Testing device for lowest flowable temperature of mixed transportation pipeline and use method

Abstract

The invention relates to the technical field of oil-gas-water three-phase mixed transportation fluid condensation point experimental testing, in particular to a device for testing the lowest flowable temperature of a mixed transportation pipeline and a using method. The device comprises a water bath box, a coil pipe, a first pressure sensor, a second pressure sensor, an ultrasonic measuring module, a temperature adjusting device and a control unit; and a plurality of coils are coiled in the water bath box. The device is reasonable and compact in structure, during use, mixed liquid of water and methanol is injected into the water bath box, the coil pipe is immersed in the mixed liquid of water and methanol, and the temperature adjusting device is arranged, so that cooling capacity can be provided for the mixed liquid in the water bath box, the temperature of the mixed liquid is reduced, and the service life of the water bath box is prolonged. The ultrasonic transmission time of fluid in the coil pipe can be measured by arranging the ultrasonic transmitting probe, the ultrasonic receiving probe and the ultrasonic measuring module, one-way flowing of all fluid is guaranteed by arranging the one-way valve, and the minimum flowable temperature of mixed transportation fluid on site under multiple influence factors can be accurately measured.

Description

Technical Field

[0001] The invention relates to the technical field of experimental testing of condensation point of oil, gas and water three-phase mixed transmission fluid, and is a testing device and a use method of the minimum flowable temperature of a mixed transmission pipeline. Background Art

[0002] The exploration and development of oil and gas fields has gradually expanded to areas with harsh natural environments such as oceans, deserts, and polar regions. These areas are difficult to carry out three-phase oil, gas, and water transportation due to the difficulty and high cost of pipeline laying, so the transportation method of three-phase oil, gas, and water is mostly adopted. Through field tests, it was found that the fluid in the three-phase mixed pipeline can be normally transported under conditions lower than the freezing point of crude oil, that is, the minimum flowable temperature of the fluid under mixed conditions is lower than the freezing point of crude oil. At present, there is no quantitative test experimental device for the minimum flowable temperature, and no perfect mechanism explanation for the minimum flowable temperature of the mixed pipeline is lower than the freezing point of crude oil has been proposed at home and abroad. It can be seen from field experience that the minimum flowable temperature of the mixed pipeline is affected by shear rate, gas-oil ratio, water content, and freezing point. In order to study this problem, it is necessary to measure the minimum flowable temperature data of the mixed pipeline under a large number of different influencing factors. However, since the experiment has very strict requirements on fluid temperature control, it is impossible to carry out experiments directly on the field pipeline. Therefore, this patent designs an experimental device for testing the minimum flowable temperature of the pipeline. Summary of the invention

[0003] The present invention provides a testing device and a method for the minimum flowable temperature of a mixed pipeline, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that when acquiring the minimum flowable temperature data of the mixed pipeline under different influencing factors, it is difficult to conduct experiments directly on the on-site pipeline due to the strict requirements of the experiment on fluid temperature control.

[0004] One of the technical solutions of the present invention is achieved through the following measures: a test device for the minimum flowable temperature of a mixed pipeline, comprising a water bath, a coil, a first pressure sensor, a second pressure sensor, an ultrasonic measurement module, a temperature regulating device and a control unit, wherein a plurality of coils are wound in the water bath, the first end of the coil is sealed to pass through the left rear portion of the water bath, the second end of the coil is sealed to pass through the left front portion of the water bath, a one-way valve is provided on the coil, an ultrasonic transmitting probe and an ultrasonic receiving probe are symmetrically installed on the outer side of the coil corresponding to the position between the one-way valve and the discharge valve, the lower end of the first pressure sensor is sealed to pass through the upper side of the water bath and then installed on the coil between the one-way valve and the left inner wall of the water bath, the lower end of the second pressure sensor is sealed to pass through the upper side of the water bath and then installed on the coil between the ultrasonic transmitting probe and the left inner wall of the water bath, a radiator is provided in the center of the coil, the radiator is connected to the temperature regulating device, a temperature sensor is installed on the upper right side of the water bath, the ultrasonic transmitting probe and the ultrasonic receiving probe are both connected to the ultrasonic measurement module, and the control unit is respectively connected to the first pressure sensor, the second pressure sensor, the ultrasonic measurement module, the temperature sensor and the temperature regulating device.

