A method and apparatus for evaluating the flow of crude oil in a pipeline.

Abstract

This invention provides an evaluation method for ensuring the flow of crude oil in a pipeline, relating to the technical field of oil extraction. The method includes: obtaining pipeline design parameters, basic crude oil physical properties, environmental parameters of the pipeline location, and equipment design parameters; constructing a mathematical model of pipeline temperature during shutdown and a soil heat transfer model; obtaining heat loss and soil heat transfer loss during shutdown based on the pipeline design parameters, basic crude oil physical properties, environmental parameters of the pipeline location, equipment design parameters, the mathematical model of pipeline temperature during shutdown, and the soil heat transfer model; obtaining the pipeline end temperature based on the heat loss and soil heat transfer loss during shutdown; obtaining a first threshold and determining whether the first threshold is lower than the pipeline end temperature. This invention provides an effective and accurate evaluation method for assessing the flowability of crude oil in pipelines, preventing wax deposition, and determining a reasonable crude oil outlet temperature.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, and in particular to an evaluation method and apparatus for ensuring the flow of crude oil in pipelines. Background Technology

[0002] Crude oil produced in my country's oilfields has a high wax content. If the operating temperature is low during transportation, the wax molecules dissolved in the crude oil near the pipe wall will crystallize and precipitate, forming a wax layer on the pipe wall. This reduces the effective flow area of ​​the pipeline, increases flow resistance, causes the pipeline operating pressure to rise, and may even lead to wax blockage, affecting the safe and stable operation of the pipeline.

[0003] Therefore, my country mostly chooses heated transportation methods for crude oil. When setting pipeline operating parameters, current standards and specifications require a temperature 3-5°C above the pour point as the threshold. However, in actual production, some crude oils, especially those with high wax content, reach peak wax precipitation and wax deposition 3-5°C above the pour point, affecting normal pipeline operation. To address this, the wax precipitation point is generally used as the minimum operating temperature to mitigate the impact of wax deposition at a minimum temperature of 3-5°C. However, since wax deposition doesn't necessarily occur below the wax precipitation point, and crude oil pipelines are generally equipped with pigging and cleaning systems to address a certain amount of wax deposition, using the wax precipitation point as the minimum temperature threshold significantly increases the pipeline's operating temperature, resulting in energy waste. Therefore, a method is needed to effectively and accurately evaluate whether crude oil pipelines meet flow assurance conditions, providing strong support for determining the operating temperature. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an evaluation method and apparatus for ensuring the flow of crude oil in a pipeline, so as to provide an evaluation method that can effectively and accurately evaluate the flowability of crude oil in a pipeline, prevent wax deposition, and determine a reasonable crude oil outlet temperature.

[0005] In a first aspect, embodiments of the present invention provide an evaluation method for ensuring the flow of crude oil in a pipeline, specifically including the following steps:

[0006] Obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters;

[0007] A mathematical model of pipeline temperature and a soil heat transfer model are constructed during the shutdown process. Based on the pipeline design parameters, the basic physical properties of crude oil, the environmental parameters of the pipeline, the equipment design parameters, the mathematical model of pipeline temperature during the shutdown process, and the soil heat transfer model, the heat loss and soil heat transfer loss during the shutdown process are obtained.

[0008] The pipeline end temperature is obtained based on the heat loss during the shutdown process and the soil heat transfer loss.

[0009] Obtain a first threshold and determine whether the first threshold is lower than the temperature at the end of the pipeline;

[0010] If so, obtain the amount of wax deposited and the maximum amount to be cleaned;

[0011] If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0012] Preferably, after the steps of obtaining the wax deposition amount and the maximum cleanup amount, the method further includes:

[0013] Determine whether the maximum cleaning amount is greater than the wax deposition amount;

[0014] If so, then the crude oil exit temperature is deemed reasonable;

[0015] If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0016] Preferably, the pipeline design parameters include pipeline length, pipeline inner diameter, pipeline wall thickness, and the thermal conductivity of the steel used in the pipeline.

[0017] The basic physical properties of crude oil include crude oil density, crude oil specific heat capacity, crude oil thermal conductivity, crude oil specific enthalpy, and pipe wall temperature;

[0018] The environmental parameters of the pipeline include the altitude along the pipeline route, ground temperature along the route, total heat transfer coefficient, soil temperature, atmospheric temperature, soil thermal conductivity, soil density, and soil specific heat capacity.

