Determination method for drag reduction performance of superhydrophilic coating

Abstract

This invention discloses a method for determining the drag reduction performance of a superhydrophilic coating, comprising the following steps: setting multiple different preset shear rates; setting multiple preset time periods; setting a preset spraying thickness of the superhydrophilic coating to be tested; obtaining multiple apparent viscosity benchmark values ​​of the oil sample under each preset shear rate; spraying the superhydrophilic coating of the preset spraying thickness onto the coaxial cylindrical rotor of a coaxial cylindrical viscometer, and generating a water ring on the surface of the superhydrophilic coating; obtaining multiple apparent viscosity comparison values ​​at each preset shear rate, measured by the coaxial cylindrical viscometer after being kept at a constant temperature for multiple preset time periods; for each preset shear rate, based on the comparison results of the apparent viscosity benchmark value and each apparent viscosity comparison value, determining the drag reduction performance and stability evaluation results of the superhydrophilic coating for the oil sample under that preset shear rate. This invention can effectively determine the drag reduction performance and stability of superhydrophilic coatings.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of pipeline transportation, in particular to a method for measuring drag reduction performance of super-hydrophilic coating. BACKGROUND

[0002] Water ring method is the most economical and energy-saving method for realizing drag reduction transportation of heavy oil at present, which forms a ring flow pattern with water phase as outer ring (i.e. water ring) and heavy oil as inner core, thereby blocking the direct contact of oil phase with the pipe wall, greatly reducing the transportation resistance of the system and realizing the transportation of heavy oil at room temperature.

[0003] At present, the main reason restricting the large-scale application of water ring method in oilfield production is that the stability of the formed water ring is poor, which is prone to instability during pipeline transportation, thereby reducing the drag reduction effect.

[0004] By constructing a super-hydrophilic coating on the pipe wall surface to improve the hydrophilicity of the inner surface of the pipe, the water holding capacity of the pipe wall surface can be enhanced, thereby improving the stability of the water ring, which can realize the drag reduction transportation of heavy oil. Therefore, evaluating the drag reduction performance of the super-hydrophilic coating is of great significance for the application and development of the water ring method.

[0005] According to the theoretical analysis of the prior art, the smaller the contact angle of water on the surface of the coating, the stronger the hydrophilicity of the coating, and the better the drag reduction performance. Therefore, in the prior art, the drag reduction performance of the super-hydrophilic coating is evaluated according to the contact angle and other parameters representing the wetting performance of the super-hydrophilic coating.

[0006] The inventors have found that the prior art at least has the following defects:

[0007] The contact angle and other characterization parameters of water on the surface of the super-hydrophilic coating can only indirectly infer the drag reduction performance of the super-hydrophilic coating, and the influence of factors such as flow shear and pipeline downtime in the actual pipeline application process on the drag reduction performance of the super-hydrophilic coating is not considered, so this method cannot directly evaluate the drag reduction performance of the super-hydrophilic coating and provide sufficient support for the application of the water ring method in actual production.

[0008] The information disclosed in the background section of this document is intended only to increase an understanding of the general context of the present application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art that is already widely known in the art. SUMMARY

[0009] The purpose of the present application is to obtain the drag reduction performance and stability of the super-hydrophilic coating by actual measurement.

[0010] The present application provides a method for measuring the drag reduction performance of a super-hydrophilic coating, comprising the steps of:

[0011] S11, set a plurality of different preset shear rates; set a plurality of preset time periods including a first preset time period; set a preset spraying thickness of the super-hydrophilic coating to be tested;

[0012] S12, respectively obtain a plurality of apparent viscosity reference values of the oil sample to be tested under each of the preset shear rates, which are measured by the coaxial cylinder viscometer after constant temperature for the first preset time period;

[0013] S13, spray the super-hydrophilic coating to be tested on the coaxial cylinder rotor of the coaxial cylinder viscometer in the preset spraying thickness, and generate a water ring on the surface of the super-hydrophilic coating;

[0014] S14, respectively obtain a plurality of apparent viscosity contrast values measured by the coaxial cylinder viscometer after constant temperature for a plurality of preset time periods under each of the preset shear rates;

[0015] S15, for the apparent viscosity reference value and the plurality of apparent viscosity contrast values corresponding to each of the preset shear rates, determine the drag reduction performance of the super-hydrophilic coating to be tested for the oil sample to be tested and the stability evaluation result under the preset shear rate according to the comparison results of the apparent viscosity reference value and each of the apparent viscosity contrast values.