[0005] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0006] The above may also include a multiphase flow pump and a sampler, the outlet of the multiphase flow pump is fixedly connected to the first end of the coil, a sampling tube is fixedly connected between the inlet of the multiphase flow pump and the tubular structure sampler, a sampling valve is installed on the sampling tube, the second end of the coil is fixedly connected to a sample outlet tube, a discharge valve is installed on the sample outlet tube, and the multiphase flow pump is connected to the control unit.

[0007] The outer side of the middle part of the sampler may be evenly spaced along the circumference with four internally and externally connected sampling holes, and a sampling branch pipe is fixedly connected between each sampling hole and the end of the sampling tube away from the multiphase flow pump.

[0008] The outer side of the water bath may be provided with a protective shell, and the inner side of the protective shell and the inner side of the water bath may be filled with a heat-insulating layer.

[0009] The second technical solution of the present invention is achieved by the following measures: a method for using a testing device for the minimum flowable temperature of a mixed pipeline, characterized by comprising the following steps:

[0010] Step 1: Close the sampling valve and the discharge valve, and connect the sampler and the sample outlet pipe to the oil outlet pipeline of the single well;

[0011] Step 2: Add a mixture of water and methanol into the water bath;

[0012] Step 3: Open the sampling valve and the discharge valve, start the multiphase flow pump, control the speed of the multiphase flow pump, and deliver the fluid with the set shear rate into the coil;

[0013] Step 4: The control unit controls the temperature regulating device to operate so that the temperature of the mixed liquid in the water bath decreases at a set rate;

[0014] Step 5: The ultrasonic measurement module transmits ultrasonic waves into the coil through the ultrasonic transmitting probe, and the ultrasonic receiving probe receives the ultrasonic waves transmitted by the ultrasonic transmitting probe and feeds them back to the ultrasonic measurement module. The ultrasonic measurement module measures the propagation time of the ultrasonic waves in the mixed fluid in the coil. When the propagation time of the ultrasonic waves from the ultrasonic transmitting probe to the ultrasonic receiving probe changes, the temperature sensor data at this time is T1;

[0015] When the data of the first pressure sensor and the second sensor suddenly change, the temperature sensor data at this time is T2;

[0016] The smaller value between T1 and T2 is the minimum flowable temperature of the mixed pipeline.

[0017] The following is a further optimization and / or improvement of the second technical solution of the above invention:

[0018] The temperature of the mixed solution in the water bath was decreased at a rate of 0.1°C / min.

[0019] The above step 1 is specifically as follows: add pure water from the sampler, open the multiphase flow pump and the discharge valve to flush the coil, introduce dry nitrogen after the flushing is completed, discharge and dry the liquid in the coil, close the sampling valve and the discharge valve, and fix the sampler and the sample outlet pipe to the oil outlet pipeline of the single well.

[0020] The invention has a reasonable and compact structure. When in use, a mixed liquid of water and methanol is added into a water bath, and the coil is immersed in the mixed liquid of water and methanol. By arranging a temperature regulating device, cooling capacity can be provided for the mixed liquid in the water bath, thereby reducing the temperature of the mixed liquid. By arranging an ultrasonic transmitting probe, an ultrasonic receiving probe, and an ultrasonic measuring module, the ultrasonic propagation time of the fluid in the coil can be measured. By arranging a one-way valve, it is ensured that all fluids flow in one direction, and the lowest flowable temperature of the mixed fluid on site under multiple influencing factors can be accurately measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Attached Figure 1 It is a schematic diagram of the top cross-sectional structure of the first embodiment.

