CN107748273B - Pipeline pressure wave velocity testing device and method based on pipe flow test loop - Google Patents

Abstract

The invention relates to a pipeline pressure wave velocity testing device and method based on a pipeline flow testing loop. The test device includes a pipe flow test loop device, an ultrasonic velocity test device and a computing device. The pipe flow test loop device includes a test pipeline system, a data acquisition system and a water bath circulation system. The three parts work together to complete the different operating conditions of the pipeline. simulation. The test method includes: measuring the viscosity-temperature curve of oil viscosity with temperature and determining abnormal points; determining the temperature distribution and residual pressure distribution along the pipeline between stations, and segmenting the pipeline between stations; using the indoor pipe flow loop test device, Based on the principle that the energy dissipation rate per unit volume of fluid is equal, the actual pipeline operating conditions are simulated; the ultrasonic velocity test device is used to measure the ultrasonic velocity under the simulated operating conditions, and the ultrasonic velocity database under the actual pipeline operating conditions is established; The sound velocity of each section of the pipeline is calculated, and the pressure wave velocity of each section of the pipeline is calculated according to the pipeline parameters.

Description

A pipeline pressure wave velocity testing device and method based on pipeline flow test loop

technical field

The invention belongs to the technical field of pipeline transportation of crude oil and refined oil, and in particular relates to a testing device and method for determining pressure wave velocity along a pipeline based on an indoor pipeline flow test loop.

Background technique

The pressure wave transmission velocity, referred to as the pressure wave velocity, is one of the most sensitive and important parameters in the pipeline transportation and transient dynamic characteristics analysis of crude oil or refined oil. There are many factors affecting the pressure wave velocity of crude oil pipelines, not only related to the physical properties of the fluid itself, such as pressure, temperature, gas content, etc., but also related to the geometric parameters of the pipeline, the mechanical properties of materials, and the support method of the structure. Therefore, it is difficult to accurately measure the pressure wave velocity of the pipeline in the prior art.

At present, the pressure wave velocity is mainly determined by direct measurement. The direct measurement method uses a pressure sensor to measure the pressure pulsation value of a pipe section of the pipeline in real time, and calculates the pressure wave velocity by determining the transfer time or the resonance frequency. Among them, the most widely used direct measurement methods are the resonant frequency measurement method and the time difference domain measurement method; the resonant frequency measurement method uses three pulsating pressure sensors with determined positions to measure the pulsating pressure values of three sections in the pipeline system. The transmission speed of the pressure wave is calculated by determining the resonant frequency; the time difference domain measurement method is to use two pulsating pressure sensors with a known distance of L to measure the pressure wave of the pressure pulsation at a certain point upstream or downstream, and measure the transmission speed of the pressure wave between the two pressure sensors. The time difference Δt, and finally the pressure wave velocity is calculated according to the distance L between the two pressure sensors and the propagation time interval Δt of the pressure wave.

The advantage of direct measurement of pressure wave velocity is simplicity. However, due to the fast pressure wave speed, a certain distance is required between the two pressure sensors, resulting in the calculated pressure wave speed being the average value of the pressure wave propagation speed in a certain length of pipe section between the two pressure sensors. In some cases, there may be gas spaces at certain positions along the pipeline. For example, after the hot oil pipeline is stopped, the temperature of the oil in the pipeline drops, and the volume of the oil shrinks. A bubble area or even an air resistance may be formed at the local position; in this case, the pressure wave velocity value measured by the direct measurement method of the pressure wave velocity will have serious errors, which cannot reflect the actual situation of the pressure wave transmission.

In practical engineering, the change of the fluid properties in the pipeline, the structural material, thickness of the pipeline, and the different support methods will cause the corresponding pressure wave velocity to change. And for waxy crude oil and heavy oil, due to poor fluidity at room temperature, heating is generally required for transportation. For the heating and transporting hot oil pipeline, the crude oil is heated to a certain temperature in the heating station and then exits the station, and the oil temperature decreases continuously during the process of flowing along the pipeline to the next heating station; therefore, there is an axial temperature drop between the two heating stations before and after. , and the axial temperature drop curve is an exponential curve. In some hot oil pipelines, pipelines with pour point depressants, and heavy oil pipelines, the temperature difference of oil products along the pipelines can reach more than 40 °C. For waxy crude oil, as the oil temperature drops, wax gradually crystallizes and forms small wax crystal particles suspended in the crude oil, and the viscosity of the crude oil increases; the temperature continues to decrease, the crude oil gels, and exhibits shear dilution and thixotropy , viscoelasticity and other non-Newtonian fluid rheological behavior. The pressure wave velocity of oil in the pipeline will increase with the increase of pressure, decrease with the increase of temperature, and increase with the increase of structural strength. In this case, the pressure wave velocity value measured by the direct measurement method of the pressure wave velocity cannot reflect the actual situation of the pressure wave transmission at each point along the pipeline.

To sum up, in the prior art, there is still no effective solution to the practical problem of how to determine the pressure wave transmission velocity at different positions along the crude oil or refined oil pipeline. Due to the theoretical and experimental difficulties, the pressure wave velocity is regarded as a constant in the engineering application of thermal oil pipelines at home and abroad. In the application of computer dynamic simulation, pipeline transient flow analysis, pipeline leakage detection (negative pressure wave method, pressure wave method) and other applications, this kind of processing often brings large errors. Therefore, it is of great practical significance to develop a new test method to determine the pressure wave velocity at different positions (different temperatures, different pressures) along the crude oil pipeline.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a test device and method for determining the pressure wave velocity at different positions along a pipeline (crude oil or refined oil) based on an indoor pipe flow test loop. Specifically, the indoor pipe flow test loop test device is used to simulate the actual pipeline operating conditions (different temperatures, different pressures) based on the principle of equal energy dissipation rate per unit volume of fluid, test the ultrasonic velocity under the simulated conditions, and calculate and determine the pipeline. Pressure wave velocity at different locations along the line.

1. The first object of the present invention is to provide a pipeline pressure wave velocity testing device based on the pipeline flow test loop.

