Coaxial microstrip antenna sensor for measuring water holdup of oil-water two-phase flow

Abstract

The invention relates to a coaxial microstrip antenna sensor for measuring the water holdup of an oil-water two-phase flow, which comprises an insertion body and an annular microstrip antenna arranged in a pipeline in the insertion body and used for transmitting a microwave signal; the pipeline outer annular microstrip antenna is arranged outside the measuring pipeline and is used for receiving microwave signals; wherein the insertion body is an insulator and is embedded into the center of the measuring pipeline, the axis of the insertion body is coaxial with the measuring pipeline, and a pipeline annular space is formed between the insertion body and the measuring pipeline; the annular microstrip antenna in the pipeline comprises an annular grounding polar plate, an annular radiation polar plate and a coaxial feeder line which are coaxially arranged, the annular grounding polar plate is embedded into the insert body and located on the inner layer, and the annular radiation polar plate is embedded into the insert body and located on the outer layer; the pipeline outer annular microstrip antenna used for receiving microwave signals is coaxially installed on the outer side of the pipe wall and comprises an annular radiation polar plate arranged on the outer wall of the pipeline, an annular shielding layer located on the periphery of the annular radiation polar plate and a coaxial feeder line.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluid measurement, and relates to a coaxial microstrip antenna sensor for full-range measurement of water holdup in oil-water two-phase flow based on the principle of microwave transmission method. Background Technique

[0002] The phenomenon of oil-water two-phase flow widely exists in modern petroleum and chemical industries and plays a very important role in industrial production and scientific research. Especially in the process of oil and gas field exploitation, a stable and reliable water holdup measurement technology provides a reliable basis for evaluating the development effect of oil wells and optimizing injection-production schemes. Oil and water, two immiscible media, flow in pipelines, forming a mixed fluid with a complex structure. During the fluid flow process, there are complex and variable flow structures, such as bubble flow, slug flow, and mixed flow, which bring difficulties to measuring fluid components, thereby affecting the control and optimization of production processes and causing waste and unreasonable allocation of resources. To meet the requirements of complex two-phase flow fluid measurement, researching a high-precision, stable, and full-range oil-water two-phase flow water holdup measurement technology has important application value and engineering significance for oilfield development.

[0003] Existing oil-water two-phase flow water holdup measurement methods mainly include conductivity method, capacitance method, ultrasonic method, microwave method, ray method, etc. The conductivity method has advantages such as low cost and fast response, and is suitable for measuring the flow parameters of multiphase flow with water as the continuous phase. However, it is greatly affected by the sensor model and electric field distribution, and loses the measurement ability under the water-in-oil condition. The capacitance method measures the water holdup of two-phase flow based on the change in the capacitance value between the plates distributed around the oil-water two-phase flow pipeline caused by the difference in the mixed dielectric constant of the mixed fluid composed of oil and water with different ratios. Compared with the conductivity method, the capacitance method has the advantage of non-contact measurement. However, affected by the conduction current in the water phase, the measurement accuracy of the capacitance sensor is limited when measuring the condition with water as the continuous phase. The ultrasonic method measures the phase holdup based on the different absorption, reflection, and scattering abilities of oil and water for ultrasonic waves, and has working characteristics such as non-invasive, non-radiative, and portable.

[0004] The microwave method is based on the difference in the dielectric constants between oil and water, and measures the water holdup according to the different transmission and reflection effects of microwave signals on oil-water two-phase flow fluids with different ratios. Measuring using microwave frequency signals has the advantages of reliable operation and high sensitivity. However, traditional sensors based on the microwave method mainly focus on measuring oil-water two-phase flow under high water cut conditions. At high water cut, the oil-water two-phase flow mainly appears as oil-in-water bubbly flow, and the distribution of oil and water in the measurement space is relatively uniform. The resonance peak on the microwave sensor spectrum is relatively stable, which is conducive to measuring the water holdup of high-sensitivity microwave sensors. When measuring the water holdup over the full range, the flow pattern of the oil-water two-phase flow changes complexly, and the sensor design faces huge challenges. In addition, the water produced in the formation has different salinities, resulting in changes in the conductivity of the water phase and the mixed dielectric constant, which brings challenges to measuring the water holdup of oil-water two-phase flow by the electrical method. Therefore, the present invention proposes to use a coaxial microstrip antenna sensor to measure the water holdup of oil-water two-phase flow in a pipeline with an inner diameter of 20 mm when the water cut changes from 0 to 100% under different salinities and flow rates. Summary of the Invention