[0022] Attached Figure 2 It is a schematic diagram of the main cross-sectional structure of the sampler in Example 1.

[0023] Attached Figure 3 This is a circuit block diagram of Embodiment 1.

[0024] Attached Figure 4 It is a schematic diagram of the main cross-sectional structure of the coil in Example 2.

[0025] The codes in the accompanying drawings are: 1 is a water bath, 2 is a coil, 3 is a sampling tube, 4 is a multiphase flow pump, 5 is an ultrasonic measurement module, 6 is an ultrasonic transmitting probe, 7 is an ultrasonic receiving probe, 8 is a temperature regulating device, 9 is a radiator, 10 is a sampler, 11 is a sampling valve, 12 is a sample outlet tube, 13 is a discharge valve, 14 is a one-way valve, 15 is a first pressure sensor, 16 is a second pressure sensor, 17 is a sampling branch pipe, 18 is a temperature sensor, 19 is a protective shell, and 20 is an insulation layer. DETAILED DESCRIPTION

[0026] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0027] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The positional relationships such as front, back, top, bottom, left, and right are described according to the layout directions of the drawings in the specification.

[0028] The present invention will be further described below in conjunction with embodiments and drawings:

[0029] Embodiment 1: As shown in the attached Figure 1 , 2 As shown in Figure 3, the test device for the minimum flowable temperature of the mixed pipeline includes a water bath 1, a coil 2, a first pressure sensor 15, a second pressure sensor 16, an ultrasonic measurement module 5, a temperature adjustment device 8 and a control unit. A plurality of coils 2 are wound in the water bath 1. The first end of the coil 2 is sealed and passes through the left rear part of the water bath 1. The second end of the coil 2 is sealed and passes through the left front part of the water bath 1. A one-way valve 14 is provided on the coil 2. An ultrasonic transmitting probe 6 and an ultrasonic receiving probe 7 are symmetrically installed on the outer side of the coil 2 corresponding to the position between the one-way valve 14 and the discharge valve 13. The lower end of the first pressure sensor 15 is sealed and passes through the water bath 1. The upper side is installed on the coil 2 between the one-way valve 14 and the left inner wall of the water bath 1. The lower end of the second pressure sensor 16 is sealed and passed through the upper side of the water bath 1 and installed on the coil 2 between the ultrasonic transmitting probe 6 and the left inner wall of the water bath 1. A radiator 9 is provided in the center of the coil 2. The radiator 9 is connected to the temperature regulating device 8. A temperature sensor 18 is installed on the upper right side of the water bath 1. The ultrasonic transmitting probe 6 and the ultrasonic receiving probe 7 are both connected to the ultrasonic measuring module 5. The control unit is respectively connected to the first pressure sensor 15, the second pressure sensor 16, the ultrasonic measuring module 5, the temperature sensor 18 and the temperature regulating device 8.

[0030] According to the requirements, the ultrasonic transmitting probe 6 is an existing well-known technology, such as the T40-16 ultrasonic transmitting probe, the ultrasonic receiving probe 7 is an existing well-known technology, such as the R40-16 ultrasonic receiving probe, the ultrasonic transmitting probe 6 and the ultrasonic receiving probe 7 are sealed and installed with a waterproof shell on the outside, the ultrasonic measuring module 5 is an existing well-known technology, such as the TDC-GP2 high-precision time converter, the ultrasonic transmitting probe 6, the ultrasonic receiving probe 7 and the temperature regulating device 8 are all located in the water bath 1, the first pressure sensor 15 and the second pressure sensor 16 are both existing well-known technologies, such as the PXW intelligent pressure transmitter controller, the pressure sensor has a range of 0MPa-60MPa, and an accuracy level of 0.1, the control unit is an existing well-known technology, such as a programmable controller, and the temperature sensor 18 is an existing well-known technology, such as The digital display temperature sensor 18 of the PYR-Exd-Dp series has a range of -50°C-260°C and an accuracy of ±0.1°C. The radiator 9 is a known technology, such as a finned tube radiator. The temperature regulating device 8 is a known technology, such as a programmable constant temperature and humidity test chamber with a TEMI-880 intelligent liquid crystal touch mode programmable controller. The outlet of the radiator 9 is fixedly connected to the inlet of the temperature regulating device 8, and the inlet of the radiator 9 is fixedly connected to the outlet of the temperature regulating device 8. The cold source of the temperature regulating device 8 circulates in the radiator 9, thereby reducing the temperature in the water bath 1. The maximum bearing pressure of the coil 2 is 2MPa, the diameter of the coil 2 is 25mm, the coil 2 is coiled four times in the water bath 1 and is in a horizontal vortex shape, and the radius of the circle formed by the center line of the outermost circle is 0.5m.