[0016] Preferably, in the present application, it further comprises:

[0017] According to the drag reduction performance and the stability evaluation result of each of the preset shear rates, the overall drag reduction performance and the stability evaluation result of the super-hydrophilic coating to be tested are generated.

[0018] Preferably, in the present application, it further comprises:

[0019] The steps S11 to S15 are respectively implemented at a plurality of different preset temperatures.

[0020] Preferably, in the present application, it comprises:

[0021] The preset spraying thickness includes a plurality of different preset spraying thicknesses, and the steps S11 to S15 are respectively implemented at a plurality of different preset spraying thicknesses.

[0022] Preferably, in the present application, it comprises:

[0023] The minimum value of the plurality of preset time periods is the first preset time period.

[0024] Preferably, in the present application, it comprises:

[0025] The first preset time period includes 0.5 hours.

[0026] Preferably, in the present application, the plurality of apparent viscosity reference values measured by the coaxial cylinder viscometer after the first preset period of constant temperature includes:

[0027] The oil sample to be measured is subjected to heat treatment and then loaded into the sample loading cylinder of the coaxial cylinder viscometer. After being kept at a constant temperature for the first preset period of time, the apparent viscosity of the oil sample to be measured is measured.

[0028] Preferably, in the present application, the spraying of the predetermined spraying thickness of the super-hydrophilic coating on the coaxial cylinder rotor of the coaxial cylinder viscometer includes:

[0029] The super-hydrophilic coating to be measured is sprayed on the surface of the coaxial cylinder rotor at 70±10°C and cured at this temperature for 1-5h. After curing, the coaxial cylinder rotor is cooled to room temperature.

[0030] Preferably 2-3h,

[0031] Preferably, in the present application, the spraying of the predetermined spraying thickness of the super-hydrophilic coating on the coaxial cylinder rotor of the coaxial cylinder viscometer further includes:

[0032] The coaxial cylinder rotor of the coaxial cylinder viscometer, on which the apparent viscosity reference values have been measured, is subjected to ultrasonic oscillation cleaning.

[0033] Preferably, in the present application, the spraying of the predetermined spraying thickness of the super-hydrophilic coating on the coaxial cylinder rotor of the coaxial cylinder viscometer further includes:

[0034] The coaxial cylinder rotor of the coaxial cylinder viscometer, on which the apparent viscosity reference values have been measured, is placed in an oven with a temperature setting of 70±10°C for 1-2h for drying and preheating.

[0035] Preferably, in the present application, the ultrasonic oscillation cleaning includes:

[0036] The coaxial cylinder rotor is sequentially placed in acetone, anhydrous ethanol and deionized water for ultrasonic oscillation cleaning, with each solvent being cleaned for 10-20min.

[0037] Preferably, in the present application, the formation of a water ring on the surface of the super-hydrophilic coating includes:

[0038] The coaxial cylinder rotor coated with the super-hydrophilic coating is immersed in the water sample to be measured for 1-2min to form a water ring on the surface of the super-hydrophilic coating,

[0039] Preferably, in the present application, the water sample to be measured includes:

[0040] Deionized water or oilfield produced water.

[0041] Preferably, in the present application, further comprising:

[0042] At a preset shear rate, a drag reduction performance stability curve is plotted with each preset time period as the horizontal coordinate value and each apparent viscosity contrast value as the vertical coordinate value.

[0043] Preferably, in the present application, further comprising:

[0044] The ratio of the apparent viscosity reference value and the apparent viscosity contrast value corresponding to each preset shear rate is fitted to generate the overall drag reduction performance curve of the super-hydrophilic coating to be measured.

[0045] Compared with the prior art, the present application has the following beneficial effects:

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application and to implement the content of the specification, and in order to make the above and other purposes, technical features and advantages of the present application more easily understood, one or more preferred embodiments are described in detail below, and are described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is a step diagram of the super-hydrophilic coating drag reduction performance measurement method in the present application;

[0049] Figure 2 is a step diagram of the super-hydrophilic coating drag reduction performance measurement method in the present application; DETAILED DESCRIPTION

[0050] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments.

[0051] Unless otherwise explicitly stated, throughout the specification and claims, the term "comprise" or its variants such as "comprises" or "comprising" will be understood to include the stated element or component, but not to exclude other elements or components.

