Device and method for simulating wax deposition test in flowing process of crude oil with different components

Abstract

The invention discloses a device and a method for simulating a wax deposition test in a flowing process of crude oil with different components. The device comprises a gas supply tank, a mixing tank, a centrifugal pump I, a wax deposition test system and a dosing and mixing tank, an outlet of the gas supply tank is connected with a mixing tank, an outlet of the mixing tank is connected with a centrifugal pump I, the centrifugal pump I is connected with a test sample inlet of a wax deposition test system through a test sample input pipeline, a test sample outlet of the wax deposition test system is connected with an inlet of a dosing mixing tank, and an outlet of the dosing mixing tank is connected with a recovery pipeline; a recovery tank is connected to the recovery pipeline, and the recovery pipeline is communicated with the test sample input pipeline. Different from the situation that the wax precipitation rule test result cannot be reproduced due to the fact that wax sample components in crude oil are reduced along with the prolonging of test time in the conventional large-size wax precipitation simulation test, the test method has very small influence on the wax components in the oil sample, and can be used for testing multiple parameters by using the same oil sample, so that the consistency of the test sample composition is ensured, and the test efficiency is improved. And the test result reproducibility is good.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas development, and particularly relates to a device and method for testing wax deposition in a process of simulating the flow of crude oils with different components. Background Art

[0002] Crude oil produced from oil wells is highly complex. This crude oil, under high pressure, consists of oil, gas, water, and other impurities. Wax exists in the crude oil as a liquid at high temperatures. When the temperature drops below the wax precipitation point, the wax precipitates as crystals. These crystals slowly settle to the bottom of the oil flow, forming wax deposits. The ability to predict and control wax (also known as paraffin) deposition is crucial to the efficient extraction of crude oil from cold environments and is part of the broader discipline of "flow assurance" in the oil industry.

[0003] To this end, laboratory-scale deposition experiments are valuable for understanding wax deposition. Previous studies have shown that wax deposition depends on temperature, flow stress, oil composition (including wax), and the properties of the deposition surface. Furthermore, wax deposition is assessed not only by measuring the amount of wax deposited, but also by the composition of the deposit and observing the microstructure and macroscopic effects on wax deposition.

[0004] For example, Chinese invention patent application number 2022100342499 discloses a crude oil wax deposition test device. This device uses a mixing tank equipped with an electric stirrer to prepare an oil-water emulsion, enabling the study of wax deposition characteristics of crude oil at varying water contents. A cold water bath controls the temperature of the experimental pipeline, simulating the soil temperature found in actual pipelines. A motor connected to a certain length of pipeline rotates to simulate the wall shear experienced by the crude oil in the pipeline. The shear rate can be calculated based on the rotational speed, corresponding to the flow of crude oil in an actual pipeline. While the crude oil does not flow axially within the pipeline in this experimental device, it can simulate the time-dependent wax deposition characteristics of this section of crude oil. This corresponds to the wax deposition characteristics of a specific section of crude oil flowing through the pipeline in an actual pipeline. This technology is suitable for studying wax deposition characteristics in conventional oil pipelines. It does not account for the impact of three-phase flow of oil, gas, and water on wax deposition during oil well production, nor does it address the study of wax aging characteristics, which is closely related to oil well wax removal. Therefore, the test results from this device cannot be used to determine the characteristics of wax deposition in oil wellbores and to optimize wax prevention techniques. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a device and method for simulating wax deposition testing during the flow of crude oil with different components. The simulation test system can test the mechanism of reducing wax deposition by adding different types of paraffin inhibitors. It can also be used to test the reduction of wax deposition in crude oil on the surface of the pipeline through pipeline surface modification, that is, it can be used to test the mechanism and effect of surface modification technologies such as wax-proof oil pipes on reducing wax deposition in oil well pipes. The simulation system can also be used to test the wax deposition of petroleum samples under controlled shear stress and gradient.

[0006] To achieve the above object, the present invention adopts the following technical solutions: The present invention first discloses a device for simulating wax deposition testing during the flow of crude oil with different components, comprising a gas supply tank, a mixing tank, a centrifugal pump, a wax deposition testing system and a dosing mixing tank; The outlet of the gas supply tank is connected to the mixing tank, the outlet of the mixing tank is connected to centrifugal pump 1, the outlet of centrifugal pump 1 is connected to the test sample flow inlet of the wax deposition test system through the test sample input pipeline, the test sample flow outlet of the wax deposition test system is connected to the inlet of the dosing mixing tank through the test sample output pipeline, the outlet of the dosing mixing tank is connected to the recovery pipeline, the recovery pipeline is connected to the recovery tank, and the recovery pipeline is connected to the test sample input pipeline.

[0007] As a further preferred technical solution, a first temperature control unit is installed on the test sample input pipeline, and a second temperature control unit is installed on the test sample output pipeline.

[0008] Preferably, a one-way ball valve and a plunger pump are installed on the test sample input pipeline between the centrifugal pump 1 and the temperature control unit 1.