[0005] The present invention designs a coaxial microstrip antenna sensor for realizing full-range measurement of the water holdup of oil-water two-phase flow. The sensor coaxially arranges two annular microstrip antennas inside and outside the measurement pipeline, and calculates the water holdup of the oil-water two-phase flow through the amplitude attenuation and phase shift generated when microwave signals are transmitted between the two annular microstrip antennas. The technical solution is as follows:

[0006] A coaxial microstrip antenna sensor for measuring the water holdup of oil-water two-phase flow, including an insert body. It is characterized in that it further includes an in-pipe annular microstrip antenna arranged inside the insert body for transmitting microwave signals; an out-of-pipe annular microstrip antenna arranged outside the measurement pipeline for receiving microwave signals; wherein,

[0007] The insert body is an insulator, embedded in the center of the measurement pipeline, its axis is coaxial with the measurement pipeline, and a pipeline annular space is formed between the insert body and the measurement pipeline;

[0008] The in-pipe annular microstrip antenna includes a coaxially arranged annular ground plate and an annular radiation plate as well as a coaxial feeder. The annular ground plate is embedded inside the insert body and located in the inner layer, and the annular radiation plate is embedded inside the insert body and located in the outer layer. The in-pipe annular microstrip antenna is not in direct contact with the fluid in the pipeline annular space;

[0009] The out-of-pipe annular microstrip antenna for receiving microwave signals is coaxially installed on the outer side of the pipe wall, and includes an annular radiation plate arranged on the outer wall of the pipeline, an annular shielding layer located on the outer periphery of the annular radiation plate, and a coaxial feeder;

[0010] The microwave signal source transmits microwave signals with a fixed frequency to the annular microstrip antenna inside the pipeline through a coaxial feeder. The microwave signals are transmitted in the oil-water two-phase flow in the annular space of the pipeline and received by the annular microstrip antenna outside the pipeline.

[0011] By calculating the amplitude attenuation and phase shift generated when the microwave signals are transmitted between the two annular microstrip antennas, the mixed dielectric constant of the fluid is calculated, and then the water holdup of the oil-water two-phase flow is solved.

[0012] Furthermore, the annular microstrip antenna outside the pipeline is coaxially installed at the same height on the outer side of the pipe wall, and its annular radiation plate is arranged closely against the outer wall of the pipe.

[0013] Furthermore, considering that the mixed dielectric constant is affected by the dielectric constants of the oil and water phases, the salinity of the water phase, the water holdup, and the flow structure, by establishing a mixed dielectric constant model under different flow patterns and different salinities, the water holdup of the oil-water two-phase flow is solved.

[0014] Furthermore, the feeding points for receiving and transmitting microwave signals are respectively located at the centers of the two annular microstrip antennas; the excitation frequency of the coaxial microstrip antenna sensor is 540 MHz.

[0015] Furthermore, the antenna radius of the annular microstrip antenna inside the pipeline for transmitting microwave signals, that is, the radius of the annular radiation plate, is 5 mm, and the lengths of the annular radiation plates of the two annular microstrip antennas are both 80 mm.

[0016] Due to the adoption of the above technical solutions, the present invention has the following measurement advantages:

[0017] (1) The coaxial sensor adopts an insert type measurement, which has a regulating effect on the complex and variable oil-water two-phase flow patterns. The microstrip antenna has various functions, is convenient to design, and has high sensitivity. The coaxial microstrip antenna sensor designed by combining the advantages of the two has high water holdup measurement accuracy.

