in that, In step S14, the diffusion mass flux of the wax molecules of the micro-unit is obtained in the region where the wax crystal particles are absent. J The calculation formula is: （5）； When the wax molecules of the micro-unit are in the region of the wax crystal particles, the diffusion mass flux of the wax molecules... J* The calculation formula is: （6）； Among them, when the tiny unit x When wax crystal particles are present, the diffusion coefficient of wax molecules D x =0, when the micro-unit has no wax crystal particles, the diffusion coefficient of wax molecules is 0. D x =D, To account for the concentration gradient of wax molecules at the locations of wax crystal particles, y c It can be any value within the tiny unit.

5. The method for determining the effective diffusion coefficient of wax molecules as described in claim 4, characterized in that, Under the same diffusion area and concentration gradient conditions, if the micro-unit contains wax crystal particles, the diffusion mass flux of the wax molecules decreases, and the diffusion mass flux J* of the wax molecules decreases. <J。 6. The method for determining the effective diffusion coefficient of wax molecules as described in claim 4, characterized in that, In step S4, the method for fitting the effective diffusion coefficient of wax molecules in the wax deposit sample in each of the wax crystal micro-images is the least squares method.

7. The method for determining the effective diffusion coefficient of wax molecules as described in claim 6, characterized in that, The ratio of the effective diffusion coefficient of wax molecules in wax deposits to the diffusion coefficient of wax molecules in crude oil varies with the concentration of solid wax crystal particles as follows: （7）； in, F w , where is the concentration of solid wax crystal particles, in wt%.

8. The method for determining the effective diffusion coefficient of wax molecules as described in claim 4, characterized in that, In step S3, the image preprocessing includes the following steps: Each of the aforementioned wax crystal microscopic images is converted to grayscale by performing grayscale processing. A grayscale image is binarized to obtain a binary image; Based on the binary image, the microscopic characteristics of the waxy sediment sample are obtained.

9. A computer device, characterized in that, include: One or more non-volatile computer-readable storage media containing computer-executable instructions, and one or more processors, wherein when the computer-executable instructions stored in the computer-readable storage medium are executed by the one or more processors, the processors perform the method for determining the effective diffusion coefficient of wax molecules as described in any one of claims 1 to 8.

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