[0009] Preferably, a second centrifugal pump is installed on the recovery pipeline between the dosing mixing tank and the recovery tank, and a second one-way ball valve is installed on the recovery pipeline between the recovery tank and the test sample input pipeline.

[0010] As a further preferred technical solution, the wax deposition test system includes an upper baffle and a lower base plate arranged in parallel with each other. The bottom of the upper baffle is designed with a flow channel for the flow of the test sample. The two ends of the flow channel extend upward from the upper baffle and form a test sample inlet and a test sample outlet. A cooling water circulation system is provided in the lower base plate, and the cooling water circulation system includes a cooling water channel running through the lower base plate, one end of the cooling water channel is a low-temperature fluid inflow end, and the other end of the cooling water channel is connected to a low-temperature fluid outflow end; An upper test plate is installed on the lower surface of the upper partition, and a lower test plate is detachably installed on the upper surface of the lower base plate. The upper test plate is a transparent glass plate, and ultrasonic thickness measuring device 1 and ultrasonic thickness measuring device 2 are respectively designed at both ends of the upper test plate.

[0011] As a further preferred technical solution, gaskets capable of adjusting the distance between the upper test plate and the lower test plate are designed on both sides of the inflow and outflow direction of the test sample, and the thickness of the gaskets is 0.1-3 mm.

[0012] As a further preferred technical solution, the upper test plate and the lower test plate are each provided with a swingable robotic arm on the left and right sides along the inflow to outflow direction of the test sample, and each robotic arm has a clamp for tightening or opening the upper partition and the lower bottom plate to facilitate replacement of the lower test plate.

[0013] Preferably, the test sample inlet and the test sample outlet are respectively equipped with a test sample inflow end pressure detector and a test sample outflow end pressure detector.

[0014] Preferably, a wireless temperature sensor and a wireless pressure sensor are respectively arranged at both ends of the surface of the lower test plate, and the wireless temperature sensor is installed 0.1-0.2 cm below the surface of the lower test plate.

[0015] As a further preferred technical solution, the device also includes a control system, and the centrifugal pump 1, the one-way ball valve 1, the plunger pump, the temperature control unit 1, the temperature control unit 2, the centrifugal pump 2, the one-way ball valve 2, the test sample inlet end pressure detector, the test sample outflow end pressure detector, the ultrasonic thickness measuring device 1, the ultrasonic thickness measuring device 2, and the wireless temperature sensor and the wireless pressure sensor on the surface of the lower test plate are electrically connected to the control system respectively.

[0016] The present invention also discloses a method for simulating wax deposition testing during the flow of crude oils with different components, comprising the following steps: S1. Setting up the wax deposition test unit The wax deposition test unit includes an upper baffle and a lower base plate arranged in parallel above and below, a test sample inlet and a test sample outlet being provided in the upper baffle, and a flow channel extending between the test sample inlet and the test sample outlet; an overlying test plate is installed on the lower surface of the upper baffle, and a lower test plate, i.e., a wax deposition test plate, is installed on the upper surface of the lower base plate; a cooling water circulation system capable of temperature control is provided under the lower part of the lower test plate to achieve a low-temperature environment for the wax deposition test plate; an ultrasonic thickness measuring device 1 and an ultrasonic thickness measuring device 2 are respectively provided at the inlet end and the outlet end of the overlying test plate, for real-time monitoring of the wax sample deposition thickness on the surface of the wax deposition test plate, so as to facilitate analysis of the influence of the wax sample deposition under different time, different pressure, and different flow rate conditions in the test system on the temperature and wax deposition rate in the test system; S2. Testing the wax deposition process in crude oil under different flow conditions By adjusting the spacing between the upper and lower test plates and coordinating the injection velocity of the test sample inlet, the shear conditions of the fluid on the deposition plate surface are controlled to simulate the shear conditions between the wellbore and surface fluids and the pipeline surface. During the test, the temperature field of wax deposition is regulated by adjusting the temperature of the fluid flowing into the test sample and the temperature and flow rate of the cooling water under the lower test plate; S3. Study on the characteristics of waxy components: After the deposition test, the upper test plate was opened, the lower test plate was removed, and the waxy deposits on the surface of the lower test plate were photographed. Then, samples were taken from the sample inflow end, the middle part, and the sample outflow end, and the samples were analyzed by gas chromatography to determine the amount of wax in the deposits and the carbon number distribution in the deposits. S4. Study on wax aging process: Using crude oil test solutions with the same wax content, varying flow rates, deposition tank temperatures, and test times yielded several different sets of test curves related to wax deposition thickness versus pressure, time, and temperature. Each curve shows how wax deposition thickness increases over time as it is deposited from the solution. After the test is completed, wax samples deposited after different test durations are collected for macroscopic and microscopic analysis of wax components. In the time period when the wax thickness increases slowly, wax deposits of different cycle durations are collected for component analysis to clarify the wax aging time. This result can be provided in the wax deposition mathematical model to make corresponding corrections to the wax aging time parameters, which can be used to calculate the aging time of wax deposits in the actual production process, so that corresponding chemical and physical wax cleaning measures can be taken before wax deposit aging occurs during the production process.