[0052] In this document, the terms "lower", "bottom", "bottom", "upper", "top", and the like can be used to describe a relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the object in use or operation in addition to the orientations depicted in the figures. For example, if an object in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of below and above. The object can also be oriented in other ways (rotated 90 degrees or at other orientations) and the spatially relative terms used herein should be interpreted accordingly.

[0053] In this document, the terms "first", "second", and the like are used to distinguish two different elements or parts, and are not intended to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", and the like can be interchangeable with each other.

[0054] Embodiment one

[0055] In order to achieve the evaluation results of the drag reduction performance and stability of the super-hydrophilic coating by actual measurement, as shown in the present application, a super-hydrophilic coating drag reduction performance measurement method is provided, comprising the steps of: Figure 1

[0056] S11, set a plurality of different preset shear rates; set a plurality of preset time periods including a first preset time period; set the preset spraying thickness of the super-hydrophilic coating to be measured;

[0057] The inventive idea of the present application includes: using the viscosity measurement means of the coaxial cylinder viscometer, comparing the apparent viscosity of the oil sample to be measured on the clean coaxial cylinder rotor with the apparent viscosity of the oil sample to be measured after spraying the super-hydrophilic coating to be measured on the coaxial cylinder rotor, and then combining the change amplitude (or, change trend) of the apparent viscosity of the coaxial cylinder rotor after spraying the super-hydrophilic coating to be measured on the coaxial cylinder rotor at different time periods to generate a quantitative measurement result; Since the apparent viscosity of the super-hydrophilic coating is directly negatively correlated with its drag reduction performance, it can be used to measure the drag reduction performance and stability of the super-hydrophilic coating to be measured.

[0058] In order to ensure the accuracy of the measurement results, the measurement environment (also referred to as the experimental environment) in the present application is preferably a constant temperature environment.

[0059] ​In the embodiment of the present application, when measuring the apparent viscosity, the apparent viscosity of the oil sample to be measured under a plurality of different preset shear rates needs to be measured respectively. The embodiment of the present application sets a plurality of different preset shear rates, and the setting mode is simultaneously applied to measuring the apparent viscosity of the oil sample to be measured on a clean coaxial cylinder rotor and measuring the apparent viscosity of the coaxial cylinder rotor after spraying the super-hydrophilic coating to be measured. It should be noted that in actual application, the specific number of preset shear rates can be set by the person skilled in the art according to the actual situation of the fluid shear rate in the pipeline during pipeline transportation, and the specific number is not limited herein.

[0060] In the embodiment of the present application, a plurality of different preset shear rates are set because the inventors have found through research that the flow rate of the fluid in the pipeline changes with the change of the oil well production in the actual production process, and the change of the flow rate causes the change of the average shear rate in the pipeline. Therefore, measuring the apparent viscosity under different shear rates can provide apparent viscosity data suitable for different production and fluid flow rates for guiding the actual production. At the same time, setting a plurality of preset shear rates can also test the drag reduction characteristics of the super-hydrophilic coating under different shear conditions, because the following situation may occur: with the continuous increase of the shear rate, the shear effect is enhanced, which causes the poor stability of the water ring, and further causes the increase of the apparent viscosity obtained by the test, which indicates that the drag reduction performance of the super-hydrophilic coating is poor. Therefore, it is necessary to understand the adaptability of the super-hydrophilic coating to different shear rates.

[0061] In the embodiment of the present application, when measuring the apparent viscosity, a plurality of preset time periods need to be set to obtain the apparent viscosity of the coaxial cylinder rotor after spraying the super-hydrophilic coating to be measured for different time periods. In addition, when the super-hydrophilic coating is not used, the apparent viscosity measured by the coaxial cylinder rotor does not change significantly after a certain period of time with the extension of the constant temperature time. Therefore, when measuring the apparent viscosity of the oil sample to be measured on the clean coaxial cylinder rotor, only the measurement data at one time point (i.e. the first preset time period) is needed. When measuring the apparent viscosity of the coaxial cylinder rotor after spraying the super-hydrophilic coating to be measured, the apparent viscosities at the time points corresponding to a plurality of preset time periods (including the first preset time period) need to be obtained. In actual application, the first preset time period can be 0.5h, and the specific setting of the plurality of preset time periods can be set by the person skilled in the art according to the actual situation of the pipeline shutdown time, and the specific number is not limited herein.

[0062] In the embodiment of the present application, the purpose of setting the preset spraying thickness of the super-hydrophilic coating to be measured is to unify the standard and obtain more objective and accurate measurement results, and to provide a basis for the best spraying thickness of the super-hydrophilic coating when the super-hydrophilic coating is used for water ring method transportation in the actual pipeline.