[0019] Preferably, the heat loss during the shutdown process is obtained using the following formula:

[0020] The heat transfer equation for crude oil:

[0021] ;

[0022] In the formula, —Crude oil density;

[0023] — Crude oil specific heat capacity;

[0024] —Crude oil temperature;

[0025] —Time variable;

[0026] —Change in the radial length of the pipeline;

[0027] — Thermal conductivity of crude oil;

[0028] —The angle with respect to the direction perpendicular to the ground;

[0029] The following boundary conditions must be met:

[0030] ;

[0031] ;

[0032] —The thermal conductivity of the steel used in pipe manufacturing;

[0033] —Inner radius of the pipe;

[0034] —Pipe wall temperature;

[0035] —Coefficient of heat transfer from crude oil to the inner wall of the pipe;

[0036] The following initial conditions must be met:

[0037] ;

[0038] —Initial temperature of crude oil;

[0039] Each structural layer outside the pipe meets the following initial conditions:

[0040] ;

[0041] —Density of the material in the nth layer of the pipe;

[0042] —Heat capacity of the nth layer material in the pipeline;

[0043] —Temperature of the nth layer of the pipeline (pipe wall, insulation layer, protective layer, etc.);

[0044] — Thermal conductivity of the nth layer material in the pipe

[0045] Each structural layer outside the tube satisfies the initial conditions:

[0046] ;

[0047] —Initial temperature of the nth layer of material in the pipe

[0048] Contact boundary conditions between different layers of the pipe wall:

[0049] n = 1, 2, 3...N-1;

[0050] —Inner radius of the pipe;

[0051] —Outer radius of the nth layer of the pipe

[0052] ;

[0053] —The thermal conductivity of the nth layer material in the pipe;

[0054] ;

[0055] — Thermal conductivity of the outermost layer material of the pipe

[0056] —Soil thermal conductivity

[0057] —Soil temperature

[0058] ;

[0059] ;

[0060] ;

[0061] The soil heat transfer equation is constructed using the following formula:

[0062] ;

[0063] —Soil density;

[0064] —Soil temperature

[0065] —Specific heat capacity of soil;

[0066] The soil heat transfer equation satisfies the following boundary conditions:

[0067] ;

[0068] —Pipe length;

[0069] ;

[0070] —Atmospheric temperature

[0071] ;

[0072] —Soil temperature at a distance H from the ground;

[0073] —Distance between the center of the pipeline and the ground surface;

[0074] Initial conditions:

[0075] ;

[0076] —Temperature of the outermost layer of the pipe.

[0077] Preferably, the pipeline end temperature is obtained using the following formula:

[0078] ;

[0079] —Oil temperature at L distance from the exit;

[0080] —Ambient medium temperature;

[0081] —Frictional heat;

[0082] —Exit temperature;

[0083] —Parameters, dimensionless.

[0084] Preferably, the wax deposition amount is obtained using the following formula:

[0085] ;

[0086] — Wax deposition thickness;

[0087] —The flow rate of wax molecules from the oil flow to the surface of the deposit;

[0088] —Crude oil density;

[0089] —The mass fraction of the entire oil sample containing sedimentary layers;

[0090] —Wax content in sediments;

[0091] —Shear stripping flux;

[0092] ;

[0093] — Radius of the sedimentary layer;

[0094] ;

[0095] —Mass diffusion coefficient;

[0096] —Concentration of wax molecules at the interface between the oil flow and the sediment;

[0097] —The concentration of wax molecules at the interface equilibrium (saturation) is related to the interface temperature Ti;

[0098] α-Shape parameters of wax crystal particles

[0099] —Temperature at the interface between the oil flow and the sediment.

[0100] Preferably, the first threshold is 3 to 5 degrees higher than the pour point of the crude oil.