[0017] The present invention has the following beneficial effects: 1. The present invention utilizes a gas storage tank and an oil-gas mixed transmission pump (i.e., centrifugal pump 1) to perform pressure testing on different gas-containing crude oils. During the test, the deposition pool (i.e., the lower test plate) can be placed horizontally or vertically to simulate wax deposition in oil wellbores and surface oil pipelines.

[0018] 2. By replacing the test sample on the lower deposition plate of the wax deposition test system, the anti-wax performance test of ordinary steel pipes, coated steel pipes, and insulated steel pipes can be realized, thereby providing a faster and more direct evaluation of the anti-wax effect of physical anti-wax measures.

[0019] 3. The surface of the overlying test plate has been treated to have heat-insulating and oleophobic properties, and will not adhere to wax deposits, ensuring that the wax sample will not precipitate on the surface of the overlying test plate.

[0020] 4. The wax deposition pool of this device is small (the size of the deposition pool is 20×20×10cm, of which the size of the wax deposition test plate is (7-10)×(20-30)×(2.5-3)cm). Unlike previous large-scale wax deposition simulation tests, where the wax content in the crude oil decreases as the test time increases, resulting in unreproducible wax deposition pattern test results, this test method has very little impact on the wax content in the oil sample. Therefore, the same oil sample can be used for multiple parameter tests, ensuring the consistency of the test sample composition and making the test results reproducible.

[0021] 5. The present invention constructs a device to simulate the wax deposition test during the flow of crude oil with different components. The wax deposition thickness is measured in real time using an ultrasonic thickness gauge designed on the surface of the upper partition. The color and other characteristics of the wax deposit can be directly observed through the overlying transparent glass plate. The lower test plate, namely the wax deposition test plate, can be removed, and the composition, micromorphology, and macrostructure of the wax deposit can be analyzed after removal.

[0022] 6. The simulated wax deposition test method provided by this invention can test the wax deposition process in crude oil under different flow conditions by controlling pressure and flow rate: one under typical wall shear stress in oil pipelines, and one under higher shear stress (20-30 Pa). The temperatures of the incoming oil and the cold deposit surface were controlled. The results were evaluated in terms of deposit height growth, deposit composition, deposit morphology, and the temperature field within the deposition pool. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other design solutions and drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the structure of the device for simulating wax deposition test during the flow of crude oil with different components; Figure 2 This is a structural diagram of the wax deposition test system; Figure 3 The growth of deposition thickness of 3% wax solution under two stress states; Figure 4 This is a curve showing the effect of adding different types of wax inhibitors at different concentrations on the yield stress of 3% wax solution.

[0025] Description of reference numerals: 1. Air supply tank; 2. Mixing tank; 3. Centrifugal pump 1; 4. One-way ball valve 1; 5. Plunger pump; 6. Temperature control unit 1; 7. Low-temperature cooling system; 8. Wax deposition test system; 9. Control system; 10. Temperature control unit 2; 11. Dosing and mixing tank; 12. Centrifugal pump 2; 13. Recovery tank; 14. One-way ball valve 2; 15. Upper test plate; 16. Pressure detector at the test sample inlet; 17. Test sample inlet; 18. Ultrasonic thickness gauge 1; 19. Ultrasonic thickness gauge 2; 20. Test sample outlet; 21. Pressure detector at the test sample outlet; 22. Lower test plate; 23. Low-temperature fluid inlet; 24. Low-temperature fluid outlet; 25. Lower base plate.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0027] The present invention can be further understood by reference to the following detailed description of the preferred embodiments of the present invention and the included Examples. Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. If the definition of a specific term disclosed in the prior art is inconsistent with any definition provided in the present invention, the definition of the term provided in the present invention shall prevail.

[0028] It should be noted that the descriptions of "one" and "two" in Centrifugal Pump One and Centrifugal Pump Two in the present invention are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features.

[0029] In a typical embodiment of the present application, a device for simulating wax deposition test during the flow of crude oil with different components is provided, referring to Figure 1 , including an air supply tank 1, a mixing tank 2, a centrifugal pump 3, a wax deposition test system 8 and a dosing mixing tank 11; the outlet of the air supply tank 1 is connected to the mixing tank 2, the outlet of the mixing tank 2 is connected to the centrifugal pump 3, the outlet of the centrifugal pump 3 is connected to the test sample inlet 17 of the wax deposition test system 8 through a test sample input pipeline, the test sample outlet 20 of the wax deposition test system 8 is connected to the inlet of the dosing mixing tank 11 through a test sample output pipeline, the outlet of the dosing mixing tank 11 is connected to a recovery pipeline, the recovery pipeline is connected to a recovery tank 13, and the recovery pipeline is connected to the test sample input pipeline.