In order to achieve the above purpose, the present invention adopts the following technical scheme: a pipeline pressure wave velocity testing device based on a pipeline flow test loop, the testing device comprising:

(1) Pipe flow loop test device. The pipe flow loop test device includes a test loop system, a water bath circulation system and a data acquisition system. The test loop system is set in the water bath circulation system, and realizes the temperature control of the constant temperature, heating and cooling of the oil in the test pipe section.

(2) Ultrasonic speed test device. The ultrasonic velocity test device is connected to the test loop system, and is used for collecting ultrasonic signals at different positions of the test loop system, and calculating the ultrasonic velocity under different operating conditions.

(3) Computing device. The computing device is connected with the ultrasonic velocity testing device, and is used to calculate the pipeline pressure wave velocity according to the obtained ultrasonic velocity, medium properties, and pipeline properties by corresponding formulas.

In the present invention, the test loop system, the water bath circulation system and the data acquisition system in the pipe flow loop test device cooperate to complete the simulation of different operating conditions of the actual crude oil pipeline; wherein, the water bath circulation system The system ensures that it will not affect the elasticity and deformation characteristics of the test pipeline in the test loop system; the data acquisition system collects and monitors the changes of each parameter under different operating conditions of the test loop system in real time, and according to The test needs to select a specific data collection frequency to store data, which ensures the accuracy of the test loop system simulating different operating conditions of the actual crude oil pipeline.

As a further preferred solution, the test loop system is composed of a test loop, an oil storage tank, a pump, a buffer tank, a flow meter, and several valves. The material of the test loop is stainless steel pipe, and the ratio of the inner diameter of the pipe to the wall thickness is less than 20. The test loop includes a test pipe section and a non-test pipe section, and the test pipe section is completely immersed in the water bath circulation system; the non-test pipe section is sequentially connected to the oil storage tank, the pump, the buffer tank, and the flow meter, and the non-test pipe section is connected to the oil storage tank, the pump, the buffer tank, and the flow meter in sequence. The test pipe section adopts a commercial water bath circulator and a seamless winding thin copper tube to form a water circulation for temperature control, and the thin copper tube is wrapped with thermal insulation material. A valve is provided on the pipeline connecting both ends of the oil storage tank with the non-testing pipe section, and a valve is provided on the pipeline connecting the buffer tank and the non-testing pipe section.

As a further preferred solution, an insulating layer is arranged outside the oil storage tank, and a heating device is arranged inside the oil storage tank; the pump adopts a peristaltic pump. In the present invention, an insulation layer is provided outside the oil storage tank to effectively keep the oil in the oil storage tank warm; a heating device and a temperature sensor are arranged inside the oil storage tank to keep the oil in the tank constant temperature , heating or cooling control. In order to minimize the influence of oil over-pump shearing and over-pump temperature rise on the rheological properties of low-temperature waxy crude oil, the present invention selects a peristaltic pump to provide power for the flow of crude oil in the pipeline, and by adjusting the frequency of the peristaltic pump, it can be Realize the regulation of the flow in the pipe.

As a further preferred solution, the buffer tank includes a buffer tank body, a pressure supply device and several valves. An insulating layer is provided outside the buffer tank body, an oil spill vent valve is provided at the bottom of the buffer tank, and a gas vent valve is provided on the top of the buffer tank. A float is arranged inside the buffer tank body, and a displacement sensor is installed above the buffer tank, which can accurately display the displacement of the float in the buffer tank and monitor the position of the float in real time. A vent valve is arranged between the buffer tank and the pressure supply device, the pressure supply device adopts a nitrogen tank, and a pressure reducing valve is arranged at the outlet of the nitrogen tank. In the present invention, the arrangement of the buffer tank can reduce the pressure fluctuation during the operation of the peristaltic pump, and make the oil run smoothly in the pipeline; on the other hand, the buffer tank can be used to apply a certain constant pressure to the fluid in the pipeline.

As a further preferred solution, the water bath circulation system is composed of a water bath, a nozzle, a water circulation pipeline, a pipeline pump, a refrigerator, and a regulating valve. An insulating layer is arranged outside the water bath to reduce heat loss, and several heaters are evenly arranged inside the water bath to heat the water in the water bath. The circulating water outlet of the water bath is arranged at both ends of the water bath and is connected with the water circulation pipe; the pipe pump is arranged on the water circulation pipe to provide power for the water to form a water circulation flow in the pipe; the inlet and outlet of the pipe pump The refrigerating machine is connected between the pipes, a regulating valve is arranged at the inlet of the refrigerating machine to adjust the cooling capacity, and the refrigerating capacity is adjusted by adjusting the opening degree of the regulating valve at the refrigerator and its inlet. The refrigerated water is sprayed out through several nozzles evenly arranged inside the water bath, so that the water in the water bath is fully mixed and the temperature distribution tends to be uniform. In the present invention, the effective control of the temperature in the water bath is achieved through the combined action of the heating capacity of the heater and the cooling capacity of the refrigerator in the water bath circulation system.

As a further preferred solution, the data acquisition system includes data acquisition of a pressure sensor, a flow sensor, a temperature sensor and a displacement sensor. (1) The pressure sensor includes a first pressure sensor, a second pressure sensor, a third pressure sensor, and a fourth pressure sensor; the first pressure sensor and the second pressure sensor are arranged on the test loop at intervals, The test loop is divided into a test pipe section and a non-test pipe section, the third pressure sensor is connected to the buffer tank, and the fourth pressure sensor is connected to the nitrogen tank; (2) the flow sensor is arranged in On the test loop, it is used to monitor the crude oil flow in the test loop; (3) the temperature sensor is arranged inside the oil storage tank to monitor the temperature of the crude oil inside the oil storage tank; (4) the The displacement sensor is arranged on the top of the buffer tank for monitoring the displacement of the float in the buffer tank.

In the present invention, the data acquisition system is also connected with a display device and a storage device, respectively, and the display device displays the collected parameters such as pressure, temperature, flow rate, and float displacement in real time, and selects a specific data acquisition frequency according to the test requirements. Data is stored in the storage device.