[0018] (2) In the research on measuring the oil-water two-phase flow by the electrical method, the traditional conductivity method is only applicable to the measurement of working conditions with water as the continuous phase, and the traditional low-frequency capacitance method has low accuracy at high water cut. The coaxial microstrip antenna sensor designed by the present invention is not affected by the conductivity of the medium in the measurement of the water holdup of the oil-water two-phase flow and can realize the full-range measurement of the water holdup. Description of the Drawings

[0019] Figure 1 is a three-dimensional schematic diagram of the structure of the coaxial microstrip antenna sensor.

[0020] Figure 2 is a side view of the coaxial microstrip antenna sensor.

[0021] Figure 3 is a cross-sectional view of the coaxial microstrip antenna sensor.

[0022] Figure 4 are the sensor amplitude-phase frequency response curves obtained by simulation under different water holding rate conditions: (a) amplitude; (b) phase.

[0023] Figure 5 is the position where the oil bubble is placed at the cross-section.

[0024] Figure 6 are the sensor sensitivity fields under different radiation plate lengths and transmitting antenna radii: (a) sensitivity field; (b) average sensitivity and uniformity error when the radiation plate length changes; (c) average sensitivity and uniformity error when the reflection antenna radius changes.

[0025] Figure 7 is the water-in-oil bubble flow simulation model.

[0026] Figure 8 is the water-in-oil bubble flow simulation result.

[0027] Figure 9 is the transitional flow simulation model.

[0028] Figure 10 is the transitional flow simulation result.

[0029] Figure 11 is the oil-in-water bubble flow simulation model.

[0030] Figure 12 is the oil-in-water bubble flow simulation result.

[0031] Figure 13 are the sensor amplitude and phase responses at different water phase salinities at 540 MHz: (a) amplitude; (b) phase.

[0032] Figure 14 is the schematic diagram of the measurement system.

[0033] Figure 15 is the schematic diagram of the microwave measurement system.

[0034] Figure 16 are the measured signals of the sensor under some working conditions with a salinity S = 180 ppm: (a) Q m = 10 m 3 / d; (b) Q m = 14 m 3 / d; (c) Q m = 18 m 3 / d.

[0035] Figure 17 is the average value of the sensor phase output response and amplitude output response at 180 ppm.

[0036] Figure 18 It is the experimental flow pattern distribution diagram of oil-water two-phase flow in a 20-mm vertically rising pipe.

[0037] Figure 19 It is the amplitude-phase response under pure water conditions when the salinity of the aqueous phase changes.

[0038] Figure 20 It is the prediction effect of the water holdup prediction model established for the split flow type: (a) VFD O / W; (b) D O / W; (c) TF; (d) D W / O.

[0039] Figure 21 It is the comparison result of the predicted water holdup and the water holdup measured by the fast-closing valve under all working conditions.

[0040] Explanation of the attached figure labels:

[0041] 1, 8: Coaxial feeder; 2: Ring-shaped shielding layer; 3: Ring-shaped radiation electrode plate for receiving microwave signals; 4: Acrylic glass pipe; 5: Inner ring space of the pipe through which the fluid flows; 6: Ring-shaped radiation electrode plate for transmitting microwave signals; 7: Ring-shaped grounding electrode plate; 9: Insertion body Specific implementation manner

[0042] To solve the problem of measuring the water holdup of oil-water two-phase flow, the present invention proposes a coaxial microstrip antenna sensor. The innovative idea is to utilize the characteristic that the electromagnetic waves radiated axially in the measurement area by two coaxially arranged microstrip antennas are relatively uniform, and to optimize the parameters of the sensor to improve the uniformity of the sensitivity distribution in the measurement area. In terms of the measurement method, a fixed-frequency measurement with a simple method and low cost is adopted.