[0030] In a further preferred embodiment, a temperature control unit 1 6 is installed on the test sample input pipeline, and a temperature control unit 2 10 is installed on the test sample output pipeline.

[0031] Preferably, a one-way ball valve 4 and a plunger pump 5 are installed on the test sample input pipeline between the centrifugal pump 3 and the temperature control unit 6.

[0032] Preferably, a second centrifugal pump 12 is installed on the recovery pipeline between the dosing mixing tank 11 and the recovery tank 13, and a second one-way ball valve 14 is installed on the recovery pipeline between the recovery tank 13 and the test sample input pipeline.

[0033] In a further preferred embodiment, referring to Figure 2 The wax deposition test system 8 includes an upper partition 15 and a lower base plate 25 arranged in parallel, wherein the upper partition is a glass plate with pressure-bearing capacity, and a flow channel for the flow of the test sample is designed at the bottom of the upper partition 15. The two ends of the flow channel extend upward from the upper partition 15 and form a test sample inlet 17 and a test sample outlet 20; a cooling water circulation system is provided in the lower base plate 25, and the cooling water circulation system includes a cooling water channel running through the lower base plate 25, one end of the cooling water channel is a low-temperature fluid inlet end 23, and the other end of the cooling water channel is The low-temperature fluid outflow end 24 is connected; further, an upper test plate is installed on the lower surface of the upper partition 15, and a lower test plate 22, i.e., a wax deposition test plate, is detachably installed on the upper surface of the lower base plate 25. The upper test plate is a transparent glass plate, and an ultrasonic thickness measuring device 18 and an ultrasonic thickness measuring device 2 19 are respectively designed at both ends of the upper test plate to monitor the wax sample deposition thickness on the surface of the lower test plate 22 in real time, so as to analyze the influence of the wax sample deposition under different time, different pressure and different flow rate conditions in the test system on the temperature and wax deposition rate in the test system.

[0034] The lower test plate of the wax deposition test system 8 is cooled by a cooling water circulation system within the lower base plate. Cooling water passes through the base plate to lower the surface temperature, inducing deposition. It is worth noting that the cooling water of the cooling water circulation system is provided by a low-temperature coolant circulation pump. This cooling water circulation system also includes an auxiliary centrifugal pump that cooperates with the cooling water channel. The surface of the overlying test plate has been treated to have heat-insulating and oleophobic properties, which prevent wax deposits from adhering to it, thereby ensuring that wax samples will not precipitate on the surface of the overlying test plate. The transparent overlying test plate allows for direct observation of the color and other characteristics of the wax deposits. The lower test plate 22 (wax deposition test plate) can be removed, and the composition, micromorphology, and macrostructure of the wax deposits can be analyzed. In addition, by replacing the test sample on the lower test plate of the wax deposition unit, the anti-wax performance of ordinary steel pipes, coated steel pipes, and insulated steel pipes can be tested, providing a more rapid and direct evaluation of the anti-wax effectiveness of physical anti-wax measures.

[0035] Furthermore, a test sample inlet pressure detector 16 and a test sample outlet pressure detector 21 are installed at the test sample inlet 17 and the test sample outlet 20 respectively, which can monitor the pressure difference between the inlet and outlet ends and the pumping flow rate in real time, and can calculate the shear stress of the sample on the deposition surface in the deposition unit.

[0036] In a further preferred embodiment, gaskets capable of adjusting the distance between the test plates are designed between the upper test plate and the lower test plate 22 on both sides of the test sample inflow and outflow direction, and the thickness of the gaskets is 0.1-3 mm.

[0037] In another preferred embodiment, the upper test plate and the lower test plate 22 each have a swingable robotic arm on the left and right sides along the inflow to outflow direction of the test sample, and each robotic arm has a clamp for tightening or opening the upper partition 15 and the lower base plate 25 to replace the lower test plate 22.

[0038] In another preferred embodiment, a wireless temperature sensor and a wireless pressure sensor are positioned at either end of the lower test plate 22. The wireless temperature sensor is mounted 0.1-0.2 cm below the surface of the lower test plate 22, and its probe accuracy is + / - 0.15°C. Pressure measurement is performed using a wireless intelligent pressure sensor with an adjustable range of 0.1-25 MPa, with an accuracy as low as 3 Pa in the lowest range used. The pressure and temperature signals are converted into voltages and input into the control system's data acquisition module.

[0039] Furthermore, the device also includes a control system 9, and the centrifugal pump 13, one-way ball valve 14, plunger pump 5, temperature control unit 16, temperature control unit 2 10, centrifugal pump 2 12, one-way ball valve 2 14, test sample inflow end pressure detector 16, test sample outflow end pressure detector 21, ultrasonic thickness measuring device 18, ultrasonic thickness measuring device 19, and wireless temperature sensor and wireless pressure sensor on the surface of the lower test plate 22 are respectively electrically connected to the control system 9.