As a further preferred solution, the ultrasonic speed test device includes an ultrasonic probe, an oscilloscope and a signal generator, and several pairs of ultrasonic probes are installed at different positions of the test loop system, and the ultrasonic probes are respectively connected with the signal generator. , the signal generator is connected with the oscilloscope.

As a further preferred solution, at several different positions of the test pipe section of the test loop system, several pairs of ultrasonic transmitting probes and receiving probes are installed in the horizontal direction. 1/3 of the diameter, so the distance between the transmitting probe and the receiving probe is also 1/3 of the diameter. The ultrasonic transmitting probe and receiving probe are placed in this way, so the distance between the transmitting probe and the receiving probe from the inner wall of the pipeline is the same as the distance between the two probes. It can be considered that the propagation speed of ultrasonic waves between the two probes is the speed of sound in an infinite medium. In addition, the inner wall of the pipe may be waxed during the experimental operation. The transmitting probe and the receiving probe are placed so as to be far away from the wax deposition layer of the pipe wall, so as to avoid the influence of the wax deposition on the test result.

2. The second object of the present invention is to provide a pipeline pressure wave velocity testing method based on the pipeline flow test loop, and the method is based on the above-mentioned pressure wave velocity testing device.

In order to achieve the above object, the pressure wave velocity test method adopted in the present invention is as follows:

(1) Measure the viscosity of oil at different temperatures, obtain the viscosity-temperature curve of oil viscosity with temperature, and determine the abnormal point of oil.

(2) Perform thermal and hydraulic calculations on the actual pipeline to determine the temperature distribution and residual pressure (also known as dynamic water pressure) distribution along the pipeline; segment the pipeline between stations, and calculate the average temperature and average pressure of each segment of the pipeline after segmenting , the fluid energy dissipation rate per unit volume.

(3) Using the indoor pipe flow loop test device, based on the principle of equal energy dissipation rate per unit volume of fluid, the operating conditions of the actual pipeline are simulated.

(4) Use the ultrasonic velocity test device to test the ultrasonic velocity (that is, the speed of sound) under simulated working conditions, and establish the ultrasonic velocity database under the actual pipeline operating temperature range, pressure range, and fluid energy dissipation rate per unit volume range.

(5) Determine the sound velocity of each segment of the pipeline after segmentation according to the ultrasonic velocity database, and calculate the pipeline pressure wave velocity by the corresponding formula according to the pipeline properties of each segment of the pipeline.

As a further preferred solution, in the step (2), the actual crude oil or refined oil pipeline parameters are obtained to perform thermal and hydraulic calculations, and the specific steps of segmenting the pipeline are:

(2-1) Obtain the pipeline throughput of the actual crude oil pipeline, the exit temperature of the heating station, the entry temperature, the buried depth of the pipeline center and the viscosity-temperature curve of the oil product, inversely calculate the total heat transfer coefficient of the actual crude oil pipeline, and determine Temperature distribution of oil between heating stations;

(2-2) Obtain the outlet pressure of the pumping station, calculate the frictional resistance along the actual crude oil pipeline according to the outlet pressure of the pumping station, the pipeline throughput, the temperature distribution of the oil between the heating stations and the viscosity-temperature curve of the oil, and determine residual pressure along the pipeline;

(2-3) Segment the pipeline between stations according to the operating temperature range and pressure range of the pipeline. As a further preferred solution, the inter-station pipeline is segmented according to the actual operating temperature range and pressure range of the crude oil pipeline. The smaller one will finally divide the pipeline, and calculate the arithmetic mean temperature, arithmetic mean pressure and fluid energy dissipation rate per unit volume of each pipeline section after the final pipeline division.

As a further preferred solution, in the step (3), the specific steps for simulating the actual pipeline operating conditions by using the pipe flow loop test device are:

(3-1) Use a buffer tank to apply a constant pressure to the fluid in the test loop to simulate the operating pressure of the actual pipeline;

(3-2) Use the water bath circulation system to adjust the temperature of the water bath to simulate the operating temperature of the actual pipeline;

(3-3) Determine the oil temperature and the size of the abnormal point; when the oil temperature is greater than the abnormal point, the pipe flow test loop will not start, and the flow rate is 0; when the oil temperature is less than the abnormal point, the energy consumption per unit volume of fluid will be determined. According to the principle of equal dispersion rate, the flow rate of the pipe flow test loop is adjusted to simulate the shearing of the fluid in the pipe during the actual pipe operation.

As a further preferred solution, in the step (3), the crude oil is placed in the oil storage tank before each use of the pipe flow test loop to simulate the actual crude oil pipeline operating conditions, and the water bath circulation system and the oil storage tank are turned on. The internal heater ensures that the temperature of the test ring is uniform and consistent with the temperature of the oil in the oil storage tank.

As a further preferred solution, in the step (4), before simulating the actual pipeline operating conditions, the ultrasonic transmitting probe and the receiving probe of the ultrasonic velocity/pressure wave velocity testing device based on the pipe flow test loop used for the first time The actual distance ΔL between them is calibrated. The calibration adopts the distilled water calibration method. The specific steps are: ① Fill the test loop with distilled water, and use the water bath circulation system to control the test temperature; ② Measure the propagation time Δt of the ultrasonic wave between the transmitting probe and the receiving probe at the test temperature, and obtain the corresponding test temperature The sound velocity of distilled water v _water , the product of the propagation time Δt and the sound velocity of distilled water v _water is the distance between the ultrasonic probes ΔL; ③ After the calibration is completed, use the nitrogen bottle connected to the buffer tank to purge the test loop with nitrogen, and the distilled water Drain the pipe and dry the pipe.

As a further preferred solution, in the step (5), the specific steps of calculating the pressure wave speed according to the sound speed of each section of the pipeline and the pipeline properties are:

(5-1) According to the average temperature, average pressure, and fluid energy dissipation rate per unit volume of the pipeline that has been divided into each section, combined with the ultrasonic velocity database, determine the sound velocity of each section that has been divided into the pipeline;

(5-2) Determine the diameter, wall thickness, pipeline restraint mode, elastic modulus and Poisson coefficient of each small section of the pipeline; calculate the pressure wave velocity of each section of the pipeline after segmentation.