[0031] When in use, a mixture of water and methanol is added to the water bath 1, and no solidification occurs below zero degrees Celsius. The coil 2 is immersed in the mixture of water and methanol. By setting the temperature regulating device 8, cold capacity can be provided for the mixture in the water bath 1, thereby reducing the temperature of the mixture. The ultrasonic transmitting probe 6 and the ultrasonic receiving probe 7 are symmetrically installed on both sides of the coil 2 along the central axis of the coil 2. By setting the ultrasonic transmitting probe 6, the ultrasonic receiving probe 7, and the ultrasonic measuring module 5, the ultrasonic propagation time of the fluid in the coil 2 can be measured. By setting the one-way valve 14, it is ensured that all fluids flow in one direction, and the lowest flowable temperature of the mixed fluid on site under multiple influencing factors can be accurately measured.

[0032] During the test, the first end and the second end of the coil 2 are connected to the oil outlet pipeline of a single well, and the temperature regulating device 8 reduces the temperature of the mixed liquid. When the fluid in the coil 2 is lower than the design temperature, the oil-gas-water mixture solidifies. When the oil-gas-water mixture solidifies, the propagation speed of the ultrasonic wave in the multiphase fluid will change, resulting in a change in the propagation time of the ultrasonic wave from the ultrasonic transmitting probe 6 to the ultrasonic receiving probe 7. The control unit obtains the temperature data of the temperature sensor 18 at this time as T1. When the readings of the first pressure sensor 15 and the second pressure sensor 16 suddenly change, it indicates that the pressure loss along the mixed pipeline increases sharply, indicating that the flow condition of the mixed fluid at the corresponding temperature deteriorates. The control unit records the temperature data of the temperature sensor 18 at this time as T2. The smaller value of T1 and T2 is the minimum flowable temperature of the mixed pipeline.

[0033] The above-mentioned test device for the minimum flowable temperature of the mixed pipeline can be further optimized and / or improved according to actual needs:

[0034] Embodiment 2: As an optimization of the above embodiment, as shown in the attached Figure 1 , 4 As shown, it also includes a multiphase flow pump 4 and a sampler 10. The outlet of the multiphase flow pump 4 is fixedly connected to the first end of the coil 2. A sampling tube 3 is fixedly connected between the inlet of the multiphase flow pump 4 and the tubular structure sampler 10. A sampling valve 11 is installed on the sampling tube 3. The second end of the coil 2 is fixedly connected to a sample outlet tube 12. A discharge valve 13 is installed on the sample outlet tube 12. The multiphase flow pump 4 is connected to the control unit.