[0040] In the present invention, the gas supply tank 1 is mainly used to add a certain amount of required test gases such as hydrocarbons and CO2 to the test sample to realize the production fluid containing light hydrocarbons, CO2 and other associated gases in the oil well production process; the mixing tank 2 is mainly used to mix the three test media of gas (light hydrocarbons, CO2, etc.), water and oil in the test sample to restore the three-phase medium of the oil well production fluid; the centrifugal pump is mainly used to pump the oil, gas and water medium in the mixing tank to the wax deposition test system 8, the plunger pump is mainly used to pump the fluid to be tested according to the test accuracy requirements, and the dosing mixing tank 11 is mainly used to add a certain concentration of specified agents such as anti-wax agents, wax removal agents, and scale inhibitors to the fluid to be tested after the test of the wax deposition characteristics of the oil, gas and water media is completed, and the test agents are used to test the anti-wax and wax removal performance of the sample to be tested. Temperature control unit 1 6 (or temperature control unit 2) preferably includes a temperature detector (or infrared temperature probe), a temperature sensor, and a signal transmitter. The infrared temperature probe measures the temperature of the test sample inlet 17 or the test sample outlet 20, and transmits the temperature signal to the control system 9 via the signal transmitter, thereby acquiring the temperature of the test wax sample. The control system 9 logically evaluates the temperature signal collected by the infrared temperature probe and the temperature signal collected by the wireless temperature sensor on the surface of the lower test plate 22, and adjusts the temperature field of the wax deposition by adjusting the temperature of the fluid in the test sample inlet 17 and the temperature and flow rate of the coolant in the lower test plate 22.

[0041] The wax deposition pool designed in the present invention is small in size (10×20 cm, with the wax deposition test plate measuring (7-10)×(2.5-3) cm). Unlike previous large-scale wax deposition simulation tests, in which the wax content in the crude oil decreases as the test time increases, resulting in unreproducible wax deposition pattern test results, this test method has very little impact on the wax content in the oil sample. Therefore, the same oil sample can be used for multiple parameter tests, ensuring the consistency of the test sample composition and making the test results reproducible.

[0042] In a second exemplary embodiment of the present invention, a method for simulating wax deposition during the flow of crude oils with different components is provided, comprising the following steps: S1. Setting up the wax deposition test unit The wax deposition test unit includes an upper baffle 15 and a lower base plate 25 arranged in parallel above and below, a test sample inlet 17 and a test sample outlet 20 are provided in the upper baffle 15, and a flow channel extending between the test sample inlet 17 and the test sample outlet 20; an overlying test plate is installed on the lower surface of the upper baffle 15, and a lower test plate 22, i.e., a wax deposition test plate, is installed on the upper surface of the lower base plate 25; a cooling water circulation system capable of temperature control is provided under the lower part of the lower test plate 22 to achieve a low-temperature environment for the wax deposition test plate; an ultrasonic thickness measuring device 18 and an ultrasonic thickness measuring device 19 are respectively provided at the inlet and outlet ends of the overlying test plate for real-time monitoring of the wax sample deposition thickness on the surface of the wax deposition test plate, so as to analyze the influence of the wax sample deposition under different time, different pressure and different flow rate conditions in the test system on the temperature and wax deposition rate in the test system; Preferably, the upper baffle 15 and lower base plate 25 are box-like structures. The upper baffle is a surface-treated, pressure-resistant glass plate (preferably polymethyl methacrylate or high-strength glass). Oil enters the lower base plate through the flow channel for the test sample in the upper baffle, flows across the surface of the lower base plate 25 (the lower test plate), and exits at the test sample outlet 20 at the other end of the upper baffle 15. The preferred dimensions of the lower deposition plate are (7-10) × (20-30) × (2.5-3) cm. The lower test plate is a replaceable test steel plate (which can be replaced with a coated steel plate, a plated steel plate, or a steel plate with varying surface roughness depending on the actual test conditions). The upper and lower test plates 22 are designed with spacers that adjust the spacing between the test plates. The spacer thickness ranges from 0.1 mm to 2 mm. During experiments, the spacer thickness is determined by the pressure of the test sample flowing through the deposition system and the shear stress conditions on the plate surface. In addition, the distance between the overlying and lower test plates and the volume flow rate are used to determine the wall shear stress, which is proportional to the flow rate but inversely proportional to the square of the flow channel height. Therefore, orders of magnitude changes in the wall shear stress are achievable. During the test, for tests between 1 and 10 Pa, the increase in wall shear stress can be kept within 1-2 Pa, while tests at higher wall shear stresses will have greater changes. The stress increase during the test is lower than that of systems with pipe geometries. For example, when the thickness of the deposit is 150 microns, it can be continuously measured by pressure difference, and the deposit sample can be obtained at any time after the test for subsequent composition and microscopic analysis.