[0101] On the other hand, the present invention provides an evaluation device for ensuring the flow of crude oil in a pipeline, comprising:

[0102] The first acquisition module is used to acquire pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0103] The second acquisition module is used to construct a mathematical model of pipeline temperature and a soil heat transfer model during the shutdown process. Based on the pipeline design parameters, the crude oil basic physical property parameters, the environmental parameters of the pipeline, the equipment design parameters, the mathematical model of pipeline temperature during the shutdown process, and the soil heat transfer model, the heat loss and soil heat transfer loss during the shutdown process are obtained.

[0104] Calculation module: used to obtain the pipeline end temperature based on the heat loss during the shutdown process and the soil heat transfer loss;

[0105] Determination module: used to obtain a first threshold and determine whether the first threshold is lower than the temperature at the end of the pipeline;

[0106] If so, obtain the amount of wax deposited and the maximum amount to be cleaned;

[0107] If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0108] The embodiments of this invention bring the following beneficial effects: This invention provides an evaluation method for ensuring the flow of crude oil in a pipeline, including: obtaining pipeline design parameters, basic physical property parameters of crude oil, environmental parameters of the pipeline environment, and equipment design parameters; constructing a mathematical model of pipeline temperature during shutdown and a soil heat transfer model; obtaining heat loss and soil heat transfer loss during shutdown based on the pipeline design parameters, basic physical property parameters of crude oil, environmental parameters of the pipeline environment, equipment design parameters, and the mathematical model of pipeline temperature during shutdown; obtaining the pipeline end temperature based on the heat loss and soil heat transfer loss during shutdown; obtaining a first threshold and determining whether the first threshold is lower than the pipeline end temperature; if so, obtaining the wax deposition amount and maximum cleaning amount; if not, increasing the outlet temperature and performing the steps of obtaining pipeline design parameters, basic physical property parameters of crude oil, environmental parameters of the pipeline environment, and equipment design parameters. This invention provides an effective and accurate evaluation method for assessing the flowability of crude oil in pipelines, preventing wax deposition, and determining a reasonable crude oil outlet temperature.

[0109] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0110] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0111] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0112] Figure 1 A flowchart of an evaluation method for ensuring crude oil flow in a pipeline, provided by an embodiment of the present invention;

[0113] Figure 2 An evaluation method for ensuring the flow of crude oil in a pipeline, provided by an embodiment of the present invention, measures the amount of wax deposition in the pipeline at an outlet temperature of 66.5°C. Detailed Implementation

[0114] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0115] Currently, most crude oil transportation in my country utilizes heated transportation methods. When setting pipeline operating parameters, the current standards and specifications stipulate that a temperature 3-5°C above the pour point should be used as the threshold. However, in actual production, some crude oils, especially those with high wax content, reach their peak wax precipitation and deposition at temperatures 3-5°C above the pour point, affecting the normal operation of the pipeline. Therefore, this invention provides a method and apparatus for evaluating the flow of crude oil in transportation pipelines. This method effectively and accurately assesses the flowability of crude oil in pipelines, prevents wax deposition, and determines a reasonable crude oil outlet temperature.

[0116] To facilitate understanding of this embodiment, a detailed description of an evaluation method for ensuring the flow of crude oil in a pipeline, as disclosed in this embodiment of the invention, will be provided first.

[0117] Example 1:

[0118] This invention provides an embodiment of a method for evaluating the flow of crude oil in a pipeline, which includes the following steps:

[0119] Obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters;

[0120] A mathematical model of pipeline temperature and a soil heat transfer model are constructed during the shutdown process. Based on the pipeline design parameters, the basic physical properties of crude oil, the environmental parameters of the pipeline, the equipment design parameters, the mathematical model of pipeline temperature during the shutdown process, and the soil heat transfer model, the heat loss and soil heat transfer loss during the shutdown process are obtained.

[0121] The pipeline end temperature is obtained based on the heat loss during the shutdown process and the soil heat transfer loss.

[0122] Obtain a first threshold and determine whether the first threshold is lower than the temperature at the end of the pipeline;

[0123] If so, obtain the amount of wax deposited and the maximum amount to be cleaned;

[0124] If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0125] Preferably, after the steps of obtaining the wax deposition amount and the maximum cleanup amount, the method further includes:

[0126] Determine whether the maximum cleaning amount is greater than the wax deposition amount;

[0127] If so, then the crude oil exit temperature is deemed reasonable;

[0128] If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0129] Preferably, the pipeline design parameters include pipeline length, pipeline inner diameter, pipeline wall thickness, and the thermal conductivity of the steel used in the pipeline.