Compared with the prior art, the beneficial effects of the present invention are:

(1) Through a kind of pipeline pressure wave velocity testing device and method based on the pipe flow test loop of the present invention, based on the principle of equal energy dissipation rate per unit volume of fluid, the pipe flow test loop is used to simulate the operating conditions of the actual pipeline ( Different throughput, different temperature, different pressure), test the ultrasonic velocity under simulated working conditions, and calculate and determine the pressure wave velocity at different positions along the pipeline, which can effectively reflect the actual situation of pressure wave transmission at different positions along the pipeline.

(2) The temperature of the test pipe section is controlled by a water bath circulation system, and the test pipe section is immersed in the water bath as a whole, which will not affect the elasticity and deformation characteristics of the pipeline, and thus will not affect the pressure wave velocity measured by the pressure sensor based on the time difference domain method.

(3) Setting a buffer tank at the outlet of the peristaltic pump, on the one hand, can reduce the pressure fluctuation during the operation of the peristaltic pump and make the oil run smoothly in the pipeline; on the other hand, the buffer tank can be used to apply a certain constant pressure to the fluid in the pipe .

(4) An oil spill vent valve is set at the bottom of the buffer tank, a gas vent valve is set on the top, and a displacement sensor is installed above, which can accurately display the displacement of the float in the buffer tank and monitor the position of the float in real time.

(5) Install several pairs of ultrasonic transmitting probes and receiving probes in the horizontal direction at several different positions of the test pipe section. The ultrasonic velocities at several different positions are measured and verified with each other, and the final result is taken as the average value; the pressure wave velocity a ₁ of the test pipe section can be calculated by formula (2) in combination with the properties of the test pipe section. The pressure wave velocity a ₁ is compared with the pressure wave velocity a ₂ measured by the time-difference method using the pressure sensors P ₁ and P ₂ , and they are verified with each other.

(6) Both the ultrasonic transmitting probe and the receiving probe are installed at the position of 1/3 of the diameter of the inner wall of the pipeline, so the distance between the transmitting probe and the receiving probe is also 1/3 of the diameter. The ultrasonic transmitting probe and receiving probe are placed in such a way that the distance between the transmitting and receiving probes from the inner wall of the pipeline is the same as the distance between the two probes, and the propagation speed of ultrasonic waves between the two probes is the ultrasonic speed in an infinite medium. In addition, the inner wall of the pipe may be waxed during the experimental operation. The transmitting probe and the receiving probe are placed so as to be far away from the wax deposition layer of the pipe wall, so as to avoid the influence of the wax deposition on the test result.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

Fig. 1 is the schematic diagram of the pressure wave velocity test device based on the pipe flow test loop of the present invention;

Fig. 2 is the structural representation of the buffer tank of the present invention;

Fig. 3 is the structural representation of the water bath circulation system of the present invention;

Figure 4 is a flow chart of the method of the present invention.

Detailed ways

It should be noted that the following detailed descriptions are all exemplary, and are intended to provide further descriptions of preferred solutions to the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

The embodiments in this application and the features in the embodiments may be combined with each other without conflict. The present invention will be further described below with reference to the accompanying drawings and embodiments.

In order to solve the problems introduced by the background art, the present invention designs a pipeline pressure wave velocity test device based on an indoor pipeline flow test loop, which simulates the actual pipeline operating conditions based on the principle of equal energy dissipation rates per unit volume of fluid, and tests The ultrasonic speed (that is, the speed of sound) under simulated working conditions is calculated to determine the pressure wave speed at different positions along the pipeline.

Example 1:

The purpose of Embodiment 1 is to provide a pipeline pressure wave velocity test device based on a pipe flow test loop, as shown in FIG. 1 , the test device includes a pipe flow loop test device and an ultrasonic velocity test device.

(1) Pipe flow loop test device

The pipe flow loop test device includes a test loop system, a water bath circulation system and a data acquisition system. The test loop system, the water bath circulation system and the data acquisition system work together to complete the simulation of different operating conditions of the actual crude oil pipeline.

In this embodiment, the test loop system is used to simulate the flow conditions (temperature, pressure, shear conditions) of crude oil in the actual pipeline, including the test loop, oil storage tank, pump, buffer tank and several valves . Specifically, the pipe material of the test loop is selected from 304 stainless steel pipe, its elastic modulus E is 200GPa, and Poisson's ratio μ is 0.25. The inner diameter of the pipe in the test ring is 21.36mm, the wall thickness is 2.5mm, and the ratio of the inner diameter D to the wall thickness e is less than 25, which meets the requirements of thin-walled round pipes. One end of the test ring near the oil storage tank is fixed, and the other end is free to expand and contract axially.

Specifically, the test loop includes a test pipe section and a non-test pipe section, wherein the test pipe section refers to the pipe between the high-precision pressure sensors P ₁ and P ₂ , and the distance between the pipes P ₁ and P ₂ is required to be greater than 10m, and the data collection frequency below 1ms. The test pipe section is immersed in the water bath circulation system as a whole, as shown in Figure 1; except for the test pipe section immersed in the water bath, the rest of the test loop adopts a commercial water bath circulator and a seamless winding thin copper tube to form a water circulation for temperature measurement. Control, the thin copper tube is wrapped with thermal insulation material.

In this embodiment, the non-testing pipe section is connected to the oil storage tank, the pump and the buffer tank in sequence, and a valve is provided on the pipeline connecting both ends of the oil storage tank to the non-testing pipe section, and the buffer A valve is arranged on the pipeline connecting the tank with the non-testing pipeline section.

Specifically, the oil storage tank adopts a tank body with a volume of 20 L, an insulating layer is arranged outside the oil storage tank to effectively keep the oil in the oil storage tank warm, and a heating device and a temperature sensor are arranged inside the oil storage tank. In this embodiment, the heating device adopts a circulating heating water coil to control the constant temperature, temperature increase and decrease of the oil in the tank. In order to minimize the influence of oil over-pump shearing and over-pump temperature rise on the rheological properties of low-temperature waxy crude oil, the present invention selects a peristaltic pump to provide power for the flow of crude oil in the pipeline, and by adjusting the frequency of the peristaltic pump, it can be Realize the regulation of the flow in the pipe.