[0043] When microwave signals propagate in a fluid medium, due to the different reflection and transmission effects of the mixed fluid on microwaves under different water holdups, the received microwave signals will undergo corresponding amplitude attenuation and phase shift. At appropriate structures and frequencies, their amplitude attenuation and phase shift will show regular changes with the change of the water holdup. Utilizing this characteristic, a sensor for full-range measurement of the water holdup can be designed.

[0044] The coaxial microstrip antenna sensor designed by the present invention consists of a transmitting microstrip antenna arranged on the insertion body at the center of the pipe and a receiving microstrip antenna on the outer wall of the pipe. The output response of the sensor obtained by acquisition shows regular changes with the change of the water holdup within the full range.

[0045] The following describes the design and measurement process of the coaxial microstrip antenna sensor in vertical oil-water two-phase flow with reference to the attached drawings:

[0046] (1) The overall structure of the coaxial microstrip antenna sensor of the present invention is as shown in Figure 1-3As shown in the figure. From the three-dimensional structure diagram, side view and cross-sectional view of the sensor, it can be seen that the sensor is composed of two circular microstrip antennas, which are used for transmitting and receiving microwave signals respectively. The circular microstrip antenna for transmitting microwave signals is composed of a circular ground plate 7 made of brass and a circular radiation plate 6 made of brass from the inside out. It is installed on an insert 9 made of resin material in the center of the pipeline 4. The insert area between 7 and 6 forms the insulating substrate of the microstrip antenna. The circular microstrip antenna does not come into direct contact with the fluid, reducing the influence of particulate fouling and oil droplet adhesion in the fluid. In this embodiment, a groove is directly dug in the insert, and the circular ground plate 7 and the circular radiation plate 6 of the circular microstrip antenna for transmitting microwave signals are embedded, and then the insert is fixed in the center of the pipeline. The circular microstrip antenna for receiving microwave signals is installed coaxially at the same height on the outer side of the pipe wall. The circular radiation plate 3 is closely attached to the outer wall of the pipe, and the outermost layer is a circular shielding layer 2 made of brass, which is grounded to shield external electromagnetic interference and prevent internal microwave leakage. The inner diameter r of the pipeline is 20 mm, and the outer diameter R is 30 mm. During measurement, the microwave signal source transmits a microwave signal with a fixed frequency to the circular microstrip antenna in the center of the pipeline through the coaxial feeder 8. The microwave signal is transmitted in the annular space 5 of the oil-water two-phase flow in the pipeline and is received by the circular microstrip antenna on the outer wall of the pipeline. According to the difference in the mixed dielectric constant of the oil and water, the microwave signal undergoes different amplitude attenuation and phase shift, and is connected to the microwave detection circuit through the coaxial feeder 1, converting the amplitude attenuation and phase shift signals into voltage signals, which are collected by the signal acquisition system. Using the amplitude attenuation and phase shift, the mixed dielectric constant of the fluid is calculated. The mixed dielectric constant is also affected by the dielectric constants of the oil and water phases, the salinity of the water phase, the water holdup rate, and the flow structure. By establishing a mixed dielectric constant model under different flow patterns and different salinities, the water holdup rate of the oil-water two-phase flow is finally solved.

[0047] (2) Simulation and optimization. The key structural parameters in the sensor structure are finally determined through simulation and optimization. The purpose of the simulation is to verify the correctness of the design and improve the resolution and stability of the sensor response through optimization methods.

[0048] The simulation is carried out by the three-dimensional electromagnetic field simulation software HFSS. The HFSS software solves electromagnetic field problems based on the finite element algorithm. First, a coaxial microstrip antenna sensor model is established in the software to simulate the sensor response. The results are as Figure 4 shown, Y w refers to the water holdup rate. When the water holdup rate changes from 0% to 100%, the phase response of the S 21 parameter of the sensor (S 21 (deg)) monotonically decreases with the increase of the water holdup rate in the range of 450 - 560 MHz, and the amplitude response (S 21(dB)) increases monotonically with the increase of water holding ratio. And with the increase of frequency, the resolution ability of the sensor to the change of water holding ratio also increases significantly. However, when the frequency exceeds 560 MHz, the phase response at a water holding ratio of 100% will be lower than -180 degrees, that is, the measured phase will flip, which is not conducive to the measurement of the full range of water holding ratio. At the same time, when the frequency is lower than 500 MHz, the resolution ability of the sensor to the change of water holding ratio decreases significantly. Therefore, when simulating, 540 MHz is used as the frequency of the microwave signal.