[0130] The basic physical properties of crude oil include crude oil density, crude oil specific heat capacity, crude oil thermal conductivity, crude oil specific enthalpy, and pipe wall temperature;

[0131] The environmental parameters of the pipeline include the altitude along the pipeline route, ground temperature along the route, total heat transfer coefficient, soil temperature, atmospheric temperature, soil thermal conductivity, soil density, and soil specific heat capacity.

[0132] Preferably, the heat loss during the shutdown process is obtained using the following formula:

[0133] The heat transfer equation for crude oil:

[0134] The heat transfer equation for crude oil:

[0135] ;

[0136] In the formula, —Crude oil density

[0137] — Crude oil specific heat capacity

[0138] —Crude oil temperature;

[0139] —Time variable;

[0140] —Change in pipe radial length

[0141] — Thermal conductivity of crude oil

[0142] — Angle with the direction perpendicular to the ground

[0143] The following boundary conditions must be met:

[0144] ;

[0145] ;

[0146] —The thermal conductivity of the steel used in pipe manufacturing;

[0147] —Inner radius of the pipe;

[0148] —Pipe wall temperature;

[0149] —Coefficient of heat transfer from crude oil to the inner wall of the pipe;

[0150] The following initial conditions must be met:

[0151] ;

[0152] —Initial temperature of crude oil

[0153] Each structural layer outside the pipe meets the following initial conditions:

[0154] ;

[0155] —Density of the material in the nth layer of the pipe;

[0156] —Heat capacity of the nth layer material in the pipeline;

[0157] —Temperature of the nth layer of the pipeline (pipe wall, insulation layer, protective layer, etc.);

[0158] —The thermal conductivity of the nth layer material in the pipe;

[0159] Each structural layer outside the tube satisfies the initial conditions:

[0160] ;

[0161] —Initial temperature of the nth layer of material in the pipe;

[0162] Contact boundary conditions between different layers of the pipe wall:

[0163] n = 1, 2, 3...N-1;

[0164] —Inner radius of the pipe;

[0165] —Outer radius of the nth layer of the pipeline;

[0166] ;

[0167] —The thermal conductivity of the nth layer material in the pipe;

[0168] ;

[0169] —The thermal conductivity of the outermost layer material of the pipe;

[0170] —Soil thermal conductivity;

[0171] —Soil temperature;

[0172] ;

[0173] ;

[0174] ;

[0175] The soil heat transfer equation is constructed using the following formula:

[0176] ;

[0177] —Soil density;

[0178] —Soil temperature;

[0179] —Specific heat capacity of soil;

[0180] The soil heat transfer equation satisfies the following boundary conditions:

[0181] ;

[0182] —Pipe length;

[0183] ;

[0184] —Atmospheric temperature

[0185] ;

[0186] —Soil temperature at a distance H from the ground;

[0187] —Distance between the center of the pipeline and the ground surface;

[0188] Initial conditions:

[0189] ;

[0190] —Temperature of the outermost layer of the pipe.

[0191] Preferably, the pipeline end temperature is obtained using the following formula:

[0192] ;

[0193] —Oil temperature at L distance from the exit;

[0194] —Ambient medium temperature;

[0195] —Frictional heat;

[0196] —Exit temperature;

[0197] —Parameters, dimensionless.

[0198] Preferably, the wax deposition amount is obtained using the following formula:

[0199] ;

[0200] — Wax deposition thickness;

[0201] —The flow rate of wax molecules from the oil flow to the surface of the deposit;

[0202] —Crude oil density;

[0203] —The mass fraction of the entire oil sample containing sedimentary layers;

[0204] —Wax content in sediments;

[0205] —Shear stripping flux;

[0206] ;

[0207] — Radius of the sedimentary layer;

[0208] ;

[0209] —Mass diffusion coefficient;

[0210] —Concentration of wax molecules at the interface between the oil flow and the sediment;

[0211] —The concentration of wax molecules at the interface equilibrium (saturation) is related to the interface temperature Ti;

[0212] α—Shape parameters of wax crystal particles;

[0213] —Temperature at the interface between the oil flow and the sediment.