In this embodiment, a buffer tank is installed at the outlet of the peristaltic pump. On the one hand, setting the buffer tank can reduce the pressure fluctuation during the operation of the peristaltic pump and make the oil run smoothly in the pipeline; on the other hand, the buffer tank can be used A constant pressure is applied to the fluid in the tube. The schematic diagram of the overall structure of the buffer tank is shown in Figure 2. The buffer tank includes a buffer tank body, a pressure supply device and several valves. An insulating layer is provided outside the buffer tank body, an oil spill vent valve is provided at the bottom of the buffer tank, and a gas vent valve is provided on the top of the buffer tank. A vent valve is arranged between the buffer tank and the pressure supply device, the pressure supply device adopts a nitrogen tank, and a pressure reducing valve is arranged at the outlet of the nitrogen tank. A float is arranged inside the buffer tank body, and a displacement sensor is installed above the buffer tank, which can accurately display the displacement of the float in the buffer tank and monitor the position of the float in real time.

In this embodiment, the water bath circulation system is mainly used for temperature control of processes such as constant temperature, heating and cooling of the oil in the test pipe section. The schematic diagram of the water bath circulation system is shown in Figure 3, including a water bath, a nozzle, a water circulation pipeline, a pipeline pump, a refrigerator and a regulating valve. A thermal insulation layer is arranged outside the water bath, and the thermal insulation layer adopts a foam thermal insulation board, which covers the outside of the water bath to reduce heat loss. Several nozzles and several heaters are evenly arranged inside the water bath. In this embodiment, six heaters are installed inside the water bath, which can heat the water in the water bath. The circulating water outlet of the water bath is arranged at both ends of the water bath and is connected with the water circulation pipe; the pipe pump is arranged on the water circulation pipe to provide power for the water to form a circulating flow in the pipe; the inlet and outlet pipes of the pipe pump The refrigerator is connected between them, and a regulating valve is arranged at the inlet of the refrigerator to adjust the cooling capacity, and the cooling capacity is adjusted by adjusting the opening degree of the refrigerator and the regulating valve at the inlet. The refrigerated water is sprayed out through several nozzles evenly arranged inside the water bath, so that the water in the water bath is fully mixed and the temperature distribution tends to be uniform. In the present invention, the effective control of the temperature in the water bath is achieved through the combined action of the heating capacity of the heater and the cooling capacity of the refrigerator in the water bath circulation system.

It should be noted that if other temperature control methods are adopted, such as (1) setting a water bath insulation pipe outside the pipeline to control the temperature or (2) seamless winding of thin copper pipes (copper pipes with thermal insulation material) outside the pipes to form a water circulation temperature control, it may be It will affect the elasticity and deformation characteristics of the test pipe section, thereby affecting the pressure wave velocity measured by the pressure sensors P ₁ and P ₂ based on the time difference domain method. The water bath circulation system is used to control the temperature, and the test pipe section is directly placed in the water bath, which will not affect the elasticity and deformation characteristics of the pipe.

In this embodiment, the data acquisition system collects parameters such as pressure, temperature, and float displacement of the test loop system in real time, and selects a specific data acquisition frequency to store data according to test requirements. Specifically, the data acquisition system includes data acquisition of a pressure sensor, a flow sensor, a temperature sensor and a displacement sensor. The pressure sensor includes a first pressure sensor, a second pressure sensor, a third pressure sensor, and a fourth pressure sensor; the first pressure sensor and the second pressure sensor adopt high-precision pressure sensors P ₁ and P ₂ , and the interval It is arranged on the test loop, and divides the test loop into a test pipe section and a non-test pipe section; the third pressure sensor is connected to the buffer tank, and the fourth pressure sensor is connected to the nitrogen tank. The flow sensor is arranged behind the test loop buffer tank, and is used for monitoring the crude oil flow in the test loop. The temperature sensor is arranged inside the oil storage tank and is used for monitoring the temperature of the crude oil inside the oil storage tank. The displacement sensor is arranged on the top of the buffer tank for monitoring the position of the float in the buffer tank.

The data acquisition system is also connected with a display device and a storage device, respectively, and the display device displays the collected parameters such as pressure, temperature, flow rate, and float displacement in real time, and selects a specific data acquisition frequency according to the test requirements in the storage device. Store data.

(2) Ultrasonic speed test device

The ultrasonic speed test device is shown in Figure 1. The ultrasonic speed test device is connected to the test loop system, and is used to collect ultrasonic signals at different positions of the test loop system to calculate and obtain ultrasonic waves under different simulated operating conditions. speed.

In this embodiment, the ultrasonic velocity testing device includes an ultrasonic probe, an oscilloscope and a signal generator. The ultrasonic probes are respectively connected with signal generators, and the signal generators are connected with the oscilloscope. As shown in Figure 1, three pairs of ultrasonic transmitting probes and receiving probes are installed in the horizontal direction at three different positions of the test pipe section. The distance between the transmitting probe and the receiving probe is also 1/3 of the diameter. The ultrasonic transmitting probe and receiving probe are placed in this way, and the distance between the transmitting and receiving probes from the inner wall of the pipeline is the same as the distance between the two probes. It can be considered that the propagation speed of ultrasonic waves between the two probes is the ultrasonic speed in an infinite medium. In addition, the inner wall of the pipe may be waxed during the experimental operation. The transmitting probe and the receiving probe are placed so as to be far away from the wax deposition layer of the pipe wall, so as to avoid the influence of the wax deposition on the test result.

(3) Computing device

The computing device is connected with the ultrasonic velocity testing device, and is used to calculate the pipeline pressure wave velocity according to the obtained ultrasonic velocity, medium properties, and pipeline properties by corresponding formulas.

Example 2:

The second object of the present invention is to provide a pressure wave velocity test method based on a pipe flow test loop, as shown in FIG. 4 .