[0049] Parameter optimization is carried out for the two main parameters affecting the sensor response (the radius R of the annular radiation plate for emitting microwave signals and the length L of the annular radiation plate). The evaluation index is the uniformity of the sensitivity distribution in the measurement space of the sensor. The calculation rule of the sensitivity distribution is as follows: First, calculate the transmission coefficient S of the sensor when it is full of water in the measurement area. w , place an oil bubble at the coordinate (x, y, z) in the detection area, and calculate the sensor response S at this time. The change in the output value of the sensor caused by the oil bubble is:

[0050] ΔS 21 (x,y,z) = S - S w (1)

[0051] Define the sensor sensitivity at the coordinate (x, y, z):

[0052]

[0053] Average sensitivity:

[0054]

[0055] Uniformity error:

[0056]

[0057] Figure 5 Shows all the positions that the small ball traverses in turn during the optimization calculation when the radius R = 5 mm and the plate length L = 80 mm. Figure 6 (a) Shows the sensitivity distribution under some structural parameters. The sensitivity distribution in the measurement space, its average sensitivity and uniformity error can be used as performance indicators. The calculation results of the indicators are as Figure 6 (b) and Figure 6 (c) shown. Considering the calculation results of the two indicators comprehensively, the inner radius of the emitting antenna is selected as R = 5 mm, and the radiation plate length of the two antennas is L = 80 mm.

[0058] After determining the optimal parameters for the sensor to measure the water holdup in oil-water two-phase flow, three typical flow patterns that occur in oil-water two-phase flow are simulated under this size and structure, including oil-in-water bubbly flow, slug flow, and water-in-oil flow pattern. Their model structures are respectively as Figure 7 、 9 、and Figure 11. In the oil-in-water bubbly flow, 1000 oil bubbles are evenly placed in a 500-mm long water-filled pipe. After removing the volume of all the oil bubbles, the proportion of the remaining space volume to the total space volume inside the pipe is the water holdup. The water holdup is changed by controlling the radius of the small balls, that is, the size of the bubbles. This structure is used to approximate the oil-in-water bubbly flow. The calculation results are as Figure 8 shown. As the water holdup increases, the phase lag angle of the sensor increases. For every 2% change in the water holdup, the average phase change of the sensor is 0.837 degrees. As Figure 9 shown, the slug flow pattern is simulated using a structure with multiple large oil plugs followed by 8 oil bubbles. The calculation results are as Figure 10 shown. For every 5% change in the water holdup, the average phase change of the sensor is 0.998 degrees. Water bubbles are placed in the oil-filled pipe to simulate the water-in-oil bubbly flow. The calculation results are as Figure 12 shown. For every 2% change in the water holdup, the average phase change of the sensor is 0.231 degrees.

[0059] Subsequently, in order to analyze the influence of the water phase salinity on the sensor output response, the response results of the sensor under the change of the water phase salinity when the pipe is filled with water are simulated and analyzed, as Figure 13 shown. At low salinity, the fluctuation of the water phase salinity has a severe impact on the sensor output response. As the salinity increases, the impact on the sensor output response tends to be stable. After reaching 10000 ppm, as the water phase salinity continues to increase, the phase response is relatively stable.

[0060] (3) Experimental verification. The effect of the sensor is verified in the vertical oil-water two-phase flow experiment. The experimental device is as Figure 14 shown. The inner diameter of the pipe is 20 mm, and the total length of the pipe is 2600 mm. In the experiment, the water phase and the oil phase are respectively transported and metered by industrial peristaltic pumps. The water phase and the oil phase are mixed using a Y-shaped connector at the bottom of the flow loop device and then introduced into the vertical upward pipe. To ensure that the mixed fluid is fully developed and stable, the sensor is placed at a position 1500 mm away from the mixing inlet. The experimental oil is industrial white oil No. 3 (density 0.01 kg / m*s, viscosity 845 kg / m 3 , dielectric constant 3.2).