[0063] S12, respectively, obtain a plurality of apparent viscosity reference values of the oil sample to be measured at each preset shear rate, which are measured by the coaxial cylinder viscometer after constant temperature for the first preset time period;

[0064] The specific manner of the step can be that the oil sample to be measured is loaded into the sample loading cylinder of the coaxial cylinder viscometer after heat treatment, and the apparent viscosity of the oil sample to be measured is measured after constant temperature for the first preset time period.

[0065] In actual application, the process of measuring the apparent viscosity of the oil sample to be measured on the coaxial cylinder rotor without the sprayed super-hydrophilic coating can further include a step of heat treatment of the oil sample to be measured, specifically: the oil sample to be measured is placed in a sealed container, and then the container is heated to 80℃ in a constant temperature bath for heat treatment for 1h; the constant temperature here refers to a fixed environmental temperature set when measuring the apparent viscosity, and the constant temperature for the first preset time period can make the temperature of the oil sample to be measured consistent with the set temperature when measuring the apparent viscosity.

[0066] The purpose of the step is to determine the reference viscosity (i.e., the apparent viscosity reference value) of the oil sample to be measured. When the oil sample to be measured is a non-Newtonian fluid at the measurement temperature, different shear rates will have different apparent viscosities. Therefore, in the embodiment of the present application, it is necessary to measure the apparent viscosity reference value corresponding to each preset shear rate. That is, the reference viscosity of the oil sample to be measured corresponding to each preset shear rate is measured at the same environmental temperature (i.e., the measurement temperature).

[0067] In actual application, the method of recording the apparent viscosity test data can be implemented in accordance with the standard SY / T 0520-2008.

[0068] Further, the embodiment of the present application can further set a plurality of different measurement temperatures to measure the reference viscosity of the oil sample to be measured corresponding to each preset shear rate at different measurement temperatures.

[0069] S13, spraying the super-hydrophilic coating to be measured on the coaxial cylinder rotor of the coaxial cylinder viscometer in the preset spraying thickness, and generating a water ring on the surface of the super-hydrophilic coating;

[0070] In the embodiment of the present application, it is also necessary to simulate the oil pipeline with a generated water ring by using the coaxial cylinder rotor, specifically by spraying the super-hydrophilic coating to be measured on the coaxial cylinder rotor, and then immersing it in the water sample to be measured after cooling, so as to form a water ring on the surface of the super-hydrophilic coating, as shown in Figure 2 The specific steps can include:

[0071] S21, sequentially placing the coaxial cylinder rotor of the coaxial cylinder viscometer into acetone, anhydrous ethanol and deionized water for ultrasonic oscillation cleaning; preferably, the cleaning time of each solvent can be 10-20min;

[0072] In order to keep the consistency of the surface state of the coaxial cylinder rotor during the determination process, the same coaxial cylinder rotor can be used in the embodiment of the present application, and the coaxial cylinder rotor is cleaned after determining each apparent viscosity reference value, so as to prepare for spraying the super-hydrophilic coating to be measured.

[0073] S22, placing the coaxial cylinder rotor into an oven with a temperature of 70±10°C for 1-2h for drying and preheating;

[0074] S23, spraying the super-hydrophilic coating to be measured on the surface of the coaxial cylinder rotor at 70±10°C, and curing for 1-5h, preferably 2-3h, and then cooling the coaxial cylinder rotor to room temperature;

[0075] S24, setting the temperature of the coaxial cylinder viscometer constant temperature circulation system to the set temperature, and loading the oil sample to be measured after heat treatment into the loading cylinder of the coaxial cylinder viscometer, and keeping the temperature constant for n (n≥0.5)h;

[0076] S25, immersing the coaxial cylinder rotor sprayed with the super-hydrophilic coating to be measured into the water sample to be measured for 1-2min to form a water ring on the surface of the super-hydrophilic coating, and then connecting the coaxial cylinder rotor with the coaxial cylinder viscometer.

[0077] In actual application, the water sample to be measured can be deionized water, and in addition, can be oilfield produced water which is more close to the actual working condition of the water ring of the oil pipeline.

[0078] S14, obtaining a plurality of apparent viscosity contrast values measured by the coaxial cylinder viscometer after constant temperature for a plurality of preset time periods at each preset shear rate;

[0079] After the water ring is formed on the super-hydrophilic coating, the drag reduction performance thereof will decrease with the extension of time, that is, the apparent viscosity thereof will increase accordingly with the extension of time; therefore, in the embodiment of the present application, a plurality of preset time periods are provided to obtain the apparent viscosity contrast values at different preset shear rates at different time points.