[0035] The first pressure sensor 15 is close to the multiphase flow pump 4, and the second pressure sensor 16 is close to the discharge valve 13. A sampler 10 is installed on the oil outlet pipeline of a single well, and the outlet end of the sample outlet pipe 12 is fixedly connected to the oil outlet pipeline, so that the oil-gas-water mixture sample flows into the coil 2 through the sampling tube 3, and the sampling valve 11 can control the flow rate of the sampling fluid. After the test is completed, the mixed fluid is directly transported back to the oil outlet pipeline through the sample outlet pipe 12, so as not to waste the tested fluid and to avoid polluting the environment after the tested fluid is discharged. The oil-gas-water mixture flows into the sampling tube 3, and the multiphase flow pump 4 continuously pumps the oil-gas-water mixture into the coil 2, forming a sustainable mixed fluid loop from the sampler 10 to the sample outlet pipe 12. The rotation speed of the multiphase flow pump 4 can be controlled by the control unit to provide a multiphase flow fluid with a set shear rate, thereby improving the accuracy of the measurement.

[0036] Embodiment 3: As an optimization of the above embodiment, as shown in the attached Figure 1 , 4As shown, four sampling holes connected inside and outside are evenly spaced along the circumference of the middle outer side of the sampler 10, and a sampling branch pipe 17 is fixedly connected between each sampling hole and the end of the sampling tube 3 away from the multiphase flow pump 4. According to the needs, the four sampling branches 17 are fixedly connected to the sampling tube 3 through the existing well-known five-way. Through such an arrangement, a sample of the oil-gas-water mixture can be obtained without changing the oil-gas-water ratio. After the test is completed, the mixed fluid is directly transported back to the oil outlet pipeline through the sample outlet pipe 12, so as not to waste the tested fluid and cause environmental pollution.

[0037] Embodiment 4: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, a protective shell 19 is provided on the outside of the water bath 1, and a heat-insulating layer 20 is filled between the inside of the protective shell 19 and the inside of the water bath 1. According to the requirements, the material of the heat-insulating layer 20 is polyurethane. The provision of the protective shell 19 can not only prevent the heat-insulating layer 20 from being damaged, but also facilitate the installation of the heat-insulating layer 20. The provision of the heat-insulating layer 20 can reduce the temperature change rate of the water bath 1 to maintain the temperature stability in the water bath 1.

[0038] Embodiment 5: As attached Figure 1 , 2 As shown in , 3, and 4, the method for using the testing device for the minimum flowable temperature of a mixed pipeline is characterized by comprising the following steps:

[0039] Step 1: Close the sampling valve 11 and the discharge valve 13, and connect the sampler 10 and the sample outlet pipe 12 to the oil outlet pipeline of the single well;

[0040] Step 2: Add a mixture of water and methanol into the water bath 1;

[0041] Step 3: Open the sampling valve 11 and the discharge valve 13, start the multiphase flow pump 4, control the rotation speed of the multiphase flow pump 4, and deliver the fluid with the set shear rate to the coil 2;

[0042] Step 4: The control unit controls the temperature regulating device 8 to operate so that the temperature of the mixed liquid in the water bath 1 decreases at a set rate;

[0043] Step 5: The ultrasonic measuring module 5 transmits ultrasonic waves into the coil 2 through the ultrasonic transmitting probe 6, and the ultrasonic receiving probe 7 receives the ultrasonic waves transmitted by the ultrasonic transmitting probe 6 and feeds them back to the ultrasonic measuring module 5. The ultrasonic measuring module 5 measures the propagation time of the ultrasonic waves in the mixed fluid in the coil 2. When the propagation time of the ultrasonic waves from the ultrasonic transmitting probe 6 to the ultrasonic receiving probe 7 changes, the temperature sensor 18 data at this time is T1;

[0044] When the data of the first pressure sensor 15 and the second sensor suddenly change, the data of the temperature sensor 18 at this time is T2;

[0045] The smaller value between T1 and T2 is the minimum flowable temperature of the mixed pipeline.

[0046] The temperature of the mixed solution in the water bath 1 was decreased at a rate of 0.1°C / min.