[0061] The working conditions of this experiment are set as follows: a total of 5 salinities are involved (180 ppm, 2500 ppm, 5000 ppm, 10000 ppm, and 15000 ppm); the total flow rate range is 8 m 3 / d to 18 m3 / d, set the interval to 2 m 3 / d; The water content has a total of 3 change intervals (10%-50%, changing at intervals of 10%; 55%-80%, changing at intervals of 5%; 82%-98%, changing at intervals of 2%). In the experiment, the configured NaCl solution was used instead of tap water for the experiment at the corresponding salinity.

[0062] The microwave sensor measurement circuit is as Figure 15 shown. The microwave signal generator is made up of ADF4351 with peripheral circuits. Six control word registers inside the ADF4351 chip are configured through the SPI bus, enabling the ADF4351 to output a microwave signal with a frequency of 540 MHz. The one-to-two power divider can evenly distribute the microwave signal into two ports. One is connected to the transmitting microstrip antenna of the coaxial microstrip antenna sensor, and the microwave signal is received by the receiving microstrip antenna after being attenuated by the measured substance. The other path serves as a reference signal. The two signals serve as the two inputs of the amplitude and phase discriminator composed of AD8302. The amplitude attenuation and phase shift of the two signals are converted into voltage signals. When AD8302 measures the amplitude, its dynamic range can be extended to 60 dB, while the phase measurement range can reach 180 degrees. The two voltage signals converted by the amplitude and phase detection circuit are connected to PXI-4472 for signal acquisition and uploaded to the upper computer for data storage and further calculation and processing. The data sampling frequency is 2 kHz, and the sampling time is 30 s.

[0063] (4) Results and analysis.

[0064] The output response of the coaxial microstrip antenna sensor is obtained through experiments, Figure 16 showing the phase response signals of the sensor when the water content changes at the total flow rates of 10 m 3 / d, 14 m 3 / d, and 18 m 3 / d at a salinity of 180 ppm. As shown in the figure, when the total flow rate is fixed, as the water content decreases, the voltage signal corresponding to the phase response of the obtained coaxial microstrip antenna sensor gradually decreases. When the total flow velocity is low, as Figure 16 (a) shows, at this time, the oil-water two-phase flow has a low turbulent energy. As the water holdup decreases, small oil bubbles coalesce into larger oil bubbles, and the distribution of the oil phase and the water phase in the measurement area becomes more uneven. Therefore, the signal fluctuates more violently, and the amplitude of the fluctuation becomes larger. As the water holdup further decreases, the flow pattern evolves into a transitional flow pattern. In the transitional flow pattern, the water phase and the oil phase are lower as the dominant phases, and the water holdup difference is obvious, corresponding to the largest signal fluctuation amplitude. As the water holdup further decreases, the phase state of the oil-water two-phase flow reverses, with the oil phase as the continuous phase and the water distributed in the oil in the form of oil bubbles. Correspondingly, the amplitude of the signal fluctuation decreases, and the jump frequency increases. When the total flow velocity increases, asFigure 16 As shown in (c), the turbulent energy of the system increases, and the dispersed phase in the oil-water two-phase flow is more easily broken up. Therefore, compared with the signals under the condition of low flow rate and the same water cut, the signal fluctuation amplitude at high flow rate is smaller and the jump frequency is higher.