[0080] S15, for the apparent viscosity reference value corresponding to each preset shear rate and the plurality of apparent viscosity contrast values, determining the drag reduction performance of the super-hydrophilic coating to be measured on the oil sample to be measured and the stability evaluation result at the preset shear rate according to the comparison results of the apparent viscosity reference value and each apparent viscosity contrast value.

[0081] By comparing the apparent viscosity benchmark value with the apparent viscosity comparison value corresponding to the first preset time period, the peak value of the drag reduction performance of the superhydrophilic coating at the initial use time of the water ring can be obtained; then, by comparing the apparent viscosity values ​​corresponding to multiple subsequent preset time periods, the stability of the drag reduction performance of the superhydrophilic coating can be further determined.

[0082] In practical applications, the ratio of the apparent viscosity baseline value to the apparent viscosity comparison value can be used as an indicator of drag reduction performance. Based on this indicator value, the peak data of the drag reduction performance of the superhydrophilic coating can be determined. In addition, a curve can be generated with each preset time period as the horizontal axis and each apparent viscosity comparison value as the vertical axis to characterize the trend of the drag reduction performance of a certain superhydrophilic coating decreasing over time. This curve can also be used to determine the time interval during which each superhydrophilic coating maintains stable drag reduction performance.

[0083] Preferably, embodiments of the present invention may further include the following steps:

[0084] S16. Based on the drag reduction performance and stability evaluation results of each preset shear rate, generate the overall drag reduction performance and stability evaluation results of the superhydrophilic coating to be tested.

[0085] The drag reduction performance and stability evaluation results obtained in step S15 are the evaluation results of the drag reduction performance and stability of the superhydrophilic coating under a single preset shear rate; by combining the drag reduction performance and stability evaluation results of each preset shear rate, the overall drag reduction performance and stability evaluation results of the superhydrophilic coating under test can be obtained.

[0086] Specifically, it could be:

[0087] At a preset shear rate, plot the drag reduction performance stability curve with each preset time period as the x-axis value and each apparent viscosity comparison value as the y-axis value.

[0088] Furthermore, after obtaining the apparent viscosity reference value and apparent viscosity comparison value obtained after being constant temperature for a first preset period for each preset shear rate, the process may further include: fitting the ratio of the apparent viscosity reference value and apparent viscosity comparison value obtained after being constant temperature for a first preset period for each preset shear rate to generate the overall drag reduction performance curve of the superhydrophilic coating to be tested.

[0089] It should be noted that, according to the embodiments of the present invention, in addition to calculating the ratio and plotting the curve, there are many other ways to quantify the drag reduction performance of the superhydrophilic coating on the oil sample by comparing the apparent viscosity reference value with the apparent viscosity comparison value. Those skilled in the art can use existing technical means in the field to achieve this according to actual needs, and no specific limitation is made here on these existing technical means.

[0090] In summary, compared to existing technologies that derive a theoretical drag-reduction performance of superhydrophilic coatings through derivation, the embodiments of this invention can measure the changes and trends in drag-reduction performance of superhydrophilic coatings under different shear conditions and usage times. Therefore, it is possible to effectively measure the drag-reduction performance and stability of superhydrophilic coatings, thereby obtaining evaluation results that are more instructive for practical production applications. This provides a theoretical basis for determining crude oil flow rate and pipeline safe shutdown time when using water ring transportation with superhydrophilic coatings in oilfield production. Consequently, it will have a positive effect on promoting the widespread application and development of the water ring method in oil pipelines.

[0091] Example 2

[0092] The technical solution in Example 1 measures the drag reduction performance of a superhydrophilic coating by measuring the results of a test oil sample at a set constant temperature. Based on this, the embodiments of the present invention can also set multiple constant temperatures to simulate different actual working environment temperatures of oil pipelines. By implementing steps S11 and S15 as in Example 1 at each different preset temperature, the drag reduction performance and stability evaluation results of the superhydrophilic coating under test at different working temperatures or the overall drag reduction performance and stability evaluation results can be obtained.

[0093] In practical applications, the specific number and value of preset temperatures can be determined by those skilled in the art as needed, and no specific limitations are made here.