[0214] Preferably, the first threshold is 3 to 5 degrees higher than the pour point of the crude oil.

[0215] Example 2:

[0216] Embodiment 2 of the present invention provides a specific example of Embodiment 1:

[0217] In Embodiment 2 of the present invention, the temperature at the end of the pipeline after 11 hours at the maximum design temperature of 66.5℃ at the outlet temperature was obtained, and the calculation results met the requirements.

[0218] Table 1: Pipeline end temperature:

[0219] ;

[0220] The wax deposition amount was calculated using the Hernandez model in the embodiments provided by this invention:

[0221] ;

[0222] Example 3:

[0223] Embodiment 3 of the present invention provides an evaluation device for ensuring the flow of crude oil in a pipeline, comprising:

[0224] The first acquisition module is used to acquire pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0225] The second acquisition module is used to construct a mathematical model of pipeline temperature and a soil heat transfer model during the shutdown process. Based on the pipeline design parameters, the crude oil basic physical property parameters, the environmental parameters of the pipeline, the equipment design parameters, the mathematical model of pipeline temperature during the shutdown process, and the soil heat transfer model, the heat loss and soil heat transfer loss during the shutdown process are obtained.

[0226] Calculation module: used to obtain the pipeline end temperature based on the heat loss during the shutdown process and the soil heat transfer loss;

[0227] Determination module: used to obtain a first threshold and determine whether the first threshold is lower than the temperature at the end of the pipeline;

[0228] If so, obtain the amount of wax deposited and the maximum amount to be cleaned;

[0229] If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

[0230] Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0231] In all examples shown and described herein, any specific values ​​should be interpreted as merely exemplary and not as limitations; therefore, other examples of exemplary embodiments may have different values.

[0232] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0233] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0234] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0235] Furthermore, in the description of the embodiments of the present invention, 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 the present invention based on the specific circumstances.

[0236] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0237] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for evaluating the flow of crude oil in a guaranteed pipeline, characterized in that, Specifically, the steps include the following: Obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters; A mathematical model of pipeline temperature and a soil heat transfer model are constructed during the shutdown process. Based on the pipeline design parameters, the basic physical properties of crude oil, the environmental parameters of the pipeline, the equipment design parameters, the mathematical model of pipeline temperature during the shutdown process, and the soil heat transfer model, the heat loss and soil heat transfer loss during the shutdown process are obtained. The pipeline end temperature is obtained based on the heat loss during the shutdown process and the soil heat transfer loss. Obtain a first threshold and determine whether the first threshold is lower than the temperature at the end of the pipeline; If so, obtain the amount of wax deposited and the maximum amount to be cleaned; After the steps of obtaining the wax deposition amount and the maximum cleanup amount, the method further includes: Determine whether the maximum cleaning amount is greater than the wax deposition amount; If so, then the crude oil exit temperature is deemed reasonable; If not, increase the outlet temperature and perform the steps of obtaining pipeline design parameters, crude oil basic physical property parameters, pipeline environment parameters, and equipment design parameters. The wax deposition amount is obtained using the following formula: ； — Wax deposition thickness; —The flow rate of wax molecules from the oil flow to the surface of the deposit; —Crude oil density; —The mass fraction of the entire oil sample containing sediment; —Wax content in sediments; —Shear stripping flux; ； — Radius of the sedimentary layer; ； —Mass diffusion coefficient; —Concentration of wax molecules at the interface between the oil flow and the sediment; —The concentration of wax molecules at the interface equilibrium (saturation) is related to the interface temperature Ti; α—Shape parameters of wax crystal particles; —Temperature at the interface between the oil flow and the sediment; If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

2. The method according to claim 1, characterized in that, The pipeline design parameters include pipeline length, pipeline inner diameter, pipeline wall thickness, and the thermal conductivity of the steel used in the pipeline. The basic physical properties of crude oil include crude oil density, crude oil specific heat capacity, crude oil thermal conductivity, crude oil specific enthalpy, and pipe wall temperature; The environmental parameters of the pipeline include the altitude along the pipeline route, ground temperature along the route, total heat transfer coefficient, soil temperature, atmospheric temperature, soil thermal conductivity, soil density, and soil specific heat capacity.