[0065] Filter and average the signals. Obtain the charts of the amplitude and phase responses of the sensor varying with the water holdup and total flow rate under different salinities. The phase (Signal_deg) and amplitude (Signal_dB) response signals at a salinity of 180 ppm are as Figure 17 shown. The phase response of the sensor has a good linearity to the change of water holdup and has a relatively sensitive response within the full range of water holdup change. The amplitude response of the sensor is not monotonic to the change of water holdup. Under the condition of high water cut, the sensor amplitude response loses the ability to distinguish the change of water holdup. Under the condition of high oil content, the amplitude response sensitivity is higher. At different flow rates and water cuts, the fluid forms a variable flow pattern structure, resulting in data fluctuations. Under the small oil-in-water bubble flow, the flow pattern structure is the most uniform, and the phase response is less affected by the flow pattern during measurement, and the result is relatively stable.

[0066] Based on the amplitude-phase fluctuation signal of the sensor, identify the flow pattern, and the divided flow pattern diagram is as Figure 18 shown. The water phase salinity information can be obtained through the data under the pure water condition, as Figure 19 shown. From the obtained salinity information, the sensor output response affected by salinity can be corrected to the response value without salinity influence through the Bessel function.

[0067] When the mixed dielectric constant of the fluid is ε m = ε' m - jε” m , its propagation constant is:

[0068]

[0069] λ0 is the free space wavelength; λ c is the cut-off wavelength. For waveguide structures (such as coaxial cables and strip lines) and free space waves, λ c = ∞; ε' m and ε” m are the real part and the imaginary part of the mixed dielectric constant respectively.

[0070] The attenuation constant α and the phase constant β after the fluid flows through can be respectively obtained as

[0071]

[0072] Therefore, the relationships between the amplitude attenuation A and the phase shift φ and the attenuation constant α and the phase constant β are established:

[0073]

[0074] l is the propagation distance of the microwave signal.

[0075] After obtaining the measured mixed dielectric constant, the relationship between the mixed dielectric constant and the water holdup is established through the mixed dielectric constant model:

[0076]

[0077] Subsequently, using the fast-closing valve experimental data, the unknown parameters A and B in the above formula are determined. Since the phase response of the microwave sensor is more sensitive to the change of water holdup, the real part of the measured mixed dielectric constant can be calculated using the phase response. The water holdup Y is obtained through the fast-closing valve experiment w . The dielectric constant ε of the aqueous phase w is obtained through the Debye relationship. The No. 3 industrial white oil is used in the experiment, and the dielectric constant ε o is generally taken as 3.2. Therefore, the model parameters A and B under each flow pattern can be determined through the fast-closing valve experimental data.

[0078] On this basis, a calculation model of water holdup for oil-water two-phase flow is established for the flow splitting type. For the sensor data of the oil-in-water fine bubble flow (VFD O / W), the predicted water holdup Y obtained through the model w pre and the water holdup Y of the fast-closing valve w exp The comparison results are as Figure 20 (a) shown. As shown in the figure, under the oil-in-water fine bubble flow (VFD O / W), the sensor has a good water holdup measurement effect, high accuracy and relatively stable. The relative error of water holdup measurement is within ±5%, the absolute average error (AAD) is 0.012, and the absolute average relative error (AAPD) is 1.29%.

[0079] For the sensor data of the oil-in-water bubble flow (D O / W) of the oil-water two-phase flow, the comparison results of the water holdup obtained through the model and the water holdup of the fast-closing valve are as Figure 20 (b) shown. In the oil-in-water bubble flow (D O / W), the sensor can still have a relatively accurate solution for the water holdup for the sensor data under different salinities. However, due to the existence of oil bubbles of different sizes in the bubble flow, the output response of the sensor fluctuates greatly, resulting in a larger error in the water holdup. Most of the data points can fit well with the water holdup of the fast-closing valve. The absolute average error (AAD) of water holdup measurement is 0.016, and the absolute average relative error (AAPD) is 2.22%. The sensor also achieves relatively accurate water holdup measurement in this flow pattern. The water holdup measurement accuracy is relatively higher at low salinity.

[0080] For the sensor data of the transition flow pattern (TF) of oil-water two-phase flow, the comparison results of the water holdup obtained by the model and the water holdup of the fast-closing valve are as Figure 20 (c) shown. In the transition flow pattern (TF), the flow structure of oil-water two-phase flow shows a complex and random phenomenon of oil-water phase inversion, resulting in a large deviation in the measurement results of water holdup.