[0047] Step one is specifically as follows: add pure water from the sampler 10, open the multiphase flow pump 4 and the discharge valve 13 to flush the coil 2, and after flushing, introduce dry nitrogen to discharge and dry the liquid in the coil 2, close the sampling valve 11 and the discharge valve 13, and fix the sampler 10 and the sample outlet pipe 12 to the oil outlet pipeline of the single well.

[0048] The data acquisition frequency of the temperature sensor 18, the first pressure sensor 15 and the second pressure sensor 16 are all 1 Hz. The temperature regulating device 8 is controlled by the control unit to reduce the temperature of the mixed liquid in the water bath 1 at a rate of 0.1°C / min. The temperature sensor 18 measures the temperature of the mixed liquid in the water bath 1.

[0049] Before using the test device for the minimum flowable temperature of the mixed pipeline, first, check whether the sealing of the pipeline connection is good, test the freezing point of crude oil according to the standard "GB / T510-2018 Determination of freezing point of petroleum products", add pure water from the sampler 10, open the multiphase flow pump 4 and the discharge valve 13 to flush the coil 2, and after the flushing is completed, introduce dry nitrogen to discharge and dry the liquid in the coil 2; then, close the sampling valve 11 and the discharge valve 13, install the sampler 10 on the oil outlet pipeline of the single well, and the outlet end of the sampling pipe 12 is fixedly connected to the oil outlet pipeline, so that the oil-gas-water mixture sample can flow into the coil 2 through the sampling pipe 3, and the sampling valve 11 can control the flow rate of the sampling fluid. After the test is completed, the mixed fluid is directly transported back to the oil outlet pipeline through the sampling pipe 12; finally, a mixture of water and methanol is added to the water bath 1.

[0050] When testing the lowest flowable temperature of the mixed pipeline, first open the sampling valve 11 and the discharge valve 13, start the multiphase flow pump 4, control the speed of the multiphase flow pump 4, and deliver the fluid with a set shear rate to the coil 2, and then the temperature regulating device 8 reduces the temperature of the mixed liquid;

[0051] When the fluid in the coil 2 is lower than the design temperature, the oil-gas-water mixture solidifies. When the oil-gas-water mixture solidifies, the propagation speed of the ultrasonic wave in the multiphase fluid changes, causing the propagation time of the ultrasonic wave from the ultrasonic transmitting probe 6 to the ultrasonic receiving probe 7 to change. The control unit obtains the temperature data of the temperature sensor 18 at this time as T1;

[0052] When the readings of the first pressure sensor 15 and the second pressure sensor 16 suddenly change, it means that the pressure loss along the mixed pipeline increases sharply, which means that the flow condition of the mixed fluid at the corresponding temperature deteriorates. The control unit records the temperature data of the temperature sensor 18 at this time as T2. The smaller value between T1 and T2 is the minimum flowable temperature of the mixed pipeline.

[0053] The empirical formula for calculating the minimum flowable temperature of a single well is determined through the test data. The quantitative formula between the minimum flowable temperature and the gas-oil ratio, water content, shear rate, and normal crude oil pour point is as follows:

[0054] t=a(T b )×(x c )×(y d )×exp(e×z f )

[0055] Where: t is the pour point, unit is K; T is the pour point of normal crude oil, unit is K; x is the water content; y is the gas-oil ratio; z is the shear rate, unit is s -1 ; a, b, c, d, e and f are coefficients. The lowest flowable temperature of mixed crude oil under multiple working conditions is measured, and the coefficients a, b, c, d, f are calculated based on multiple experimental data.