3. The method according to claim 1, characterized in that, The heat loss during shutdown is obtained using the following formula: The heat transfer equation for crude oil: ； In the formula, —Crude oil density; — Crude oil specific heat capacity; —Crude oil temperature; —Time variable; —Change in the radial length of the pipeline; — Thermal conductivity of crude oil; —The angle with respect to the direction perpendicular to the ground; The following boundary conditions must be met: ； ； —The thermal conductivity of the steel used in pipe manufacturing; —Inner radius of the pipe; —Pipe wall temperature; —Coefficient of heat transfer from crude oil to the inner wall of the pipe; The following initial conditions must be met: ； —Initial temperature of crude oil; Each structural layer outside the pipe meets the following initial conditions: ； —Density of the material in the nth layer of the pipe; —Heat capacity of the nth layer material in the pipeline; —Temperature of the nth layer of the pipeline (pipe wall, insulation layer, protective layer, etc.); —The thermal conductivity of the nth layer material in the pipe; Each structural layer outside the tube satisfies the initial conditions: ； —Initial temperature of the nth layer of material in the pipeline; Contact boundary conditions between different layers of the pipe wall: n=1,2,3...N-1; —Inner radius of the pipe; —Outer radius of the nth layer of the pipeline; ; —The thermal conductivity of the nth layer material in the pipe; ； —The thermal conductivity of the outermost layer material of the pipe; —Soil thermal conductivity; —Soil temperature; ; ； The soil heat transfer equation is constructed using the following formula: ； —Soil density; —Soil temperature; —Specific heat capacity of soil; The soil heat transfer equation satisfies the following boundary conditions: ； —Pipe length; ； —Atmospheric temperature; ； —Soil temperature at a distance H from the ground; —Distance between the center of the pipeline and the ground surface; Initial conditions: ; —Temperature of the outermost layer of the pipe.

4. The method according to claim 1, characterized in that, The pipeline end temperature is obtained using the following formula: ； —Oil temperature at L distance from the exit; —Ambient medium temperature; —Frictional heat; —Exit temperature; —Parameters, dimensionless.

5. The method according to claim 1, characterized in that, The first threshold is 3 to 5 degrees higher than the pour point of the crude oil.

6. An evaluation device for ensuring the flow of crude oil in a pipeline, characterized in that, include: The first acquisition module is used to acquire pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters. The second acquisition module is used to construct a mathematical model of pipeline temperature and a soil heat transfer model during the shutdown process. Based on the pipeline design parameters, the crude oil basic physical property parameters, the environmental parameters of the pipeline, the equipment design parameters, the mathematical model of pipeline temperature during the shutdown process, and the soil heat transfer model, the heat loss and soil heat transfer loss during the shutdown process are obtained. Calculation module: used to obtain the pipeline end temperature based on the heat loss during the shutdown process and the soil heat transfer loss; Determination module: used to obtain a first threshold and determine whether the first threshold is lower than the temperature at the end of the pipeline; If so, obtain the amount of wax deposited and the maximum amount to be cleaned; After the steps of obtaining the wax deposition amount and the maximum cleanup amount, the method further includes: Determine whether the maximum cleaning amount is greater than the wax deposition amount; If so, then the crude oil exit temperature is deemed reasonable; If not, increase the outlet temperature and perform the steps of obtaining pipeline design parameters, crude oil basic physical property parameters, pipeline environment parameters, and equipment design parameters. The wax deposition amount is obtained using the following formula: ； — Wax deposition thickness; —The flow rate of wax molecules from the oil flow to the surface of the deposit; —Crude oil density; —The mass fraction of the entire oil sample containing sediment; —Wax content in sediments; —Shear stripping flux; ； — Radius of the sedimentary layer; ； —Mass diffusion coefficient; —Concentration of wax molecules at the interface between the oil flow and the sediment; —The concentration of wax molecules at the interface equilibrium (saturation) is related to the interface temperature Ti; α—Shape parameters of wax crystal particles; —Temperature at the interface between the oil flow and the sediment; If not, increase the outlet temperature and perform the steps described above to obtain pipeline design parameters, crude oil basic physical property parameters, pipeline environmental parameters, and equipment design parameters.

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