[0043] S2. Connect the device to simulate the wax deposition test during the flow of crude oil with different components The outlet of the gas supply tank 1 is connected to the inlet of the mixing tank 2, the outlet of the mixing tank 2 is connected to the centrifugal pump 3, the outlet of the centrifugal pump 3 is connected to the test sample inlet 17 of the wax deposition test system 8 through the test sample input pipeline, the test sample outlet 20 of the wax deposition test system 8 is connected to the inlet of the dosing mixing tank 11 through the test sample output pipeline, the outlet of the dosing mixing tank 11 is connected to the recovery pipeline, and the other end of the recovery pipeline is connected to the test sample input pipeline; and further install a one-way ball valve 4, a plunger pump 5 and a temperature control unit 6 on the test sample input pipeline, install a temperature control unit 2 10 on the test sample output pipeline, connect a recovery tank 13 on the recovery pipeline, install a centrifugal pump 2 12 on the recovery pipeline between the dosing mixing tank 11 and the recovery tank 13, and install a one-way ball valve 2 14 on the recovery pipeline between the recovery tank 13 and the test sample input pipeline; S3. Testing the wax deposition process in crude oil under different flow conditions By adjusting the spacing height between the upper test plate and the lower test plate 22 and coordinating the injection flow rate of the test sample inlet 17, the shear conditions of the fluid on the deposition plate surface are controlled to simulate the shear conditions between the wellbore and the surface fluid and the pipeline surface; During the test, the temperature field of wax deposition is regulated by adjusting the temperature of the fluid at the test sample inlet 17 and the temperature and flow rate of the coolant at the lower test plate 22; A temperature-controlled cooling water circulation system is located beneath the lower test plate 22. Cooling water is supplied by a low-temperature coolant circulation pump, increasing the flow rate to achieve a temperature difference of 0.1°C across the lower test plate. Furthermore, thermistors measure the temperature of the oil entering and leaving the sedimentation tank. The sedimentation surface temperature is measured by two additional thermistors, placed 0.23 cm below the surface of the copper plate under the pressure tap. The thermistor probes have a specified accuracy of ±0.15°C. Differential pressure measurements are performed using an intelligent pressure sensor.

[0044] S3. Study on the characteristics of waxy components: After the deposition test is completed, the clamps on both sides of the test plate are opened, the upper test plate is opened, and the lower test plate 22 is removed. The wax-like deposits on the surface of the test plate are photographed. Then, samples are taken from three locations, namely the sample inflow end, the middle part, and the sample outflow end. The samples are analyzed by gas chromatography to determine the amount of wax in the deposits and the carbon number distribution in the deposits. S4. Study on wax aging process: Using crude oil test solutions with the same wax content, varying flow rates, deposition tank temperatures, and test times yielded several different sets of test curves related to wax deposition thickness versus pressure, time, and temperature. Each curve shows how wax deposition thickness increases over time as it is deposited from the solution. After the test, wax samples were collected after different test durations for macroscopic and microscopic analysis of wax composition (primarily to simulate the wax composition characteristics after different production times within the wellbore and to investigate wax aging characteristics). During the period when wax thickness growth slowed, wax deposits were collected at different cycle lengths for component analysis to determine the timing of wax aging. This information can be used to modify the wax aging time parameters in the mathematical model of wax deposition and calculate the actual aging time of wax deposits during production. This allows for the implementation of appropriate chemical and physical wax removal measures before wax deposit aging occurs. During crude oil flow, diffusion causes wax molecules to move toward the crude oil-sediment interface, but not all molecules precipitate at the interface and form a new deposit. Some dissolved wax molecules continue to diffuse into the wax deposit, increasing the wax concentration in the deposit. This phenomenon is known as "wax aging." This is because the crystalline network formed by the wax deposits can trap liquid crude oil and form a porous medium. Once wax aging occurs, the wax components become extremely hard and dense, making wax removal extremely difficult. This has led to many oil wells experiencing sucker rods becoming stuck in the tubing, resulting in the entire tubing being scrapped. Therefore, determining the exact wax aging time is crucial for determining the timing of wax removal measures.

[0045] During the above test process, the velocity, pressure, temperature, wax deposition thickness and deposition morphology of the fluid flow in the sedimentation tank are recorded in real time, and can therefore be automatically input into the software for wax deposition law analysis.

[0046] The present invention's simulated wax deposition test method can measure wax deposition in crude oil under different flow conditions by controlling pressure and flow rate, including one under typical wellbore wall shear stress and one under higher shear stress. The temperature of both the incoming oil and the cold deposit surface can be controlled. This test method can be performed with very small oil and wax samples, with a test volume of 300-500 ml. The device can control shear conditions and temperature fields, and can measure and observe deposition height, composition, micromorphology, and macrostructure.

[0047] In summary, the present invention can test the mechanism of reducing wax deposition in test samples with different oil, gas and water ratios by adding different types of paraffin inhibitors. This method can examine the results from aspects such as the growth of sediment height, sediment composition, sediment morphology and temperature field in the sedimentation pool.