[0081] For the sensor data of the dispersed water-in-oil bubble flow pattern (D W / O) of oil-water two-phase flow, the comparison results of the water holdup obtained by the model and the water holdup of the fast-closing valve are as Figure 20 (d) shown. Finally, the measurement accuracy of the water holdup is AAD = 0.021 and AAPD = 11.63%. Since the corresponding water holdup is low in the dispersed water-in-oil bubble flow, the value of the denominator is small in the AAPD calculation, resulting in a large AAPD.

[0082] Finally, the predicted water holdup data of different water salinities under all flow patterns are compared with the experimental data of the fast-closing valve, and the results are as Figure 21 shown. The experimental results show that the absolute average error (AAD) of the water holdup prediction is 0.0232, and the absolute average relative error (AAPD) is 4.69%, achieving a high-precision water holdup measurement effect.

Claims

1. A coaxial microstrip antenna sensor for measuring water holdup of oil-water two-phase flow, comprising an insert, characterized in that: It also includes an inner-pipe annular microstrip antenna arranged in the insert body, used for transmitting microwave signals; an outer-pipe annular microstrip antenna arranged outside the measuring pipe, used for receiving microwave signals; wherein, The insert is an insulator, embedded in the center of the measuring pipeline, with its axis coaxial with the measuring pipeline, and a pipeline annular space is formed between the insert and the measuring pipeline; The in-pipe annular microstrip antenna comprises a coaxially arranged annular grounding plate and annular radiating plate and a coaxial feeder, wherein the annular grounding plate is embedded in the insert and located in the inner layer, and the annular radiating plate is embedded in the insert and located in the outer layer, and the in-pipe annular microstrip antenna does not directly contact the fluid located in the annular space of the pipeline; The pipeline outer annular microstrip antenna for receiving microwave signals is coaxially installed on the outer side of the pipeline wall, and includes an annular radiation plate arranged on the outer wall of the pipeline, an annular shielding layer located on the outer periphery of the annular radiation plate, and a coaxial feed line; The microwave signal source transmits a microwave signal of a fixed frequency to the annular microstrip antenna in the pipeline through a coaxial feeder, the microwave signal is transmitted in the oil-water two-phase flow in the annular space of the pipeline, and the microwave signal is received by the annular microstrip antenna outside the pipeline; The mixed dielectric constant of the fluid is calculated based on the amplitude attenuation and phase shift caused by the microwave signal transmitted through two annular microstrip antennas, and then the water holdup of the oil-water two-phase flow is solved.

2. The coaxial microstrip antenna sensor for measuring water holdup of oil-water two-phase flow according to claim 1, characterized in that: The pipeline outer annular microstrip antenna is coaxially installed at an equal height on the outer side of the pipeline wall, and its annular radiation plate is arranged close to the outer wall of the pipeline.

3. The coaxial microstrip antenna sensor for measuring water holdup of oil-water two-phase flow according to claim 1, characterized in that: Considering that the mixed dielectric constant is affected by the dielectric constant of the oil-water two-phase, the salinity of the water phase, the water holdup and the flow structure, a mixed dielectric constant model under different flow patterns and salinities is established to solve the water holdup of the oil-water two-phase flow.

4. The coaxial microstrip antenna sensor for measuring water holdup of oil-water two-phase flow according to claim 1, characterized in that: The feeding points for receiving and transmitting microwave signals are respectively located at the centers of the two annular microstrip antennas; the excitation frequency of the coaxial microstrip antenna sensor is 540 MHz.

5. The coaxial microstrip antenna sensor for measuring water holdup of oil-water two-phase flow according to claim 1, characterized in that: The antenna radius of the annular microstrip antenna in the pipeline that transmits microwave signals, that is, the radius of the annular radiation plate, is 5 mm, and the lengths of the annular radiation plates of the two annular microstrip antennas are both 80 mm.

Images