[0094] Example 3

[0095] Based on Embodiment 1 and Embodiment 2, the embodiments of the present invention can further set multiple coating thicknesses, and by implementing steps S11 to S15 as in Embodiment 1 under each different coating thickness, determine the drag reduction performance and stability evaluation results or the overall drag reduction performance and stability evaluation results of the superhydrophilic coating under different preset coating thicknesses.

[0096] In practical applications, the specific number and value of the coating thickness can be determined by those skilled in the art as needed, and no specific limitations are made here.

[0097] In one embodiment of the present invention, the specific implementation steps can be as follows:

[0098] S31. Prepare 500ml of the oil sample to be tested and put it into a sealed container. Place the sealed container in a constant temperature bath with the temperature set at 80℃ for heat treatment for 1 hour.

[0099] S32. Set the temperature of the coaxial cylindrical viscometer constant temperature circulation system to 50℃, load the heat-treated oil sample into the sample cylinder of the coaxial cylindrical viscometer, and then keep the oil sample at 50℃.

[0100] Isothermal operation allows for sufficient heat exchange between the oil sample and the sample container, thereby raising the temperature of the oil sample to the experimentally set 50°C. For determination processes without the use of a superhydrophilic coating, since the temperature of the oil sample can reach the set temperature within 0.5 hours, and its apparent viscosity does not change with the extension of isothermal time, the isothermal time can be controlled at 0.5 hours.

[0101] S33. Set the shear rates to 30s⁻¹, 50s⁻¹, and 70s⁻¹, start the coaxial cylindrical viscometer, measure the apparent viscosity of the oil sample, and record the data.

[0102] S34. Change the measurement temperature to 60℃ and 70℃ in sequence, and repeat the operations of S32 and S33 to obtain the reference values ​​of apparent viscosity at different temperatures (50℃, 60℃, 70℃) and different shear rates (30s-1, 50s-1, 70s-1).

[0103] S35. The purpose of determining the apparent viscosity baseline value is to provide a benchmark for subsequent measurements using the superhydrophilic coating. If, under the same conditions, the measured apparent viscosity value after applying the superhydrophilic coating is less than the apparent viscosity baseline value, it indicates that the superhydrophilic coating has good drag reduction performance. Therefore, after obtaining the apparent viscosity baseline value, the strength of the drag reduction performance of the superhydrophilic coating can be evaluated by spraying a superhydrophilic coating onto the surface of the coaxial cylindrical rotor and then conducting an apparent viscosity test.

[0104] Before applying the superhydrophilic coating, the surface of the coaxial cylindrical rotor must first be cleaned. The cleaning method involves immersing the coaxial cylindrical rotor in acetone, anhydrous ethanol, and deionized water in sequence for ultrasonic cleaning, with each solvent cleaning for 15 minutes.

[0105] S36. After cleaning the coaxial cylindrical rotor, place the rotor in an oven with the temperature set at 70℃ for drying and preheating to ensure that the rotor surface is clean and dry. The drying and preheating time is 2 hours.

[0106] S37. Prepare a superhydrophilic coating. Spray the superhydrophilic coating at 70°C onto the surface of the coaxial cylindrical rotor that contacts the oil sample to be tested, forming a superhydrophilic coating with a thickness of 0.8 mm. Then, place the coaxial cylindrical rotor back into an oven set at 70°C for curing the superhydrophilic coating for 3 hours. After curing, remove the coaxial cylindrical rotor from the oven and allow it to cool naturally to room temperature.

[0107] S38. Set the temperature of the coaxial cylindrical viscometer's isothermal circulation system to 50℃. Load the heat-treated oil sample into the sample container of the coaxial cylindrical viscometer, and then maintain the oil sample at 50℃ for isothermal testing. For measurements using a superhydrophilic coating, extending the isothermal time may affect the obtained apparent viscosity measurement, resulting in the following two situations:

[0108] (1) When the superhydrophilic coating has a strong water retention capacity, the water ring formed on its surface has a strong stability. Therefore, the surface water ring will not become unstable after the constant temperature time is extended, and the apparent viscosity does not change significantly with the extension of the constant temperature time.

[0109] (2) When the superhydrophilic coating has insufficient water retention capacity, the stability of the water ring formed on its surface is weak. After the isothermal time is extended, the surface water ring will become unstable, which is manifested as the apparent viscosity increasing with the extension of the isothermal time.