[0048] The present invention will be further described below in conjunction with the embodiments: Example 1: The wax deposition test apparatus described above for simulating the flow of crude oils with different components was used to test a model oil containing 3 wt% multi-component wax under low and high wall shear stress conditions (3-4 Pa and 20-30 Pa, respectively). The test method used was the same as the wax deposition test method described above for simulating the flow of crude oils with different components.

[0049] Adding 0.1 wt% polyethylene-butylene to the dosing tank 11 has been shown to reduce the yield stress of the gelled solution by a factor of 10, effectively increasing the initial deposition rate. However, under low shear stress conditions, the deposit eroded from the surface, while under high shear stress conditions, the deposit remained intact.

[0050] The experimental results explain the effect of wax removal agent dosage on wax deposition under various environmental conditions, including temperature and flow rates. If the surface temperature is above the cloud point, wax nucleus- and cloud-point-suppressing polymers prevent deposition. These polymers produce a deposit with sufficiently low mechanical strength that the thickness can be controlled by erosion. Gas chromatography and optical microscopy reveal the composition of the deposit.

[0051] like Figure 3 Figure 3 shows the growth of deposit height for a 3% wax solution under two stress regimes: low stress (3-4 Pa, top curve) and high stress (20-30 Pa, bottom curve). The overlay of three replicates for each stress level demonstrates the repeatability of the measurements.

[0052] Example 2: The device, which simulates the wax deposition test during the flow of crude oil with different components, was used to carry out control test and evaluation experiments.

[0053] Deposition tests were conducted with the wax deposition test system facing sideways to demonstrate that deposit growth was due to the combined effects of heat and mass transfer, rather than gravity. Deposit growth was identical in both cases. Therefore, under the conditions tested, any gravity effects in this system were insignificant. The actual thickness of the wax layer was independently measured to verify the height inferred from the pressure drop measurements. After the deposition test, the top cover was removed, and the height of the deposit was measured using a camera mounted above the surface. The camera was equipped with an adapter and objective lens. The height was determined by the difference between the focal length of the wax gel top surface and the focal length of the metal deposition surface.

[0054] Example 3: Visual observation of wax deposition was performed using a device that simulates the wax deposition test during the flow of crude oils with different components.

[0055] Testing was conducted under two flow regimes: one under typical wall shear stresses found in oil pipelines, and one under higher shear stresses. The temperatures of the incoming oil and the cold deposit surface were controlled. The results were examined in terms of deposit height growth, deposit composition, deposit morphology, and the temperature field within the sedimentation pool.

[0056] like Figure 4 As shown in Figure 2, three wax inhibitor systems were studied, and experimental results demonstrated that two of the inhibitors significantly reduced the yield stress of gelled waxy oils. The first inhibitor was based on poly(ethylene-butylene), a polymer made from butadiene. Addition ratios of 0.05-0.1 wt% were controlled, and these PEB polymers reduced the yield stress by three orders of magnitude. The second wax inhibitor system included two ethylene-vinyl acetate copolymers. Testing of the fluid yield stress revealed that these polymers provided yield stress increases ranging from 3 to 1000 times, depending on the length of the wax.

[0057] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art will be able to devise numerous other modifications and implementations without departing from the technical principles of the present invention, and these modifications and implementations will fall within the scope and spirit of the principles disclosed herein. More specifically, within the scope of the present disclosure, the drawings, and the claims, various variations and improvements may be made to the components and / or layout of the subject combination arrangement. In addition to variations and improvements to the components and / or layout, other uses will also be apparent to those skilled in the art.

Claims

1. A device for simulating wax deposition during the flow of crude oils with different components, characterized by: It includes an air supply tank, a mixing tank, a centrifugal pump, a wax deposition test system and a dosing mixing tank; the outlet of the air supply tank is connected to the mixing tank, the outlet of the mixing tank is connected to the centrifugal pump, the outlet of the centrifugal pump is connected to the test sample inlet of the wax deposition test system through a test sample input pipeline, the test sample outlet of the wax deposition test system is connected to the inlet of the dosing mixing tank through a test sample output pipeline, the outlet of the dosing mixing tank is connected to the recovery pipeline, the recovery pipeline is connected to a recovery tank, and the recovery pipeline is in communication with the test sample input pipeline.

2. The device for testing wax deposition during the flow of crude oils with different components as claimed in claim 1, characterized in that: The test sample input pipeline is installed with a first temperature control unit, and the test sample output pipeline is installed with a second temperature control unit.

3. The device for simulating wax deposition during the flow of crude oils with different components as claimed in claim 2, characterized in that: A one-way ball valve and a plunger pump are installed on the test sample input pipeline between the centrifugal pump 1 and the temperature control unit 1.