[0056] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A device for testing the minimum flowable temperature of a mixed pipeline, characterized in that It includes a water bath, a coil, a first pressure sensor, a second pressure sensor, an ultrasonic measurement module, a temperature adjustment device and a control unit. Several coils are wound in the water bath. The first end of the coil is sealed and passes through the left rear part of the water bath, and the second end of the coil is sealed and passes through the left front part of the water bath. A one-way valve is arranged on the coil. An ultrasonic transmitting probe and an ultrasonic receiving probe are symmetrically installed on the outer side of the coil corresponding to the position between the one-way valve and the discharge valve. The lower end of the first pressure sensor is sealed and passes through the upper side of the water bath and is installed on the coil between the one-way valve and the left inner wall of the water bath. The lower end of the second pressure sensor is sealed and passes through the upper side of the water bath and is installed on the coil between the ultrasonic transmitting probe and the left inner wall of the water bath. A radiator is arranged in the center of the coil, and the radiator is connected to the temperature adjustment device. A temperature sensor is installed on the upper right side of the water bath. The ultrasonic transmitting probe and the ultrasonic receiving probe are both connected to the ultrasonic measurement module. The control unit is respectively connected to the first pressure sensor, the second pressure sensor, the ultrasonic measurement module, the temperature sensor and the temperature adjustment device.

2. The device for testing the minimum flowable temperature of a mixed pipeline according to claim 1, characterized in that It also includes a multiphase flow pump and a sampler. The outlet of the multiphase flow pump is fixedly connected to the first end of the coil. A sampling tube is fixedly connected between the inlet of the multiphase flow pump and the tubular structure sampler. A sampling valve is installed on the sampling tube. The second end of the coil is fixedly connected to a sample outlet tube. A discharge valve is installed on the sample outlet tube. The multiphase flow pump is connected to a control unit.

3. The testing device for the minimum flowable temperature of a mixed pipeline according to claim 2, characterized in that Four sampling holes connected inside and outside are evenly distributed along the circumference on the outer side of the middle part of the sampler, and a sampling branch pipe is fixedly connected between each sampling hole and the end of the sampling tube away from the multiphase flow pump.

4. The testing device for the minimum flowable temperature of a mixed pipeline according to claim 1, 2 or 3, characterized in that A protective shell is arranged on the outside of the water bath, and a heat-insulating layer is filled between the inside of the protective shell and the inside of the water bath.

5. A method for using the testing device for the minimum flowable temperature of a mixed pipeline according to any one of claims 1 to 4, characterized in that The following steps are involved: Step 1: Close the sampling valve and the discharge valve, and connect the sampler and the sample outlet pipe to the oil outlet pipeline of the single well; Step 2: Add a mixture of water and methanol into the water bath; Step 3: Open the sampling valve and the discharge valve, start the multiphase flow pump, control the speed of the multiphase flow pump, and deliver the fluid with the set shear rate into the coil; Step 4: The control unit controls the temperature regulating device to operate so that the temperature of the mixed liquid in the water bath decreases at a set rate; Step 5: The ultrasonic measurement module transmits ultrasonic waves into the coil through the ultrasonic transmitting probe, and the ultrasonic receiving probe receives the ultrasonic waves transmitted by the ultrasonic transmitting probe and feeds them back to the ultrasonic measurement module. The ultrasonic measurement module measures the propagation time of the ultrasonic waves in the mixed fluid in the coil. When the propagation time of the ultrasonic waves from the ultrasonic transmitting probe to the ultrasonic receiving probe changes, the temperature sensor data at this time is T1; When the data of the first pressure sensor and the second sensor suddenly change, the temperature sensor data at this time is T2; The smaller value between T1 and T2 is the minimum flowable temperature of the mixed pipeline.

6. The method for using the device for testing the minimum flowable temperature of a mixed pipeline according to claim 5, characterized in that The temperature of the mixed solution in the water bath was decreased at a rate of 0.1°C / min.

7. The method for using the device for testing the minimum flowable temperature of a mixed pipeline according to claim 5 or 6, characterized in that Step one is as follows: add pure water from the sampler, open the multiphase flow pump and the discharge valve to flush the coil, introduce dry nitrogen after flushing, discharge and dry the liquid in the coil, close the sampling valve and the discharge valve, and fix the sampler and the sample outlet pipe to the oil outlet pipeline of the single well.

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