[0110] Therefore, for experiments using superhydrophilic coatings, different isothermal times (i.e., multiple preset time periods) can be selected for subsequent apparent viscosity measurements to obtain the variation law of apparent viscosity under each preset time period, and ultimately obtain the stability of the drag reduction performance of the superhydrophilic coating. When the apparent viscosity does not change much with the extension of isothermal time, it indicates that the drag reduction performance of the superhydrophilic coating is relatively stable, which is more beneficial to actual oilfield production. In this example, for the apparent viscosity measurement experiment using the superhydrophilic coating, the preset time periods were 0.5h, 4h, and 8h, respectively.

[0111] S39. Superhydrophilic coatings only exhibit drag-reducing properties after a water ring forms on their surface. Before testing the drag-reducing performance of a superhydrophilic coating, a water ring must first be formed on its surface. Therefore, the portion of a coaxial cylindrical rotor coated with the superhydrophilic coating, cooled to room temperature, is immersed in the water sample to be tested for 1.5 minutes to promote the formation of the surface water ring. The water sample can be selected according to experimental requirements; deionized water or oilfield produced water can be used. After the water ring is formed, the coaxial cylindrical rotor is connected to a viscometer.

[0112] S40, set the shear rates to 30s⁻¹, 50s⁻¹ and 70s⁻¹, start the coaxial cylindrical viscometer, measure the apparent viscosity of the sample and record the data;

[0113] S41: Change the temperature to 60℃ and 70℃ in sequence, and change the isothermal time to 4h and 8h in sequence. Repeat the operations of S32 to S40 to obtain the comparison values ​​of apparent viscosity at different temperatures (50℃, 60℃, 70℃), different shear rates (30s-1, 50s-1, 70s-1), and different isothermal times (0.5h, 4h, 8h) after the presence of the superhydrophilic coating and the formation of a surface water ring.

[0114] S42: Compare the apparent viscosity values ​​obtained in step S41 at different temperatures (50℃, 60℃, 70℃) and different shear rates (30s⁻¹, 50s⁻¹, 70s⁻¹) with the baseline apparent viscosity values ​​obtained in step S34 to determine the drag reduction performance of the superhydrophilic coating. Compare the apparent viscosity values ​​obtained in step S41 at different isothermal times (0.5h, 4h, 8h) to determine the stability of the drag reduction performance of the superhydrophilic coating.

[0115] In this example, two types of superhydrophilic coatings, superhydrophilic coating A and superhydrophilic coating B, were used for experimental determination. The measured baseline value of apparent viscosity and the comparison value of apparent viscosity of superhydrophilic coatings A and B are shown in Table 1.

[0116] Table 1: Results of drag reduction effect measurement of superhydrophilic coatings A and B

[0117]

[0118]

[0119] As shown in Table 1, the apparent viscosity comparison values ​​of superhydrophilic coatings A and B are both much smaller than the benchmark value, indicating that both superhydrophilic coatings have good drag reduction performance. In comparison, the apparent viscosity comparison value of superhydrophilic coating A is smaller than that of superhydrophilic coating B, therefore, the drag reduction performance of superhydrophilic coating A is better than that of superhydrophilic coating B.

[0120] Next, the apparent viscosity comparison values ​​of superhydrophilic coating A and superhydrophilic coating B under different isothermal times (multiple preset time periods) are shown in Table 2.

[0121] Table 2: Results of the stability test of drag reduction effect of superhydrophilic coatings A and B at 50℃

[0122]

[0123] As shown in Table 2, the apparent viscosity of superhydrophilic coating A did not change significantly with the extension of isothermal time, while the apparent viscosity of superhydrophilic coating B increased significantly with the extension of isothermal time. Therefore, the drag reduction performance of superhydrophilic coating A is more stable than that of superhydrophilic coating B.