4. The device for testing wax deposition during the flow of crude oils with different components as claimed in claim 1, characterized in that: A second centrifugal pump is installed on the recovery pipeline between the dosing mixing tank and the recovery tank, and a second one-way ball valve is installed on the recovery pipeline between the recovery tank and the test sample input pipeline.

5. The device for simulating wax deposition during the flow of crude oils with different components as claimed in claim 1, characterized in that: The wax deposition test system includes an upper baffle and a lower base plate arranged in parallel. The bottom of the upper baffle is designed with a flow channel for the flow of the test sample. The two ends of the flow channel extend upward from the upper baffle and form a test sample inlet and a test sample outlet. A cooling water circulation system is provided in the lower base plate, and the cooling water circulation system includes a cooling water channel running through the lower base plate, one end of the cooling water channel is a low-temperature fluid inflow end, and the other end of the cooling water channel is connected to a low-temperature fluid outflow end; An upper test plate is installed on the lower surface of the upper partition, and a lower test plate is detachably installed on the upper surface of the lower base plate. The upper test plate is a transparent glass plate, and ultrasonic thickness measuring device 1 and ultrasonic thickness measuring device 2 are respectively designed at both ends of the upper test plate.

6. The device for testing wax deposition during the flow of crude oils with different components as claimed in claim 5, characterized in that: The upper test plate and the lower test plate are designed with gaskets on the left and right sides of the test sample in the inflow and outflow direction, which can adjust the distance between the two test plates.

7. The device for testing wax deposition during the flow of crude oils with different components as claimed in claim 5, characterized in that: The upper test plate and the lower test plate each have a swingable robotic arm on the left and right sides along the inflow to outflow direction of the test sample. Each robotic arm has a clamp for tightening or opening the upper partition and the lower base plate to facilitate replacement of the lower test plate.

8. The device for testing wax deposition during the flow of crude oils with different components as claimed in claim 1, characterized in that: The test sample inlet and the test sample outlet are respectively equipped with a test sample inflow end pressure detector and a test sample outflow end pressure detector.

9. The device for testing wax deposition during the flow of crude oils with different components according to any one of claim 5, characterized in that: A wireless temperature sensor and a wireless pressure sensor are respectively arranged at both ends of the surface of the lower test plate. The wireless temperature sensor is installed 0.1-0.2 cm below the surface of the lower test plate.

10. A method for simulating wax deposition during the flow of crude oils with different components, characterized in that: The following steps are involved: S1. Setting up the wax deposition test unit The wax deposition test unit includes an upper baffle and a lower base plate arranged in parallel above and below, a test sample inlet and a test sample outlet being provided in the upper baffle, and a flow channel extending between the test sample inlet and the test sample outlet; an overlying test plate is installed on the lower surface of the upper baffle, and a lower test plate, i.e., a wax deposition test plate, is installed on the upper surface of the lower base plate; a cooling water circulation system capable of temperature control is provided under the lower part of the lower test plate to achieve a low-temperature environment for the wax deposition test plate; an ultrasonic thickness measuring device 1 and an ultrasonic thickness measuring device 2 are respectively provided at the inlet end and the outlet end of the overlying test plate, for real-time monitoring of the wax sample deposition thickness on the surface of the wax deposition test plate, so as to facilitate analysis of the influence of the wax sample deposition under different time, different pressure, and different flow rate conditions in the test system on the temperature and wax deposition rate in the test system; S2. Testing the wax deposition process in crude oil under different flow conditions By adjusting the spacing between the upper and lower test plates and coordinating the injection velocity of the test sample inlet, the shear conditions of the fluid on the deposition plate surface are controlled to simulate the shear conditions between the wellbore and surface fluids and the pipeline surface. During the test, the temperature field of wax deposition is regulated by adjusting the temperature of the fluid flowing into the test sample and the temperature and flow rate of the cooling water under the lower test plate; S3. Study on the characteristics of waxy components: After the deposition test, the upper test plate was opened, the lower test plate was removed, and the waxy deposits on the surface of the lower test plate were photographed. Then, samples were taken from the sample inflow end, the middle part, and the sample outflow end, and the samples were analyzed by gas chromatography to determine the amount of wax in the deposits and the carbon number distribution in the deposits. S4. Study on wax aging process: Using crude oil test solutions with the same wax content, varying flow rates, deposition tank temperatures, and test times yielded several different sets of test curves related to wax deposition thickness versus pressure, time, and temperature. Each curve shows how wax deposition thickness increases over time as it is deposited from the solution. After the test is completed, wax samples deposited after different test durations are collected for macroscopic and microscopic analysis of wax components. In the time period when the wax thickness increases slowly, wax deposits of different cycle durations are collected for component analysis to clarify the wax aging time. This result can be provided in the wax deposition mathematical model to make corresponding corrections to the wax aging time parameters, which can be used to calculate the aging time of wax deposits in the actual production process, so that corresponding chemical and physical wax cleaning measures can be taken before wax deposit aging occurs during the production process.

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