In order to achieve the above object, the present invention adopts the following technical scheme: the method is based on the pressure wave velocity test device of the indoor pipe flow test loop, and the determination of the pressure wave velocity at different positions at various points along the actual pipeline is realized through the following operation steps:

Step (1): Measure the viscosity of the oil at different temperatures, obtain the viscosity-temperature curve of the oil viscosity changing with temperature, and determine the abnormal point of the oil.

Specifically, a rotational viscometer is used to measure the viscosity of the oil at different temperatures.

Step (2): Calculate and segment the actual pipeline operating conditions. Obtain the actual crude oil pipeline parameters and other related data, perform thermal and hydraulic calculations, and determine the temperature distribution and residual pressure (also known as dynamic water pressure) distribution along the pipeline between stations; Average temperature, average pressure, and rate of fluid energy dissipation per unit volume of each pipe section. The specific steps are:

Step (2-1): Obtain parameters such as the pipeline throughput of the actual crude oil pipeline, the exit temperature of the heating station, the entry temperature, the buried depth of the pipeline center and the viscosity-temperature curve of the oil product, and inversely calculate the total heat transfer of the actual crude oil pipeline coefficient, and determine the temperature distribution of oil between heating stations;

Step (2-2): Obtain the exit pressure of the pumping station, and calculate the frictional resistance along the actual crude oil pipeline according to parameters such as the exit pressure of the pumping station, the pipeline throughput, the temperature distribution of the oil between the heating stations, and the viscosity-temperature curve of the oil. , and determine the residual pressure along the pipeline;

Step (2-3): Segment the pipeline between stations according to the operating temperature range and pressure range of the pipeline. Preliminarily divide the pipeline between stations according to the pressure drop of 1MPa in each section and the temperature drop of 1℃ in each section, and finally divide the pipeline according to the smaller section after the preliminary division, and calculate the arithmetic average temperature and arithmetic average pressure of each section of the pipeline after the final division. and the rate of fluid energy dissipation per unit volume.

Step (3): Using the indoor pipe flow loop test device, based on the principle of equal energy dissipation rate per unit volume of fluid, simulate the operating conditions of the actual pipeline.

Before simulating the actual pipeline operating conditions in step (3), calibrate the actual distance ΔL _i between the transmitting probe and the receiving probe of the initial use of the pipeline flow test loop ultrasonic velocity test device; the test accuracy is high and can be accurately To 2 significant figures after the decimal point (unit mm). The calibration adopts the distilled water calibration method. The specific steps are: ① Fill the test loop with distilled water, and use the water bath circulation system to control the test temperature; ② Measure the propagation time Δt _i of the ultrasonic wave between the transmitting probe and the receiving probe at the test temperature to obtain the test temperature Corresponding distilled water sound velocity v _water , the product of the propagation time Δt _i and the distilled water sound velocity v _water is the distance ΔL _i between the ultrasonic probes; ③ After the calibration is completed, use the nitrogen bottle connected to the buffer tank to purge the test loop with nitrogen , drain the distilled water out of the pipe and dry the pipe.

Before using the pipe flow test loop to simulate the actual operating conditions of the crude oil pipeline, first place the crude oil in the oil storage tank, turn on the water bath circulation system and the heater in the oil storage tank, and ensure that the temperature of the test loop and the internal temperature of the oil storage tank are ensured. The oil port temperature is uniform. During the test, as shown in Figure 1, open valve 2 and valve 3, close valve 4, turn on the peristaltic pump, and start the pipeline according to the set flow. After running for a period of time, when no gas is discharged from the oil inlet of the oil storage tank, open valve 3 Further exhaust the test loop; after no gas is discharged, open valve 4, close valve 2 and valve 3, and use a buffer tank to apply a constant pressure to the fluid in the loop. At the same time, the data acquisition system is turned on to record and save the hourly values of the pressure sensor and temperature sensor during the pipeline operation.

Specifically, the specific steps of using the pipe flow loop test device to simulate the actual pipeline operating conditions are as follows:

Step (3-1): Use a buffer tank to apply a constant pressure to the fluid in the test loop to simulate the actual pipeline operating pressure; because the test loop is short (about ten meters) and the frictional resistance is small, the pressure along the loop is approximately the constant pressure applied;

Step (3-2): utilize the water bath circulation system to adjust the temperature of the water bath to simulate the operating temperature of the actual pipeline;

Step (3-3): Determine the oil temperature and the size of the abnormal point. When the oil temperature is greater than the abnormal point, the oil is a Newtonian fluid, and the ultrasonic velocity of the fluid has nothing to do with the flow state of the oil in the pipe. In this case, for the convenience of operation, the pipe flow test loop is not activated and the flow rate is 0; when the oil temperature is less than the abnormal point, the flow rate of the pipe flow test loop is adjusted based on the principle of equal fluid energy dissipation rate per unit volume. Simulate the shearing of the fluid in the pipe during the operation of the actual pipe.

Step (4): use the ultrasonic speed test device to test the ultrasonic speed (that is, the speed of sound) under the simulated working conditions, and establish the ultrasonic speed database under the actual pipeline operating temperature range, pressure range, and fluid energy dissipation rate per unit volume range.

If the distance between the transmitting probe and the receiving probe is ΔL, and the transmission time of ultrasonic waves therebetween is Δt ₁ , then the ultrasonic velocity v=ΔL/Δt ₁ . Use multiple pairs of ultrasonic probes to measure the ultrasonic velocity values at multiple different locations and verify each other, and take the average value of the final results.

Step (5): Determine the sound velocity of each section of the pipeline after segmentation based on the ultrasonic velocity database, and calculate the pressure wave velocity of each section of the pipeline after the segmentation in combination with the pipeline parameters. According to the average temperature, average pressure, and fluid energy dissipation rate per unit volume of each segment of the pipeline, combined with the ultrasonic velocity database, determine the sound speed of each segment of the pipeline; and determine the diameter D, wall thickness e, and pipeline constraints of each segment. mode, the elastic modulus E of the pipe and the Poisson coefficient μ, the pressure wave velocity a ₁ of each section of the pipe after segmenting can be calculated from the formula (2).