[0124] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the drag reduction performance of a super-hydrophilic coating for determining the flow rate of crude oil and the safe shutdown time of a pipeline during the production process in an oil field using a water ring method for transporting crude oil with the aid of a super-hydrophilic coating, characterized in that, The method comprises the steps of: S11, setting a plurality of different preset shear rates; setting a plurality of preset time periods including a first preset time period; setting a preset spraying thickness of the super-hydrophilic coating to be tested; S12, obtaining a plurality of apparent viscosity reference values of the oil sample to be tested under each preset shear rate, which are measured by the coaxial cylinder viscometer after constant temperature for the first preset time period; S13, spraying the super-hydrophilic coating to be tested on the coaxial cylinder rotor of the coaxial cylinder viscometer in the preset spraying thickness, and generating a water ring on the surface of the super-hydrophilic coating; S14, obtaining a plurality of apparent viscosity contrast values measured by the coaxial cylinder viscometer after constant temperature for a plurality of preset time periods under each preset shear rate; S15, for the apparent viscosity reference value and the plurality of apparent viscosity contrast values corresponding to each preset shear rate, determining the drag reduction performance of the super-hydrophilic coating to be tested on the oil sample to be tested and the stability evaluation result under the preset shear rate according to the comparison results of the apparent viscosity reference value and each apparent viscosity contrast value; S16, under a preset shear rate, drawing a drag reduction performance stability curve with each preset time period as the horizontal coordinate value and each apparent viscosity contrast value as the vertical coordinate value; S17, fitting the ratio of the apparent viscosity reference value measured by the coaxial cylinder viscometer after constant temperature for the first preset time period to the apparent viscosity contrast value corresponding to each preset shear rate, and generating an overall drag reduction performance curve of the super-hydrophilic coating to be tested.

2. The method of drag reduction performance determination of superhydrophilic coating according to claim 1, characterized in that, Further comprising: According to the drag reduction performance and the stability evaluation result of each preset shear rate, the overall drag reduction performance and the stability evaluation result of the super-hydrophilic coating to be tested are generated.

3. The method of claim 2, wherein the drag reduction performance of the superhydrophilic coating is determined by, Further comprising: The steps S11 to S15 are respectively implemented under a plurality of different preset temperatures.

4. The method of claim 2, wherein the drag reduction performance of the superhydrophilic coating is determined by, Including: The preset spraying thickness includes a plurality of, and the steps S11 to S15 are respectively implemented under a plurality of different preset spraying thicknesses.

5. The method of claim 2, wherein the drag reduction performance of the superhydrophilic coating is determined by, Including: The minimum value of the plurality of preset time periods is the first preset time period.

6. The method of drag reduction performance determination of superhydrophilic coating according to claim 1, characterized in that, Including: The first preset time period includes 0.5 hours.

7. The method of drag reduction performance determination of superhydrophilic coating according to claim 1, characterized in that, The plurality of apparent viscosity reference values measured by the coaxial cylinder viscometer after constant temperature for the first preset time period include: After the oil sample to be tested is heat-treated, it is loaded into the sample loading cylinder of the coaxial cylinder viscometer, and after constant temperature for the first preset time period, the apparent viscosity of the oil sample to be tested is measured.

8. The method of drag reduction performance determination of superhydrophilic coating according to claim 1, characterized in that, The step of spraying the super-hydrophilic coating to be tested on the coaxial cylinder rotor of the coaxial cylinder viscometer in the preset spraying thickness includes: The super-hydrophilic coating to be tested is sprayed on the surface of the coaxial cylinder rotor at 70±10ºC, and is cured at this temperature for 1-5h, and after curing, the coaxial cylinder rotor is cooled to room temperature.

9. The method of drag reduction performance determination of superhydrophilic coating according to claim 1, wherein, The step of spraying the super-hydrophilic coating to be tested on the coaxial cylinder rotor of the coaxial cylinder viscometer in the preset spraying thickness further includes: The coaxial cylinder rotor of the coaxial cylinder viscometer on which the apparent viscosity reference value is measured is ultrasonically oscillated and cleaned.

10. The method of drag reduction performance determination of superhydrophilic coating according to claim 1, characterized in that, The step of spraying the super-hydrophilic coating to be tested on the coaxial cylinder rotor of the coaxial cylinder viscometer in the preset spraying thickness further includes: The coaxial cylinder rotor of the coaxial cylinder viscometer, whose apparent viscosity benchmark value is determined, is placed in an oven with a temperature setting of 70±10ºC for 1-2h for drying and preheating.

11. The method of drag reduction performance determination of superhydrophilic coating according to claim 9, characterized in that, The ultrasonic oscillation cleaning comprises: The coaxial cylinder rotor is sequentially placed in acetone, anhydrous ethanol and deionized water for ultrasonic oscillation cleaning, 10-20min for each solvent.

12. The method of drag reduction performance determination of superhydrophilic coating according to claim 9, wherein, The water ring generated on the surface of the super-hydrophilic coating comprises: The coaxial cylinder rotor coated with the super-hydrophilic coating is immersed in the water sample to be tested for 1-2min, and a water ring is formed on the surface of the super-hydrophilic coating.

13. The method of drag reduction performance determination of superhydrophilic coating according to claim 12, characterized in that, The water sample to be tested comprises: Deionized water or oilfield produced water.

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