According to the principle of mass conservation of the liquid during the filling process of the pipeline when the pressure wave propagates along the pipeline, and considering the elastic deformation of the pipeline and the constraints of the pipeline, the calculation formula of the pressure wave velocity in the pipeline can be deduced as:

In the formula, K and ρ are the volume elastic coefficient and density of the medium, which are related to the properties and temperature of the medium. The units are Pa and kg/m ³ respectively; E is the elastic modulus of the pipe, the unit is Pa; D and e are the pipe diameter and the pipe wall thickness, respectively, the unit is m; μ is the Poisson coefficient of the pipe, dimensionless; C ₁ is a correction coefficient related to the way of piping restraint.

For a uniform elastic thin-walled circular tube (D/e>25), C ₁ corresponding to the following three constraints is:

① One end of the pipe is fixed, and the other end is free to expand.

②The two ends of the pipe are fixed without axial displacement; C ₁ =1-μ ² ;

③The pipe is free to expand and contract in the axial direction, and the pipe is connected by multiple expansion nodes: C ₁ =1.

When the ratio of diameter to thickness D/e<25, the pipe wall is thicker, and the stress distribution of the pipe wall is uneven, which changes the deformation characteristics of the pipe. In this case, the following corrections apply:

① One end of the pipe is fixed, and the other end is free to expand.

②The two ends of the pipeline are fixed without axial displacement;

③The pipe can be freely expanded and retracted in the axial direction, and the pipe is connected by multiple expansion nodes:

According to fluid mechanics theory and wave theory, the calculation formula of _sound wave propagation velocity v in infinite medium is: Therefore, the volume elasticity coefficient k of the medium can be calculated by the following formula: k= _ρvsound ² . Therefore, formula (1) can be rewritten as follows:

When the fluid flows in a circular tube, the formula for calculating the energy dissipation rate per unit volume of fluid is:

In the formula, V is the average flow velocity, m/s; D is the inner diameter of the pipe, m; f is the Fanning friction coefficient, which has the following relationship with the Darcy friction coefficient λ: λ=4f.

In this embodiment, according to the diameter D of the test pipe section, the wall thickness e, the pipe restraint method (one end is fixed and the other end can be freely stretched), the elastic modulus E of the pipe material and the Poisson coefficient μ, the test can be calculated from the formula (2). The pressure wave velocity a ₁ of the pipe section.

In this embodiment, a pair of ratios are set to compare the propagation velocity of the pressure wave in the test pipeline. The pressure wave velocity of the test pipe section can also be measured by the time difference method using the pressure sensors P ₁ and P ₂ . If the pressure wave travel time Δt ₂ between the pressure sensors P ₁ and P ₂ , and the distance between P ₁ and P ₂ is L, then the average pressure wave speed between P ₁ and P ₂ is a ₂ =L/Δt ₂ . Compare the pressure wave velocity a ₁ and the pressure wave velocity a ₂ and verify each other.

It should be understood by those skilled in the art that the above steps of the present invention can be implemented by a general-purpose computer device. devices, or they are separately fabricated into individual integrated circuit modules, or multiple modules or steps in them are fabricated into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (9)

1. A pipeline pressure wave velocity testing method based on a pipeline flow test loop is based on a pipeline pressure wave velocity testing device based on the pipeline flow test loop, and the testing device comprises a pipeline flow test loop device, an ultrasonic wave velocity testing device and a calculating device: the pipe flow loop test device consists of a test loop system, a water bath circulation temperature control system and a data acquisition system, wherein the test loop system is arranged in the water bath circulation temperature control system for temperature control; the data acquisition system acquires and monitors the change of each parameter in the test process of the test loop system in real time, and can select preset data acquisition frequency to store data in a readable storage device according to test requirements; the ultrasonic speed testing device is connected with the test loop system and used for acquiring ultrasonic signals at different positions of the test loop system to calculate and obtain ultrasonic speeds under different operating conditions; the calculating device is connected with the ultrasonic velocity testing device and used for calculating the pressure wave velocity of the pipeline according to the acquired ultrasonic velocity, the medium property and the pipeline property, and the pressure wave velocity testing method is characterized by comprising the following steps of:

(1) measuring the viscosity of the oil product at different temperatures to obtain a viscosity-temperature curve of the viscosity of the oil product changing along with the temperature, and determining the abnormal point of the oil product;

(2) acquiring parameters of an actual crude oil or finished oil pipeline, performing pipeline thermal calculation and hydraulic calculation, and determining the on-way temperature distribution and the dynamic water pressure distribution of the pipeline between stations; segmenting the pipeline between stations, and calculating the average temperature, pressure and unit volume fluid energy dissipation rate of each segmented pipeline;

(3) simulating the operation condition of an actual pipeline by using an indoor pipe flow loop test device based on the principle that the energy dissipation rates of fluid in unit volume are equal;

(4) testing the ultrasonic speed under a simulation working condition by using an ultrasonic speed testing device, and establishing an ultrasonic speed database under an actual pipeline operation temperature interval, a pressure interval and a unit volume fluid energy dissipation rate interval;

(5) determining the sound velocity of each divided small section of the pipeline by combining an ultrasonic velocity database according to the average temperature, the average pressure and the energy dissipation rate of the fluid in unit volume of each divided small section of the pipeline; and calculating to obtain the pressure wave velocity of each segmented pipeline by combining the diameter, the wall thickness, the pipeline constraint mode, the elastic modulus of the pipe and the Poisson coefficient of each segment of the pipeline.

2. The pipe flow test loop-based pipe pressure wave velocity test method of claim 1, wherein the test loop system comprises a test loop, an oil storage tank, a pump, a buffer tank and a plurality of valves; the material of the test loop is a stainless steel pipe, the ratio of the inner diameter to the wall thickness of the pipe is less than 20, the test loop comprises a test pipe section and a non-test pipe section, and the test pipe section is wholly immersed in the water bath circulation system; the non-test pipe section is sequentially connected with the oil storage tank, the pump, the buffer tank and the flowmeter, two ends of the oil storage tank are respectively provided with a valve on a pipeline connected with the non-test pipe section, and the buffer tank is provided with a valve on a pipeline connected with the non-test pipe section.

3. The pipeline pressure wave velocity testing method based on the pipe flow test loop as claimed in claim 2, wherein an insulating layer is arranged outside the oil storage tank, and a heating device is arranged inside the oil storage tank; the pump adopts a peristaltic pump, and the buffer tank comprises a buffer tank body, a pressure supply device and a plurality of valves; the buffer tank body is externally provided with a heat insulation layer, the bottom of the buffer tank is provided with an oil spill emptying valve, and the top of the buffer tank is provided with a gas release valve; a vent valve is arranged between the buffer tank and the pressure supply device, the pressure supply device adopts a nitrogen tank, and a pressure reducing valve is arranged at the outlet of the nitrogen tank; a floater is arranged inside the buffer tank body, and a displacement sensor is arranged above the buffer tank.

4. The pipe pressure wave velocity testing method based on the pipe flow test loop, according to claim 1, wherein the water bath circulating system comprises a water bath, a spray pipe, a water circulating pipeline, a pipeline pump, a refrigerator and a regulating valve; the heat insulation layer is arranged outside the water bath, and a plurality of spray pipes and a plurality of heaters are uniformly arranged inside the water bath; circulating water outlets of the water bath are arranged at two ends of the water bath and are connected with the water circulating pipeline; the water circulation pipeline is provided with a pipeline pump for providing power for the water to form circular flow in the pipeline; the refrigerating machine and the regulating valve are connected between the inlet pipeline and the outlet pipeline of the pipeline pump, and the refrigerating capacity is regulated by regulating the opening degree of the refrigerating machine and the regulating valve at the inlet of the refrigerating machine; the refrigerated water is sprayed out through a plurality of spray pipes uniformly arranged in the water bath.

5. The method of claim 1, wherein the data acquisition system comprises a pressure sensor, a flow sensor, a temperature sensor, and a displacement sensor; the pressure sensors comprise a first pressure sensor, a second pressure sensor, a third pressure sensor and a fourth pressure sensor, the first pressure sensor and the second pressure sensor are arranged on the test loop at intervals, the test loop is divided into a test pipe section and a non-test pipe section, the third pressure sensor is connected with the buffer tank, and the fourth pressure sensor is connected with the nitrogen tank; the flow sensor is arranged on the test loop and used for monitoring the flow of crude oil or product oil in the test loop; the temperature sensor is arranged in the oil storage tank and used for monitoring the temperature of crude oil or finished oil in the oil storage tank; the displacement sensor is arranged on the top of the buffer tank and used for monitoring the displacement of the floater in the buffer tank.

6. The method of claim 1, wherein the ultrasonic velocity measuring device comprises an ultrasonic probe, an oscilloscope and a signal generator, pairs of ultrasonic transmitting and receiving probes are installed at different positions on the test pipe section, and the transmitting and receiving probes are installed at 1/3 positions from the diameter of the inner wall of the pipe, so that the distance between the transmitting and receiving probes is 1/3 of the diameter.

7. The method for testing the pressure wave velocity of the pipeline based on the pipe flow test loop according to claim 1, wherein the distance Δ L between the ultrasonic wave transmitting probe and the ultrasonic wave receiving probe is calibrated when the pressure wave velocity testing device is used for the first time; the calibration adopts a distilled water calibration method, and the specific steps are as follows:

(1) filling the test loop with distilled water, and controlling the test loop to a test temperature by adopting a water bath circulating system:

(2) measuring the propagation time delta t of the ultrasonic wave between the transmitting probe and the receiving probe at the test temperature, and obtaining the sound velocity vwater of the distilled water corresponding to the test temperature, wherein the product of the propagation time delta t and the sound velocity vwater of the distilled water is the distance delta L between the ultrasonic probes;

(3) and after calibration is finished, performing nitrogen purging on the test loop by using a nitrogen bottle connected with the buffer tank, discharging distilled water out of the pipeline and drying the pipeline.

8. The pipeline pressure wave velocity testing method based on the pipe flow test loop as claimed in claim 1, wherein in the step (2), the specific steps of performing thermal and hydraulic calculation on the actual crude oil or product oil pipeline and segmenting the pipeline are as follows:

acquiring the pipeline output of an actual pipeline, the outlet temperature and the inlet temperature of a heating station, the ground temperature of the center embedded position of the pipeline and the viscosity-temperature curve of oil products, reversely calculating the total heat transfer coefficient of the actual crude oil pipeline, and determining the temperature distribution of the oil products between the heating stations;

acquiring the outlet pressure of a pump station, calculating the friction resistance of an actual crude oil pipeline along the line according to the outlet pressure of the pump station, the pipeline output, the temperature distribution of oil products between heating stations and the viscosity-temperature curve of the oil products, and determining the residual pressure along the pipeline;

determining an actual operating temperature interval and a pressure interval of a crude oil or finished oil pipeline, segmenting the pipeline between stations, primarily dividing the pipeline between stations according to the pressure drop of each segment of 1MPa and the temperature drop of each segment of 1C, finally dividing the pipeline according to the smaller pipeline segment after primary division, and calculating the arithmetic average temperature, the arithmetic average pressure and the fluid energy dissipation rate of unit volume of each segment of the pipeline after the pipeline is finally divided.

9. The pipe flow test loop-based pipe pressure wave velocity test method according to claim 1, wherein in the step (3), the specific steps of simulating the actual pipe operation condition by using the indoor pipe flow loop test device are as follows:

applying a certain constant pressure to the fluid in the test loop by using a buffer tank to simulate the actual pipeline operating pressure;

regulating the temperature of the water bath by using a water bath circulation system, and simulating the running temperature of an actual pipeline;

judging the temperature of the oil product and the size of the abnormal point, and when the temperature of the oil product is higher than the abnormal point, the pipe flow test loop is not started, and the flow is 0; when the oil temperature is lower than the abnormal point, the flow of the pipe flow test loop is adjusted based on the principle that the energy dissipation rate of fluid in unit volume is equal, and the shearing condition of fluid in the pipe in the actual operation process of the pipe is simulated.